Diastolic Myocardial Mechanics in Hypertrophic Cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is characterized by myocardial hypertrophy, fiber disarray, and fibrosis interfering with myocardial force generation and relaxation. Because conventional Doppler echocardiographic methods inadequately assess diastolic function in HCM, the aim of this study was to determine local and global left ventricular (LV) relaxation mechanics in patients with HCM. Methods: Seventy-two patients with HCM and 32 normal controls were studied. Using Velocity Vector Imaging, longitudinal and circumferential strain, strain rate, and rotation at the base, middle, and apex of the septal and lateral LV walls were measured. Differences between patients' functional class subgroups were assessed using analysis of variance, and Tukey's post hoc analysis was used to compare patients in HCM clinical subgroups with normal controls. Results: Longitudinal strain and systolic and early diastolic strain rates were lower than normal in patients with HCM, whereas their circumferential values were higher. This suggests that shortening and relaxation orientation in HCM was more circumferential. The ratio of peak early diastolic to peak systolic strain rate decreased longitudinally and circumferentially in moderately to severely symptomatic (New York Heart Association class III or IV) patients (0.95 ± 0.35 vs 0.89 ± 0.35, P < .001). LV untwist was similarly prolonged in all HCM subgroups. LV relaxation assessed using the early apical reverse rotation fraction was significantly lower in patients with worse functional status (34 ± 14% vs 18 ± 4% in class I or II vs class III or IV). Left atrial volume increased, paralleling the severity of symptoms and the degree of diastolic dysfunction. Conclusions: The evaluation of biplane myocardial mechanics offers new insights into the evaluation of diastolic function and its relationship to clinical status.