Rest and Stress Longitudinal Systolic Left Ventricular Mechanics in Hypertrophic Cardiomyopathy: Implications for Prognostication

Background Exercise intolerance is the most common symptom in hypertrophic cardiomyopathy (HCM). We examined whether inability to augment myocardial mechanics during exercise would influence functional performance and clinical outcomes in HCM. Methods Ninety-five HCM patients (32 nonobstructive, 32 labile-obstructive, 31 obstructive) and 26 controls of similar age and gender distribution were recruited prospectively. They underwent rest and treadmill stress strain echocardiography, and 61 of them underwent magnetic resonance imaging. Mechanical reserve (MRES) was defined as percent change in systolic strain rate (SR) immediately postexercise. Results Global strain and SR were significantly lower in HCM patients at rest (strain: nonobstructive, −15.6 ± 3.0; labile-obstructive, −15.9 ± 3.0; obstructive, −13.8 ± 2.9; control, −17.7% ± 2.1%, P −1 , P  = .002); and immediately postexercise (strain: nonobstructive, −15.6 ± 3.0; labile-obstructive, −17.6 ± 3.6; obstructive, −15.6 ± 3.6; control, −19.2 ± 3.1%; P  = .001; SR: nonobstructive, −1.41 ± 0.37; labile-obstructive, −1.64 ± 0.38; obstructive, −1.32 ± 0.29; control, −1.82 ± 0.29 s −1 , P P  = .001, respectively). Postexercise SR and MRES were associated with exercise capacity ( r  = 0.47 and 0.42, P r  = 0.74, P  = .003). Postexercise SR was correlated with extent of late gadolinium enhancement ( r  = 0.34, P  = .03). By Cox regression, exercise SR and MRES predicted ventricular tachycardia/ventricular fibrillation (VT/VF) even after adjustment for age, gender, family history of sudden cardiac death, septum ≥ 3 cm and abnormal blood pressure response ( P  = .04 and P  = .046, respectively). Conclusions Nonobstructive and obstructive patients have reduced MRES compared with labile-obstructive and controls. Postexercise SR correlates with LGE and exercise capacity. Exercise SR and MRES predict VT/VF.