Sudden Death in Children with Hypertrophic Cardiomyopathy

Abstract

Source: Yetman A, McCrindle B, et al. Myocardial bridging in children with hypertrophic cardiomyopathy—a risk factor for sudden death. N Engl J Med. 1998;339:1201–1209.Sudden death in children with hypertrophic cardiomyopathy is suspected to be due to myocardial ischemia. In a retrospective study, Yetman et al reviewed coronary artery angiograms in 36 children (age 7.1 ± 5.8 years) with hypertrophic cardiomyopathy. Angiographic findings were compared to history before and after angiography and clinical evidence of myocardial ischemia on ECG, echocardiograms, exercise testing, 24-hour Holter monitoring, and Thallium perfusion testing.The prevalence of myocardial bridging, resulting in systolic and diastolic compression of the left anterior coronary artery by abnormal bands of myocardium, was increased in 10 of 36 of children studied. Myocardial bridging was significantly associated with a history of chest pain (p= 0.04), cardiac arrest (p=0.004), and ventricular tachycardia (p<0.001). Patients with bridging were more likely to exhibit an abnormal fall in blood pressure during exercise (p<0.001) and a significantly shorter mean duration of exercise tolerance (p=0.008). Kaplan-Meier actuarial analysis demonstrated a higher probability of sudden death in patients with bridging compared to those who had no coronary artery compression (p=0.004). Three patients who had the abnormal bands of myocardium divided surgically had resolution of signs and symptoms of ischemia. The authors conclude that myocardial ischemia in children with hypertrophic cardiomyopathy may be due to myocardial bridging and may be one of the primary causes of sudden death in these patients.Although hypertrophic cardiomyopathy (also known as IHSS) is relatively rare, it is the most common cause of sudden death in adolescents and young adults. It is usually familial and often asymptomatic. Among athletes who die suddenly during exercise, hypertrophic cardiomyopathy is the most common identifiable cause.1 Predictors of sudden death in IHSS, primarily derived from studies in adults, include a history of sudden death in family members, ventricular tachycardia on Holter monitor, and a history of syncope. With the exception of Amiodarone (which is used for ventricular arrhythmias), neither surgical nor medical interventions have been shown to prevent sudden, unexpected death.It has long been thought that either myocardial ischemia resulting in myocardial infarction or lethal arrhythmia was the final common pathway leading to death.2 In this report, Yetman et al describe a small series of patients with hypertrophic cardiomyopathy who have an unusually high prevalence of “myocardial bridging” on coronary angiography. The authors found a strong association of myocardial bridging with other variables related to myocardial ischemia and sudden death, including chest pain, prior cardiac arrest, ventricular tachycardia, and evidence of ischemia on exercise testing. This association is provocative because surgical division of the abnormal bridges of myocardium causing compression of coronary arteries could effectively reduce ischemia and the risk of sudden death. Unfortunately, the small size of the study (a common problem in the study of any uncommon disease) did not allow an assessment of a potential surgical cure on the subsequent occurrence of sudden death. Clearly a multi-center prospective study of children with hypertrophic cardiomyopathy is needed to have adequate statistical power to assess the predictive value of myocardial bridging for sudden death and the potential benefit of surgery. Nonetheless, given the strong association with other factors for sudden death, the search for myocardial bridging by coronary angiography certainly appears to be warranted in all children with severe hypertrophic cardiomyopathy, particularly those with other risk factors for sudden unexpected death.