Biomedical subjects
Publications and source records attributed to B J Maron.
As hypertrophic cardiomyopathy is a common cause of sudden deaths among athletes, differentiating this condition from the non-pathological "athlete's heart" presents an important challenge.
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The genetic causes of hypertrophic cardiomyopathy are diverse and thus present challenges in the development of genetic tests to identify patients at risk
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The European Society of Cardiology has convened a Task Force on Sudden Cardiac Death in order to provide a comprehensive, educational document on this important topic. The main document has been published in the European Heart Journal in August 2001. The Task Force has now summarized the most important clinical issues on sudden cardiac death and provided tables with recommendations for risk stratification and for prophylaxis of sudden cardiac death. The present recommendations are specifically intended to encourage the development and revision of national guidelines on prevention of sudden cardiac death. The common challenge for cardiologists, physicians of other medical specialties and health professionals throughout Europe is to realize the potential for sudden cardiac death prevention and to contribute to public health efforts to reduce its burden.
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BACKGROUND: Clinical impact of atrial fibrillation (AF) in hypertrophic cardiomyopathy (HCM) is largely unresolved. Thus, we analyzed the prognostic implications of AF in a large, community-based HCM population assembled from Italian and US cohorts. METHODS AND RESULTS: Occurrence of AF and outcome were assessed in 480 consecutive HCM patients (age at diagnosis, 45+/-20 years; 61% male) who were followed up for 9.1+/-6.4 years. AF occurred in 107 patients (22%; incidence, 2%/y) and was independently predicted by advancing age, congestive symptoms, and increased LA size at diagnosis. Patients with AF had increased risk for HCM-related death (OR, 3.7; P<0.002) because of excess heart failure-related mortality but not sudden, unexpected death. This risk associated with AF was substantially greater in patients with outflow obstruction or with earlier development of AF (</=50 years of age). AF patients were also at increased risk for stroke (OR, 17.7; P=0.0001) and severe functional limitation (OR for NYHA class III or IV, 2.8; P<0.0001). Compared with those with exclusively paroxysmal AF, patients developing chronic AF showed higher combined probability of HCM-related death, functional impairment, and stroke (P<0.0001). In a subgroup of 37 patients with AF (35%), the clinical course was largely benign in the absence of stroke and severe symptoms. CONCLUSIONS: In a community-based HCM population, AF (1) was common, with 22% prevalence over 9 years; (2) was associated with substantial risk for heart failure-related mortality, stroke, and severe functional disability, particularly in patients with outflow obstruction, those </=50 years of age, or those developing chronic AF; and (3) was nevertheless compatible with benign outcome in 35% of patients.
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In a consecutive, prospectively assessed and unselected hypertrophic cardiomyopathy (HC) cohort closely resembling the true disease state, QTc dispersion (and QTc) on the 12-lead electrocardiogram did not prove to be a reliable predictor of HC-related sudden death. Therefore, QT dispersion would not appear to be useful in devising future risk stratification strategies for predicting sudden death in HC.
Atrial fibrillation (AF) is the most common sustained arrhythmia in patients with hypertrophic cardiomyopathy (HCM), and it bears numerous pathophysiologic consequences that potentially affect patient outcome and symptoms. However, studies regarding the impact of AF on the long-term prognosis of HCM patients have been limited in number, with sometimes conflicting results. Recently, studies on community-based patient populations showed that AF is associated with long-term clinical deterioration, embolic complications, and increased cardiovascular mortality due to heart failure and stroke. The consequences of AF on the long-term prognosis of HCM patients are not uniformly unfavorable, however, and in about one third of patients the arrhythmia is compatible with an uneventful course.
Highly trained athletes show a variety of electrocardiographic (ECG) changes, including a striking increase of R or S wave voltage, either flat or deeply inverted T waves, and deep Q waves, that suggest the presence of structural cardiovascular disease, such as hypertrophic cardiomyopathy or arrhythmogenic right ventricular cardiomyopathy, which represent the most common causes of sudden death in young competitive athletes. Despite a number of previous observational surveys, the determinants and clinical significance of these abnormal ECG patterns in trained athletes are still uncertain. Therefore, ECG patterns were compared with cardiac morphology (by echocardiography) in a large population of 1005 athletes, who were engaged in a variety of 38 sporting disciplines. We found abnormal ECGs in 40% of our athletes, but structural cardiac diseases were identified in only 5%. In the absence of cardiac disease, other determinants were recognized as responsible for abnormal ECG patterns, including the extent of morphologic cardiac remodeling, participation in an endurance type of sport, and male gender. Finally, a small but important subset of athletes showed striking ECG abnormalities that strongly suggested the presence of cardiovascular disease in the absence of pathologic cardiac conditions or morphologic changes, suggesting that these ECG alterations may be the consequence of athletic conditioning itself.
OBJECTIVES: In an experimental model of sudden death from chest wall impact (commotio cordis), we sought to define the chest wall areas important in the initiation of ventricular fibrillation (VF). BACKGROUND: Sudden death can result from an innocent chest blow by a baseball or other projectile. Observations in humans suggest that these lethal blows occur over the precordium. However, the precise location of impact relative to the risk of sudden death is unknown. METHODS: Fifteen swine received 178 chest impacts with a regulation baseball delivered at 30 mph at three sites over the cardiac silhouette (i.e., directly over the center, base or apex of the left ventricle [LV]) and four noncardiac sites on the left and right chest wall. Chest blows were gated to the vulnerable portion of the cardiac cycle for the induction of VF. RESULTS: Only chest impacts directly over the heart triggered VF (12 of 78: 15% vs. 0 of 100 for noncardiac sites: p < 0.0001). Blows over the center of the heart (7 of 23; 30%) were more likely to initiate VF than impacts at other precordial sites (5 of 55; 9%, p = 0.02). Peak LV pressures generated instantaneously by the chest impact were directly related to the risk of VF (p < 0.0006). CONCLUSIONS: For nonpenetrating, low-energy chest blows to cause sudden death, impact must occur directly over the heart. Initiation of VF may be mediated by an abrupt and substantial increase in intracardiac pressure. Prevention of sudden death from chest blows during sports requires that protective equipment be designed to cover all portions of the chest wall that overlie the heart, even during body movements and positional changes that may occur with athletic activities.
OBJECTIVES: We sought to determine whether the development of left ventricular hypertrophy (LVH) can be demonstrated during adulthood in genetically affected relatives with hypertrophic cardiomyopathy (HCM). BACKGROUND: Hypertrophic cardiomyopathy is a heterogeneous cardiac disease caused by mutations in nine genes that encode proteins of the sarcomere. Mutations in cardiac myosin-binding protein C (MyBPC) gene have been associated with age-related penetrance. METHODS: To further analyze dormancy of LVH in patients with HCM, we studied, using echocardiography and 12-lead electrocardiography, the phenotypic expression caused by MyBPC mutations in seven genotyped pedigrees. RESULTS: Of 119 family members studied, 61 were identified with a MyBPC mutation, including 21 genetically affected relatives (34%) who did not express the HCM morphologic phenotype (by virtue of showing normal left ventricular wall thickness). Of these 21 phenotype-negative individuals, 9 were children, presumably in the prehypertrophic phase, and 12 were adults. Of the 12 adults with normal wall thickness < or = 12 mm (7 also with normal electrocardiograms), 5 subsequently underwent serial echocardiography prospectively over four to six years. Of note, three of these five adults showed development of LVH in mid-life, appearing for the first time at 33, 34 and 42 years of age, respectively, not associated with outflow obstruction or significant symptoms. CONCLUSIONS: In adults with HCM, disease-causing MyBPC mutations are not uncommonly associated with absence of LVH on echocardiogram. Delayed remodeling with the development of LVH appearing de novo in adulthood, demonstrated here for the first time in individual patients with prospectively obtained serial echocardiograms, substantiates the principle of age-related penetrance for MyBPC mutations in HCM. These observations alter prevailing perceptions regarding the HCM clinical spectrum and family screening strategies and further characterize the evolution of LVH in this disease.
INTRODUCTION: This consensus statement summarizes the proceedings of The Expert Consensus Conference on Arrhythmias in the Athlete of the North American Society of Pacing and Electrophysiology (NASPE) on detecting, evaluating, and treating athletes with cardiovascular disorders that predispose to cardiac arrhythmias. METHODS AND RESULTS: The participants in the open policy conference were selected by the codirectors (Drs. Estes and Olshansky) based on expertise and contributions to the literature. All participants provided a referenced summary of their presentation. The writing group used the information from all published scientific studies, clinical trials, registries, clinical experience, and expert opinion to make recommendations regarding screening, evaluation, management, eligibility for competition, and a range of other medical, social, and legal issues regarding the recreational and competitive athlete. The codirectors of the symposium synthesized the participants' reports for this and made revisions according to suggestions of all members of the writing committee. The manuscript was reviewed by four independent reviewers assigned by the NASPE Committee for the Development of Position Statements and NASPE Board of Trustees. CONCLUSION: Despite considerable advances in knowledge regarding the diagnosis, therapy, and mechanisms of arrhythmias in the athlete, much remains unknown. Continued basic, clinical, and epidemiologic research is needed. Current screening techniques to detect athletes lack sensitivity and specificity. Evaluation of standardized screening programs with tracking of long-term outcomes is needed. Officials from athletic, academic, medical, and legal institutions need to form strategic partnerships to develop policy related to assessment of risk and assumption of responsibility for athletic activities.