Coronary collateral vessels: their significance for left ventricular histologic structure.

Whether coronary collateral vessels protect the left ventricular myocardium is unknown. Light microscopic morphometry was carried out on myocardial tissue samples from 56 surgically treated patients with coronary artery disease. Transmural biopsy of the myocardium perfused by the left anterior descending coronary artery was obtained during open heart surgery. In initial reproducibility studies of biopsy samples of 17 patients a sampling error for evaluation of myocardium was defined and differences in transmural fibrosis exceeding +/- 6.2 percent were considered biologically significant. Stenosis of the left anterior descending artery was determined from preoperative angiography. Group A (control group) comprised patients with less than 75 percent area reduction of the left anterior descending coronary artery (mean +/- standard deviation 65 +/- 10 percent). Patients in group B (more than 95 percent area reduction [mean 99 +/- 2 percent] without collateral supply on arteriography) were compared with patients in group C (identical stenosis [mean 99 +/- 2 percent] but with collateral supply). Fibrosis averaged 17 percent in group A, 68 percent in group B (p less than 0.001 versus group A) and 29 percent in group C (p greater than 0.05 versus group A, p less than 0.001 versus group B). Thus, in severe coronary stenosis myocardium supplied by collateral vessels shows less fibrosis on biopsy sample than does myocardium without collateral supply.