Experimental Comparison of Esmolol- and Blood-Based Cardioplegia for Long Aortic Clamping Times

Objectives

After cardiac surgery, long aortic clamping times and extracorporeal circulation times are associated with worse outcomes. 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 minutes of ischemia at 36 °C, hearts received either ECCP at 32 °C for 3 minutes or Cala at 36 °C for 2 minutes every 20 minutes. During 90 minutes 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 minutes of reperfusion, CF was significantly higher in the ECCP group: 85 ± 43% of BL in the ECCP group versus 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% versus 59 ± 13% in the Cala group (p = 0.002), and dLVP/dt_min was 88 ± 34% versus 40 ± 7% (p = 0.001). Troponin I levels measured in Cala hearts at the end of reperfusion were higher than in ECCP hearts (Cala 1,102.6 ± 361.3 ng/mL vs. ECCP 442.3 ± 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 120 minutes.