Minimally Circulatory-Assisted On-Pump Beating Coronary Artery Bypass Grafting for Patients With Complex Conditions for Off-Pump Surgery

Off-pump coronary artery bypass grafting (OPCAB) in patients with acute myocardial infarction (AMI) is difficult because of circulatory deterioration during displacement of the heart. At our institution, we performed minimally circulatory-assisted on-pump beating coronary artery bypass grafting (MICAB) in these patients. During MICAB, support flow was controlled at a minimal level to maintain a systemic blood pressure of approximately 100 mm Hg and a pulmonary arterial systolic pressure of <30 mm Hg, providing optimal pulsatile circulation for end-organ perfusion and prevention of heart congestion. From September 2006 to March 2012, MICAB was performed in 37 patients. Either emergent or urgent MICAB was performed in 27 patients following AMI because of hemodynamic instability during reconstruction. Elective MICAB was performed in the remaining 10 patients because of dilated left ventricle (LV) or small target coronary arteries. The details of bypass grafts, perioperative renal function, and early and mid-term morbidity and mortality were compared between the patients who received MICAB and the 37 consecutive patients who underwent OPCAB during the study period at our hospital. The assist flow indices (actual support flow/body surface area) during anastomosis to the left anterior descending artery, left circumflex artery, and right coronary artery were 0.95 ± 0.48 L/min/m² , 1.32 ± 0.53 L/min/m² , and 1.15 ± 0.47 L/min/m² , respectively, in the emergent and urgent patients following AMI, and 0.44 ± 0.39 L/min/m² , 1.25 ± 0.39 L/min/m² , and 1.14 ± 0.43 L/min/m² , respectively, in the elective patients with either dilated LVs or small target vessels. The lowest mixed venous oxygen saturation during pump support in the MICAB group was significantly higher than that in the OPCAB group (83.8 ± 10.8%, 71.6 ± 7.5%, P < 0.001). Comparing MICAB and OPCAB, the median number of distal bypass grafts for both groups was 4 (25th, 75th percentile: 3, 4) (P = 0.558); the complete revascularization rates were 94.6 and 97.3%, respectively (not significant [NS]); the acute patency rates were 98.9 and 99.2%, respectively (NS); and the 30-day mortality rates were 2.7 and 0%, respectively (NS). No instances of either cerebrovascular complications or newly occurring postoperative renal failure were noted in either group. There were no statistically significant differences between the groups with respect to early and mid-term results (freedom from all-cause death: 82.9 vs. 86.5%, respectively, and freedom from cardiac events at 3 years: 96.4 vs. 96.4%, respectively). MICAB is a safe alternative to OPCAB, particularly in patients with AMI and dilated LV. MICAB is associated with high rates of complete revascularization and acute graft patency, adequate preservation of end-organ function, and early and mid-term results comparable with those observed following OPCAB.