Experimental comparison of esmolol- and blood-based cardioplegia for long aortic clamping times.

Objectives: Various cardioplegia solutions aim to protect the myocardium during cardiac surgery. This study compares hemodynamic performance, myocardial metabolism, and ultrastructural preservation in rat hearts after applying esmolol crystalloid cardioplegia(ECCP) or Calafiore blood cardioplegia(Cala).

Materials and methods: Hearts from 18 Wistar rats were perfused in a Langendorff system. Following 120 min of ischemia at 36°C, hearts received either ECCP at 32°C for 3 min or Cala at 36°C for 2 min every 20 min. During 90 min of reperfusion, coronary blood flow(CF), left ventricular developed pressure(LVDP), and contraction/relaxation velocities (+/-dp/dt) were recorded. Myocardial oxygen consumption, lactate production, and troponin I levels were measured. Electron microscopy was used for ultrastructural assessment.

Results: Baseline(BL) values of LVDP, CF and +/-dp/dt were similar between the two groups. After 90 min of reperfusion, CF was significantly higher in the ECCP group: 85±43% of BL in the ECCP group vs. 42±24% of BL in the Cala group(p=0.002). At the end of reperfusion, hearts exposed to ECCP had higher LVDP (91±40%) values than Cala (43±10%), indicating improved cardiac recovery with ECCP. Myocardial contraction and relaxation were notably better in the ECCP group: dLVP/dt max was 111 ±40% vs. 59±13% in the Cala group(p=0.002); dLVP/dt min 88±34% vs. 40±7%(p=0.001). Troponin I levels measured in Cala hearts at the end of reperfusion were higher than in ECCP hearts (Cala 1102.6 ±361.3]ng/ml vs. ECCP442.3 ±788.4]ng/ml,p=0.036).

Conclusion: In rat hearts, ECCP offers better hemodynamic recovery and protects the myocardium from ischemia/reperfusion-related damage better than Cala blood cardioplegia even with aortic clamping times of 12.