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Normothermic retrograde blood cardioplegia with or without preceding ischemic preconditioning
P K Kaukoranta1, M P Lepojärvi, K V Ylitalo
1Department of Anesthesiology, Oulu University Hospital, Finland.
Insights
Five minutes of preconditioning ischemia before coronary artery bypass grafting did not improve myocardial protection compared to standard cardioplegia. This study found no additional benefits in protecting the heart during surgery.
Area of Science:
- Cardiology
- Cardiac Surgery
- Ischemic Heart Disease
Background:
- Myocardial preconditioning is a potent protective mechanism against prolonged ischemia.
- Its added benefit over cardioplegia during coronary artery bypass grafting (CABG) remains unclear.
Purpose of the Study:
- To investigate if a brief preconditioning ischemia offers additional myocardial protection compared to standard cardioplegia in CABG patients.
Main Methods:
- Thirty CABG patients were randomized into control (cardioplegia) and preconditioned (5-min global ischemia then cardioplegia) groups.
- Transcardiac measurements of oxygen saturation, pH, and lactate were taken.
- Myocardial biopsies assessed adenosine triphosphate (ATP) levels.
- Creatine kinase-MB and troponin T measured myocardial injury.
Main Results:
- Preconditioning increased lactate and acid production, with a trend towards decreased ATP levels.
- ATP levels were significantly lower in the preconditioned group post-cross-clamp.
- Postoperative cardiac enzyme efflux was higher in the preconditioned group, but outcomes were similar.
Conclusions:
- A 5-minute preconditioning ischemia does not provide additional myocardial protection during CABG.
- Normothermic retrograde blood cardioplegia alone is as effective as when combined with brief preconditioning ischemia.
Background:
Preconditioning has been suggested as the most powerful mechanism of myocardial protection against prolonged ischemia. However, whether preconditioning offers additional benefits over cardioplegia during coronary artery bypass grafting is not known.
Methods:
Thirty patients undergoing coronary artery bypass grafting were randomized into two groups. After aortic cross-clamping, group 1 received antegrade blood and blood cardioplegia followed by normothermic retrograde blood cardioplegia (controls), whereas group 2 patients were subjected to 5 minutes of global ischemia followed by reperfusion with antegrade and retrograde blood cardioplegia (preconditioned). The transcardiac differences in oxygen saturation, pH, and lactate were measured during cardiopulmonary bypass. Myocardial biopsy specimens were taken from half of the patients for adenosine triphosphate determination. The extent of myocardial injury was estimated by monitoring the postoperative leakage of creatine kinase-MB and troponin T. Immediate hemodynamic recovery and postoperative complications were also observed.
Results:
The 5-minute preconditioning induced marked lactate and acid production, and myocardial adenosine triphosphate levels tended to decrease. The heart continued to produce lactate and acid during retrograde cardioplegia, but the transcardiac pH and lactate differences were similar in both groups. Adenosine triphosphate level measured at the end of the cross-clamp period was decreased to a half and one third of the preclamp values in the control and preconditioned groups, respectively. The postoperative creatine kinase-MB and troponin T effluxes tended to be more elevated in the preconditioned group, yet hemodynamic recovery and the number of postoperative complications were similar in both groups.
Conclusions:
The results show that a 5-minute preconditioning ischemia does not offer any additional benefits over normothermic retrograde blood cardioplegia during coronary artery bypass grafting.