Duration of pressure overload alters regression of coronary circulation abnormalities

Using a rat model of ascending aortic banding and debanding, we examined how the duration of pressure overload affects reversibility in coronary circulation abnormalities after relief of pressure overload. Four-week banding increased left ventricular dry weight-to-body weight ratio to 158 +/- 8% of that of sham-operated controls. In isolated nonworking hearts perfused with crystalloid solution, peak mean coronary flow rate (CFR) was measured after brief ischemia. CFR and CFR/dry tissue weight significantly decreased (75 +/- 5 and 54 +/- 3% of that of controls at 100 mmHg of coronary perfusion pressure; 75 +/- 5 and 54 +/- 4% at 150 mmHg, respectively). Four weeks after debanding was performed, CFR and CFR/dry tissue weight increased to similar levels in controls. On the other hand, 10-wk banding produced the same degree of myocardial hypertrophy and decreases in CFR and CFR/dry tissue weight as in 4-wk banded rats. Four weeks after debanding was performed, CFR had not changed. CFR/dry tissue weight increased because of regression of myocardial hypertrophy but was significantly lower than that in rats debanded after 4 wk of banding. Thus the duration of pressure overload does not affect the degree of coronary circulation abnormalities in the progression process but does affect it in the regression process.