Acute Myocardial Infarction in the Rat Model: Esmolol-Based Cardioplegia versus Potassium-Based Cardioplegia

Objectives: Esmolol-based cardioplegia has been shown to have beneficial advantages for cardioprotection compared to potassium-based cardioplegia. We investigated the influence of an esmolol crystalloid cardioplegia (ECCP), esmolol blood cardioplegia (EBCP), and Calafiore BCP (Cala), on cardiac function, metabolism, and infarct size in stable rat hearts and compared these three solutions with Buckberg BCP (Buck) in infarcted rat hearts.

Methods: The hearts of 42 male Wistar rats were excised and inserted into a blood-perfused isolated Langendorff heart apparatus. Eighteen hearts were subjected to arrest with ECCP, EBCP, or Cala for 90-min global ischemia. Further 24 hearts underwent acute myocardial infarction by ligation of the left anterior descending coronary artery (LAD) at least 30 minutes before aortic clamping. In the infarcted hearts, after aortic clamping, ECCP, EBCP, Cala, or Buck was administered. During reperfusion, coronary blood flow, left ventricular developed pressure (LVPdp), left ventricular end diastolic pressure (LVEDP), dLVP/dtmax, and dLVP/dtmin were recorded. Additionally, oxygen consumption and lactate production were determined. The infarct size in infarcted hearts was measured by Triphenyl tetrazolium chloride staining.

Results: In hearts without infarction, esmolol-based cardioplegia hemodynamically (LVDP [ECCP 100% of baseline (BL), EBCP 86% of BL, Cala 57% of BL], LVDP/dtmax [ECCP 128% of BL, EBCP 109% of BL, Cala 85% of BL], LVDP/dtmin [ECCP 114% of BL, EBCP 80% of BL, Cala 73% of BL]) recovered better from ischemia/reperfusion. Accordingly, coronary flow (ECCP 99% of BL, EBCP 71% of BL, Cala 48% of BL) was better after esmolol-based cardioplegia. At the end of reperfusion, myocardial oxygen consumption was lower in Cala (52% of BL) than in the ECCP (99% of BL) and EBCP (64% of BL).

In hearts with infarction, LVDP (ECCP 84% of BL, EBCP 60% of BL, Cala 56% of BL), LVDP/dtmax (ECCP 97% of BL, EBCP 72% of BL, Cala 79% of BL), and LVDP/dtmin (ECCP 92% of BL, EBCP 59% of BL, Cala 69% of BL) showed better hemodynamic recovery only with ECCP, while the results for ECBP and Cala were similar. In infarcted hearts, coronary flow recovered better after administration of esmolol-based cardioplegia (ECCP 72% of BL, EBCP 81% of BL, Cala 54% of BL, Buck 55% of BL).

Conclusion: In stable perfused hearts and in an in vitro model of acute myocardial infarction, esmolol-based cardioplegia shows better myocardial protection compared to potassium-based BCP solutions.