Abstract 413: Predictors of Exercise Capacity in Patients With Hypertrophic Cardiomyopathy: A Multi-modality Imaging Study
Background: There is variation in exercise capacity in hypertrophic cardiomyopathy (HCM) patients, despite similar degree of diastolic dysfunction, left ventricular outflow tract obstruction (LVOTO) and mitral regurgitation (MR). Pulse wave velocity (PWV), measured by cardiac magnetic resonance (CMR), is a marker of aortic stiffness and is abnormal in HCM vs. controls. We tested the association between maximal oxygen consumption (VO2 max) and various clinical/imaging predictors in HCM patients with preserved ejection fraction.
Methods: Fifty consecutive, newly referred HCM patients (62% men, 44 +/− 13 years, 78 % on beta-blockers, 18 % hypertensives) underwent Doppler echocardiography (echo), cardiopulmonary exercise testing and CMR for symptom evaluation. Deceleration time (DT, msec), myocardial performance index (MPI or isovolumic contraction time + isovolumic relaxation time/ejection time), post exercise MR and LVOT gradient (mm Hg) were measured on echo. VO2 max (ml/kg/minute) was measured. LV volumetric indices were measured by CMR. PWV (m/s) was measured on velocity-encoded CMR as Δx/Δt (Δx = aortic path length between mid-ascending and mid-descending aorta, and Δt = time delay between arrival of the foot of PW between 2 points).
Results: On echo, maximal post-exercise LVOT gradient, degree of MR, DT, MPI, degree of MR and VO2 max were 104±52 (range 65–198), 1±1, 240±79, 0.7±0.5 and 25±6 respectively. On CMR, mean basal septal thickness (cm), PWV, EF, ESV and EDV index (ml/m2), were 1.9±0.5 (range 1.6 –2.3), 9.2±7, 64 %±6, 32 ±8, 87±16, 110±29 and respectively. Regression analyses testing the predictors of VO2 max are shown in table⇓. There was no association between age and PWV (r = 0.01, p-value 0.9).
Conclusion: In HCM patients, age and PWV are stronger predictors of VO2 max compared to LV thickness, MR, LVOTO and diastolic indices. Aortic stiffness might additionally influence exercise capacity in HCM patients, and could be a potential therapeutic target.