PRECONDITIONING THE HUMAN HEART DURING AORTOCORONARY BYPASS-SURGERY.
EUR J CARDIO-THORAC
270 - 276.
Ischaemic preconditioning, with brief periods of ischaemia separated by reperfusion, increases myocardial resistance to infarction. In addition, preconditioning leads to preservation of myocardial adenosine triphosphate (ATP) during ischaemia. We propose that ischaemic preconditioning may share fundamental similarities with intermittent aortic cross-clamping utilised during aorto-coronary bypass surgery. The aim of this study was to test the hypothesis that controlled aortic cross-clamping is a form of preconditioning using conservation of ATP as the end point. Patients randomised to the preconditioned group (preconditioned, n = 10 patients), received a preconditioning stimulus of two 3-min periods of cross-clamping separated by 2 min of reperfusion prior to an ischaemic insult of 10 min ischaemia and ventricular fibrillation. In the control group (control, n = 10 patients) hearts received 10 min cross-clamping with fibrillation without prior preconditioning. Myocardial ATP, creatine phosphate (CP), and lactate were determined from biopsy specimens taken at the onset of cardiopulmonary bypass (A), at the end of preconditioning (B), and at the end of 10 min of ischaemic insult (C). Results: expressed as mean +/- SE (mumol/g dry weight). Preconditioning resulted in a significant depletion of the myocardial ATP content (preconditioned, B: 11.7 +/- 0.9 vs A: 19.8 +/- 1.4; P < 0.01). Furthermore 10 min of ischaemia resulted in a significant depletion of ATP in the control patients (control, C: 7.2 +/- 0.3 vs B: 19.5 +/- 1.2; P < 0.005). Preconditioning slowed down the rate of myocardial ATP depletion in the preconditioned group to such an extent that, at the end of the prolonged ischaemic insult, preconditioned hearts had significantly higher ATP content than the controls (preconditioned, C: 11.5 +/- 0.8 vs control, C: 7.2 +/- 0.3; P < 0.005). Pronounced effects of ischaemia on myocardial CP content and lactate production were also observed. These data demonstrate that ischaemic preconditioning with two 3-min periods of aortic cross-clamping, separated by 2 min of reperfusion, limit myocardial ATP wastage during a 10-min period of sustained ischaemia. This may suggest that controlled intermittent aortic cross-clamping may be a form of ischaemic preconditioning and may offer protection to the myocardium during extensive aorto-coronary bypass surgery.
|Title:||PRECONDITIONING THE HUMAN HEART DURING AORTOCORONARY BYPASS-SURGERY|
|Keywords:||PRECONDITIONING, INTERMITTENT AORTIC CROSS-CLAMPING, ATP|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Cardiovascular Science|
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