Differential Effects of Single versus Double Aortic Clamping on Myocardial Protection during Coronary Bypass

- >> Version of Record - Mar 1, 2009 What is This? Downloaded from imr.sagepub.com by guest on October 16, 2014 The Journal of International Medical Research 2009; 37: 341 350 [first published online as 37(2) 6] Differential Effects of Single versus Double Aortic Clamping on Myocardial Protection During Coronary Bypass O TIRYAKIOGLU, U SAYAR, S DEMIRTAS, T GONCU, G YUMUN AND A OZYAZICIOGLU . Cardiovascular Surgery, Bursa Yuksek Ihtisas Education and Research Hospital, Bursa, Turkey The effects of double (n = 60, group 1) versus single (n = 60, group 2) aortic clamping on myocardial function and protection were investigated during coronary artery bypass grafting using a heartlung pump. In group 1, after opening the cross clamp, proximal anastomosis was completed using side clamps and, in group 2, distal and proximal anastomosis was completed with a single clamp. Cross clamping time in the single-clamp patients (group 2; 77.1 min) was significantly higher than in the double-clamp patients (group 1; 62.9 min). Troponin T was significantly higher in group 2 than in group 1 h and 24 h after surgery. Post-operative left ventricular ejection fraction decreased in both groups, but this was not statistically significant. Post-operative wall motion score index and myocardial performance index increased significantly in both groups compared with the pre-operative level. Overall, the doubleclamp technique provided better myocardial protection than the singleclamp technique and neither technique seemed to have a negative impact on the early post-operative global functioning of the left ventricle, however the effect of these techniques on the global functioning of the left ventricle in the late postoperative period needs to be evaluated. Myocardial damage during cardiac surgery is one of the most important factors in mortality and morbidity.1 It increases the need for high-dosage inotropic agents and intra-aortic balloon pump use in the early post-operative period, eventually leading to myocardial fibrosis in the late post-operative period.2 Myocardial ischaemia can develop during cardiac surgery, when the heart is stopped to create a bloodless and still area, due to disequilibrium between the oxygen given and the amount needed, and myocardial protection during surgery can decrease the amount of ischaemic myocardial damage that occurs.2 The risk of ischaemia may be reduced by lowering the oxygen consumption and providing more oxygen and metabolites. When the heart stops after placing a cross clamp on the aorta it needs much less oxygen than when it is empty, Downloaded from imr.sagepu3b.c4om1by guest on October 16, 2014 palpitating or in fasciculation, and lowering the temperature of the heart also reduces the cellular metabolic rate. Whilst the heart is not working, the infusion of solutions containing oxygen to the coronary tissues, as well as the infusion of solutions rich in metabolites for aerobic and anaerobic energy production, helps to equilibrate oxygen and substrate levels.1,2 In the single-clamp technique, the heart is started after the proximal anastomosis has been performed, whereas in the doubleclamp technique the cross clamp is taken out after the distal anastomosis has been finished, the heart is started and the proximal anastomosis is then performed using a side clamp. At this stage the left internal mammary artery (LIMA), or the right internal mammary artery (RIMA) if used, starts to work. The heart is fed and the ischaemia time is shortened. In the past 50 years many techniques have been developed for protecting the heart during coronary bypass surgery. In 1950, hypothermia during cardiac surgery in dogs was used3 and, in 1955, the first experimental study of cardiac arrest with a cardioplegic solution containing potassium was performed.4 In 1973, it was shown that, in comparison with the fibrillating heart, oxygen consumption by heart muscle is lower whilst in arrest with potassium.5 In later years Tyers et al.6 showed that cardioplegia with a low potassium concentration is safe. To date, studies using single or double aortic clamps have mostly investigated their effects on the neurological complications associated with cardiac surgery. The present study, however, aimed to investigated the effects of single or double clamping of the aorta on myocardial function and protection in coronary artery bypass graft (CABG) surgery using a heartlung pump. Patients and methods PATIENTS Patients undergoing elective CABG at the . Bursa Yuksek Ihtisas Education and Research Hospital, Bursa, Turkey, from May 2006 to December 2007, were included in this prospective, randomized study. Written informed consent for participation was obtained. from each patient and the Bursa Yuksek Ihtisas Education and Research Hospital Ethics Committee approved the protocol. Patients in whom three or four CABG were needed were included. Excluded patients were those who needed only one or two CABGs, those with an aortic diameter 4 cm, those who had calcific aorta disease, those who needed another operation as well as CABG (such as ventricular aneurismectomy, mitral valve replacement, or aortic valve replacement), those who had renal or hepatic failure, those who were operated on in emergency conditions, those who had chronic obstructive pulmonary disease (COPD), or those who were taken in for revision of or had undergone previous cardiac surgery. RANDOMIZATION AND SURGICAL PROCEDURES Cases were randomized to one of two groups undergoing elective CABG using either a double clamp (group 1) or single clamp (group 2) of the aorta. In group 1, proximal anastomosis was performed after taking out the cross clamp and positioning a side clamp. In group 2, distal and proximal anastomoses were performed under one clamp. Both techniques were performed by the same surgeon and the same surgical team. All cases were taken into cardiopulmonary bypass under hypothermic conditions (28 31 C) with 2.2 l/min per m2 total systemic blood flow. In all cases, standard median sternotomy was performed. Later, the LIMA Downloaded from imr.sagepu3b.c4om2by guest on October 16, 2014 and a convenient vena saphena manga graft from the lower extremity were removed and prepared. Cardiopulmonary bypass was performed by arterial cannulation to the ascending aorta and two-stage venous cannulation to the right atrium auricula. A cardioplegia cannula (Bicakcilar, Istanbul, Turkey) was inserted into the aortic root and all cases were initially given anterograde cold crystalloid cardioplegia (St Thomas Hospital cardioplegic solution II [Plegisol], Abbott Laboratories, Chicago, IL, USA) to provide myocardial protection. A temperature probe inserted into the apex of the left ventricle was used to ensure that cardioplegia maintained the temperature between 12 C and 15 C; myocardial temperature was measured every 10 min in both groups. At 5 min following cold crystalloid cardioplegia infusion the mean myocardial (...truncated)