The role of myocardial reperfusion and hypertrophy in the development of heart rupture in experimental myocardial infarction

Balloon dilatation was used to explore the strength of the left ventricular wall in rats. The rupture pressure of the left ventricle was 645 +/- 22 mm Hg and that of the right ventricle was 247 +/- 15 mm Hg in intact animals. Left ventricular hypertrophy induced by 50% ascending aortic stenosis increased rupture pressure proportionally to the degree of hypertrophy. In transmural myocardial infarction occupying 40-55% of the left ventricular wall volume, the rupture pressure within 10 days of myocardial infarction was the same as that in the intact myocardium. Following 24 hours of ischemia, myocardial reperfusion produced no effects, but after 2 or 4 hours of ischemia it reduced the strength of the heart wall by 50%. It was concluded that early thrombolytic therapy might be a risk factor for cardiac rupture in myocardial infarction.