Burned-out Phase in Apical Hypertrophic Cardiomyopathy (Echocardiographic Data of 230 Patients with Apical HCM)

Background: Apical Hypertrophic Cardiomyopathy (ApHCM)is a rare formof hypertrophic cardiomyopathy with sarcomere protein gene mutations, which predominantly affects the apex of the left ventricle. Sudden Cardiac Death (SCD) and cardiovascular morbidity are less likely to occur in patients with isolated ApHCM. However, recent data suggested annual cardiac death rates of 0.5 - 4%, approaching those for classic HCM. Objectives: The present study aimed to assess the prevalence of burned-out ApHCM and its predictors. Methods: In this retrospective cross-sectional study, echocardiographic data and electrocardiography features of 230 patients with ApHCM including premature ventricular contraction and atrial fibrillation were gathered and analyzed at baseline and after a mean follow-up of five years. All data were obtained from the data registry of Rajaie Cardiovascular Medical and Research Center, Tehran, Iran. The data were included in a retrospective study, which was approved by the local Ethics Committee. The patients were divided into two groups as follows: 1- Left Ventricular Ejection Fraction (LVEF) >= 50% and 2- LVEF < 50% known as burned-out ApHCM. Data analysis was also based on LVEF. Generalized Estimating Equation (GEE) regression was performed to assess the association between the patients' characteristics and burned-out ApHCM. The clinical features demonstrating P < 0.05 in the univariate GEE analysis were included in a multivariate model to identify the independent predictors. Results: The prevalence of burned-out ApHCM, defined as LVEF < 50%, was 13.9%. There was no significant difference between males and females in this regard (P = 0.48). After a mean follow-up of five years, atrial fibrillation was significantly more common in the patients with LVEF < 50% (48.7% vs. 24.4%, P = 0.007). Additionally, left atrial enlargement was identified as the most important predictor of BO-ApHCM (odds ratio = 2.4, P = 0.003). Moreover, right ventricular dysfunction was more severe in the patients with burned-out ApHCM (P < 0.001). Conclusions: The prevalence of burned-out HCM was higher in the present study than in the previous studies (13.9%). Besides, right ventricular systolic dysfunction and left atrial enlargement were two main predictors of the ApHCM progression.