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Background: Atrial fibrillation (AF), the most common sustained arrhythmia in hypertrophic cardiomyopathy (HCM), is capable of producing symptoms that impact quality of life and is associated with risk for embolic stroke. However, the influence of AF on clinical course and outcome in HCM remains incompletely resolved. Methods: Records of 1558 consecutive patients followed at the Tufts Medical Center Hypertrophic Cardiomyopathy Institute for 4.8±3.4 years (from 2004 to 2014) were accessed. Results: Of the 1558 patients with HCM, 304 (20%) had episodes of AF, of which 226 (74%) were confined to symptomatic paroxysmal AF (average, 5±5; range, 1 to >20), whereas 78 (26%) developed permanent AF, preceded by 7±6 paroxysmal AF episodes. At last evaluation, 277 patients (91%) are alive at 62±13 years of age, including 89% in New York Heart Association class I or II. No difference was found in outcome measures for patients with AF and age- and sex-matched patients with HCM without AF. Four percent of patients with AF died of HCM-related causes (n=11), with annual mortality 0.7%; mortality directly attributable to AF (thromboembolism without prophylactic anticoagulation) was 0.1% per year (n=2 patients). Patients were treated with antiarrhythmic drugs (most commonly amiodarone [n=103] or sotalol [n=78]) and AF catheter ablation (n=49) or the Maze procedure at surgical myectomy (n=72). Freedom from AF recurrence at 1 year was 44% for ablation patients and 75% with the Maze procedure ( P P Conclusions: Transient symptomatic episodes of AF, often responsible for impaired quality of life, are unpredictable in frequency and timing, but amenable to effective contemporary treatments, and infrequently progress to permanent AF. AF is not a major contributor to heart failure morbidity or a cause of arrhythmic sudden death; when treated, it is associated with low disease-related mortality, no different than for patients without AF. AF is an uncommon primary cause of death in HCM virtually limited to embolic stroke, supporting a low threshold for initiating anticoagulation therapy.

Background—The risks of sports participation for implantable cardioverter-defibrillator (ICD) patients are unknown. Methods and Results—Athletes with ICDs (age, 10–60 years) participating in organized (n=328) or high-risk (n=44) sports were recruited. Sports-related and clinical data were obtained by phone interview and medical records. Follow-up occurred every 6 months. ICD shock data and clinical outcomes were adjudicated by 2 electrophysiologists. Median age was 33 years (89 subjects

The American Heart Association (AHA) commends the recently released Institute of Medicine (IOM) report, Strategies to Improve Cardiac Arrest Survival: A Time to Act (2015). The AHA recognizes the unique opportunity created by the report to meaningfully advance the objectives of improving outcomes for sudden cardiac arrest. For decades, the AHA has focused on the goal of reducing morbidity and mortality from cardiovascular disease though robust support of basic, translational, clinical, and population research. The AHA also has developed a rigorous process using the best available evidence to develop scientific, advisory, and guideline documents. These core activities of development and dissemination of scientific evidence have served as the foundation for a broad range of advocacy initiatives and programs that serve as a foundation for advancing the AHA and IOM goal of improving cardiac arrest outcomes. In response to the call to action in the IOM report, the AHA is announcing 4 new commitments to increase cardiac arrest survival: (1) The AHA will provide up to $5 million in funding over 5 years to incentivize resuscitation data interoperability; (2) the AHA will actively pursue philanthropic support for local and regional implementation opportunities to increase cardiac arrest survival by improving out-of-hospital and in-hospital systems of care; (3) the AHA will actively pursue philanthropic support to launch an AHA resuscitation research network; and (4) the AHA will cosponsor a National Cardiac Arrest Summit to facilitate the creation of a national cardiac arrest collaborative that will unify the field and identify common goals to improve survival. In addition to the AHA’s historic and ongoing commitment to improving cardiac arrest care and outcomes, these new initiatives are responsive to each of the IOM recommendations and demonstrate the AHA’s leadership in the field. However, successful implementation of the IOM recommendations will require a timely response by all stakeholders identified in the report and a coordinated approach to achieve our common goal of improved cardiac arrest outcomes.

We appreciated the interest of Barison and colleagues in our International Consensus Statement on the treatment of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D).1 Our document provided a comprehensive overview and recommendations for risk stratification and therapy of patients fulfilling the diagnostic criteria for ARVC/D. These criteria had been addressed by a previous International Task Force consensus document dedicated to diagnosis of ARVC/D.2 According to the revised criteria proposed by the International Task Force in 2010, the diagnosis of ARVC/D is based on the presence of major and minor criteria encompassing electrocardiographic, arrhythmic, morphological, histopathologic, and genetic factors. Diagnosis of definite ARVC/D is fulfilled in the presence of 2 major criteria or 1 major plus 2 minor or 4 minor criteria from different groups; the ARVC/D diagnosis is possible or borderline in the presence of insufficient criteria. In their Letter to the Editor, Barison and colleagues emphasized the valuable role of cardiac magnetic resonance (CMR) for diagnosis of ARVC/D, which relies on its ability to combine evaluation of ventricular size, function, and regional wall motion with characterization by late-gadolinium enhancement (LGE) of fibro-fatty myocardial scar, which is the hallmark lesion of ARVC/D. We totally agree that CMR is becoming the gold standard tool for detection of structural and functional ventricular abnormalities in ARVC/D. In the 2010 International Task Force consensus document, CMR was appropriately included among the diagnostic imaging techniques, and specific CMR reference values for normal (and abnormal) ventricular size, systolic function, and regional dyssynergy were provided. Tissue characterization by LGE was not included among these diagnostic criteria because of the potential risk of misdiagnosis of ARVC/D related to the difficulty of assessing LGE at the level of the thin right ventricular wall and possible confusion with normal epicardial fat tissue. More recently, the frequent involvement by the disease of the left ventricular wall in the form of epicardial-mediomural LGE has been recognized. As pointed out by the authors, LV LGE may enhance sensitivity for early/minor or predominant left variants of the ARVC/D; however, its diagnostic accuracy remains to be established. The prognostic role of CMR and, in particular, of postcontrast sequences for tissue characterization in patients with a diagnosis of definitive ARVC/D remains elusive. In our consensus statement on the treatment of ARVC/D, we performed a systematic review of outcome studies on ARVC/D available in the literature to identify predictor variables that were associated with an increased risk of major arrhythmic events (ie, sudden cardiac death, appropriate defibrillator interventions, or defibrillator therapy on fast ventricular tachycardia/ventricular fibrillation), nonsudden cardiac death, or heart transplantation in at least 1 published multivariable analysis. Although the predicting value of CMR for worse arrhythmic outcome was shown in the general population of patients showing premature ventricular beats with a left bundle branch morphology4 and in patients with suspected diagnosis of ARVC/D,5 no specific features of CMR, either alone or in combination, have been reported yet as independent predictors of life-threatening arrhythmic events in patients with a definite diagnosis of ARVC/D. This lack of evidence underscores the importance of undertaking future studies on this field.

Recent observations indicate that some hospital telemetry systems used for monitoring of patient heart rhythm have clinically significant latency, or delay between the real-time status of the patient and the ECG information displayed on the patient monitor. If these systems are used for clinical care that requires instantaneous monitoring, then patient safety may be compromised. The purpose of this advisory is to inform healthcare providers about this potential problem, clarify the intended use of the systems, detail measures to reduce risk, and recommend steps to manufacturers and stakeholders to minimize this problem in current and future telemetry systems. Wireless telemetry electrocardiographic monitoring is a cornerstone of hospital management for patients with cardiovascular conditions or at risk for cardiovascular conditions. Since the first transmission of an ECG by telephone wire by Willem Einthoven was reported in 1906,1,2 advances in signal processing and communications have led to rapid innovation in wireless communication for telemetry systems in acute care settings.3 The first wireless systems introduced in the 1970s were fairly simple in design. They transmitted analog telemetry signals using 1 dedicated frequency channel for each patient.4 In the 1980s, networked telemetry systems led to the creation of centralized telemetry viewing stations in intensive and acute care units. Starting in the 1990s, digital telemetry systems allowed for computerized signal recording, storage, and retrieval.5,6 As computing power increased, the networking capability of these systems increased, allowing for monitoring of electrocardiographic, hemodynamic, and other clinical data from multiple patients on a single networked system. By 2000, wireless communication in the hospital extended beyond telemetry systems, and the US Federal Communications Commission established a protected range of frequencies for wireless medical devices to minimize electromagnetic interference from other in-band radiofrequency sources.7,8 Today, networked wireless telemetry systems …

The ability to resuscitate cardiac arrest victims is a critical component of health-related topics in the athlete population. Even with screening, there will remain people who experience sudden cardiac arrest. An effective resuscitation strategy requires multiple elements, including planning for an event, appropriate team members who can provide cardiopulmonary resuscitation (CPR), rapid availability of automated external defibrillators (AEDs) and other appropriate equipment, and calls for emergency medical services (EMS). The chain of survival as articulated by the American Heart Association (AHA) calls for immediate recognition of cardiac arrest and activation of EMS, early CPR, rapid defibrillation, effective advanced life support, and integrated post–cardiac arrest care.1,2 Inadequacy in any one of these facets will reduce the chances of survival. AEDs are portable devices capable of detecting and terminating ventricular tachycardia and fibrillation. All require human input to place the pads and turn on the device. Some are fully automated in that they will analyze the rhythm and provide a shock if the arrhythmia is deemed shockable. However, most are semiautomated in that they require continued human input, including activation to analyze the rhythm, and then if the arrhythmia is deemed shockable, further activation to shock. Ease of use has been demonstrated for both automated and semiautomated AEDs. AEDs are manufactured by many companies, with subtle differences in sensing algorithms and shock energy. The sensitivity and specificity of AEDs are excellent and likely better than human analysis of arrhythmias.3 In arrhythmia libraries, the sensitivity of most devices approaches 100%, as does the specificity.3 Whether one manufacturer’s algorithms are more accurate than others is not clear. Some devices will correct for CPR artifact, analyze the quality of the CPR, or both. Nearly all current AEDs incorporate biphasic waveforms; however, the specifics of the waveform and the energy vary …

Sudden cardiac death in a young athlete is a tragic and high-profile event. The best way to prevent such deaths is, however, highly debated. The Italian experience informed the European recommendation for the inclusion of a 12-lead ECG in screening tests for all athletes.1,2 Although American authors have acknowledged the possible benefits of such an approach, many have expressed concern over the portability of such a model to the US healthcare system. Concern has focused in particular on the idea of mandatory testing, cost effectiveness, the availability of practitioners qualified to interpret ECGs, and the burden of false-positive results. With professional sports organizations such as the International Olympic Committee, the National Basketball Association, the National Football League, and the Union of European Football Associations endorsing or implementing screening programs for their athletes, with a recent analysis suggesting a degree of cost effectiveness in line with other accepted medical interventions,3 and with the American Heart Association offering a cautious endorsement to the idea of local programs,4 volunteer-led testing programs across the US have begun to emerge. Thus, although no detailed guidance for the interpretation of the athlete's ECG exists, many physicians will be called on to interpret an athlete's ECG. Editorial see p 669 A principal obstacle to such interpretation is the difficulty in distinguishing abnormal patterns from physiological effects of training. Many clinical and ECG findings that may be a cause of concern in the general population are normal for athletes. In addition, the test characteristics of the ECG for different findings vary according to age, sex, ethnicity, sport, and level of training. In particular, different challenges exist for younger athletes because of the evolution of the ECG with age. This is further complicated by historical …

Case presentation : A 61-year-old moderately obese (body mass index 28.1 kg/m2) hypertensive diabetic man without any prior cardiac history collapsed suddenly at a town meeting. Bystander cardiopulmonary resuscitation was initiated, an automated external defibrillator available at the town hall was deployed, and a single shock was delivered. He regained a pulse and spontaneous respirations. He was transported to the local hospital, where he was stabilized, but remained comatose. The patient was immediately transferred to a tertiary hospital, where a therapeutic hypothermia protocol was initiated. No ECG or laboratory evidence of a transmural myocardial infarction (MI) was present. He regained consciousness 2 days after resuscitation. Coronary angiography demonstrated significant obstruction of 3 major coronary arteries, with mild global impairment of left ventricular function with an ejection fraction of 45%. Coronary bypass surgery was performed, and after implantable cardioverter-defibrillator (ICD) placement, he was discharged on a statin, a β-blocker, aspirin, and an angiotensin-converting enzyme inhibitor. The patient has no residual neurological or cognitive deficits. He has done well clinically in a cardiac rehabilitation program stressing exercise, diet, and lifestyle changes to achieve an ideal body weight. Sudden cardiac death (SCD) from cardiac arrest is the most common cause of death worldwide, accounting for >50% of all deaths from cardiovascular disease.1–4 SCD results in ≈250 000 to 300 000 deaths annually in the United States,1–4 and is characterized by unexpected cardiovascular collapse due to an underlying cardiovascular cause.1,2 SCD represents a major challenge for the clinician because most episodes occur in individuals without previously known cardiac disease.1–4 Because most individuals experiencing SCD currently are not identifiable as being at high risk, community-based public access to defibrillation programs is essential to save lives and improve neurological and functional outcomes for …

2011;57;1330-1337; originally published online Feb 14, 2011; J. Am. Coll. Cardiol. Richard L. Page, David J. Slotwiner, William G. Stevenson, and Cynthia M. Tracy Michael D. Ezekowitz, Warren M. Jackman, Craig T. January, James E. Lowe, L. Samuel Wann, Anne B. Curtis, Kenneth A. Ellenbogen, N.A. Mark Estes, III, on Practice Guidelines of Cardiology Foundation Foundation/American Heart Association Task Force Atrial Fibrillation (Update on Dabigatran): A Report of the American College 2011 ACCF/AHA/HRS Focused Update on the Management of Patients With This information is current as of March 11, 2012 http://content.onlinejacc.org/cgi/content/full/57/11/1330 located on the World Wide Web at: The online version of this article, along with updated information and services, is

Despite improvements in cardiovascular implantable electronic device (CIED) design, application of timely infection control practices, and administration of antibiotic prophylaxis at the time of device placement, CIED infections continue to occur and can be life-threatening. This has prompted the study of all aspects of CIED infections. Recognizing the recent advances in our understanding of the epidemiology, risk factors, microbiology, management, and prevention of CIED infections, the American Heart Association commissioned this scientific statement to educate clinicians about CIED infections, provide explicit recommendations for the care of patients with suspected or established CIED infections, and highlight areas of needed research.

Consistent with the national focus on healthcare quality, the American College of Cardiology (ACC) and the American Heart Association (AHA) have developed a multifaceted strategy to facilitate the process of improving clinical care. The first aspect of this effort is the creation of clinical practice guidelines that carefully synthesize available evidence to guide better patient care. Such guidelines are written to suggest diagnostic or therapeutic interventions that apply to patients in most circumstances, but clinical judgment is required to adapt these guidelines to the care of individual patients. The guidelines are based on available evidence, providing varying degrees of recommendation (Table 1). Occasionally, the evidence supporting a particular aspect or process of care is so strong that failure to perform such actions reduces the likelihood of optimum patient outcomes. Table 1. Applying classification of …

Preamble e472 1. Introduction e473 2. General Principles e475 3. Sinus Tachyarrhythmias e480 4. Nonsinus Focal Atrial Tachycardia and MAT e481 5. Atrioventricular Nodal Reentrant Tachycardia e482 6. Manifest and Concealed Accessory Pathways e483 7. Atrial Flutter e485 8. Junctional Tachycardia e487 9. Special Populations e487

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is an inheritable heart muscle disease that predominantly affects the right ventricle (RV) and predisposes to ventricular arrhythmias and sudden cardiac death (SCD).1–17 In the last three decades, there have been a significant number of studies defining the pathogenesis, genetic aspects, and clinical manifestations of the disease (See ‘Etiology, pathogenesis, diagnosis and natural history’ in the online-only Data Supplement). In 1994 and 2010, an International Task Force (ITF) document proposed guidelines for the standardized diagnosis of ARVC/D based on electrocardiographic (ECG), arrhythmic, morphological, histopathologic, and clinico-genetic factors.18,19 The growing knowledge regarding arrhythmic outcome, risk factors, and life-saving therapeutic interventions, make it particularly timely to critically address and place into perspective the issues relevant to the clinical management of ARVC/D patients. The present ITF consensus statement is a comprehensive overview of currently used risk stratification algorithms and approaches to therapy, either pharmacological or nonpharmacological, which often poses a clinical challenge to cardiovascular specialists and other practitioners, particularly those infrequently engaged in the management of ARVC/D. This document should be regarded as a guide to clinical practice where rigorous evidence is still lacking, because of the relatively low disease prevalence and the absence of controlled studies. Recommendations are based on available data derived from nonrandomized and observational studies and consensus within the conference panellists. When development of prognostic-therapeutic algorithms was controversial, management decisions were recommended to be individualized. Recommendation and level of evidence of specific management options were classified according to predefined scales, as outlined in Tables 1 and 2 (http://www.escardio.org/guidelines-surveys/esc-guidelines/about/Pages/rules-writing.aspx). Because randomized studies are not available, most consensus recommendations on treatment of ARVC/D are based on data derived from follow-up registries and/or experts opinions (ie, level of evidence B or C). View this table: Table 1. Classes of Recommendations View this table: Table 2. Levels of Evidence All members of …

Over the last decade, the Controversies in Cardiovascular Medicine section has established a position as a popular and frequently downloaded section of Circulation . Controversy is inherent to medicine and other disciplines when a course of action must be taken on the basis of insufficient evidence. Like debates at scientific meetings, published controversies generate considerable interest because of the purposefully polarized positions taken by experts on topics in which clinical uncertainty or equipoise exists. In fact, …

A group of relatively uncommon but important genetic cardiovascular diseases (GCVDs) are associated with increased risk for sudden cardiac death during exercise, including hypertrophic cardiomyopathy, long-QT syndrome, Marfan syndrome, and arrhythmogenic right ventricular cardiomyopathy. These conditions, characterized by diverse phenotypic expression and genetic substrates, account for a substantial proportion of unexpected and usually arrhythmia-based fatal events during adolescence and young adulthood. Guidelines are in place governing eligibility and disqualification criteria for competitive athletes with these GCVDs (eg, Bethesda Conference No. 26 and its update as Bethesda Conference No. 36 in 2005). However, similar systematic recommendations for the much larger population of patients with GCVD who are not trained athletes, but nevertheless wish to participate in any of a variety of recreational physical activities and sports, have not been available. The practicing clinician is frequently confronted with the dilemma of designing noncompetitive exercise programs for athletes with GCVD after disqualification from competition, as well as for those patients with such conditions who do not aspire to organized sports. Indeed, many asymptomatic (or mildly symptomatic) patients with GCVD desire a physically active lifestyle with participation in recreational and leisure-time activities to take advantage of the many documented benefits of exercise. However, to date, no reference document has been available for ascertaining which types of physical activity could be regarded as either prudent or inadvisable in these subgroups of patients. Therefore, given this clear and present need, this American Heart Association consensus document was constituted, based largely on the experience and insights of the expert panel, to offer recommendations governing recreational exercise for patients with known GCVDs.

Sudden cardiac death (SCD) resulting from cardiac arrest remains the leading cause of cardiovascular mortality worldwide and accounts for ≈250 000 deaths annually in the United States.1–4 The majority of cardiac arrests occur in patients with a prior myocardial infarction (MI) at a rate ≈5 times that of the general population.3 Studies evaluating the time dependence of mortality immediately after an MI have consistently demonstrated that the greatest risk for SCD is in patients with impaired left ventricular (LV) ejection fraction (LVEF).1–4 Despite revascularization and widespread use of β-blockers, angiotensin-converting enzyme inhibitors, statins, and antiplatelet agents, the risk of SCD remains highest in the first 30 days in these patients.1–4 On the basis of these observations, strategies for the prevention of SCD need to be implemented early after an MI in high-risk patients. Article see p 743 Although depressed LVEF identifies patients with increased mortality risk immediately after MI and is widely used as a risk stratification tool, it does not allow a distinction between those who will die of an arrhythmia and those who will die of other cardiovascular causes.4–8 Variable and unpredictable recovery of LV function after MI has consistently been noted immediately after an MI.5–7 Improvement in LVEF commonly begins within 3 days in patients who are revascularized with myocardial stunning and improved function of viable myocardium as the mechanisms.5–7 In the contemporary era of primary percutaneous coronary intervention for MI, of all revascularized patients with LVEF ≤40% at day 3, 24% will improve to have an LVEF ≥40% at 6 months.5–7 Other noninvasive and invasive risk stratification techniques used alone or in combination with the LVEF also …

Risk stratification methodsshould provide information about the likelihood of SCD andnon-SCD to identify potentially effective interventions, suchas implantable cardioverter-defibrillator (ICD) therapy thatprevents SCD and reduces mortality. LVEF has been estab-lished as a useful marker of increased mortality after MI, butit does not identify patients at increased risk of arrhythmicdeath relative to total mortality. Among the risk stratificationtechniques evaluated alone or in conjunction with LVEF toidentify patients at high risk for arrhythmic mortality arespontaneous or induced ventricular arrhythmias, the signal-averaged electrocardiography, QT interval dispersion, micro-volt T-wave alternans, increased QRS duration, baroreceptorsensitivity, and heart rate variability and turbulence.

Background —Sudden death due to relatively innocent chest-wall impact has been described in young individuals (commotio cordis). In our previously reported swine model of commotio cordis, ventricular fibrillation (with T-wave strikes) and ST-segment elevation (with QRS strikes) were produced by 30-mph baseball impacts to the precordium. Because activation of the K + ATP channel has been implicated in the pathogenesis of ST elevation and ventricular fibrillation in myocardial ischemia, we hypothesized that this channel could be responsible for the electrophysiologic findings in our experimental model and in victims of commotio cordis. Methods and Results —In the initial experiment, 6 juvenile swine were given 0.5 mg/kg IV glibenclamide, a selective inhibitor of the K + ATP channel, and chest impact was given on the QRS. The results of these strikes were compared with animals in which no glibenclamide was given. In the second phase, 20 swine were randomized to receive glibenclamide or a control vehicle (in a double-blind fashion), with chest impact delivered just before the T-wave peak. With QRS impacts, the maximal ST elevation was significantly less in those animals given glibenclamide (0.16±0.10 mV) than in controls (0.35±0.20 mV; P =0.004). With T-wave impacts, the animals that received glibenclamide had significantly fewer occurrences of ventricular fibrillation (1 episode in 27 impacts; 4%) than controls (6 episodes in 18 impacts; 33%; P =0.01). Conclusions —In this experimental model of commotio cordis, blockade of the K + ATP channel reduced the incidence of ventricular fibrillation and the magnitude of ST-segment elevation. Therefore, selective K + ATP channel activation may be a pivotal mechanism in sudden death resulting from low-energy chest-wall trauma in young people during sporting activities.

Prediction and prevention of sudden cardiac arrest (SCA) remains one of the great challenges of contemporary cardiology. As the most common cause of death in the United States, SCA accounts for an estimated 350 000 deaths annually and represents a leading cause of disability and healthcare costs.1,2 Early cardiopulmonary resuscitation and defibrillation are essential steps in resuscitation of individuals with the life-threatening ventricular arrhythmias that most commonly cause SCA.3–10 In an effort to improve survival from cardiac arrest, public access to defibrillation (PAD) programs have promoted the chain-of-survival concept with sequential steps in the prehospital phase that result in improved survival.11 These interventions include rapid access to emergency medical services by calling 911, cardiopulmonary resuscitation (CPR), defibrillation when indicated, and initiation of advanced medical care.11 Survival depends directly on the time to defibrillation, and early defibrillation has emerged as the most important intervention, with survival decreasing by 10% with each minute of delay in defibrillation.12,13 Articles pp 1374 and 1380 A confluence of multiple factors over the last several years has resulted in the coming of age of PAD programs. Among these is the recognition that incorporation of the automated external defibrillator (AED) into the chain of survival shortens time to definitive therapy and improves survival.3–13 Good Samaritan laws, passed in all 50 states, are supplemented by the federal Cardiac Arrest Survival Act and provide broad-based legal immunity for those purchasing or using an AED.14 At the same, there has been a growing recognition that not providing access to an AED as a prudent measure of public protection may subject one to liability in public locations.14 Finally, a substantial body of robust clinical data, including multiple prospective randomized trials and a meta-analysis, support incorporation of the AED into PAD programs.2–13 Interest …

Background— The risks of sports participation for implantable cardioverter-defibrillator (ICD) patients are unknown. Methods and Results— Athletes with ICDs (age, 10–60 years) participating in organized (n=328) or high-risk (n=44) sports were recruited. Sports-related and clinical data were obtained by phone interview and medical records. Follow-up occurred every 6 months. ICD shock data and clinical outcomes were adjudicated by 2 electrophysiologists. Median age was 33 years (89 subjects Conclusions— Many athletes with ICDs can engage in vigorous and competitive sports without physical injury or failure to terminate the arrhythmia despite the occurrence of both inappropriate and appropriate shocks. These data provide a basis for more informed physician and patient decision making in terms of sports participation for athletes with ICDs.

The heart of the athlete has intrigued cardiologists since the original description of increased cardiac dimensions in elite Nordic skiers more than a century ago.1 Athletes exhibit structural and electric cardiac abnormalities that mimic findings associated with cardiovascular disease.2 Some early observers regarded the heart of a conditioned athlete as weakened by strenuous training and thereby subject to progressive deterioration in function.3 Structural findings include chamber enlargement and ventricular hypertrophy.2,3 Electric abnormalities include increased QRS voltage, abnormal Q waves, and T-wave inversions.2,3 Currently, the athlete’s heart is regarded as a benign increase in cardiac mass with circulatory and morphological alterations in response to athletic training.2,3 Contemporary evidence supports the notion that this represents adaptive physiology, not preclinical disease.2,3 Despite considerable advances in diagnostic tests, significant challenges remain in differentiating the athlete’s heart from some types of cardiac disease.2–4 ECG and morphological changes found in athletes can mimic findings of hypertrophic cardiomyopathy, dilated cardiomyopathy, arrhythmogenic right ventricular (RV) cardiomyopathy (ARVC), and other cardiovascular diseases.2–4 The absence of a definitive diagnostic test or gold standard for many cardiovascular commonly results in diagnostic uncertainty.2–4 Article see p 1783 This overlap of normal and abnormal findings has represented a clinical challenge because diagnostic criteria lacked sufficient sensitivity and specificity to reliably distinguish physiological enlargement of the athlete’s RV from ARVC.5 The importance of this distinction is underscored by the fact that in the United States, ARVC is responsible for 4% of cases of athletic sudden deaths.2 Sudden deaths are attributed to ARVC in 22% of athletes in the Veneto region of Italy.2 Because of the recognized shortcomings of the 1994 International Task Force Criteria for the diagnosis …

Developed in Collaboration With the American Association for Thoracic Surgery and Society of Thoracic Surgeons Andrew E. Epstein, MD, FACC, FAHA, FHRS, Chair ; John P. DiMarco, MD, PhD, FACC, FHRS; Kenneth A. Ellenbogen. MD, FACC, FAHA, FHRS; N.A. Mark Estes III, MD, FACC, FAHA, FHRS; Roger A.

Sudden cardiac death (SCD) in a young athlete commonly brings to the forefront the many gaps in knowledge regarding how to predict and prevent these rare tragic events.1–3 Although the number of athletic sudden deaths is relatively small, with ≈100 to 150 competitive deaths during sports in the United States annually, they represent an important and emotionally charged public health issue, perhaps out of proportion to the relative risks of other pediatric deaths (Figure 1).1–5 Despite identification of the cardiovascular conditions that predispose to these events, much remains unknown regarding many fundamental issues related to athletic sudden death. The precise frequency with which these events occur in the United States remains unclear because of the absence of athletic death registries (and indeed any SCD registry) with mandatory reporting requirements.1–8 In fact, whether these events are more common in athletes is not at all certain. Additionally, significant gaps in evidence exist related to effectiveness of preventing sudden death in the athlete with preparticipation screening strategies. There are many limitations to the available evidence supporting the notion that athletic restriction improves outcomes. The effectiveness of cardiopulmonary resuscitation and automated external defibrillator (AED) programs, evident in casinos and airports, has not necessarily been shown in athletes.9 The ongoing debates related to prediction and prevention of athletic sudden death persists because the standards of evidence-based medicine have not been fulfilled with appropriately designed randomized controlled trials. Figure 1. Causes of death in the US population aged 1 to 21 years. Injury, homicide, and suicide dwarf the number of sudden deaths in athletes. SCD indicates sudden cardiac death. Data from the Centers for Disease Control and Prevention (http://webappa.cdc.gov/sasweb/ncipc/leadcaus10.html). On average, every 3 days in the United States a competitive athlete experiences a SCD, and many …

Samuel J. Asirvatham, Ed. 711 pages. Oxford, UK: Oxford University Press, 2013. $147.98. ISBN:13 978-0199941193 Over the past decade there has been a rapid evolution of the techniques of invasive electrophysiology, mapping, and ablation. Considerable progress has been made in identifying the mechanisms and anatomic location of cardiac arrhythmias, thereby allowing the cure of most arrhythmias with ablation techniques. Although several excellent textbooks are available with content on basic and clinical electrophysiology, and cardiac rhythm management devices, as well, there remains a clear gap in textbooks focusing on contemporary invasive electrophysiology and ablation techniques. In an attempt to bridge this gap in contemporary textbooks, Dr Asirvatham has assembled a team of Mayo Clinic contributors to produce a manual rather than a textbook. This practical, superbly illustrated 711-page manual is focused on contemporary techniques of invasive electrophysiology including mapping, imaging, diagnostic maneuvers, and ablation. The book is a practical, concise, multiauthored text written and edited by colleagues from the Mayo Clinic. It consists of 2 sections, including 9 chapters in section I. This is followed by 20 case studies in section II designed to test the principles presented in the initial section of the manual. The chapters include an introductory 62-page masterfully written contribution by Dr Asirvatham covering fluoroscopic views, electrograms, and relevant anatomy. It is replete with high-quality radiographic images effectively coupled with color anatomic …

Background— The prognostic significance of syncope has not been investigated systematically in hypertrophic cardiomyopathy, and treatment strategies have been based largely on intuition and experience. Methods and Results— We assessed the relationship between syncope and sudden death in 1511 consecutive patients with hypertrophic cardiomyopathy. Unexplained (n=153) or neurally mediated (n=52) syncope occurred in 205 patients (14%). Over a 5.6±5.2-year follow-up, 74 patients died suddenly. Relative risk of sudden death was 1.78 (95% confidence interval 0.88 to 3.51, P =0.08) in patients with unexplained syncope and 0.91 (95% confidence interval 0.00 to 3.83, P =1.0) in those with neurally mediated syncope compared with patients without syncope. In multivariable analysis, the temporal proximity of unexplained syncope to initial patient evaluation was independently associated with risk of sudden death ( P =0.006). Patients with unexplained syncope within 6 months before the initial evaluation showed a 5-fold increase in risk compared with patients without syncope (adjusted hazard ratio 4.89, 95% confidence interval 2.19 to 10.94), a relationship that was maintained throughout all age groups (5 years before initial evaluation) did not show an increased risk of sudden death (adjusted hazard ratio 0.38, 95% confidence interval 0.05 to 2.74). Conclusions— In the present large cohort of patients with hypertrophic cardiomyopathy, unexplained syncope was a risk factor for sudden death. Patients with syncopal events that occurred in close temporal proximity to the initial evaluation showed a substantially higher risk of sudden death than patients without syncope. Older patients with remote syncopal events did not show an increased risk.

Background. Commotio cordis (CC), sudden cardiac death secondary to blunt, innocent-appearing chest wall blows in sports and other daily activities, is being reported with increasing frequency. Children and adolescents are most at-risk for this phenomenon. In an experimental animal model, it has been shown that ventricular fibrillation (VF) can be induced with a baseball blow to the chest wall during the vulnerable period of repolarization. We hypothesized that in this model, larger subjects would require higher impact velocities to induce VF. Methods. Under general anesthesia, 41 juvenile swine (16 to 55 kg) were placed prone in a sling and received chest wall blows at 30 to 60 mph with a lacrosse ball aimed directly over the cardiac silhouette. Impacts were timed to occur during the vulnerable period for VF (10 –30 ms prior to the T-wave peak). Animals were divided into 4 groups based on weight (16 to 25kg, 26 to 35kg, 36 to 45kg, and 46 to 55kg) and the frequency of VF was analyzed. Results. In 419 impacts, the smallest animals (16 to 25kg) were most vulnerable to VF and incidence of VF decreased incrementally as animal size increased. Impacts at 30 mph only induced VF in the smallest animals. In the largest animals (46 to 55kg), VF was only induced at impacts of 60 mph (figure ). Conclusion. Impact velocity and subject size are important variables in the generation of CC. In this animal model, smaller animals are more vulnerable to generation of VF across a wider range of impact velocities. These data might underlie the higher vulnerability to CC that has been observed in children and young adults and has implications for the prevention of CC with chest wall protectors.

Introduction: The Multidisciplinary Study of Right Ventricular Dysplasia is an NIH-funded, multicenter, prospective registry of patients meeting Task-Force criteria for arrhythmogenic right ventricular dysplasia (ARVD). Previous studies have used the occurrence of “life-threatening” fast VT or VF as a surrogate for sudden cardiac death in patients with an ICD, however the patient characteristics associated with sudden cardiac death in ARVD remain poorly defined. Methods: All patients in the ARVD registry that underwent implantation of an ICD were studied. Baseline characteristics of patients who received ICD therapy for fast VT/VF (with a cycle length of Results: 80 patients in the ARVD registry underwent implantation of an ICD. Of those, 61 patients (76%) had an ICD implanted for secondary prevention and 19 patients (24%) for primary prevention. Over a mean follow-up of 1.7 years, 17.5% of patients experienced appropriate ICD therapy for fast VT/VF, including 18% of patients with an ICD implanted for secondary prevention and 15.8% of patients with and ICD implanted for primary prevention. Among all baseline imaging, echocardiographic, and electrcardiographic characteristics, none were significantly associated with the occurance of fast VT/VF during follow-up. In a Kaplan-Meier analysis, there was no significant diffference in the cumulative risk of ICD therapy for fast VT/VF between primary or secondary prevention cohorts (log rank p-value = 0.69). Conclusions: In this registry of patients meeting the current Task Force criteria for ARVD, there is a high incidence of “life-threatening” fast VT/VF during follow-up, and the probability of fast VT/VF is similar in patients with an ICD for secondary prevention compared to those with an ICD for primary prevention. Furthermore, baseline characteristics do not reliably predict a future risk of life threatening arrhythmias in this cohort.

Habitual physical activity reduces coronary heart disease events, but vigorous activity can also acutely and transiently increase the risk of sudden cardiac death and acute myocardial infarction in susceptible persons. This scientific statement discusses the potential cardiovascular complications of exercise, their pathological substrate, and their incidence and suggests strategies to reduce these complications. Exercise-associated acute cardiac events generally occur in individuals with structural cardiac disease. Hereditary or congenital cardiovascular abnormalities are predominantly responsible for cardiac events among young individuals, whereas atherosclerotic disease is primarily responsible for these events in adults. The absolute rate of exercise-related sudden cardiac death varies with the prevalence of disease in the study population. The incidence of both acute myocardial infarction and sudden death is greatest in the habitually least physically active individuals. No strategies have been adequately studied to evaluate their ability to reduce exercise-related acute cardiovascular events. Maintaining physical fitness through regular physical activity may help to reduce events because a disproportionate number of events occur in least physically active subjects performing unaccustomed physical activity. Other strategies, such as screening patients before participation in exercise, excluding high-risk patients from certain activities, promptly evaluating possible prodromal symptoms, training fitness personnel for emergencies, and encouraging patients to avoid high-risk activities, appear prudent but have not been systematically evaluated.

The majority of deaths yearly in the United States (approximately 1 million) are the result of cardiovascular disease. Many of these deaths occur because of sudden and unexpected disturbances of the normal heart rhythm that result in ineffective pumping of the blood to the brain and other vital organs. Cardiac arrest from these life-threatening disturbances of the heart rhythm is a leading cause of disability and a major source of healthcare costs in the United States. It is estimated that more than 350 000 cases of cardiac arrest occur annually in this country. Cardiac arrest is usually caused by a disturbance of the cardiac rhythm called “ventricular fibrillation,” wherein the left chamber of the heart develops a very rapid rhythm that prevents blood from pumping out to the body and that is incompatible with life. Immediate therapy with defibrillation is the only effective treatment. Defibrillation involves delivering a shock to the chest wall through adhesive pads or paddles to reestablish a normal cardiac rhythm. Although standard defibrillators must be operated by trained medical personnel, automated external defibrillators (AEDs) are now available for use by trained medical and minimally trained lay personnel. Using AEDs can result in more cases of survival from cardiac arrest. To improve the prehospital care of victims of cardiac arrest, the American Heart Association has developed the Chain of Survival, wherein a sequence of interventions results in improved survival after a cardiac arrest. These steps include early access to the emergency medical services by calling 911, early cardiopulmonary resuscitation (CPR) when needed, early defibrillation when indicated, and early advanced medical …

Background— Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a condition associated with the risk of sudden death (SD). Methods and Results— We conducted a multicenter study of the impact of the implantable cardioverter-defibrillator (ICD) for prevention of SD in 132 patients (93 males and 39 females, age 40±15 years) with ARVC/D. Implant indications were a history of cardiac arrest in 13 patients (10%), sustained ventricular tachycardia in 82 (62%), syncope in 21 (16%), and other in 16 (12%). During a mean follow-up of 39±25 months, 64 patients (48%) had appropriate ICD interventions, 21 (16%) had inappropriate interventions, and 19 (14%) had ICD-related complications. Fifty-three (83%) of the 64 patients with appropriate interventions received antiarrhythmic drug therapy at the time of first ICD discharge. Programmed ventricular stimulation was of limited value in identifying patients at risk of tachyarrhythmias during the follow-up (positive predictive value 49%, negative predictive value 54%). Four patients (3%) died, and 32 (24%) experienced ventricular fibrillation/flutter that in all likelihood would have been fatal in the absence of the device. At 36 months, the actual patient survival rate was 96% compared with the ventricular fibrillation/flutter-free survival rate of 72% ( P Conclusions— In patients with ARVC/D, ICD therapy provided life-saving protection by effectively terminating life-threatening ventricular arrhythmias. Patients who were prone to ventricular fibrillation/flutter could be identified on the basis of clinical presentation, irrespective of programmed ventricular stimulation outcome.

Case Report : A 20-year-old asymptomatic man was diagnosed with hypertrophic cardiomyopathy (HCM) after routine physical examination during which a systolic heart murmur was detected. Echocardiography showed massive left ventricular (LV) hypertrophy with ventricular septal thickness of 36 mm extending into the anterolateral wall (30 mm); outflow obstruction was absent. Ambulatory (Holter) ECG showed 3 isolated premature ventricular contractions, and blood pressure response to exercise was normal. Echocardiographic examinations in parents and siblings were negative for HCM. Although 2 centers advised against an implantable cardioverter-defibrillator (ICD) based on the presence of only 1 risk factor for sudden death (ie, extreme hypertrophy), a prophylactic device was recommended by a third cardiac consultant. After an uneventful 16-month period during which the ICD neither detected nor treated arrhythmias, an unprovoked episode of ventricular fibrillation triggered a defibrillation shock that immediately restored sinus rhythm (Figure 1). Figure 1. Primary prevention of sudden death in HCM. Continuous recording of a stored intracardiac ventricular electrogram from a young asymptomatic man with extreme LV hypertrophy (septal thickness 36 mm). The ICD senses ventricular fibrillation and automatically delivers a defibrillation shock (arrow), which restores normal rhythm. HCM is the most common genetic cardiovascular disease, and since its description 45 years ago, sudden death has been its most visible and devastating consequence.1–5 Indeed, HCM is the most common cause of sudden cardiac death in young people (including trained athletes).5 Such events usually occur in previously healthy individuals without significant symptoms or as the initial clinical manifestation of the disease, thus generating considerable anxiety and a sense of vulnerability among patients and families.2–5 Identification of high-risk patients and efforts at prevention of sudden death represent important clinical challenges in HCM.6 The ICD was introduced 25 years ago as a treatment strategy for lethal ventricular tachyarrhythmias.7 …

Background —The CABG Patch trial compared prophylactic implantable cardiac-defibrillator (ICD) implantation with no antiarrhythmic therapy in coronary bypass surgery patients who had a left ventricular ejection fraction P =0.63). The mechanisms of death were classified, and hypotheses were tested about the effects of ICD therapy on arrhythmic and nonarrhythmic cardiac deaths in the CABG Patch Trial and the Multicenter Automatic Defibrillator Implantation Trial (MADIT). Methods and Results —The 198 deaths in the trial were reviewed by an independent Events Committee and classified by the method of Hinkle and Thaler. Only 54 deaths (27%) occurred out of hospital; 145 deaths (73%) were witnessed. Seventy-nine (82%) of the 96 deaths in the control group and 76 (75%) of the 102 deaths in the ICD group were due to cardiac causes. Cumulative arrhythmic mortality at 42 months was 6.9% in the control group and 4.0% in the ICD group ( P =0.057). Cumulative nonarrhythmic cardiac mortality at 42 months was 12.4% in the control group and 13.0% in the ICD group ( P =0.275). Death due to pump failure was significantly associated with death >1 hour from the onset of symptoms, dyspnea within 7 days of death, and overt heart failure within 7 days of death. Conclusions —In the CABG Patch Trial, ICD therapy reduced arrhythmic death 45% without significant effect on nonarrhythmic deaths. Because 71% of the deaths were nonarrhythmic, total mortality was not significantly reduced.

Cardiac arrest most commonly occurs as a consequence of acute myocardial ischemia or develops with identifiable substrate such as scar because of previous myocardial infarction, cardiomyopathy, or hypertrophy.1,2 Despite extensive noninvasive and invasive evaluation, cardiac arrest remains unexplained without evidence of structural heart disease in ≈10% of individuals surviving sudden cardiac arrest.1,2 Autopsy data confirm that a similar minority of victims of sudden death have no identifiable cardiac abnormality at postmortem evaluation.1,2 It is now recognized that inherited electrophysiological abnormalities, termed primary electrical diseases, are the common underlying cause of these unexplained cardiac arrests. Such tragic events disproportionately affect people

Background Surgical ablation of the arrhythmogenic focus in patients with life-threatening ventricular tachyarrhythmias can be curative. However, the surgical techniques have been plagued by a high perioperative mortality rate (averaging ≈12%). Reconstruction of the left ventricle may reduce mortality. Methods and Results Reconstruction of the left ventricle with a pericardial patch, or endoaneurysmorrhaphy, was performed with mapping-guided subendocardial resection for recurrent ventricular tachycardia in 25 patients over a 5-year period. Postoperatively, electrophysiological studies were conducted to assess the results of surgery, which were further evaluated during long-term follow-up with survival analyses. The study included 25 patients, 60±9 years of age, with coronary artery disease, discrete left ventricle aneurysms, and malignant ventricular tachyarrhythmias. Left ventricular ejection fraction was 24±6% preoperatively. Left ventricular endocardial mapping, endocardial resection, and endoaneurysmorrhaphy were performed in all patients. There was no operative or postoperative (30-day) mortality. Postoperative ventricular tachycardia was induced in 2 of the 25 patients (8%); left ventricular function increased to 32±9% (range, 19% to 52%). At a mean follow-up of 37±16 months (range, 6 to 65 months), there had been 6 deaths, including 1 sudden cardiac death, 2 congestive heart failure deaths, and 3 noncardiac deaths. Analysis of multiple variables failed to identify predictors of postoperative inducibility, sudden cardiac death, cardiac death, or total mortality. Conclusions Endoaneurysmorrhaphy with a pericardial patch combined with mapping-guided subendocardial resection frequently cures recurrent ventricular tachycardia with low operative mortality and improvement of ventricular function. Long-term follow-up demonstrates low sudden cardiac death rates.