Warm blood versus St. Thomas cardioplegia for myocardial protection in patients undergoing coronary artery bypass grafting

Aim
We retrospectively analyzed early results of coronary artery bypass grafting (CABG) surgery using antegrade intermittent warm blood or St. Thomas cold crystalloid cardioplegia.

Material and methods
From January 2015 to May 2018, in 556 patients undergoing isolated CABG, cardiac arrest was obtained using warm blood (WB group, n = 402) or St. Thomas cardioplegia (ST group, n = 154). Myocardial enzymes’ release was calculated at the end of CABG (time 0), 24, and 48 hours postoperatively.

Results
In-hospital mortality was 1.74% in the WB group, 0.65% in the ST group. As compared with the WB group, in the ST group the number of distal coronary artery anastomoses per patient was significantly higher (2.9 ±0.9 vs. 2.6 ±0.8) (p = 0.003), despite a similar required number of cardioplegia doses per patient (2.2 ±0.9 vs. 2.3 ±0.9). The incidence of perioperative myocardial infarction, low cardiac output syndrome, myocardial enzymes release, rate of CK-MB/CK ratio > 10% was similar. As compared with the WB group, in the ST group the proportion of patients with CK-MB/CK ratio > 5% was lower at each time point of evaluation, with a significant difference at time 0 (30.5% vs. 48%) (p = 0.0005), whereas the need for blood transfusion per patient was higher (1.3 ±2.0 vs. 0.54 ±1.3) (p < 0.0001). Within the WB group, the rate of CK-MB/CK ratio > 5% was significantly reduced when dose administration was repeated within 18 minutes compared to 20–25 minutes (36% vs. 59%) (p < 0.0001). Duration of the extracorporeal circulation and of the aortic cross-clamping, and the mean number of coronary bypasses were not identified as risk factors either for the CK-MB/CK ratio greater than 10% or greater than 5%.

Conclusions
Based on a single-center experience, both types of cardioplegia are associated with equivalent clinical results. St. Thomas cardioplegia, despite the greater number of grafts per patient and therefore greater extracorporeal circulation and aortic cross-clamping times, and greater postoperative need for blood transfusion, appears to be associated with a lower rate of CK-MB ratio > 5%. Warm blood cardioplegia allows better protection when administered in an 18-minute re-dosing interval.