Reperfusion of the human myocardium by saphenous vein bypass grafts. Biochemical considerations

The adenine nucleotide content of the human myocardium in the distribution of the left anterior descending coronary artery (LAD) was measured before and after saphenous vein bypass grafting. The purposes of the study were twofold: (1) to relate the level of adenosine triphosphate (ATP) before bypass grafting to the percent stenoses of the LAD and (2) to determine the benefit or lack of benefit of bypass grafting on ATP content. Eighteen patients with angiographically determined LAD lesions of 40% to 100% underwent bypass grafting with standard cardiopulmonary bypass and cardioplegia. Transmural needle biopsy specimens were obtained from the center of the area perfused by the LAD immediately before cross-clamping of the aorta and 30 minutes after reperfusion of the myocardium via the native LAD and the graft. The tissue was divided into thirds: The endocardial and epicardial thirds were analyzed for ATP by high-pressure liquid chromatography and the middle third was viewed by light microscopy. The percent narrowing of the LAD correlated well (r = -0.71) with the ratio of ATP to total adenine nucleotides (TAN) in the endocardium. Epicardial ATP did not correlate with the percent stenoses of the LAD. The endocardial ATP/TAN ratio increased in the group as a whole from 0.51 ± 0.27 (mean ± SD) to 0.64 ± 0.26 (p < 0.01) after bypass grafting, and this was most impressive in those eight patients with LAD lesions > 90% (0.32 ± 0.20 before grafting to 0.60 ± 0.29 after grafting, p < 0.005). However, the epicardial ATP/TAN ratio decreased from 0.75 ± 0.15 before grafting to 0.64 ± 0.17 after grafting (p < 0.05), and this decrease occurred regardless of the percent narrowing of the LAD. There was no difference in vacuolization between the pre-grafting and post-grafting biopsy specimens, and intramyocardial hemorrhage was not observed. This study has demonstrated a close relationship between the degree of LAD stenosis and endocardial ATP content. Also, the endocardium supplied by arteries with > 90% lesions had significantly increased ATP while the epicardium had decreased ATP content after bypass grafting.