Abnormal Longitudinal Myocardial Functional Reserve Assessed by Exercise Tissue Doppler Echocardiography in Patients with Hypertrophic Cardiomyopathy

Abstract

BACKGROUND: Previous studies have shown that mitral annular velocities are reduced in patients with hypertrophic cardiomyopathy (HCM). However, the response of systolic and diastolic velocities of the mitral annulus to exercise in patients with HCM has not been explored previously. Because pathologic left ventricular (LV) hypertrophy is associated with myocardial fibrosis, particularly in the subendocardium, we hypothesized that mitral annular systolic and diastolic velocities during exercise and at rest would be abnormal in patients with HCM. METHODS: Mitral septal annular systolic (S') and early diastolic (E') velocities were measured at rest and during graded supine bicycle exercise (25 W, 3-minute increments) in 40 patients with HCM (29 male, mean age 56 years) and 41 age- and sex-matched control subjects. LV diastolic and systolic longitudinal function reserve index were calculated using a new formula. RESULTS: There were no significant differences in mitral inflow velocities (early mitral filling velocity [E], E/A, deceleration time of E velocity [DT]) at rest between the two groups except late mitral filling (A) velocity, which was higher in control group. Increase in E' with exercise was significantly smaller in patients with HCM compared with control subjects (1.7 +/- 1.3 vs 3.4 +/- 2.5 cm/s from base to 25 W, P = .0006; 2.2 +/- 1.9 vs 4.5 +/- 2.8 cm/s from base to 50 W, P = .0002). Although LV ejection fraction at rest was significantly higher in patients with HCM compared with that of control subjects (71 +/- 7 vs 66 +/- 7, P = .0019), S' at rest (6.0 +/- 1.2 vs 6.8 +/- 1.1 cm/s, P = .011) was significantly lower in patients with HCM. Although a significant increase in S' was detected with exercise in control subjects, increase in S' with exercise was blunted in patients with HCM (6.4 +/- 1.4 vs 8.5 +/- 2.5 cm/s at 25 W, P = .0004; 7.0 +/- 1.4 vs 9.5 +/- 2.4 cm/s at 50 W, P < .0001). Longitudinal systolic (0.37 +/- 0.85 vs 1.47 +/- 1.75 cm/s at 25 W, P = .0034; 0.79 +/- 1.08 vs 2.32 +/- 1.66 cm/s at 50 W, P = .0001) and diastolic (1.29 +/- 1.06 vs 2.84 +/- 2.12 cm/s at 25 W, P = .0002; 1.63 +/- 1.46 vs 3.77 +/- 2.31 cm/s at 50 W, P < .0001) function reserve index was significantly lower in patients with HCM compared with that of control subjects. CONCLUSION: Augmentation of LV longitudinal function during exercise is blunted in patients with HCM, suggesting longitudinal functional reserve and resting longitudinal function is abnormal in these patients.