Comparison of Changes in Intra-myocardial Amino Acids During Use of Calafiore and Modified Del Nido Cardioplegic Solutions in Routine Coronary Artery Bypass Surgery

Twenty consecutive patients undergoing elective primary coronary artery bypass grafting were enrolled in this study. Patients were excluded from this study if they had suffered from previous myocardial infarction, had reduced ejection fraction or were undergoing combined or repeated surgery. Patients were randomly assigned to undergo surgery using one of two methods for myocardial protection:

• Group 1: Calafiore intermittent antegrade warm blood cardioplegia (consisting of normothermic pump blood, potassium chloride 2 mEq/ml and magnesium sulfate 50%). This cardioplegic solution was administered at 37 degrees C following application of the aortic cross-clamp and repeated after completion of each distal coronary anastomosis as described previously.
• Group 2: Modified del Nido intermittent antegrade cold blood cardioplegic solution (consisting of 750 ml of lactated Ringer solution, 200 ml of pump blood, 13 ml of sodium bicarbonate 8.4%, 16 ml of mannitol 20%, 4 ml of magnesium sulfate 50%, 13 ml of lidocaine 2% and 13 ml of potassium chloride 2 mEq/ml). This solution was administered as a 1-liter bolus at 3-4 degrees C following application of the aortic cross-clamp, and repeated as a 500 ml bolus if cross-clamp time extended beyond 60 minutes (none of the patients in this study).

Each patient enrolled in the study gave a written informed consent for the publication of the study data, and the study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki as reflected in a priori approval by the local human research committee number 171 dated 13 April 2022

Collection of blood samples and myocardial biopsies Peripheral blood samples were collected immediately prior to surgery and at 4, 12, 24 and 48 hours postoperatively and were used for determination of blood concentrations of cardiac enzymes (CK-MB and troponin I).

Myocardial biopsies (4-14 mg wet weight) were taken using a Tru-cut needle from the apex of the left ventricle in every patient as follows: