Reversal of Coronary Circulation Abnormalities After Relief of Pressure Overload in the Rat

Abstract

We tested the hypothesis that impaired coronary autoregulation and decreased coronary flow reserve in hypertrophied hearts may regress after relief of pressure overload. We banded the ascending aortas of Wistar rats for 4 weeks. Debanding was then performed on some of these banded rats. Four weeks after banding or debanding, the chest was opened and in vivo left ventricular pressure was measured. The heart was isolated and perfused with Tyrode’s solution containing bovine red blood cells (Ht, 30%) and serum albumin (15 g/1). The perfusate was oxygenated with a gas mixture containing 20% O₂, 3% CO₂, and 77% N₂. The left ventricular cavity was kept empty. Coronary perfusion pressure-flow relationships were obtained over a range of coronary perfusion pressures between 25 and 175 mmHg. Reactive hyperemic response was estimated after 40-s ischemia at 50, 100, and 150 mmHg perfusion pressure. In vivo peak systolic left ventricular pressure increased to 178 ± 8 mmHg in the hearts of the banded group (103 ± 6 in the hearts of sham-operated rats). The increased pressure produced significant myocardial hypertrophy (3.51 ± 0.16 vs 2.41 ± 0.05 mg/g heart weight/body weight ratio). After debanding, peak systolic left ventricular pressure decreased to the control level, and myocardial hypertrophy regressed to 15% above the control value. Coronary autoregulation was observed in control hearts, but was impaired in the hearts of the banded group over the whole range of perfusion pressures.