Mechanisms of exercise intolerance in patients with hypertrophic cardiomyopathy

Aim

To determine the relation between echocardiogram findings and exercise capacity in hypertrophic cardiomyopathy (HCM).

Methods and Results

Sixty-three patients (48 ± 15 years) were referred for cardiopulmonary testing and exercise echocardiography. They were classified by morphology: proximal (n = 11), reverse curvature (n = 32), apical (n = 7), and concentric HCM (n = 13).

There were more women in proximal and reverse curvature groups. Proximal HCM patients were older. Maximal left ventricular thickness was highest in reverse curvature group. At peak exercise, concentric HCM achieved the lowest percent predicted maximal Vo₂. Excluding apical group, no significant differences in gradient were noted between groups. Overall, no statistically significant correlation was found between peak Vo₂, wall thickness, and gradient. Significant correlations were noted between peak Vo₂ and indexed left atrial (LA) volume (r = −0.52), lateral E′ (r = 0.50), and lateral E/E′ ratio (r = −0.46). A multivariate model including age, lateral E′, indexed LA volume, and mitral A wave explained 46% of the variance in peak Vo₂ (P = .01).

Conclusion

Lateral E′ and indexed LA volume are negatively correlated with functional capacity. Although patients with concentric morphology achieved the lowest peak Vo₂, wall thickness and gradient did not predict exercise capacity.