Diastolic Stress Echocardiography in Patients With Hypertrophy Cardiomyopathy: Association With Exercise Capacity

Diastolic dysfunction plays a major role in precipitating congestive heart failure in patients with hypertrophic cardiomyopathy (HCM). In many such patients, symptoms are unmasked only during exercise because left ventricular (LV) filling pressure is normal at rest but increase with exercise. We sought to establish whether abnormal postexercise diastolic parameters are associated with reduced exercise capacity in patients with HCM. We examined 590 patients with asymptomatic/minimally symptomatic HCM (age 54 ± 14 years, 57% men, body mass index 30 ± 6 kg/m², 84% on β blockers) with HCM by 2-dimensional and Doppler echocardiography at rest and after maximal treadmill exercise echocardiography (TSE). A complete echocardiogram (including LV ejection fraction, LV thickness, LV outflow tract [LVOT] gradient, degree of mitral regurgitation) was recorded. Diastolic parameters (septal and lateral [e'] velocities of the mitral annulus, peak early [E] and late [A] mitral inflow velocity, E/A ratio, E/e', right ventricular systolic pressure [RVSP], and left atrial volume index) were recorded at rest and after TSE. Exercise functional capacity was recorded and divided into <85% or >85% of age-gender predicted metabolic equivalents (AGP-METs). After maximal exercise, 32% patients had at least moderate mitral regurgitation, mean LVOT gradient was 61 ± 59 mm Hg, E/A ratio was 1.2 ± 1.0, average E/e' ratio 12.9 ± 1.0, and peak RVSP was 36 ± 15 mm Hg. Only 42% of patients achieved >85% of AGP-METs; the mean METs was 7 ± 3. On multivariable logistic regression analysis, higher body mass index (odds ratio [OR] 1.05), β-blocker use (OR 2.58), higher left atrial volume index (OR 1.02), higher peak stress LVOT gradient (LVOTG) (OR 1.06), peak stress E/e' (OR 1.04), and higher RVSP (OR 1.03) were independently associated with <85% AGP-METs achieved (all p <0.05). In conclusion, in patients with asymptomatic/minimally symptomatic HCM who underwent TSE, there is a significant and independent association between abnormal diastolic response to exercise and reduced exercise capacity in HCM. Incorporating diastolic parameters during stress echocardiography could provide incremental diagnostic utility in deciphering the exact etiology of dyspnea in such patients.