Non-invasive evaluation of mammary artery flow reserve and adequacy to increased myocardial oxygen demand

Objective. To evaluate the Row reserve and adequacy to meet myocardial requests in stress conditions of mammary artery-left anterior descending (IMA-LAD) grafts using a non-invasive method,Methods: Patients (20)) with angiographic evidence of normofunctioning left IMA-LAD grafts were submitted to dypiridamole Tl-201 myocardial scintigraphy and concomitant transthoracic echo-doppler evaluation of the IMA flow at a mean interval of 32.5 months after surgery. Results: Under basal conditions, the mean peak and end How velocities in systole were 0.39 and 0.06 ms, respectively. In diastolr, the mean peak and end Bow velocities were 0.27 and 0.02 mis and mean tele-diastolic flow velocity was 0.14 ms, with a mean systolic;diastolic ratio of 1.51. After dypiridamole infusion, mean systolic velocities were 0.47 (peak) and 0.23(end) m/s-respectively + 20 and + 283% whereas mean diastolic velocities were 0.56 (peak) and 0.06 (end) m/s, + 107 and + 200% respectively. Mean tele-diastolic flow velocity increased to 0.32 m/s (+ 128%) and the systolic-diastolic index changed to 0.85 In all cases no significant scintigraphic evidence of induced ischemia was demonstrated in the LAD region. Conclusions: Transthoracic echo-doppler evaluation combined with Tl-201 myocardial scintigraphy is a useful tool for the assessment of IMA flow reserve and adequacy to stress conditions. In the late postoperative period, the IMA shows the possibility of increasing the flow velocity, almost 2-fold; the increase in flow: is prevalently diastolic and leads to a complete reversal of the physiological systolic/diastolic flow ratio. The flow reserve of IMA is always able to meet the augmented myocardial oxygen demand after dypiridamole infusion. (C) 1998 Elsevier Science B.V. All rights reserved.