Transcutaneous ultrasound measurement of blood-flow in internal mammary artery to coronary artery grafts.

Transcutaneous doppler ultrasound was used to examine internal-mammary-artery (IMA) blood-flow in 26 patients with IMA coronary bypass grafts. The ungrafted right IMA could be seen in all of 19 patients, the grafted left IMA in 16 of 26, and the grafted right IMA in 3 of 7. The velocity profile recorded from the proximal part of the grafted IMA is distinct from that of an ungrafted artery, with a systolic peak which reflects graft capacitance in the face of high intramyocardial resistance, and a diastolic peak which represents graft conductance when intramyocardial resistance is low. Total graft blood-flow can be estimated from the mean velocity and the measured vessel diameter; resting flows ranged from 22 to 79 ml/min. In recently grafted patients, resting graft blood-flow correlated with myocardial "run-off" estimated from preoperative arteriograms; graft blood-flow increased appropriately with exercise. This simple, non-invasive technique to measure IMA graft blood-flow may find applications for routine postoperative follow-up of patients with IMA grafts and for studies on the physiology and pharmacology of coronary artery blood-flow.