The effect of preconditioning (ischemic and pharmacological) on myocardial necrosis following coronary artery bypass graft surgery.

OBJECTIVES: Ischemic preconditioning is known to protect the human heart from ischemic injury during coronary artery bypass graft (CABG) surgery but is not practised routinely. Adenosine A1 receptor agonists may confer protection in this setting by mimicking preconditioning. The aim of this study was to compare preconditioning, by ischemia or an adenosine A1 receptor agonist (GR79236X), with an established method of myocardial protection in CABG, namely intermittent cross-clamp fibrillation.

METHODS: In this prospective double-blind study, 30 CABG patients were randomised to receive: (a) intermittent cross-clamp fibrillation (control), (b) pharmacological preconditioning (GR79236X), or (c) ischemic preconditioning (two 3-min periods of ischemia, each followed by 2 min of reperfusion). Surgery was performed under standardised conditions by one surgeon (WBP). The primary endpoint was cardiac troponin T release.

RESULTS: Mean cardiopulmonary bypass time was 91+/-11.6 (S.D.) min. Mean ischemic time was 33+/-5.5 (S.D.) min with no inter-group difference. Mean troponin T at 72 h was highest in the control group (1.32+/-0.99 (S.D.) microg/l), similar in the GR79236X group (1.22+/-1.22 (S.D.) microg/l; P=0.85) and significantly reduced in the ischemic preconditioning group (0.58+/-0.40 (S.D.) microg/l; P=0.04).

CONCLUSIONS: Ischemic preconditioning is superior to the other techniques at limiting myocardial necrosis during CABG. Pharmacological preconditioning may confer some benefit but this was not statistically shown using a specific adenosine A1 agonist (GR79236X).