The value of nuclear angiography in the preoperative assessment of patients undergoing elective aortic surgery.

Eighteen patients undergoing elective aortic surgery, either for peripheral vascular insufficiency or abdominal aneurysm, were studied preoperatively by nuclear angiography. By this technique the resting ventricular function of each patient was measured. Nuclear angiography is a safe non-invasive technique which has been shown to have excellent correlation with conventional contrast angiography in the assessment of ejection fraction. Throughout the intraoperative period, measurements of the central venous pressure and pulmonary capillary wedge pressure were taken simultaneously at approximately five-minute intervals. An average of 18 data points was established in each case. The correlation between central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) was examined. Ten of our patients had preoperative resting ejection fractions less than 55 per cent. In only four of these patients (40 per cent) was correlation between CVP and PCWP judged to be good intraoperatively. Eight of our patients had preoperative ejection fractions greater than 55 per cent. Six of these (75 per cent) showed good correlation between CVP and PCWP intraoperatively. We also assessed our ability to predict by purely clinical means which patients would show poor correlation between CVP and PCWP. Evaluation on purely clinical grounds was as good as the scans at predicting in which patients CVP would not correlate with PCWP and we feel that the routine use of this test would not modify our use of Swan Ganz catheters for intraoperative monitoring in patients undergoing aortic surgery, in the future.