Comparison of Right Ventricular Functional Response to Exercise in Hypertrophic Versus Idiopathic Dilated Cardiomyopathy

Although the biventricular nature of the disease has been confirmed by morphologic studies, information on right ventricular (RV) function in hypertrophic cardiomyopathy (HC) is lacking. The aim of the study was to hemodynamically characterize RV performance in HC versus idiopathic dilated cardiomyopathy (IDC) during exercise. The hemodynamic data of 63 patients with HC who underwent hemodynamic exercise testing with thermodilution-derived assessment of RV ejection fraction were analyzed. The results were compared to a healthy control group (n = 20) and to patients with IDC (n = 86). The baseline RV ejection fraction was increased in the patients with HC compared to those with IDC (39 ± 10% vs 33 ± 12%; p = 0.002), but did not differ compared to controls (42 ± 7% vs 39 ± 10%; p = NS). An increase in end-diastolic volume from rest to exercise contributed to stroke volume augmentation in those with HC (121 ± 38 vs 136 ± 55 ml/m²; p = 0.01) and control subjects (116 ± 34 vs 138 ± 31 ml/m²; p = 0.002) but not in those with IDC (117 ± 47 vs 120 ± 52 ml/m²; p = NS). At peak exercise the RV ejection fraction in those with HC was reduced compared to that in the controls (45 ± 11% vs 59% ± 9%; p <0.001), but it was increased compared to that in those with IDC (45 ± 11% vs 35% ± 11%; p <0.001). In conclusion, the extent of the pulmonary pressure increase was more pronounced in those with HC than in those with IDC, but the degree of functional impairment of the right ventricle was less severe, probably owing to its ability to recruit preload and contractile reserve with exercise.