[Current state of non-invasive methods in the study of coronary arteries and surgical bypass grafts]

[Patency study of internal mammary artery grafts: the usefulness of echo-enhancers for identifying the flow signal by color Doppler echocardiography]

OBJECTIVES

a) To study the capacity of the technique of high-frequency color Doppler to detect flow signal of left internal mammary artery grafts; b) to assess the usefulness of an echo-enhancer agent to facilitate the detection of the signal, and c) to evaluate the patency of the graft according to its pulsed Doppler velocity profile pattern.

METHODS

39 consecutive patients were studied. A Hewlett-Packard 5500 echocardiograph was used, with a high-frequency probe (S12) applied at the high left parasternal border. When a graft signal was not elicited after a predetermined 5-minute check period, an intravenous dose of 4 g of Levovist (Schering España) at 400 mg/ml was administrated. According to previous studies, a pulsed Doppler flow profile with a predominantly diastolic pattern was considered a normal graft patency, while a systolic one was deemed as abnormal.

RESULTS

Graft flow was identified by color Doppler in 33/39 patients (85%). The additional use of an echo-enhancer in 6 patients with no detected signal increased this proportion to 38/39 (97%). Normal flow patterns were seen in 34/38 (89%). Among the four patients with abnormal pattern, 1 case of early myocardial infarction was observed, while angiographic studies showed distal occlusion of the graft in 1 or the presence of competitive flow in 2 patients.

CONCLUSIONS

The high-frequency color Doppler technique allows the detection of a flow signal from internal mammary artery grafts in most patients. The administration of an echo-enhancer agent is useful in those with non detectable signals. An abnormal pulsed Doppler velocity pattern indicates graft malfunction.