The efficacies of modified mechanical post conditioning on myocardial protection for patients undergoing coronary artery bypass grafting

Durdu et al. Journal of Cardiothoracic Surgery 2012, 7:73 http://www.cardiothoracicsurgery.org/content/7/1/73 RESEARCH ARTICLE Open Access The efficacies of modified mechanical post conditioning on myocardial protection for patients undergoing coronary artery bypass grafting Serkan Durdu1,2*, Mustafa Sirlak1, Demir Cetintas1, Mustafa Bahadir Inan1, Sadik Eryılmaz1, Evren Ozcinar1, Levent Yazicioglu1, Atilla Halil Elhan3, Ahmet Ruchan Akar1,2 and Adnan Uysalel1 Abstract Background: Coronary artery bypass grafting (CABG) with cardioplegic cardiac arrest and cardiopulmonary bypass (CPB) is associated with myocardial injury. The aim of this study was to investigate whether a modified mechanical post-conditioning (MMPOC) technique has a myocardial protective effect by enhancing early metabolic recovery of the heart following revascularization. Methods: A prospective, randomized trial was conducted at a single-center university hospital performing adult cardiac surgery. Seventy-nine adult patients undergoing first-time elective isolated multivessel coronary artery bypass grafting were prospectively randomized to MMPOC or control group. Anesthetic, cardiopulmonary bypass, myocardial protection, and surgical techniques were standardized. The post reperfusion cardiac indices, inotrope use and biochemical-electrocardiographic evidence of myocardial injury were recorded. The incidence of postoperative complications was recorded prospectively. Results: Operative characteristics, including CPB and aortic cross-clamp time, were similar between the two groups (p>0.05). The MMPOC group had lower troponin I and other cardiac biomarkers level post CPB and postoperatively, with greater improvement in cardiac indices (p<0.001). MMPOC shortened post surgery hospitalization from 9.1 ± 2.1 to 7.5 ± 1.6 days (p<0.001). Conclusions: MMPOC technique promotes early metabolic recovery of the heart during elective CABG, leading to better myocardial protection and functional recovery. Keywords: Cardiopulmonary bypass, Myocardial protection, Ischemia-reperfusion injury, Coronary artery bypass grafting, Post-conditioning Background Reperfusion has the potential to cause additional reversible and irreversible damage to the myocardium, which is called reperfusion injury [1,2]. The existence of postconditioning (POC) is the newest evidence that has emerged to support the concept of reperfusion injury. * Correspondence: 1 Department of Cardiovascular Surgery, Heart Center, Ankara University School of Medicine, Mamak Street, 06340, Dikimevi-Ankara, Turkey 2 Stem Cell Institute, Ankara University, Ankara, Turkey Full list of author information is available at the end of the article The term post conditioning refers to the phenomenon in which multiple brief periods of reperfusion interspersed with brief periods of ischemia (10–60 s) result in a reduction in infarct size [3,4]. Generally, three cycles of ischemia/reperfusion are required to produce a maximal POC effect, although four and six cycles have been shown to be effective by some investigators [3,4]. However, it is the interval of reperfusion and ischemia that is the most critical factor in determining how efficacious POC will be. POC protocols shown to be maximally effective at reducing infarct size range from 10 to 60 s depending on the specific species being studied [3,4]. © 2012 Durdu et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Durdu et al. Journal of Cardiothoracic Surgery 2012, 7:73 http://www.cardiothoracicsurgery.org/content/7/1/73 The aim of our study was to determine the efficacy of a modified type of mechanical post-conditioning (MMPOC) in patients undergoing elective coronary revascularization, with specific attention to biochemical markers of ischemic injury and post-surgical recovery of the patients and to show whether there is room for protection by post-conditioning amongst all the other cardioprotective factors. Methods Patients and protocol This study was approved by the Institutional Review Board of the University of Ankara and consisted of 79 patients undergoing elective primary coronary revascularization with ≥99% stenosis of the left anterior descending (LAD) artery. So as to include patients with relatively large volumes of at-risk myocardium, we limited our analysis to those patients exhibiting proximal occlusion of the LAD. Patients undergoing valve replacement, combined valve replacement/coronary revascularization, or preoperative coronary revascularization was excluded from the study. Informed consent was obtained from all patients before enrollment. Randomisation Patients were allocated to the MMPOC group or the study group using a computer-generated randomization code. Participants were randomly assigned in a 1:1 ratio. The study was open label and the primary investigator, who was not the treating physician and nurses informed the participants about their allocated treatment. Data for primary outcomes were assessed by use of a computer. Data collection and definitions Baseline, procedural, and follow-up data were stored prospectively in a database located at the University of Ankara. Patients’ preoperative risk factors were recorded and EuroSCOREs were calculated for each patient. Patients’ preoperative characteristics were recorded including age, sex, size, preexisting medical conditions, preoperative medications, preoperative ejection fractions. Intraoperative variables of which number of coronary bypass grafts, duration of cardiopulmonary bypass (CPB), duration of aortic cross-clamp, requirement for inotropic drugs, and/or intra-aortic balloon support, and blood product use were included. Postoperative data comprised myocardial infarction, cardiac tamponade, reoperation for occlusion or other causes, requirement of intra-aortic balloon pump support, neurologic complications, renal dysfunction, chest tube drainage during the first 24 postoperative hours, total chest tube drainage, the length of mechanical ventilator support, pneumonia, multiorgan failure, gastrointestinal complications, sepsis, coma, the Page 2 of 8 length of intensive care unit (ICU) stay, and readmission within 90 days after surgery. Adverse events were defined as death, perioperative myocardial infarction, stroke, re-exploration due to bleeding, respiratory insufficiency, and renal failure. Perioperative myocardial infarction (MI) was defined as either new Q waves or ischemic ST segment changes with concomitant elevations of creatine kinase isoenzyme (CK-MB) > 5 times the upper limit of the reference range or a CK-MB to total creatine kinase (CK) ratio > 10% occurring within 48 hours after surgery or troponin I (TnI) > 1 ng/mL. Renal dysfunction was defined as rise of s (...truncated)