Impaired longitudinal systolic-diastolic coupling and cardiac response to exercise in patients with hypertrophic cardiomyopathy.

ABSTRACT

BACKGROUND: In patients with hypertrophic cardiomyopathy (HCM), impaired augmentation of stroke volume and diastolic dysfunction contribute to exercise intolerance. Systolic-diastolic (S-D) coupling characterizes how systolic contraction of the left ventricle (LV) primes efficient elastic recoil during early diastole. Impaired S-D coupling may contribute to the impaired cardiac response to exercise in patients with HCM. METHODS: Patients with HCM (n = 25, age = 47 ± 9 years) and healthy adults (n = 115, age = 49 ± 10 years) underwent a cardiopulmonary exercise testing (CPET) and echocardiogram. S-D coupling was defined as the ratio of LV longitudinal excursion of the mitral annulus during early diastole (EDexc) and systole (Sexc) and compared between groups. Peak oxygen uptake (peak V̇O2) (Douglas bags), cardiac index (C2H2 rebreathe), and stroke volume index (SVi) were assessed during CPET. Linear regression was performed between S-D coupling and peak V̇O2, peak cardiac index, and peak SVi. RESULTS: S-D coupling was lower in HCM (Controls 0.63 ± 0.08, HCM 0.56 ± 0.10, p < 0.001). Peak V̇O2 and stroke volume reserve were lower in patients with HCM (Peak VO2 Controls 28.5 ± 5.5, HCM 23.7 ± 7.2 mL/kg/min, p < 0.001, SV reserve Controls 39 ± 16, HCM 30 ± 18 mL, p = 0.008). In patients with HCM, S-D coupling was associated with peak V̇O2 (r = 0.47, p = 0.018), peak cardiac index (r = 0.60, p = 0.002), and peak SVi (r = 0.63, p < 0.001). CONCLUSION: Systolic-diastolic coupling was impaired in patients with HCM and was associated with fitness and the cardiac response to exercise. Inefficient S-D coupling may link insufficient stroke volume generation, diastolic dysfunction, and exercise intolerance in HCM.