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Intermittent warm blood cardioplegia does not provide adequate myocardial resuscitation after global ischaemia
A B Ericsson1, T Kawakami, J Vaage
1Department of Thoracic Surgery, Karolinska Hospital, Stockholm, Sweden.
Insights
Continuous warm blood cardioplegia better preserved left ventricular function after global ischemia than intermittent delivery. Intermittent cardioplegia led to decreased function and increased mortality in this porcine model.
Area of Science:
- Cardiovascular Surgery
- Cardiac Anesthesia
- Cardiomyocyte Protection
Background:
- Intermittent warm blood cardioplegia is a debated method for myocardial protection during cardiac surgery.
- Surgeons often question its adequacy in preserving heart function during ischemic events.
Purpose of the Study:
- To compare the efficacy of intermittent versus continuous warm blood cardioplegia.
- To evaluate their effectiveness in myocardial resuscitation following global ischemia.
Main Methods:
- Pigs underwent cardiopulmonary bypass and 30 minutes of global ischemia.
- Continuous (n=7) or intermittent (n=10) warm blood cardioplegia was administered for 45 minutes.
- Left ventricular function was assessed using pressure-volume loops and the conductance catheter technique post-reperfusion.
Main Results:
- Continuous cardioplegia maintained global left ventricular function (PRSW unchanged).
- Intermittent cardioplegia significantly decreased global left ventricular function (PRSW decreased, P=0.04).
- Diastolic function deteriorated in both groups, but more so with intermittent cardioplegia (EDPVR increased, P=0.005).
Conclusions:
- Continuous warm blood cardioplegia provided superior myocardial protection compared to intermittent delivery in this model.
- Intermittent warm blood cardioplegia was associated with reduced left ventricular function post-ischemia.
Objective:
Intermittent warm blood cardioplegia is controversial, and many surgeons consider it inadequate for myocardial protection. The purpose of this study was to compare intermittent and continuous warm blood cardioplegia as resuscitation in hearts exposed to global ischaemia.
Methods:
Pigs were put on cardiopulmonary bypass (CPB) and subjected to 30 min of warm, "unprotected", global ischaemia, followed by continuous (n = 7) or intermittent (n = 10, 12 ml/kg every 10 min) warm (34 degrees C) antegrade blood cardioplegia for 45 min (delivery pressure 75-80 mmHg) and weaned from CPB 45 to 60 min later. Indices of left ventricular function were acquired with the conductance catheter technique and pressure-volume loops at baseline and after 90 min of reperfusion.
Results:
Cardioplegia was delivered during 17% of the cross-clamp time. Global left ventricular function, evaluated by preload recruitable stroke work (PRSW), was unchanged after continuous cardioplegia; 95 (76-130) (median (quartile interval)) to 91 (90-104) erg/ml x 10(3), but decreased after intermittent cardioplegia; 122 (100-128) to 64 (23-93) erg/ml x 10(3). Two pigs in the intermittent group weaned from CPB, but died before post-bypass measurement. A 95% confidence interval for the difference in post-bypass mean PRSW was estimated as 32 +/- 30 erg/ml x 10(3) (corresponding to P = 0.04 for comparison between treatments). The end-diastolic pressure-volume relation (EDPVR) increased from 0.17 (0.14-0.20) (continuous) and 0.15 (0.12-0.22) (intermittent) mmHg/ml to 0.27 (0.22-0.33) (P = 0.018) and 0.39 (0.25-0.66) (P = 0.005) mmHg/ml, respectively, indicating deterioration in diastolic function. No difference between groups was found in EDPVR, stiffness constant, troponin T release or myocardial water content.
Conclusion:
Following acute global ischaemia left ventricular global function was, in this model, less preserved using warm intermittent compared to warm continuous cardioplegia.