Doppler echocardiographic assessment of internal mammary artery flow after minimally invasive coronary artery bypass

Minimally invasive direct coronary artery bypass (MIDCAB) is a new technique for left internal mammary artery (LIMA) to left anterior descending bypass through a mini-thoracotomy without cardiopulmonary bypass. To evaluate noninvasive follow-up of these pts, 20 pts, aged 60±10 yrs, were studied by transthoracic Doppler after MIDCAB. All pts had intraoperative confirmation of LIMA patency. A 7 MHz linear array transducer (15 pts) or a 3.75 MHz phased array transducer (5 pts) was placed at the parasternal 2^nd, 3^rd, 4^th intercostal space to record LIMA flow velocity. Right internal mammary artery (RIMA) flow velocity was recorded in 11 pts as a control (examples shown). All pts were studied 1-3 days after MIDCAB and 10 pts had additional studies in 1 month. Doppler data were available from 95% of attempted studies. LIMA and RIMA peak systolic velocity (S) and time velocity integral (TVI), peak diastolic velocity (D) and TVI, D/S, and D TVI % = [D TVI/(S TVI + D TVI)] were assessed: (mean values below, velocity in cm/sec). S S TVI D D TVI D/S D TVI % RIMA 77 17 16 6 0.4 26 LIMA (1-3 d) 59 14 39*18*1.2*55*LIMA (1 mo) 58 13 76*34*2.4*72*(*p < 0.01 vs. RIMA). Diastolic LIMA Doppler flow data were significantly > RIMA control, consistent with a distinct coronary artery flow pattern. These changes persisted after 1 month. Transthoracic Doppler may be useful to assess LIMA patency after MIDCAB.