The impact of continuous retrograde cardioplegia compared with intermittent antegrade cardioplegia on left and right ventricular functions during coronary artery grafting in patients with left ventricular dysfunction ( transesophageal echocardiography examination and electron microscopic evaluation)

Abstract

Background During coronary artery bypass grafting (CABG), both the quality of myocardial protection and the preoperative myocardial status directly influence the postoperative cardiac outcome, recovery, and complications. The aim of this study was to compare the protective effects of continuous retrograde cold blood cardioplegia with intermittent antegrade cold blood cardioplegia at systemic normothermia on left ventricular (LV) and right ventricular (RV) systolic and diastolic functions in patients with poor myocardial contractility, who underwent CABG surgery, in terms of the intraoperative course and the postoperative clinical outcome. Patients and methods Patients were randomly divided into two equal groups (20 patients each) according to the myocardial protection technique: antegrade group: intermittent antegrade cold blood cardioplegia and retrograde group: continuous retrograde cold blood cardioplegia. In the antegrade group, warm cardioplegia was administered through an aortic root catheter with infusion pressure not exceeding 150 mmHg. The initial dose used was 10 ml/kg, followed by 5 ml/kg every 30 min afterwards. In the retrograde group, cardioplegia was administered through a coronary sinus cannula at the same volume and composition, but with pressure not exceeding 40 mmHg and was continuously infused. Systemic temperature was allowed to drift to 35πC. Hemodynamic parameters were recorded after induction of anesthesia, after weaning from bypass, and before transportation to ICU. Transesophageal echocardiography examination (for the assessment of RV and LV systolic and diastolic functions) was carried out at the same time points. Cardiac enzymes and serum lactate were measured after induction, after weaning from bypass, and 8 h postoperatively. Clinical outcomes in terms of the use of postoperative inotropic support or the need for defibrillation or pacing were recorded. Electron microscopic evaluation of RV and LV biopsies was carried out using a semiquantitative method with scoring from 0 (apparently normal) to 3 (severely damaged). Results Electron microscopic evaluation of LV and RV myocardial biopsies indicated significantly less cellular edema, mitochondrial degeneration, and myofibrillar damage in the retrograde group as compared with the antegrade group. Echo data showed no statistically significant difference between the antegrade group and the retrograde group. The need for vasodilators or inotropes and weaning time were significantly lower in the retrograde group. Conclusion We conclude that retrograde cold blood cardioplegia provided myocardial protection and even early recovery of myocardium after CABG surgery.