Improvement of myocardial stress perfusion after off-pump revascularization using bilateral internal thoracic in situ grafts versus Y-composite grafts

Background. There is a concern that revascularization using bilateral internal thoracic arteries (ITA) as a composite graft may not supply sufficient blood flow to a wider area of myocardium when compared with grafting using bilateral in situ ITAs. Methods. One-hundred three patients who underwent off-pump coronary artery bypass using bilateral ITAs for revascularization of the left coronary system were studied prospectively. Bilateral ITAs were used as in situ grafts in 49 patients (group 1) and as a Y-composite graft in 54 patients (group 2). Resting and stress myocardial single-photon emission computed tomography (SPECT) was performed preoperatively and 3 months postoperatively. Myocardial perfusion was automatically quantified and expressed as a percentage of the maximal uptake. The left coronary territory was divided into 16 segments. A total of 379 segments (154 segments in group 1; 225 segments in group 2) that indicated decreased stress perfusion preoperatively were included in this study. Results. Resting myocardial perfusion revealed no significant differences with regard to both the preoperative (77.5 +/- 9.3% vs 78.8 +/- 8.8%) and postoperative SPECT (78.3 +/- 10.0% vs 77.2 +/- 10.5%) between groups 1 and 2 (p = not significant [NS]). However, stress myocardial perfusion was significantly lower in group 1 preoperatively (62.5 +/- 10.8% vs 65.4 +/- 10.1%, p < 0.01). Although it improved postoperatively, there were no differences regarding postoperative stress myocardial perfusion between the two groups (75.5 +/- 11.3% vs 75.0 +/- 11.7%; p = NS). The degree of improvement regarding stress myocardial perfusion (difference between the preoperative and postoperative values) was higher in group 1 than in group 2 (13.0 +/- 9.4% vs 9.6 +/- 10.0%, p < 0.005). Conclusions. Myocardial SPECT demonstrated that revascularization using bilateral in situ ITAs exhibited a greater level of improvement with regard to stress perfusion postoperatively compared with Y-composite grafts. However, because there was no considerable difference with regard to postoperative stress perfusion between the two groups, revascularization using a Y-composite graft might also be sufficient for revascularization of the left coronary territory.