Abstract 1059: Left Atrial Volume and E/E′ Ratio are Most Predictive of Exercise Capacity in Hypertrophic Cardiomyopathy
Hypertrophic cardiomyopathy (HCM) is characterized by LVH and myocardial disarray which result in ischemia, diastolic dysfunction and arrhythmias. While many experience functional limitation, the precise mechanisms are still unknown. We aim to determine the relation between echocardiogram findings and exercise capacity. We studied 48 patients (48 ± 15 years; 15 females) referred for symptom-limited cardiopulmonary testing and stress echocardiography for clinical reasons: 23 had a proximal HCM pattern (group I), 7 had a classic reverse curvature pattern (group II), 4 had an apical pattern (group III) and 14 had a concentric pattern (group IV). At baseline, patients in group I were significantly older than in other groups (54 ± 13 (I) vs. 41 ± 12 (II), 38 ± 12(III) and 44 ± 17 years (IV); p=0.04). No other significant difference in clinical characteristics was noted between groups. The maximal septum thickness was higher in groups I and II than in III and IV (19 (16 – 23), 22 (17–33), 17, and 16 (13–18) mm, respectively; p=0.05). Groups I and II were more likely to have resting gradient of >10 mm Hg (68% and 18%, respectively vs. 14% in IV; p=0.01) and to present rest systolic anterior movement (74% and 15% vs. 11% in IV; p <0.001). A higher prevalence of abnormal transmitral inflow E to lateral E′ ratio (E/E′) was also noted in Group I (80%, p=0.05): high ratios are known to be associated with high pulmonary wedge pressure in non-HCM populations. At peak exercise, group I achieved a lower peak VO2 (21.8 ±2.1 vs. 27.1±6.6 in II 36.6 ±5.1 in III and 29.4 ±2.7 ml/kg/min in IV; p=0.03). No significant differences in Valsalva and exercise gradients and delta rest-to-peak gradients were noted between patterns. In age-adjusted multivariate analysis, only negative correlations between E/E′ (R2=0.45; p=0.03) and indexed LA volume (R2=0.39; p=0.009) and peak VO2 were significant. In contrast, no correlation was found between maximal exercise capacity and LV dimensions, conventional Doppler indices of diastolic function, lateral E′ or gradients. Lateral E/E′ and indexed LA volume are negatively correlated with functional capacity even after age-adjustment. Although patients with proximal HCM achieved the lowest peak VO2, gradient and morphology were not related to exercise capacity.