Background: Transthoracic Doppler echocardiography of internal mammary artery grafts (MAGs) has been tested by the supraclavicular approach, but little information is available about the parasternal approach.
Objective: To evaluate the usefulness of parasternal transthoracic Doppler echocardiography to assess the patency of left and right MAGs.
Patients and methods: Forty-eight patients with previous MAGs were divided into two groups on the basis of coronary angiography: 42 patients had patent MAGs and six patients had severe MAG stenosis. Doppler echocardiography of MAGs was performed on all patients, both at baseline and after low-dose dipyridamole infusion. Systolic and diastolic time-velocity integrals and their ratios were obtained, and MAG flow reserve was calculated.
Results: Patients with patent MAGs had a predominant diastolic flow, while a prominent systolic pattern was found in the presence of MAG stenosis. In patients with stenosis, baseline Doppler analysis showed a lower diastolic peak velocity (DPV) (P<0.01), diastolic time-velocity integral (P<0.05), and diastolic and systolic time-velocity integral ratios (both P<0.005), and a reduced MAG flow reserve (P<0.001). In the overall population, when adjusting for clinical variables, a multilinear regression analyis underscored MAG flow reserve (beta=0.38, P<0.01) and baseline DPV (beta=0.29, P<0.05) as independent determinants of MAG stenosis (cumulative R2=0.25, P<0.005).
Conclusions: Doppler echocardiographic evaluation of MAGs is a reliable, noninvasive tool to assess MAG patency and functional status of the vessel. MAG blood flow reserve and baseline DPV are independent determinants of MAG stenosis.