Hypothermic Low Flow Fibrillation for Unclampable Aorta in Coronary Artery Bypass Grafting: Alternative to Off-Pump CABG

Background: Severe calcific disease of the ascending aorta may prohibit cross-clamping during coronary artery bypass grafting (CABG) due to unacceptable morbidity and mortality associated with atheroembolic complications. Clampless hypothermic noncardioplegic low flow fibrillation (HLFF) may minimize neurologic complications while allowing for complete revascularization. Methods: From 2002 to 2019, 142 patients with unclampable aorta (UCA) underwent isolated CABG using clampless HLFF. Short-term and long-term outcomes were compared with an isolated conventional on-pump CABG cohort (n = 268) risk-matched (RM) for type of CABG, STS score, age, and sex. Results: UCA and RM cohort patients were comparable in terms of age (73.7 ± 7.8 vs. 72.7 ± 8.7, p = 0.281), sex (34.4% vs. 32.5% female, p = 1.000), STS score (4.01 ± 3.43 vs. 3.80 ± 3.33, p = 0.539), and number of diseased vessels (p = 0.323). 90% of patients underwent central cannulation; UCA group patients received a comparable number of arterial (p = 0.432) or venous grafts (p = 0.493). Incidence of stroke was 6.3% in the UCA cohort and 2.6% in the RM cohort (p = 0.059). Need for reoperation, postoperative transfusions, incidence of atrial fibrillation, and renal impairment was similar (all p > 0.050). UCA patients spent a longer time on the ventilator, in the ICU, and in the hospital (all p = 0.001). Operative mortality was not different between UCA and RM groups (3.5% vs. 4.5%, p = 0.797) as was all-cause mortality over long-term follow-up (p = 0.093). Conclusions: While a higher incidence of stroke was observed, without reaching statistical significance, hypothermic fibrillatory arrest remains a valuable and safe tool for coronary revascularization in UCA patients, offering comparable short-term and long-term survival outcomes allowing for complete revascularization.