Isovolumic Relaxation Time as an Indicator of Diastolic Dysfunction in Hypertrophic Cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is clinically characterized by the presence of left ventricular hypertrophy in the absence of hypertension and valvular heart disease. Diastolic dysfunction is an important pathology in patients with HCM, and it is characterized by abnormal relaxation, increased left ventricular filling pressure, pulmonary congestion, and ultimately cardiac symptoms. The present study aimed to assess the isovolumic relaxation time (IVRT) in patients with HCM as an important indicator of diastolic dysfunction. Methods: Nineteen control subjects and 35 patients with HCM were included in the present study. Diagnosis was based on the confirmation of unexplained myocardial hypertrophy in the left ventricle by conventional echocardiography. The peak velocity of early (E) and late (A) filling, E-wave deceleration time (DT), and the E/A ratio were assessed using pulsed-wave Doppler (PWD) echocardiography at the tip of the mitral valve leaflets in the apical 4-chamber view. The IVRT was measured in the 4-chamber view via the PWD method. To that end, the filtering gain of the images was adjusted and the IVRT was estimated. Results: The mean age of the patients was 31±16 years. The IVRT more significantly increased in the patients with HCM than in the control group (P<0.01). The IVRT rose more significantly in the patients with no left ventricular outflow tract (LVOT) obstruction than in those with LVOT gradients (97±38 vs 82±29; P<0.001). The mean septal thickness was 24±7 mm in the patients with HCM, and increased septal thickness was significant in the patients who received implantable cardioverter defibrillators (P<0.05). Conclusions: The diastolic function was impaired in our patients with HCM. Moreover, the IVRT as a noninvasive index of the diastolic function was prolonged in those with HCM.