Preconditioning Enhances Myocardial Protection in Patients Undergoing Open Heart Surgery

Abstract

To date, ischemic preconditioning is regarded as the most powerful form of endogenous myocardial protection. For the purpose of surgical myocardial protection, a few clinical studies have investigated the effects of ischemic preconditioning in conjunction with hypothermia or blood cardioplegia during open heart surgery, but the results were controversial. We now tested the hypothesis that preconditioning improves myocardial protection in patients undergoing cold crystalloid cardioplegic arrest. 36 patients needing mitral prosthetic valve replacement for rheumatic heart disease were studied. Patients were evenly divided into two groups at random. Preconditioning was elicited by two cycles of 3 minutes ischemia by occlusion of vena cava and aortic cross-clamping followed by 2 minutes reperfusion under cardiopulmonary bypass. All hearts were arrested using 4 degrees C St. Thomas' Hospital solution before the intracardiac operative program. Myocardial protective effects were mainly assessed by electrocardiac activities, leakage of myocardial enzymes, myocardial contractility, and early postoperative recovery. The results indicated that there was a significant reduction of ST-segment shifting (ST-segment elevation, 0.07 +/- 0.02 vs 0.22 +/- 0.07 mV, p < 0.05, at 4 hours post reperfusion) and smaller release of creatine kinase-MB (87 +/- 11.5 vs 143 +/- 17.2 IU/L, p < 0.05, at 12 hours post reperfusion) in the preconditioning group. Preconditioning also enhanced myocardial contractility (dp/dtmax = 1490 +/- 75 vs 1280 +/- 88 mmHg/sec, at 30 minutes post reperfusion, p < 0.05) and promoted early postoperative recovery. The present study suggests that ischemic preconditioning reduces ischemia-reperfusion injury in human hearts even when combined with cold crystalloid cardioplegia.

Evaluation by Cardiac Troponin I: The Effect of Ischemic Preconditioning as an Adjunct to Intermittent Blood Cardioplegia on Coronary Artery Bypass Grafting

“…The significant increases in CI and decreases in CTnI exhibited by the IPC patients suggest that IPC exerts its beneficial effect by reducing infarct size. Some published papers also showed improved results in surgery outcome similar to ours 4‐8,12‐15 . In contrast, other groups with protocols of either one or two cycles of five‐minute ischemia and followed by 5‐10 minutes of reperfusion did not seem to have any beneficial effect compared to controls 10,11 .…”

Mitochondrial ATP-Sensitive Potassium Channel Plays a Dominant Role in Ischemic Preconditioning of Rabbit Heart

“…With the current increasing interest in minimally invasive direct coronary artery bypass grafting and OPCAB [29,30], preconditioning may be helpful in protecting an area of the heart which is undergoing revascularization without cardiopulmonary bypass and cardioplegia. In a certain clinical setting, however, even a brief period of ischemia may be inadvisable.…”

“…The currently popular myoprotective strategy of infusing cold blood or rich crystalloid cardioplegia still results in significant mechanical or electrical derangements. Many researchers have tried to add the beneficial effects of pharmacological preconditioning to potassium cardioplegia and have had mixed results [30]. If the mitochondrial K ATP channel is a site of cardioprotection, drugs that selectively activate the mitochondrial K ATP channel can be considered as an additive to the cardioplegic solution.…”

Nicorandil – Review of Pharmacological Properties and Clinical Applications

“…Clinical evidence suggests a role for myocardial protection obtained from brief periods of antecedent ischemia in the setting of coronary angioplasty [34] , cardiac surgery [35] and acute myocardial infarction [36] . Studies in human beings suggest that nicorandil administration mimics the benefi cial effect of ischemic preconditioning [34,37] .…”