Effect of permanent right internal mammary artery occlusion on right coronary artery supply: A randomized placebo-controlled clinical trial.

BACKGROUND: Natural, non-surgical internal mammary artery (IMA) bypasses to the coronary circulation have been shown to function as extracardiac sources of myocardial blood supply. The goal of this randomized, placebo-controlled, double blind trial was to test the efficacy of permanent right IMA (RIMA) device occlusion on right coronary artery (RCA) occlusive blood supply, and on clinical and ECG signs of myocardial ischemia.

METHODS: This was a prospective superiority trial in 100 patients with chronic coronary artery disease (CAD) randomly allocated (1:1) to RIMA vascular device occlusion (verum group) or to RIMA sham procedure (placebo group). The primary study endpoint was RCA collateral flow index (CFI) as obtained during a 1-minute ostial RCA balloon occlusion at baseline before and at follow-up exam 6weeks after the trial intervention. CFI is the ratio between simultaneous mean coronary occlusive divided by mean aortic pressure both subtracted by central venous pressure. Simultaneously obtained secondary study endpoints were the registration of angina pectoris and quantitative intracoronary (i.c.) ECG ST-segment shift.

RESULTS: CFI change during the follow-up period was +0.036±0.068 in the verum group and-0.021±0.097 in the placebo group (P=.0011). Angina pectoris during the same RCA balloon occlusions had disappeared at follow-up in 14/49 patients of the verum group, and in 4/49 patients of the placebo group (P=.0091). Simultaneous i.c. ECG ST-segment shift change revealed diminished myocardial ischemia at follow-up in the verum group, and more severe ischemia in the placebo group.

CONCLUSION: Permanent RIMA device occlusion augments right coronary artery supply to the effect of diminishing clinical and electrocardiographic signs of myocardial ischemia during a brief controlled coronary occlusion.