Flow measurements and simultaneously performed angiography of aorto-coronary bypass grafts during bypass surgery

The function of aorto-coronary bypass grafts is usually assessed by the run-off, determined from postoperatively performed cineangiograms. The reliability of this method was tested by comparing the electromagnetically measured graft flow with the run-off, qualitatively estimated from cineangiograms. The electromagnetic flow measurements and cineangiography were performed simultaneously during bypass surgery. The run-off was classified by three independent observers into three classes (poor, moderate, and good). The average mean flow rates corresponding to the three classes were: poor: Q = (43 +/- 11)ml/min; moderate: Q = (48 +/- 14)ml/min; good; Q = (63 +/- 22)ml/min. Although the differences between the flow rates of the three classes were found significant (except between poor and moderate run-off), there was a wide range of overlapping. Especially in grafts with low flow rates (Q less than 70 ml/min) there were pronounced disagreements between the qualitative estimation of flow and the electromagnetically measured flow. Using videodensitometric flow measurements as a check test, the uncertainties in classification proved to be caused by the lack of reliability of the observer. The flow rates in aorto-coronary bypass grafts can be determined reliably only by means of quantitative methods, e.g., electromagnetic or videodensitometric flow measurements.