Echocardiography Study of Hypertrophic Cardiomyopathy Phenotypes: An Indian Perspective

Background: Hypertrophic cardiomyopathy (HCM) is a genetic disorder with a heterogeneous phenotype. Historically, only obstructive and nonobstructive forms have been described. Improvements in imaging techniques have led to elaborative description of various new phenotypes, although there are limited epidemiological data regarding these phenotypes from within our population. Aims and Objectives: •To identify HCM patients from a cohort of cardiomyopathy patients. •To describe their demographic profile and mode of presentation based on the presenting symptoms. •To subclassify the selected HCM population into various phenotypes based on echocardiography. Results: There were 233 patients of HCM in this study. The mean age of the patients was 53 ± 14.5 years with male preponderance (70%). Thirty-six percent patients were asymptomatic, 37% mildly symptomatic (in class I-II), and 27% severely symptomatic (in class III-IV). Patients were classified into six phenotypes consisting of five classically described phenotypes and one atypical phenotype. Reverse curvature phenotype was most prevalent (49%) and symptomatic phenotype with 19.3% having significant resting left ventricular outflow tract (LVOT) obstruction. Other phenotypes were 19% apical mid, 11% neutral, 6% sigmoid, and 4% atypical. Male: female ratio for reverse curvature phenotype was 3:1, apical (mid) phenotype 2.4:1, and both apical and neutral phenotypes 2:1. Sigmoid phenotype had female-to-male ratio of 2.5:1. Conclusion: HCM patients require phenotype specific approach for complete assessment. Transthoracic echocardiography with myocardial contrast plays a pivotal role in identifying morphological phenotypes, effects on cardiac remodeling and hemodynamics which consequently influence mode of presentation. Reverse curvature, apical mid, and sigmoid phenotypes are comparatively more symptomatic, have larger left atrial size and segment thickness compared to less symptomatic apical and neutral phenotypes. Symptom status of the patient seems to be dependent on age, septal contour, severity of LVOT obstruction, left atrial volume, and maximal segment thickness.