Modifying Factors in the Phenotypic Expression of Hypertrophic Cardiomyopathy

Abstract

The objectives of this study were to assess the role of potential modifying factors in the phenotypic expression of hypertrophic cardiomyopathy (HCM) and to assess therapeutic options that might cause regression of left ventricular (LV) mass in HCM.A total of 269 patients were carefully phenotyped and LV mass was determined by cardiac MRI. The role of gender, insulin-like growth factor-I (IGF-I) and genetic polymorphism in the angiotensin converting enzyme (ACE) and endothelin-1 (ET-1) genes in determining LV mass in HCM was assessed. The relationship between brain natriuretic peptide (BNP) and HCM caused by known sarcomeric mutations was also assessed. The role of ACE inhibition and/or blockade was also assessed in regression of LV hypertrophy in non-obstructive HCM patients.Female patients were found to have relatively thicker hearts with smaller cavities than male patients as in LV hypertrophy caused by pressure overload. Higher physiological levels of IGF-I were associated with lesser degrees of LVH which may be due to increased muscular efficiency. BNP levels were associated with the disease causing mutation but not to the degree of LVH. Mutations associated with an adverse prognosis had significantly higher BNP levels. The insertion/deletion (I/D) ACE gene but not ET-1 gene polymorphism was associated with LV mass in HCM. Treatment with enalapril alone or in combination with losartan resulted in a 7% and 8.5% reduction in LV mass respectively over 6 months.HCM is a complex disease with many potential phenotypic modifiers. These studies suggest that identifying modifying factors is important to explore therapeutic options in the management of these patients. In addition further studies exploring the long term impact of such therapies on disease progression are indicated and their role in disease prevention in pre-clinical states.