Warm blood versus St. Thomas cold crystalloid cardioplegia in patients affected by acute coronary syndromes undergoing coronary artery bypass surgery

Background: We have evaluated in a single-center retrospective study early and mid-term outcomes of intermittent warm blood and St. Thomas cold crystalloid cardioplegia in patients referred for coronary artery bypass grafting (CABG) due to acute coronary syndromes (ACS). From January 2018 to December 2023, 336 consecutive patients underwent isolated on-pump CABG (unstable angina=234, 69.6%; N-STE-myocardial infarction=66, 19.6%; STE-myocardial infarction=36, 10.7%). Myocardial protection was achieved using warm blood cardioplegia (WBC, n=215, 64%) or cold crystalloid cardioplegia (CCC, n=121, 36%). Primary endpoints of the study were the rate of operative mortality and low cardiac output syndrome, cardiac enzymes CK-MB, and troponin-I release in the postoperative period, i.e., at time 0 and 12 and 24 h after CABG. Secondary endpoints were the assessment of postoperative ventricular systolic function and mid-term results. Results Baseline characteristics and preoperative variables including cardiac enzymes values were similar. Based on the diferent administration protocol, as compared with CCC group, in WBC group, required number of cardioplegia’s doses per patient was higher (2.6±0.8 vs 2.1±0.8; P<0.0001), despite lower number of distal coronary artery anastomoses (2.8±0.7 vs 3.0±0.8; P=0.027) and shorter time of aortic cross-clamping (60±21 vs 67±21 min; P=0.006). Completeness of revascularization was similar (100% vs 98%). Postoperative low cardiac output syndrome (5.8% vs 4.6%), mortality rate (3.3% vs 1.4%), left-ventricular ejection fraction (0.52±0.07 vs 0.53±0.07), overall CK-MB and troponin-I enzymes release were similar for two cardioplegia groups (P=NS, for all measurements). Within the WBC group, troponin-I and CK-MB release at time 0, 12, and 24 h were lower when cardioplegia was repeated within 18 min in comparison with a longer time of administration (P<0.05, for both measurements). The rate of CK-MB/CK-total ratio>5% was signifcantly lower at 12 and 24 h after CABG when WBC was repeated within 18 min (P<0.05). Cross-clamp duration (65±30 vs 64±22 min) did not signifcantly correlate with CK-MB/CK-total ratio>5% (P=0.81) in comparison to lower ratios. Five-year survival was similar (97%±1.5% vs 96%±3.0%; P=0.83). Conclusions WBC and CCC seem to guarantee equivalent and satisfactory outcomes. A better protection appears to be achieved when WBC was administered in 18-min re-dosing interval.