St Thomas' Hospital polarizing blood cardioplegia improves hemodynamic recovery in a porcine model of cardiopulmonary bypass.

Objective: Cardiac surgery demands highly effective cardioprotective regimens. We previously demonstrated improved cardioprotection with "polarized" compared with "depolarized" arrest. This study uses a clinically relevant porcine model of cardiopulmonary bypass to compare the efficacy of blood-based St Thomas' Hospital polarizing cardioplegia (STH-Pol-B) with blood-based St Thomas' Hospital hyperkalemic cardioplegia (STH2-B).

Methods: Pigs were monitored and subjected to normothermic cardiopulmonary bypass, cardiac arrest via antegrade cold (4°C) blood cardioplegia (STH2-B, control group: n = 6 or STH-Pol-B, study group: n = 7), and global ischemia (60 minutes) followed by on-pump reperfusion (60 minutes) and subsequent off-pump reperfusion (90 minutes). At termination, tissue samples were taken for analysis of high-energy phosphates, ultrastructure, and microRNAs. The primary endpoint of this study was creatine kinase-muscle/brain release during reperfusion.

Results: Creatine kinase-muscle/brain was comparable in both groups. After pigs were weaned from cardiopulmonary bypass, hemodynamic parameters such as mean arterial pressure (P = .007), left ventricular systolic pressure (P < .001), external heart work (P = .012), stroke volume (P = .015), as well as dp/dt (P = .027), were improved with polarizing cardioplegia. Wedge pressure was significantly lower in the study group (P < .01). Energy charge was comparable between groups. MicroRNA-708-5p was significantly lower (P = .019) and microRNA-122 expression significantly (P = .046) greater in STH-Pol-B hearts.

Conclusions: Polarized cardiac arrest offers similar myocardial protection and enhances functional recovery in a porcine model of cardiopulmonary bypass. Differential expression of microRNAs may indicate possible new ischemia-reperfusion markers. These results confirm the noninferiority and potential of polarized versus depolarized arrest.