Complete reversibility of cat right ventricular chronic progressive pressure overload

Abstract

Chronic, progressive pressure overload of the cat right ventricle produces persistent, ongoing abnormalities of contractile, energetic, and biochemical function in vitro at a time when in vivo pump function is still normal. The present study tested the reversibility of the in vitro changes in this clinically relevant hypertrophy model. Fourteen sham-operated and 14 reversal cats were studied. After banding the animals as 1-kg kittens, right ventricular pressures were normal. Before band removal (25.2 ± 0.5 weeks later for the control group and 25.5 ± 0.3 weeks later for the hypertrophy reversal group), systolic right ventricular pressures were 24 ± 1 mm Hg for controls and 71 ± 5 mm Hg for the hypertrophy reversal group (P < 0.05). At study, 19.5 ± 1.1 weeks after a second sham operation for controls or 18.7 ± 0.7 weeks after band removal for the hypertrophy reversal group, these pressures were 24 ± 1 mm Hg for controls and 23 ± 1 mm Hg for the hypertrophy reversal group (P = NS); cardiac output was 0.18 ± 0.01 liters/kg per min for controls and 0.19 ± 0.01 liters/kg per min for the hypertrophy reversal group (P = NS). The ratio of right ventricle to body weight was normal in both groups, as was the right ventricular papillary muscle myocyte cross-sectional area and the myocardial collagen concentration. A right ventricular papillary muscle from each cat was studied at 29° C in a polarographic myograph. Preloaded shortening velocity was 0.79 ± 0.04 muscle lengths/sec for controls and 0.86 ± 0.03 muscle lengths/sec for the hypertrophy reversal group (P = NS); extent of shortening was 0.15 ± 0.01 muscle lengths for controls and 0.16 ± 0.01 muscle lengths for the hypertrophy reversal group (P = NS). At optimum isometric length, active tension was 59.7 ± 3.1 mN/mm2 for controls and 57.0 ± 1.9 mN/mm2 for the hypertrophy reversal group (P = NS); resting tension was 15.6 ± 1.2 mN/mm2 for controls and 13.6 ± 1.6 mN/mm2 for the hypertrophy reversal group (P = NS). Active and resting oxygen consumption levels did not differ in two groups. This study demonstrate that - in the compensated stage of chronic, progressive pressure overload of the cat right ventricle - the contractile, energetic, and biochemical abnormalities of the hypertrophied myocardium are fully reversible.