RISK FACTORS

         Before you decide to invest in our common stock, you should consider carefully the risks described below, together with the other information contained in this prospectus. We believe the risks described below are the risks that are material to us as of the date of this prospectus. If any of the following risks comes to fruition, our business, financial condition, results of operations and future growth prospects would likely be materially and adversely affected. In these circumstances, the market price of our common stock could decline, and you may lose all or part of your investment.

Risks related to our business and industry

We have a history of net losses and may never become profitable.

        We have incurred net losses from our inception through June 30, 2007, including net losses of $11.1 million for the year ended December 31, 2005, $6.7 million for the year ended December 31, 2006 and $3.6 million for the six months ended June 30, 2007. As of June 30, 2007, we had total shareholders' deficit of approximately $79.9 million. We expect our operating expenses to increase as we, among other things:

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expand our sales and marketing activities;



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invest in designing, manufacturing and building our inventory of future generations of the CardioNet System;



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hire additional personnel;



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invest in infrastructure; and



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incur the additional expenses associated with being a public company.

With increasing expenses, we will need to substantially increase our revenues to become profitable. Because of the risks and uncertainties associated with further developing and marketing the CardioNet System, we are unable to predict the extent of any future losses or when we will become profitable, if at all.

Our business is dependent upon physicians prescribing our services; if we fail to obtain those prescriptions, our revenues could fail to grow and could decrease.

        The success of our business is dependent upon physicians prescribing our services for patients and cross-selling the respective Company and PDSHeart customer bases. Our success in obtaining prescriptions and cross-selling will be directly influenced by a number of factors, including:

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the ability of the physicians with whom we work to obtain sufficient reimbursement and be paid in a timely manner for the professional services they provide in connection with the use of our arrhythmia monitoring solutions, particularly the CardioNet System;



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our ability to educate physicians regarding, and convince them of, the benefits of the CardioNet System over existing treatment methods such as Holter monitors and event monitors; and



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the perceived clinical efficacy of the CardioNet System.

        If we are unable to educate physicians regarding the benefits of the CardioNet System, obtain sufficient prescriptions and cross-sell our respective customer bases, revenues from the provision of our arrhythmia monitoring solutions could fail to grow and could decrease.

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We and the physicians with whom we work are dependent upon reimbursement for the fees associated with our services; the absence or inadequacy of reimbursement would cause our revenues to fail to grow or decrease.

        We receive reimbursement for our services from commercial payors and from Medicare Part B carriers where the services are performed on behalf of the Centers for Medicare and Medicaid Services, or CMS. The Medicare Part B carriers in each state change from time to time, which may result in changes to our reimbursement rates, increased administrative burden and reimbursement delays.

        In addition, our physician customers receive reimbursement for professional interpretation of the information provided by our products and services from commercial payors or Medicare carriers within the state where they practice. The efficacy, safety, performance and cost-effectiveness of our products and services, on a stand-alone basis and relative to competing services, will determine the availability and level of reimbursement we and our physician customers receive. Our ability to successfully contract with payors is critical to our business because physicians and their patients will select arrhythmia monitoring solutions other than ours in the event that payors refuse to adequately reimburse our technical fees and physicians' professional fees.

        Many commercial payors refuse to enter into contracts to reimburse the fees associated with medical devices or services that such payors determine to be "experimental and investigational." Commercial payors typically label medical devices or services as "experimental and investigational" until such devices or services have demonstrated product superiority evidenced by a randomized clinical trial. We recently completed a clinical trial in which the CardioNet System provided higher diagnostic yield than traditional loop event monitoring. Prior to our clinical trial, the CardioNet System was labeled "experimental and investigational" by 21 commercial payors, representing over 95 million covered lives. Subsequent to our trial, three commercial payors, representing over 11 million covered lives removed the designation of the CardioNet System as "experimental and investigational" and several of the remaining payors have informed us that they do not believe the data from this trial justifies the removal of this designation. Other commercial payors may also find the data from our clinical trial not compelling. Additional commercial payors may also label the CardioNet System as "experimental and investigational" and, as a result, refuse to reimburse the technical and professional fees associated with the CardioNet System.

        Administration of the claims process for the many commercial payors is complex. As a result we sometimes bill payors for services for which we have no reimbursement contract. These payors may require that we return any funds that they pay in respect of these claims.

        If commercial payors or Medicare decide not to reimburse our services or the related services provided by physicians, or the rates of such reimbursement change, or if we fail to properly administer claims, our revenues could fail to grow and could decrease.

Reimbursement by Medicare is highly regulated and subject to change; our failure to comply with applicable regulations, could decrease our revenues and may subject us to penalties or have an adverse impact on our business.

        We receive approximately 30% of our revenues as reimbursement from Medicare. The Medicare program is administered by CMS, which imposes extensive and detailed requirements on medical services providers, including, but not limited to, rules that govern how we structure our relationships with physicians, how and when we submit reimbursement claims, how we operate our monitoring facilities and how and where we provide our arrhythmia monitoring solutions. Our failure to comply with applicable Medicare rules could result in discontinuing our reimbursement under the Medicare payment program, our being required to return funds already paid to us, civil monetary penalties, criminal penalties and/or exclusion from the Medicare program.

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        In addition, reimbursement from Medicare is subject to statutory and regulatory changes, rate adjustments and administrative rulings, all of which could materially affect the range of services covered or the reimbursement rates paid by Medicare for use of our arrhythmia monitoring solutions. For example, CMS adopted a new payment policy in January 2007 that reduced the rate of reimbursement for a number of services reimbursed by Medicare. Although this modification to Medicare's reimbursement rates did not affect the amount paid by Medicare for reimbursement of the fees associated with the CardioNet System, it resulted in the reduction of reimbursement rates for event services by 3% to 8%, depending on the type of service, and Holter services by 8% as compared to the corresponding rates in effect in 2006. Based on current proposed Medicare rates for 2008 through 2010, we expect that reimbursement for event and Holter services will continue to decline at an annual rate similar to 2007. In addition, we cannot predict whether future modifications to Medicare's reimbursement policies could reduce the amounts we receive from Medicare for the solutions we provide. In addition, Medicare's reimbursement rates can affect the rate that commercial payors are willing to pay for our products and services. Any future limitation or reduction in the reimbursement rates provided by Medicare for our arrhythmia monitoring solutions could result in a reduction in the rates we receive from commercial payors.

Reimbursement for the CardioNet System by Medicare and other commercial payors is complicated by the lack of a specific CPT code, which may result in lower prescription rates or varying reimbursement rates.

        When we bill Medicare and certain other commercial payors for the service we provide in connection with the CardioNet System, we submit the bill using the nonspecific billing, or CPT, code "93799." Unlike dedicated CPT codes approved by the American Medical Association, or AMA, and CMS, claims using non-specific codes may require semi-automated or manual processing, as well as additional review by payors. The claims processing requirements associated with a nonspecific code can make our services less attractive to physicians. Furthermore, the Medicare reimbursement rate for non-specific codes is determined by local Medicare carriers. As a result, the reimbursement rates relating to our CardioNet System are subject to change without notice.

        A request to the AMA for a specific CPT code that describes our CardioNet System has been made. If this request is approved by the AMA CPT Editorial Panel, the specific CPT code could be available for use in 2009. However, we cannot guarantee that we will receive a specific CPT code for the CardioNet System in that timeframe, or ever. Moreover, if we do receive a CPT code, the reimbursement rate associated with that code, which would be subject to change on an annual basis through a public notice and comment process, may be lower than our current reimbursement rates.

A reduction in sales of our services or a loss of one or more of our key commercial payors would adversely affect our business and operating results.

        A small number of commercial payors represent a significant percentage of our revenues. In the year ended December 31, 2006, our top 10 commercial payors by revenues accounted for approximately 37.4% of our total revenues. Our agreements with these commercial payors typically allow either party to the contract to terminate the contract by providing between 60 and 120 days prior written notice to the other party at any time following the end of the initial term of the contract. Our commercial payors may elect to terminate or not to renew their contracts with us for any reason and, in some instances can unilaterally change the reimbursement rates they pay. In the event any of our key commercial payors terminate their agreements with us, elect not to renew their agreements with us or elect not to enter into new agreements with us upon expiration of their agreements with us on terms as favorable as our current agreements, our business, operating results and prospects would be adversely affected.

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Consolidation of commercial payors could result in payors eliminating coverage of our CardioNet System or reduced reimbursement rates for our CardioNet System.

        The commercial payor industry is undergoing significant consolidation. When payors combine their operations, the combined company may elect to reimburse our CardioNet System at the lowest rate paid by any of the participants in the consolidation. If one of the payors participating in the consolidation does not reimburse for the CardioNet System at all, the combined company may elect not to reimburse for the CardioNet System. Our reimbursement rates tend to be lower for larger payors. As a result, as payors consolidate, our average reimbursement rate may decline.

Our acquisition of PDSHeart, as well as any other companies or technologies we may acquire in the future, could prove difficult to integrate and may disrupt our business and harm our operating results and prospects.

        Our recent acquisition of PDSHeart involves numerous risks, including the risk that we will not take advantage of the cross-selling opportunities brought about by the acquisition. In addition, our acquisition of PDSHeart, as well as acquisitions in which we may engage in the future, involve risks associated with our assumption of the liabilities of an acquired company, which may be liabilities that we were or are unaware of at the time of the acquisition, potential write-offs of acquired assets and potential loss of the acquired company's key employees or customers.

        We may encounter difficulties in successfully integrating our operations, technologies, services and personnel with that of the acquired company, and our financial and management resources may be diverted from our existing operations. For example, following our acquisition of PDSHeart we have offices in Pennsylvania, California, Florida, Georgia and Minnesota. Our offices in multiple states creates a strain on our ability to effectively manage our operations and key personnel. If we elect to consolidate our facilities we may loose key personnel unwilling to relocate to the consolidated facility, may have difficulty hiring appropriate personnel at the consolidated facility and may have difficulty providing continuity of service through the consolidation.

        Physician and patient satisfaction or performance problems with an acquired business, technology, service or device could also have a material adverse effect on our reputation. Additionally, potential disputes with the seller of an acquired business or its employees, suppliers or customers and amortization expenses related to goodwill and other intangible assets could adversely affect our business, operating results and financial condition.

        We may not be able to realize the anticipated benefits of the PDSHeart acquisition or any other acquisition we may pursue or to profitably deploy acquired assets. If we fail to properly evaluate and execute acquisitions, our business may be disrupted and our operating results and prospects may be harmed.

If we are unable to manage our expected growth, our revenues and operating results may be adversely affected.

        Our business plans call for rapid expansion of our sales and marketing operations and growth of our research and development, product development and administrative operations. We had a sales force of 27 account executives at December 31, 2006 and 77 account executives at June 30, 2007. We currently intend to expand our sales force to 88 individuals by December 31, 2007. We expect this expansion will place a significant strain on our management and operational and financial resources. Our current and planned personnel, systems, procedures and controls may not be adequate to support our anticipated growth. To manage our growth we will be required to improve existing and implement new operational and financial systems, procedures and controls and expand, train and manage our growing employee base. If we are unable to manage our growth effectively, revenue growth may not be

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realized or may not be sustainable, may not result in improved operating results or earnings, and our business, financial condition and results of operations could be harmed.

Our business is dependent upon having sufficient monitors and sensors. If we do not have enough monitors or sensors or experience delays in manufacturing, we may be unable to fill prescriptions in a timely manner, physicians may elect not to prescribe the CardioNet System, and our revenues and growth prospects could be harmed.

        When a physician prescribes the CardioNet System to a patient, our customer service department begins the patient hook-up process, which includes procuring a monitor and sensors from our distribution department and sending them to the patient. While our goal is to provide each patient with a monitor and sensors in a timely manner, we have experienced and may in the future experience delays due to the availability of monitors, primarily when converting to a new generation of monitor or, more recently, in connection with the increase in prescriptions following our acquisition of PDSHeart.

        We may also experience shortages of monitors or sensors due to manufacturing difficulties. Multiple suppliers provide the components used in the CardioNet System, but our facilities in San Diego, California are registered and approved by the United States Food and Drug Administration, or FDA, as the ultimate manufacturer of the CardioNet System. Our manufacturing operations could be disrupted by fire, earthquake or other natural disaster, a work stoppage or other labor-related disruption, failure in supply or other logistical channels, electrical outages or other reasons. If there was a disruption to our facilities in San Diego, we would be unable to manufacture the CardioNet System until we have restored and re-qualified our manufacturing capability or developed alternative manufacturing facilities.

        We are currently in the process of developing the next generation of the CardioNet System, called C3, which will feature several technology enhancements. We expect that we will begin filling prescriptions with the C3 monitors and sensors in the second half of 2007. In order to produce the quantities of the C3 that we believe will be required to meet anticipated market demand, we will need to increase our C3 manufacturing capacity significantly over the current level. There are technical challenges to increasing manufacturing capacity, including the investment of substantial funds and hiring and retaining management and technical personnel who have the necessary manufacturing experience. We may not successfully complete this process in a timely manner or at all. If we are unable to do so, we would not be able to produce sufficient quantities of our next generation C3 monitors and sensors to satisfy anticipated demand and to replace our inventory of existing monitors and sensors prior to their obsolescence.

        Our primary manufacturer of components for the CardioNet System has announced the closing of its facility near San Diego, California where it was manufacturing these components. Following the closing of this facility, all monitor and sensor production will take place at its facility in Tempe, Arizona. The transfer of production to the new production facility poses several risks to our supply of CardioNet System monitors, including potential issues related to the quality of our monitors and sensors, training of a new workforce and production shortages and delays.

        Our success in obtaining future prescriptions from physicians is dependent upon our ability to promptly deliver monitors and sensors to our patients, and a failure in this regard would have an adverse effect on our revenues and growth prospects.

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Interruptions or delays in telecommunications systems or in the data services provided to us by QUALCOMM or the loss of our wireless or data services could impair the delivery of our CardioNet System services.

        The success of the CardioNet System is dependent upon our ability to store, retrieve, process and manage data and to maintain and upgrade our data processing and communication capabilities. The monitors we use in connection with the CardioNet System rely on a third party wireless carrier to transmit data over its data network during times that the monitor is removed from its base. All data sent by our monitors via this wireless data network or via landline is routed directly to QUALCOMM data centers and subsequently routed to our monitoring center. We are dependent upon these third parties to provide data transmission and data hosting services to us. We do not have an agreement directly with this third party wireless carrier. Although we do have an agreement with QUALCOMM that has an initial termination date in September 2010, QUALCOMM may terminate their agreement with us if certain conditions occur, including if QUALCOMM's agreement with the third party wireless carrier terminates. If we fail to maintain our relationships with QUALCOMM or if we lose our wireless carrier services, we would be forced to seek alternative providers of data transmission and data hosting services, which might not be available on commercially reasonable terms or at all.

        As we expand our commercial activities, an increased burden will be placed upon our data processing systems and the equipment upon which they rely. Interruptions of our data networks or the data networks of QUALCOMM for any extended length of time, loss of stored data or other computer problems could have a material adverse effect on our business, financial condition and results of operations. Frequent or persistent interruptions in our arrhythmia monitoring services could cause permanent harm to our reputation and could cause current or potential users of the CardioNet System to believe that our systems are unreliable, leading them to switch to our competitors. Such interruptions could result in liability, claims and litigation against us for damages or injuries resulting from the disruption in service.

        Our systems are vulnerable to damage or interruption from earthquakes, floods, fires, power loss, telecommunication failures, terrorist attacks, computer viruses, break-ins, sabotage, and acts of vandalism. Despite any precautions that we may take, the occurrence of a natural disaster or other unanticipated problems could result in lengthy interruptions in these services. We do not carry business interruption insurance to protect against losses that may result from interruptions in service as a result of system failures. Moreover, the communications and information technology industries are subject to rapid and significant changes, and our ability to operate and compete is dependent in significant part on our ability to update and enhance the communication technologies used in our systems and services.

The market for arrhythmia monitoring solutions is highly competitive. If our competitors are better able to develop or market monitoring solutions that are more effective, or gain greater acceptance in the marketplace, than any solutions we develop, our commercial opportunities will be reduced or eliminated.

        The market for arrhythmia monitoring solutions is evolving rapidly and becoming increasingly competitive. Our industry is highly fragmented and characterized by a small number of large providers and a large number of smaller regional service providers. These third parties compete with us in recruiting and retaining qualified personnel, acquiring technology and developing solutions complementary to our programs. In addition, as companies with substantially greater resources than ours enter our market, we will face increased competition. If our competitors are better able to develop and patent arrhythmia monitoring solutions than us, or develop more effective and/or less expensive arrhythmia monitoring solutions that render our solutions obsolete or non-competitive or deploy larger or more effective marketing and sales resources than ours, our business will be harmed and our commercial opportunities will be reduced or eliminated.

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If we need to raise additional funding in the future, we may be unable to raise such capital when needed, or at all, and the terms of such capital may be adverse to our stockholders.

        We believe that the net proceeds from this offering, together with our existing cash and cash equivalent balances, will be sufficient to meet our anticipated cash requirements for the foreseeable future. However, our future funding requirements will depend on many factors, including:

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the costs associated with manufacturing and building our inventory of our next generation C3;



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the costs of hiring additional personnel and investing in infrastructure;



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the reimbursement rates associated with our products and services;



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actions taken by the FDA and other regulatory authorities affecting the CardioNet System and competitive products;



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our ability to secure contracts with additional commercial payors providing for the reimbursement of our services;



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the emergence of competing technologies and products and other adverse market developments;



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the costs of preparing, filing, prosecuting, maintaining and enforcing patent claims and other intellectual property rights or defending against claims of infringement by others; and



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the costs of investing in additional lines of business outside of arrhythmia monitoring solutions.

        If we need to, or choose to, raise additional capital in the future, such capital may not be available on reasonable terms, or at all. If we raise additional funds by issuing equity securities, substantial dilution to existing stockholders would likely result. If we raise additional funds by incurring additional debt financing, the terms of the debt may involve significant cash payment obligations as well as covenants and financial ratios that may restrict our ability to operate our business.

Our manufacturing facilities and the manufacturing facilities of our suppliers must comply with applicable regulatory requirements. If we or our suppliers fail to achieve or maintain regulatory approval of these manufacturing facilities, our growth could be limited and our business could be harmed.

        We currently manufacture the monitors and sensors for the CardioNet System in San Diego, California. Monitors used in the provision of services by PDSHeart are purchased from several third parties. Our manufacturing facilities must be evaluated and qualified under a quality system to ensure they meet production and quality standards. Suppliers of components of and products used to manufacture the CardioNet System and the manufacturers of the monitors used in the provision of services by PDSHeart must also comply with FDA and foreign regulatory requirements, which often require significant resources and subject us and our suppliers to potential regulatory inspections and stoppages. We or our suppliers may not satisfy these requirements. If we or our suppliers do not maintain regulatory approval for our manufacturing operations, our business would be harmed.

Our dependence on a limited number of suppliers may prevent us from delivering our devices on a timely basis.

        We currently rely on a limited number of suppliers of components for the CardioNet System. If these suppliers became unable to provide components in the volumes needed or at an acceptable price, we would have to identify and qualify acceptable replacements from alternative sources of supply. Qualifying suppliers is a lengthy process. Delays or interruptions in the supply of our requirements could limit or stop our ability to provide sufficient quantities of devices on a timely basis, meet demand for our services, which could have a material adverse effect on our business, financial condition and results of operations.

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We could be subject to medical liability or product liability claims which may not be covered by insurance and which would adversely affect our business and results of operations.

        The design, manufacture and marketing of services of the types we provide entail an inherent risk of product liability claims. Any such claims against us may require us to incur significant defense costs, irrespective of whether such claims are founded. In addition, we provide information to health care providers and payors upon which determinations affecting medical care are made, and claims may be made against us resulting from adverse medical consequences to patients resulting from the information we provide. In addition, we may become subject to liability in the event that the monitors and sensors we use fail to correctly record or transfer patient information or if we provide incorrect information to patients or health care providers using our services. We have also agreed to indemnify QUALCOMM for any claims resulting from the provision of our services. If we incur one or more significant claims against us, if we are required to indemnify QUALCOMM as a result of the provision of our services, or if we are required to undertake remedial actions in response to any such claims, such claims or actions would adversely affect our business and results of operations.

        Our liability insurance is subject to deductibles and coverage limitations. In addition, our current insurance may not continue to be available to us on acceptable terms, if at all, and, if available, the coverages may not be adequate to protect us against any future claims. If we are unable to obtain insurance at an acceptable cost or on acceptable terms with adequate coverage or otherwise protect against any claims against us, we will be exposed to significant liabilities, which may harm our business.

If we do not obtain and maintain adequate protection for our intellectual property, the value of our technology and devices may be adversely affected.

        Our business and competitive positions are dependent in part upon our ability to protect our proprietary technology. To protect our proprietary rights, we rely on a combination of trademark, copyright, patent, trade secret and other intellectual property laws, employment, confidentiality and invention assignment agreements with our employees and contractors, and confidentiality agreements and protective contractual provisions with our partners and other third parties. We attempt to protect our intellectual property position by filing trademark applications and U.S., foreign and international patent applications related to our proprietary technology, inventions and improvements that are important to the development of our business.

        As of June 30, 2007, we had 14 issued U.S. patents, seven foreign patents and 42 pending U.S., foreign and international patent applications relating to various aspects of the CardioNet System. As of June 30, 2007, we also had eight trademark registrations and four pending trademark applications in the United States for a variety of word marks and slogans. We do not believe that any single patent, trademark or other intellectual property right of ours, or combination of our intellectual property rights, is likely to prevent others from competing with us using a similar business model. There are many issued patents and patent applications held by others in our industry and the electronics field. Our competitors may independently develop technologies that are substantially similar or superior to our technologies, or design around our patents or other intellectual property to avoid infringement. In addition, we may not apply for a patent relating to products or processes that are patentable, we may fail to receive any patent for which we apply or have applied, and any patent owned by us or issued to us could be circumvented, challenged, invalidated, or held to be unenforceable, or rights granted thereunder may not adequately protect our technology or provide a competitive advantage to us. For example, with respect to one of our U.S. patents, we have a corresponding foreign patent, the claims of which were amended substantially more so than in the U.S., to overcome art that was of record in the U.S. patent. If a third-party challenges the validity of any patents or proprietary rights of ours, we may become involved in intellectual property disputes and litigation that would be costly and time-consuming.

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        Although third parties may infringe our patents and other intellectual property rights, we may not be aware of any such infringement, or we may be aware of potential infringement but elect not to seek to prevent such infringement or pursue any claim of infringement, and the third party may continue its potentially infringing activities. Any decision whether or not to take action in response to potential infringement of our patent or other intellectual property rights may be based on any one or more of a variety of factors, such as the potential costs and benefits of taking such action, and business and legal issues and circumstances. Litigation of claims of infringement of a patent or other intellectual property rights may be costly and time-consuming and divert the attention of key company personnel, and may not be successful or result in any significant recovery of compensation for any infringement or enjoining of any infringing activity. Litigation or licensing discussions may also involve or lead to counterclaims or proceedings that could be brought by a potential infringer to challenge the validity or enforceability of our patents and other intellectual property.

        To protect our trade secrets and other proprietary information, we generally require our employees, consultants, contractors and outside collaborators to enter into written nondisclosure agreements. These agreements, however, may not provide adequate protection to prevent any unauthorized use, misappropriation or disclosure of our trade secrets, know-how or other proprietary information. These agreements may be breached, and we may not become aware of, or have adequate remedies in the event of, any such breach. Also, others may independently develop the same or substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets.

Our ability to market our services may be impaired by the intellectual property rights of third parties.

        Our success is dependent in part upon our ability to avoid infringing the patents or proprietary rights of others. Our industry and the electronics field are characterized by a large number of patents, patent filings and frequent litigation based on allegations of patent infringement. Competitors may have filed applications for or have been issued patents and may obtain additional patents and proprietary rights related to devices, services or processes that we compete with or are similar to ours. We may not be aware of all of the patents or patent applications potentially adverse to our interests that may have been or may later be issued to or filed by others. U.S. patent applications may be kept confidential while pending in the Patent and Trademark Office. If other companies have or obtain patents relating to our products or services, we may be required to obtain licenses to those patents or to develop or obtain alternative technology. We may not be able to obtain any such licenses on acceptable terms, or at all. Any failure to obtain such licenses could impair or foreclose our ability to make, use, market or sell our products and services.

        Based on the litigious nature of our industry and the electronics field and the fact that we may pose a competitive threat to some companies who own or control various patents, it is always possible that one or more third parties may assert a patent infringement claim seeking damages and to enjoin the manufacture, use, sale and marketing of our products and services. If a third-party asserts that we have infringed its patent or proprietary rights, we may become involved in intellectual property disputes and litigation that would be costly and time-consuming and could impair or foreclose our ability to make, use, market or sell our products and services. For example, a competitor initiated a patent infringement lawsuit against us in November 2004, which we defended and ultimately settled in March 2006. Other lawsuits may have already been filed against us without our knowledge, or may be filed prior to the completion of this offering. Additionally, we have received and expect to continue to receive notices from third parties suggesting that we are infringing their patents and inviting us to license such patents. We do not believe, however, that we are infringing any such patent or that a license to any such patent is necessary. Should litigation over such patents arise, which could occur if, for example, a third party files a lawsuit alleging infringement of such patents or if we file a lawsuit challenging such patents as being invalid or unenforceable, we intend to vigorously defend against any

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allegation of infringement. If we are found to infringe the patent or intellectual property rights of others, we may be required to pay damages, stop the infringing activity or obtain licenses or rights to the patents or other intellectual property in order to use, manufacture, market or sell our products and services. Any required license may not be available to us on acceptable terms or at all. If we succeed in obtaining such licenses, payments under such licenses would reduce any earnings from our products. In addition, licenses may be non-exclusive and, accordingly, our competitors may have access to the same technology as that which may be licensed to us. If we fail to obtain a required license or are unable to alter the design of our product candidates to make a license unnecessary, we may be unable to manufacture, use, market or sell our products and services, which could significantly affect our ability to achieve, sustain or grow our commercial business. Moreover, regardless of the outcome, patent litigation against or by us could significantly disrupt our business, divert our management's attention and consume our financial resources. We cannot predict if or when any third party will file suit for patent or other intellectual property infringement.

We are highly dependent on our Chief Executive Officer and other key employees, and if we are not able to retain them or to recruit and retain additional qualified personnel, our business may suffer.

        We are highly dependent upon our Chief Executive Officer and other key employees. The loss of their services could have a material adverse effect on our business, financial condition and results of operations. In particular, our Chief Executive Officer, James M. Sweeney, is critical to the operations and function of the company. In addition, in the event we desire to appoint a replacement to Mr. Sweeney following his resignation or termination, such replacement must be approved by Silicon Valley Bank. The employment of our executive officers and key employees with us is "at will," and each employee can terminate his or her relationship with us at any time. We do not carry "key person" life insurance on any of our employees other than James M. Sweeney, our Chief Executive Officer.

        We will need to hire additional senior executives and qualified scientific, commercial, regulatory, sales, quality assurance and control and administrative personnel as we continue to expand our commercial activities. We may not be able to attract and retain qualified personnel on acceptable terms given the competition for such personnel among companies that provide arrhythmia monitoring solutions. We have offices in Pennsylvania, California, Florida, Georgia and Minnesota. Competition for personnel with arrhythmia monitoring experience in each of those areas is intense. If we fail to identify, attract, retain and motivate these highly skilled personnel, or if we lose current employees, we may be unable to continue our business operations.

If we fail to obtain and maintain necessary FDA clearances, our business would be harmed.

        The monitors and sensors that we manufacture and sell as part of the CardioNet System are classified as medical devices and are subject to extensive regulation by the FDA. Further, we maintain establishment registration with the FDA as a distributor of medical devices. FDA regulations govern manufacturing, labeling, promotion, distribution, importing, exporting, shipping and sale of these devices.

        The CardioNet System, including our C3 System, and our arrhythmia detection algorithms maintain FDA 510(k) clearance from the FDA. Modifications to the CardioNet System or our algorithms that could significantly affect safety or effectiveness, or that could constitute a significant change in intended use, would require a new clearance from the FDA. If in the future we make changes to the CardioNet System or our algorithms, the FDA could determine that such modifications require new FDA clearance, and we may not be able to obtain such FDA clearances in a timely fashion or at all.

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        We are subject to continuing regulation by the FDA, including quality regulations applicable to the manufacture of the CardioNet System and various reporting regulations and regulations that govern the promotion and advertising of medical devices. The FDA could find that we have failed to comply with one of these requirements, which could result in a wide variety of enforcement actions, ranging from a warning letter to one or more severe sanctions, including the following:

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fines, injunctions and civil penalties;



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recall or seizure of the CardioNet System;



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operating restrictions, partial suspension or total shutdown of production;



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refusal to grant 510(k) clearance of new components or algorithms;



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withdrawing 510(k) clearance already granted to one or more of our existing components or algorithms; and



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criminal prosecution.

        Any of these enforcement actions could be costly and significantly harm our business, financial condition and results of operations.

Enforcement of federal and state laws regarding privacy and security of patient information may adversely affect our business, financial condition or operations.

        The use and disclosure of certain health care information by health care providers and their business associates have come under increasing public scrutiny. Recent federal standards under the Health Insurance Portability and Accountability Act of 1996, or HIPAA, establish rules concerning how individually-identifiable health information may be used, disclosed and protected. Historically, state law has governed confidentiality issues, and HIPAA preserves these laws to the extent they are more protective of a patient's privacy or provide the patient with more access to his or her health information. As a result of the implementation of the HIPAA regulations, many states are considering revisions to their existing laws and regulations that may or may not be more stringent or burdensome than the federal HIPAA provisions. We must operate our business in a manner that complies with all applicable laws, both federal and state, and that does not jeopardize the ability of our customers to comply with all applicable laws. We believe that our operations are consistent with these legal standards. Nevertheless, these laws and regulations present risks for health care providers and their business associates that provide services to patients in multiple states. Because these laws and regulations are recent, and few have been interpreted by government regulators or courts, our interpretations of these laws and regulations may be incorrect. If a challenge to our activities is successful, it could have an adverse effect on our operations, may require us to forego relationships with customers in certain states and may restrict the territory available to us to expand our business. In addition, even if our interpretations of HIPAA and other federal and state laws and regulations are correct, we could be held liable for unauthorized uses or disclosures of patient information as a result of inadequate systems and controls to protect this information or as a result of the theft of information by unauthorized computer programmers who penetrate our network security. Enforcement of these laws against us could have a material adverse effect on our business, financial condition and results of operations.

We may be subject, directly or indirectly, to federal and state health care fraud and abuse laws and regulations and, if we are unable to fully comply with such laws, could face substantial penalties.

        Our operations may be directly or indirectly affected by various broad state and federal health care fraud and abuse laws, including the Federal Healthcare Programs' Anti-Kickback Statute, which prohibits any person from knowingly and willfully offering, paying, soliciting or receiving remuneration,

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directly or indirectly, to induce or reward either the referral of an individual for an item or service, or the ordering, furnishing or arranging for an item or service, for which payment may be made under federal health care programs, such as the Medicare and Medicaid programs. For some of our services, we directly bill physicians for our services, who in turn bill payors. Although we believe such payments to be proper and in compliance with laws and regulations, we may be subject to claims that we are in violation of these laws and regulations. If our past or present operations are found to be in violation of these laws, we or our officers may be subject to civil or criminal penalties, including large monetary penalties, damages, fines, imprisonment and exclusion from Medicare and Medicaid program participation. If enforcement action were to occur, our business and results of operations could be adversely affected.

The operation of our call centers and monitoring facilities is subject to rules and regulations governing Independent Diagnostic Testing Facilities; failure to comply with these rules could prevent us from receiving reimbursement from Medicare and some commercial payors.

        We have call centers and monitoring facilities in Pennsylvania, Georgia, Florida, and Minnesota that analyze the data obtained from arrhythmia monitors and report the results to physicians. In order for us to receive reimbursement from Medicare and some commercial payors, we must have a call center certified as an Independent Diagnostic Testing Facility, or IDTF. Certification as an IDTF requires that we follow strict regulations governing how the center operates, such as requirements regarding the experience and certifications of the technicians who review data transmitted from our monitors. These rules and regulations vary from location to location and are subject to change. If they change, we may have to change the operating procedures at our monitoring facilities and call centers, which could increase our costs significantly. If we fail to obtain and maintain IDTF certification, our services may no longer be reimbursed by Medicare and some commercial payors, which could have a material adverse impact on our business.

We may be subject to federal and state false claims laws which impose substantial penalties.

        Many of the physicians and patients who use our services file claims for reimbursement with government programs such as Medicare and Medicaid. As a result, we may be subject to the federal False Claims Act if we knowingly "cause" the filing of false claims. Violations may result in substantial civil penalties, including treble damages. The federal False Claims Act also contains "whistleblower" or "qui tam" provisions that allow private individuals to bring actions on behalf of the government alleging that the defendant has defrauded the government. In recent years, the number of suits brought in the medical industry by private individuals has increased dramatically. Various states have enacted laws modeled after the federal False Claims Act, including "qui tam" provisions, and some of these laws apply to claims filed with commercial insurers.

        We are unable to predict whether we could be subject to actions under the federal False Claims Act, or the impact of such actions. However, the costs of defending claims under the False Claims Act, as well as sanctions imposed under the False Claims Act, could significantly affect our financial performance.

Changes in the regulatory environment may constrain or require us to restructure our operations, which may harm our revenues and operating results.

        Health care laws and regulations change frequently and may change significantly in the future. We may not be able to adapt our operations to address every new regulation, and new regulations may adversely affect our business. We cannot assure you that a review of our business by courts or regulatory authorities would not result in a determination that adversely affects our revenues and operating results, or that the health care regulatory environment will not change in a way that restricts our operations. In addition, as a result of the focus on health care reform in connection with the 2008

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presidential election, there is risk that Congress may implement changes in laws and regulations governing health care service providers, including measures to control costs, or reductions in reimbursement levels, which may adversely affect our business and results of operations.

Changes in the health care industry or tort reform could reduce the number of arrhythmia monitoring solutions ordered by physicians, which could result in a decline in the demand for our solutions, pricing pressure and decreased revenues.

        Changes in the health care industry directed at controlling health care costs or perceived over-utilization of arrhythmia monitoring solutions could reduce the volume of solutions ordered by physicians. If more health care cost controls are broadly instituted throughout the health care industry, the volume of cardiac monitoring solutions could decrease, resulting in pricing pressure and declining demand for our services, which could harm our operating results. In addition, it has been suggested that some physicians order arrhythmia monitoring solutions even when the services may have limited clinical utility in large part to establish a record for defense in the event of a claim of medical malpractice against the physician. Legal changes making it more difficult to bring medical malpractice cases, known as tort reform, could reduce the amount of our services prescribed as physicians respond to reduced risks of litigation, which could harm our operating results.

Risks related to the securities market and investment in our common stock

There may not be a viable public market for our common stock.

        Prior to this offering, there has been no public market for our common stock. The initial public offering price for our common stock will be determined through negotiations between us and the representatives of the underwriters and may not be indicative of the market price of our common stock following this offering. If you purchase shares of our common stock, you may not be able to resell those shares at or above the initial public offering price. We cannot predict the extent to which investor interest in our company will lead to the development of an active trading market on the Nasdaq Global Market or any other stock market or how liquid any such market might become. An active public market for our common stock may not develop or be sustained after the offering. If an active public market does not develop or is not sustained, it may be difficult for you to sell your shares of common stock at a price that is attractive to you, or at all.

Our quarterly operating results and stock price may be volatile or may decline regardless of our operating performance, and you may not be able to resell your shares at or above the initial public offering price.

        Following this offering, the market price for our common stock is likely to be volatile, in part because our shares have not been traded publicly. In addition, the market price of our common stock may fluctuate significantly in response to a number of factors, most of which we cannot control, including:

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changes in reimbursement rates or policies by payors;



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adoption of the CardioNet System by physicians;



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changes in Medicare rules or regulations;



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the development of increased compensation for arrhythmia monitoring solutions;



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price and volume fluctuations in the overall stock market;



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changes in operating performance and stock market valuations of other early stage companies generally;

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•

the seasonal nature of our revenues, which have typically been moderately lower during summer months, which we believe may be due to physician and patient vacation schedules and patient reluctance to initiate cardiac monitoring during months when patients are more likely to be more active;



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the financial projections we may provide to the public, any changes in these projections or our failure to meet these projections;



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changes in financial estimates by any securities analysts who follow our common stock, our failure to meet these estimates or failure of those analysts to initiate or maintain coverage of our common stock;



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ratings downgrades by any securities analysts who follow our common stock;



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the public's response to press releases or other public announcements by us or third parties, including our filings with the SEC and announcements relating to payor reimbursement decisions, product development, litigation and intellectual property impacting us or our business;



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market conditions or trends in our industry or the economy as a whole;



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the development and sustainability of an active trading market for our common stock;



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future sales of our common stock by our officers, directors and significant stockholders;



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other events or factors, including those resulting from war, incidents of terrorism, natural disasters or responses to these events; and



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changes in accounting principles.

        In addition, the stock markets, and in particular the Nasdaq Global Market, have experienced extreme price and volume fluctuations that have affected and continue to affect the market prices of equity securities of many health care companies. Stock prices of many health care companies have fluctuated in a manner unrelated or disproportionate to the operating performance of those companies. In the past, stockholders have instituted securities class action litigation following periods of market volatility. If we were involved in securities litigation, we could incur substantial costs, and our resources and the attention of management could be diverted from our business.

Future sales of our common stock or securities convertible into our common stock may depress our stock price.

        Sales of a substantial number of shares of our common stock or securities convertible into our common stock in the public market could occur at any time. These sales, or the perception in the market that the holders of a large number of shares intend to sell shares, could reduce the market price of our common stock. After this offering, we will have             outstanding shares of common stock based on the number of shares outstanding as of June 30, 2007, assuming an initial public offering price of $    per share, the mid-point of the price range set forth on the cover page of this prospectus. This includes the shares that we are selling in this offering, which may be resold in the public market immediately unless held by an affiliate of ours. Of the remaining shares,            shares may be sold upon the expiration of lock-up agreements at least 180 days after the date of this offering and the remaining shares may be sold from time to time after the expiration of such lock-up agreements and applicable holding periods specified in Rule 144 under the Securities Act of 1933, as amended, or the Securities Act, as more fully described in the "Shares Eligible for Future Sale" section of this prospectus. In addition, following the offering, we will have outstanding warrants to purchase up to 12,500 shares of our common stock that, if exercised, would result in these additional shares becoming available for sale upon expiration of the lock-up agreements.

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        In July 2007, the SEC announced proposed revisions to Rule 144. If the proposed changes to Rule 144 are approved, the holding period for restricted shares of our common stock after the completion of this offering may be reduced to six months under specified circumstances, the restrictions on the sale of restricted shares of our common stock held by our affiliates may be reduced and certain other restrictions on resale of the shares of our common stock under Rule 144 may be modified to make it easier for our stockholders under specified circumstances to sell their shares upon the expiration of the lock-up agreements beginning 180 days after the date of this prospectus. We do not know whether these proposed revisions to Rule 144 will be adopted as proposed or in a modified form, or at all.

        After this offering, based on the number of shares outstanding as of June 30, 2007, assuming an initial public offering price of $    per share, the mid-point of the price range set forth on the cover page of this prospectus, holders of up to approximately            shares of common stock (including shares of our common stock issuable upon the exercise of warrants) will have rights, subject to some conditions, to require us to file registration statements covering their shares or to include their shares in registration statements that we may file for ourselves or other stockholders. These rights will terminate    years following the completion of this offering, or for any particular holder with registration rights who holds less than one percent of our outstanding capital stock, at any time following this offering when all securities held by that stockholder that are subject to registration rights may be sold pursuant to Rule 144 under the Securities Act within a single 90 day period. We also intend to register all shares of common stock that we may issue after this offering under our equity compensation plans. Once we register these shares, they can be freely sold in the public market upon issuance, subject to the lock-up agreements described above.

        We agreed to register the            shares of our common stock that will be issued at the closing of this offering upon conversion of our mandatorily redeemable convertible preferred stock within 90 days of the completion of this offering, and use commercially reasonable best efforts to cause the registration statement to become effective within 180 days after the completion of this offering. Once registered, these shares will be freely tradable. If we fail to register these shares when and as required, we will be required to pay liquidated damages at a rate of 0.5% of the original purchase price of the mandatorily redeemable convertible preferred stock, plus accrued and unpaid dividends, for the initial failure and 1.0% of the original purchase price of the mandatorily redeemable convertible preferred stock, plus accrued and unpaid dividends, for each 30-day period thereafter that the failure goes uncured.

        If a large number of our shares of our common stock or securities convertible into our common stock are sold in the public market after they become eligible for sale, the sales could reduce the trading price of our common stock and impede our ability to raise future capital.

Anti-takeover provisions in our charter documents and Delaware law might deter acquisition bids for us that you might consider favorable.

        Upon completion of this offering, our amended and restated certificate of incorporation and bylaws will contain provisions that may make the acquisition of our company more difficult without the approval of our board of directors. These provisions will:

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establish a classified board of directors so that not all members of our board are elected at one time;



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authorize the issuance of undesignated preferred stock, the terms of which may be established and shares of which may be issued without stockholder approval, and which may include rights superior to the rights of the holders of common stock;

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•

prohibit stockholder action by written consent, which requires all stockholder actions to be taken at a meeting of our stockholders;



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provide that the board of directors is expressly authorized to make, alter, or repeal our bylaws; and



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establish advance notice requirements for nominations for elections to our board or for proposing matters that can be acted upon by stockholders at stockholder meetings.

        In addition, upon our reincorporation, we are governed by the provisions of Section 203 of the Delaware General Corporation Law which, subject to certain exceptions, prohibits stockholders owning in excess of 15% of our outstanding voting stock from merging or combining with us. These anti-takeover provisions and other provisions under Delaware law could discourage, delay or prevent a transaction involving a change of control of our company, even if doing so would benefit our stockholders. These provisions could also discourage proxy contests and make it more difficult for you and other stockholders to elect directors of your choosing and cause us to take other corporate actions you desire.

If you purchase shares of common stock sold in this offering, you will incur immediate and substantial dilution.

        If you purchase shares of common stock in this offering, you will incur immediate and substantial dilution in the amount of $            per share, assuming an initial public offering price of $            per share, the mid-point of the price range set forth on the cover page of this prospectus, to the extent that the initial public offering price is substantially higher than the pro forma net book value per share of our outstanding common stock would be after this offering. This dilution is due in large part to the fact that, when they purchased their shares, our earlier investors paid substantially less than the initial public offering price. In addition, you may also experience additional dilution upon future equity issuances or the exercise of stock options to purchase common stock granted to our employees, consultants and directors under our stock option and equity incentive plans. See the "Dilution" section of this prospectus.

Our existing principal stockholders, executive officers and directors will continue to have substantial control over us after this offering, which may prevent you and other stockholders from influencing significant corporate decisions and may harm the market price of our common stock.

        Upon completion of this offering, assuming no exercise of the underwriters' over-allotment option and including stock options that are exercisable within 60 days of June 30, 2007, our existing principal stockholders, executive officers and directors, together with their affiliates, will beneficially own, in the aggregate, approximately            % of our outstanding common stock. These stockholders may have interests that conflict with yours and, if acting together, have the ability to determine the outcome of matters submitted to our stockholders for approval, including the election and removal of directors and any merger, consolidation or sale of all or substantially all of our assets. In addition, these stockholders, acting together, may have the ability to control our management and affairs. Accordingly, this concentration of ownership may harm the market price of our common stock by:

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delaying, deferring or preventing a change of control;



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impeding a merger, consolidation, takeover or other business combination involving us; or



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discouraging a potential acquirer from making a tender offer or otherwise attempting to obtain control of us.

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If securities or industry analysts do not publish research or publish inaccurate or unfavorable research about our business, our stock price and trading volume could decline.

        The trading market for our common stock will depend in part on the research and reports that securities or industry analysts publish about us or our business. We do not currently have and may never obtain research coverage by securities and industry analysts. If no securities or industry analysts commence coverage of our company, the trading price for our stock would be negatively impacted. If we obtain securities or industry analyst coverage and if one or more of the analysts who covers us downgrades our stock or publishes inaccurate or unfavorable research about our business, our stock price would likely decline. If one or more of these analysts ceases coverage of us or fails to publish reports on us regularly, demand for our stock could decrease, which could cause our stock price and trading volume to decline.

Because management has broad discretion as to the use of the net proceeds from this offering, you may not agree with how we use them, and such proceeds may not be applied successfully.

        Our management will have considerable discretion over the use of proceeds from this offering. We intend to use the net proceeds from this offering:

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to pay off a term loan and a success fee to Silicon Valley Bank;



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to make payments to former stockholders of PDSHeart;



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to build our inventory of future generations of the CardioNet System, increase our sales and marketing capabilities for our CardioNet System, hire additional personnel, invest in infrastructure and pursue new markets and geographies;



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to acquire or license products, technologies or businesses; and



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for working capital and general corporate purposes.

We have no present understandings, commitments or agreements with respect to the acquisition or license of any products, technologies or businesses.

        A significant portion of the net proceeds from this offering have not been allocated for any specific transaction. As a result, our management will have broad discretion in the application of certain of the net proceeds from this offering and could spend such proceeds in ways that do not necessarily improve our operating results or enhance the value of our common stock. You will be relying on the judgment of our management concerning these uses, and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately. The failure of our management to apply these funds effectively could result in unfavorable returns and uncertainty about our prospects, each of which could cause the price of our common stock to decline.

We do not expect to pay any cash dividends for the foreseeable future.

        The continued expansion of our business may require substantial funding. In addition, the terms of our loan and security agreements with Silicon Valley Bank prohibit us from paying cash dividends under certain circumstances. Accordingly, we do not anticipate that we will pay any cash dividends on shares of our common stock for the foreseeable future. Even if we are not prohibited from paying dividends, any determination to do so in the future will be at the discretion of our board of directors and will depend upon our results of operations, financial condition, contractual restrictions, restrictions imposed by applicable law and other factors our board of directors deems relevant. Accordingly, if you purchase shares in this offering, realization of a gain on your investment will depend on the appreciation of the price of our common stock, which may never occur. Investors seeking cash dividends in the foreseeable future should not purchase our common stock.

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