Abstract
OBJECTIVE: To determinate the alterations suffering by myocardium in the hypothermic retrograde continuous blood cardioplegia with antegrade warm cardioplegic induction. METHOD: A metabolic analysis of hypothermic retrograde continuous blood cardioplegia with antegrade warm cardioplegic induction was performed in a prospective study of 15 patients scheduled for elective coronary artery bypass grafting. Arterial and coronary sinus blood samples were simultaneously taken: before establishing cardiopulmonary bypass, after anterograde warm cardioplegic induction, when the aortic clamp was removed and 10, 30 and 60 minutes after reperfusion to analyze the oxygen content and lactate concentration. Four transmural left ventricular biopsy samples were obtained: before aortic clamping, immediately after the initial cardioplegia bolus, immediately before aortic declamping and 30 minutes after reperfusion to analyze the levels of ATP, ADP, AMP and lactate in the myocardium. The CK-MB isoenzyme was analysed in venous blood samples. RESULTS: There were no mortalities in the group. Inotropic support was not necessary in any patients and no peri- or post-operative myocardial infarction was detected. There was a decrease in the arterial-venous extraction of oxygen and lactate in the heart during reperfusion, a partial recovery occurred at 60 minutes of reperfusion. The levels of ATP and the other nucleotides in the myocardium were maintained during aortic clamping, but these levels decreased during the first 30 minutes of reperfusion. The lactate accumulated in the heart muscle during aortic clamping with a decrease occurring during reperfusion. CONCLUSIONS: From a metabolic point of view the method could not avoid an anaerobic metabolism during cross-clamping and only after 60 minutes of reperfusion there was a satisfactory metabolic recovery. These alterations are probably a reflection of cellular ischemic injury that occurs during cross-clamping and they seem to be of transitory effect. A better myocardium protection was observed with the addiction of anterograde warm induction cardioplegia.
Highlights
In spite of the great development in surgical techniques of off-pump coronary artery bypass grafting, myocardial protection has not lost its importance due to high number of cases in which it is of extreme necessity
The levels of adenosine triphosphate (ATP) and the other nucleotides in the myocardium were maintained during aortic clamping, but these levels decreased during the first 30 minutes of reperfusion
From a metabolic point of view the method could not avoid an anaerobic metabolism during crossclamping and only after 60 minutes of reperfusion there was a satisfactory metabolic recovery. These alterations are probably a reflection of cellular ischemic injury that occurs during cross-clamping and they seem to be of transitory effect
Summary
In spite of the great development in surgical techniques of off-pump coronary artery bypass grafting, myocardial protection has not lost its importance due to high number of cases in which it is of extreme necessity. Several studies have shown better clinical results using continuous sanguineous cardioplegia [4,5,6,7] and retrograde perfusion through the coronary sinus [8,9]. The method of retrograde cardioplegia is considered better for patients with significant injury of the left coronary artery trunk and in patients submitted to redo coronary artery bypass grafting (CABG) [10,11]. Clinical works on myocardial protection rarely identified significant differences in the results [12,13], works using metabolic analysis are important as it is possible to verify small differences in the results
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