Morphometric evaluation of the time course of right ventricular hypertrophy after left coronary artery ligation in rats.

1. In order to describe the time course of compensatory right ventricular hypertrophy after infarction, rats submitted to left coronary obstruction and sham-operated controls were compared in terms of heart weight, chamber weight and right ventricular fiber diameter 1, 8 and 21 days after surgery. 2. One day after infarction, only the left ventricle weight increased (0.583 +/- 0.045 g vs 0.698 +/- 0.062 g, P less than 0.05), while right ventricular weight and fiber diameter suffered no change. 3. Eight days after infarction, heart weight (0.781 +/- 0.127 g vs 0.856 +/- 0.100 g, P greater than 0.05) as well as right ventricular fiber diameter (16.5 +/- 1.0 microns vs 17.5 +/- 2.1 microns, P greater than 0.05) and left ventricular weight did not differ between sham-operated animals and animals with left coronary obstruction. However, a significant increase in right ventricular weight was observed in infarcted animals (0.168 +/- 0.026 g vs 0.242 +/- 0.017 g, P less than 0.05). 4. Twenty-one days after infarction, right ventricular weight (0.198 +/- 0.034 g vs 0.316 +/- 0.118 g, P less than 0.05), heart weight (0.864 +/- 0.095 g vs 0.985 +/- 0.105 g, P less than 0.05) and right ventricular fiber diameter (15.0 +/- 1.8 microns vs 21.3 +/- 2.3 microns, P less than 0.05) were significantly increased in infarcted animals, whereas left ventricular weight (0.665 +/- 0.065 g vs 0.669 +/- 0.039 g, P greater than 0.05) was unchanged. 5. We conclude that hypertrophy occurs in the right ventricle of randomized infarcted rats 21 days after infarction, and that this phenomenon precedes the increase in fiber diameter.(ABSTRACT TRUNCATED AT 250 WORDS)