Frequency of deep venous thrombosis in asymptomatic patients with coronary artery bypass grafts.

The frequency of deep vein thrombosis (DVT) in patients undergoing coronary artery bypass graft (CABG) surgery has not been established. Therefore to estimate the frequency of clinically silent DVT, we performed ultrasound examinations of the leg veins in 29 asymptomatic CABG patients before hospital discharge. We used high-resolution B-mode ultrasonography with color Doppler imaging. Fourteen (48.3%, 95% confidence interval 30.1 to 66.4%) had 20 documented leg vein thromboses, and all but one patient had DVT limited to the calf veins. Of the 20 thrombi 10 (50.0%) were present in the leg ipsilateral and 10 (50.0%) in the leg contralateral to the saphenous vein harvest site. None of the DVTs were suspected clinically. DVT was not associated with any local sign attributed to saphenous vein harvest such as pitting edema, incisional drainage, or local tenderness or with any putative risk factor for DVT such as cigarette use, distant history of malignancy, or varicose veins. Follow-up of these patients 5 to 11 months after CABG surgery showed no clinical evidence of DVT or pulmonary embolism. Our findings indicate that asymptomatic DVT of the calf occurs with surprisingly high frequency, 44.8% after CABG surgery. Future studies in patients undergoing CABG surgery should address the natural history of asymptomatic DVT, determine its clinical importance, and develop optimal strategies for prophylaxis and treatment.