Usefulness of flow reserve in the left internal mammary artery to determine graft patency to the left anterior descending coronary artery

Two-dimensional Doppler echocardiography (DE) and intravascular Doppler-tip ped guidewire (flowire) have been used to measure flow in aortocoronary con duits at rest and during hyperemia, but they have not been compared. We inv estigated which flow velocity parameters obtained with these 2 different te chniques can predict left internal mammary artery (LIMA) graft patency. Twe nty-nine patients with previous coronary artery bypass grafting referred fo r evaluation of symptoms of coronary artery disease were studied after card iac catheterization using the flowire and DE. Proximal LIMA graft flow velo city wets measured at rest and during hyperemia produced by 140 mu g/kg/min of intravenous adenosine infusion over 6 minutes with both methods. Normal LIMA grafts and left anterior descending artery (LAD) distal to the anasto mosis were present in 16 patients, whereas 13 had >70% graft or native vess el stenosis. The coronary flow velocity reserve (r = 0.79) and the diastoli c-to-systolic velocity ratio during hyperemia (r = 0.73) correlated very we ll between the 2 techniques. Among the variables obtained with the 2 techni ques, the intragraft coronary flow velocity reserve measured by both method s was the only independent predictor of graft/recipient LAD potency. This v ariable had a sensitivity and specificity of 86% at a cutoff point of 2.07 with the flowire method and 83% at a cutoff point of 1.54 with DE. The area s below the receiver-operating characteristic curves were 0.91 and 0.93, re spectively. Coronary flow velocity reserve measurements obtained with DE ap pears a reliable noninvasive method for assessing LIMA graft and/or LAD dis tal to the anastomosis patency in patients after bypass surgery and correla te very well with those directly obtained by intravascular Doppler. (C)1999 by Excerpta Medica, Inc.