The Use of Electromagnetic Flow Measurements for Detection of Early Stenosis in Aortocoronary Bypass Grafts

The value of electromagnetic flow measurements for the detection of graft stenosis during aortocoronary bypass and subsequent prevention of early closure by reimplantation of the graft was assessed. Postoperative angiograms were studied in 102 grafts in 55 patients in whom flow was measured during operation. Patients with recurrent angina or insufficient improvement after operation were selected to include many early occluded grafts; 30 grafts became occluded within six months. Applying a criterion of acceptable specificity based on flow pattern analysis, only 6 grafts were found to be abnormal immediately after implantation. It appears that in most instances, early closure is caused by a process of scar tissue formation which takes several months to develop completely. As a rule, the graft is patent after implantation and flow pattern analysis has nothing to offer. The value of flow pattern analysis during operation for the prevention of early closure is limited, and its value for the prediction of long-term prognosis of the grafts remains to be evaluated.