A new method for the prediction of peripheral vascular resistance from the preoperative angiogram

The preoperative angiogram is widely used to estimate runoff prior to infrainguinal bypass grafting, but the traditional method of angiographic scoring (0, 1, 2, or 3 based on the number of patent tibial vessels) correlates poorly with measurements of peripheral vascular resistance. We assigned a score of 0, 1, or 2 to each of four parameters (anterior and posterior tibial arteries [AT and PT], peroneal artery [PER], and plantar arch [ARCH]) on the preoperative angiograms of 39 patients admitted for elective femoral bypass grafting. These scores were then examined for their ability to correlate with the peripheral vascular resistance measured in each patient at the time of surgery. Multiple linear regression suggested that the scores assigned to the AT, PT, and ARCH were significantly correlated with observed resistance, but the PER subscore was not. Multiple linear regression of the AT, PT, and ARCH subscores suggested that resistance could be predicted from the equation: In (Resistance [mm Hg/ml/min]) = 0.786 - 0.268(AT) - 0.25(PT) - 0.358(ARCH), for which r = 0.78 and p less than 0.001. The ability of this relationship to predict resistance was tested by a division of the patient population into two roughly equal groups based on their observed resistance at surgery. When tested in this fashion, this equation had a sensitivity of 88% and a specificity of 82%. These findings suggest that the preoperative angiogram can be graded in a simple, yet unambiguous way, which allows a reasonable prediction of peripheral vascular resistance.