Extensive myocardial blood flow distribution through individual coronary artery bypass grafts.

The regional myocardial perfusion distribution of coronary artery bypass grafts were studied in 61 patients who received 162 grafts. Selective intragraft instillations of radioactive-labeled macroaggregated albumin particles were used to study perfusion. The extent of individual graft perfusion was assessed in 100 patent grafts. Regional myocardial blood flow distribution was similar to the blood flow distribution of the native vessel receiving the graft in 64 of 100 grafts and less than that expected of the native vessel in 12 grafts. However, 24 grafts demonstrated a blood flow distribution pattern which extended beyond the normal distribution expected of the native vessel receiving the graft. This extensive perfusion could be attributed to collateral vessels or retrograde flow. A high incidence of both graft and native vessel occlusion was found in areas receiving blood from these distant grafts with extensive distributions (16/24), and left ventricular wall motion was preserved or significantly improved postoperatively in 28/31 segments in such areas. When comparing angiographic and scintigraphic methods of evaluating myocardial perfusion, the angiogram underestimated the full extent of graft blood flow distribution in 13 of 24 instances (54 percent).

Improvement of myocardial perfusion and left ventricular function after coronary artery bypass grafting in patients with unstable angina.

Changes in myocardial perfusion and left ventricular function were evaluated pre- and post-operatively (3--6 months) in 14 patients with unstable angina who underwent coronary artery bypass surgery. Perfusion was studied with intracoronary and intragraft injections of radiolabeled macroaggregated albumin particles. Of 20 abnormal perfusion areas identified preoperatively, 13 demonstrated improved perfusion post-operatively. Segmental analysis of the left ventriculogram demonstrated improved wall motion in 29 abnormally contracting segments; 18 normalized. Areas which showed improvement of left ventricular perfusion were invariably associated with improvement of left ventricular wall motion. Five patients showed improvement in perfusion and contraction in areas of apparent old myocardial infarction. Thirteen of the 14 patients had significantly less angina whether or not there was evidence of improved perfusion. However, only those patients who demonstrated improved perfusion had a significant improvement in their treadmill exercise tolerance postoperatively. Thus, patients with unstable angina have perfusion defects which may be reversed as a result of saphenous vein graft surgery. Reversal of these perfusion abnormalities results in improved left ventricular performance and better exercise tolerance postoperatively.