1029-18 Early, Long-term Therapy with Enalapril but not Metoprolol or Digoxin Attenuates Cardiocyte Hypertrophy in Dogs with Moderate Heart Failure

LV remodeling (enlargement, sphericity and myocyte hypertrophy), is a key process in the progressive deterioration of LV function observed in heart failure (HF). In dogs with moderate HF (LV ejection fraction 30–40%), we previously showed that early, long-term (3 months) monotherapy with enalapril (ENA, 10mg bid, n=7) and metoprolol (MET, 25mg bid, n=7) but not digoxin (DIG, 0.25mg qd, n=7) prevented the progressive LV enlargement observed in untreated dogs (CON, n=7). In the present study, we used the same cohorts of dogs to examine the effects of these agents on myocyte hypertrophy. Myocyte cross-sectional area (MCSA) was evaluated histologically from frozen LV sections obtained at the end of therapy. From each section, 5 fields (radial orientation). each containing at least 100 myocytes, were selected randomly for analysis using computer-based planimetry. LV tissue from 7 normal (NL) dogs was used for comparison.Average MCSA (μm2)NLCONDIGMETENA616±18924±63922±73979±41711±58**P<005MCSA was larger in CON, MET and DIG dogs compared to NL and ENA dogs (*P<0.05). No significant difference was present in MCSA between ENA and NL dogs. Only ENA attenuated myocyte hypertrophy in dogs with moderate HF