Society of Cardiovascular Anesthesiologists

Literature Reviews

Intermittent antegrade warm myocardial protection compared to intermittent cold blood cardioplegia in elective coronary surgery - do we have to change?

Ulrich F. W. Franke, Simone Korsch, Thorsten Wittwer, Johannes M. Albes, Jens Wippermann, Mirko Kaluza, Parwis B. Rahmanian and Thorsten Wahlers European Journal of Cardio-Thoracic Surgery. 23 (3) 341-346, 2003

Reviewer: Hong Liu, MD.
University of California Davis

Objective: Intermittent antegrade warm blood cardioplegia is a simple and cost-effective method of myocardial preservation. However, there are few prospective trials comparing this to established cardioplegic strategies.

Methods: In a prospective, randomized trial intermittent antegrade warm blood cardioplegia (33°C) (n=100) was compared to intermittent antegrade cold (4°C) blood cardioplegia (n=100), with respect to clinical outcome and myocardial protection as characterized by cardiac troponin-I (cTNI) and creatine kinase MB isoenzyme (CK-MB) measurements.

Results: Preoperative clinical characteristics were comparable in both groups. Defibrillation after cardiac arrest was significantly less frequent (18% versus 43%, P<0.001) and of lower intensity (3.4±10.8J versus 10.8±20.6 J, P<0,001) in the warm cardioplegia group. In addition, the postoperative ischemia markers were significantly lower in the warm cardioplegia group, cTNI: 2.01 vs. 0.95 ng/ml (P<0.001) and CK-MB: 0.30 vs. 0.23 uM (P=0.007) within the first 24 h.

Conclusion: Intermittent antegrade warm blood cardioplegia is a safe and simple myocardial preservation method for elective coronary artery bypass surgery. Significantly lower postoperative ischemic markers suggest an improved myocardial protection compared to intermittent antegrade cold blood cardioplegia in these patients.

Comments: Interest in warm blood cardioplegia was sparked by its clinical use by warm heart surgery investigators in the early 1990s reports that the arrested, normothermic heart requires 75-80% less oxygen than does the normal working heart. In order to compare intermittent antegrade warm blood cardioplegia to a standardized cardioplegia protocol with intermittent antegrade cold blood cardioplegia, these authors used a highly selected group of patients. The results were consistent with previous reports that demonstrated lower mortality, less frequent use of an intra-aortic balloon pump (IABP), lower incidence of inotropic support for weaning from cardiopulmonary bypass, earlier weaning from ventilation, and improving late survival with warm blood cardiopeglia(1).

The suggested explanation why myocardial protection using cold cardioplegia was less effective was a prolonged disturbance of cardiac metabolism and ion homeostasis. In particular, adenosine triphosphate-dependent reactions were impaired, resulting in negative affects on membrane stability, energy production, enzyme function, aerobic glucose utilization, adenosine triphosphate generation and utilization, cyclic adenosine monophosphate production, and osmotic homeostasis. Biagioli et al. demonstrated a significant increase in oxidative stress as measured by the glutathione redox status following cold blood cardioplegia. Mehlhorn and colleagues found an activation of constitutive nitric oxide synthase (cNOS or NOS-III) and an increased cGMP content after hypothermic blood cardioplegia compared to warm blood cardioplegia.

Because patient selections in the majority of current studies were limited to low risk groups, the results of these studies should only be directly extrapolated to this patient population. One study demonstrated few differences between warm and cold cardioplegia in a high-risk patient population (2). Although the benefits of warm cardioplegia in different studies vary, they consistently demonstrate that it was superior to cold cardioplegia with respect to myocardial protection. However, the advantages of combining warm and cold cardioplegia remain controversial (3) and suggest the need for further studies.

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