The effect of ramipril on left ventricular mass, myocardial fibrosis, diastolic function, and plasma neurohormones in Maine Coon cats with familial hypertrophic cardiomyopathy without heart failure. 
Hypertrophic cardiomyopathy (HCM) is the most common heart disease of cats, resulting in left ventricular (LV) hypertrophy, myocardial fibrosis, and diastolic dysfunction.  Ramipril will reduce LV mass, improve diastolic function, and reduce myocardial fibrosis in cats with HCM without congestive heart failure (CHF).  This prospective, blinded, placebo-controlled study included 26 Maine Coon and Maine Coon cross-bred cats with familial HCM but without CHF.  Cats were matched for LV mass index (LVMI) and were randomized to receive ramipril (0.5 mg/kg) or placebo q24h for 1 year, with investigators blinded.  Plasma brain natriuretic peptide (BNP) concentration, plasma aldosterone concentration, Doppler tissue imaging (DTI), and systolic blood pressure were measured at baseline and every 3 months for 1 year.  Cardiac magnetic resonance imaging (cMRI) was performed to quantify LV mass and myocardial fibrosis by delayed enhancement (DE) cMRI at baseline and 6 and 12 months.  Plasma angiotensin-converting enzyme (ACE) activity was measured on 16 cats 1 hour after PO administration.  Plasma ACE activity was adequately suppressed (97%) in cats treated with ramipril.  LV mass, LVMI, DTI, DE, blood pressure, plasma BNP, and plasma aldosterone were not different in cats treated with ramipril compared with placebo (P = .85, P = .94, P = .91, P = .89, P = .28, P = .18, and P = .25, respectively).  Treatment of Maine Coon cats with HCM without CHF with ramipril did not change LV mass, improve diastolic function, alter DE, or alter plasma BNP or aldosterone concentrations in a relevant manner.