In patients with hypertrophic cardiomyopathy, left ventricular outflow tract obstruction at rest is a strong, independent predictor of progression to severe symptoms of heart failure and of death.

M ore than 50 years after its contemporary description, hypertrophic cardiomyopathy (HCM) remains the most common cause of sudden death in the young. [1][2][3][4][5][6] Although several clinical markers have proved to be useful guides for risk stratification, 3-5,7 current strategies do not identify all HCM patients at risk for sudden death. 3,5,8,9 Over the last Background-Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden death in the young, although not all patients eligible for sudden death prevention with an implantable cardioverter-defibrillator are identified. Contrast-enhanced cardiovascular magnetic resonance with late gadolinium enhancement (LGE) has emerged as an in vivo marker of myocardial fibrosis, although its role in stratifying sudden death risk in subgroups of HCM patients remains incompletely understood. Methods and Results-We assessed the relation between LGE and cardiovascular outcomes in 1293 HCM patients referred for cardiovascular magnetic resonance and followed up for a median of 3.3 years. Sudden cardiac death (SCD) events (including appropriate defibrillator interventions) occurred in 37 patients (3%

Background-Nonobstructive hypertrophic cardiomyopathy (HCM) has been regarded as the predominant hemodynamic form of the disease on the basis of assessment of outflow gradient under resting conditions. We sought to prospectively define the prevalence, clinical profile, and significance of left ventricular (LV) outflow tract obstruction under resting conditions and with physiological exercise in a large HCM cohort. Methods and Results-We prospectively analyzed 320 consecutive HCM patients (age, 47Ϯ17 years), measuring LV outflow gradient at rest, with Valsalva maneuver, and with exercise echocardiography. LV outflow obstruction was present at rest and/or with exercise in 225 patients (70%); 119 had rest gradients Ն50 mm Hg and were not exercised.Of the other 201 patients with gradients Ͻ50 mm Hg at rest (average, 4Ϯ9 mm Hg), 106 developed mechanical obstruction to LV outflow resulting from mitral valve-septal contact after exercise (80Ϯ43 mm Hg), including 76 with marked gradients Ն50 mm Hg and 46 with heart failure symptoms. The remaining 95 patients (30%) had no or small gradients (Ͻ30 mm Hg) both at rest and with exercise. Valsalva maneuver underestimated the presence and magnitude of exercise-induced obstruction. Conclusions-Among those patients who come to clinical evaluation, HCM is a predominantly obstructive disease in which LV outflow gradients, frequently associated with heart failure symptoms and often identified only with exercise, are evident in most patients (ie, 70%