Reduction of oxidative stress does not affect recovery of myocardial function: warm continuous versus cold intermittent blood cardioplegia

Influence of Coronary Artery Bypass Grafts on Blood Aminothiols in Patients with Coronary Artery Disease

Coronary artery disease (CAD) and the coronary artery bypass graft (CABG) are associated with a decreased blood glutathione (bGSH) level. Since GSH metabolism is closely related to other aminothiols (homocysteine and cysteine) and glucose, the aim of this study was to reveal the associations of bGSH with glucose and plasma aminothiols in CAD patients (N = 35) before CABG and in the early postoperative period. Forty-three volunteers with no history of cardiovascular disease formed the control group. bGSH and its redox status were significantly lower in CAD patients at admission. CABG had no significant effect on these parameters, with the exception of an increase in the bGSH/hemoglobin ratio. At admission, CAD patients were characterized by negative associations of homocysteine and cysteine with bGSH. All these associations disappeared after CABG. An association was found between an increase in oxidized GSH in the blood in the postoperative period and fasting glucose levels. Thus, CAD is associated with the depletion of the intracellular pool and the redox status of bGSH, in which hyperhomocysteinemia and a decrease in the bioavailability of the extracellular pool of cysteine play a role. The present study indicates that CABG causes disruptions in aminothiol metabolism and induces the synthesis of bGSH. Moreover, glucose becomes an important factor in the dysregulation of GSH metabolism in CABG.

Antioxidant activity in off and on-pump coronary artery bypass grafting and valve replacement surgery

OBJECTIVES

Cardiac surgeries initiate oxidative stress, increasing organ dysfunction development and mortality. The present study investigated the superoxide dismutase (SOD) activity, as an antioxidant enzyme, in patients undergoing coronary artery bypass (CABG) and heart valve replacement surgeries.

METHODS

A prospective study was performed on patients with proven coronary artery disease (CAD) or valvular heart disease (VHD) candidates for on- or off-pump CABG and valve replacement surgery. Serum SOD activity was measured preoperatively, at 24 h postoperatively, and at the time of discharge. In addition, echocardiography was performed before surgery and at discharge.

RESULTS

A total of 48, 51, and 47 patients were enrolled in the on-pump, off-pump CABG, and valve replacement groups, respectively. Baseline serum SOD activity showed no significant association with BMI, age, and blood pressure in either CAD or VHD patients. The SOD values decreased at the 24 h postoperative time and then increased at the time of discharge in all groups, except for a slight decrease in the on-pump group. The changes in serum SOD values were not significantly different for the three surgical groups.

CONCLUSIONS

The serum SOD activities fell significantly after CABG and valve replacement surgery. Further investigation is emphasized for the role of SOD in oxidative stress after cardiac surgery.

Mechanisms of oxidative stress and myocardial protection during open-heart surgery

Cold heart protection via cardioplegia administration, limits the amount of oxygen demand. Systemic normothermia with warm cardioplegia was introduced due to the abundance of detrimental effects of hypothermia. A temperature of 32-33°C in combination with tepid blood cardioplegia of the same temperature appears to be protective enough for both; heart and brain. Reduction of nitric oxide (NO) concentration is in part responsible for myocardial injury after the cardioplegic cardiac arrest. Restoration of NO balance with exogenous NO supplementation has been shown useful to prevent inflammation and apoptosis. In this article, we discuss the "deleterious" effects of the oxidative stress of the extracorporeal circulation and the up-to-date theories of "ideal'' myocardial protection.

On-versus Off-Pump Coronary Artery Bypass Grafting: No Difference in Early Postoperative Kidney Function Based on TNF-α or C-Reactive Protein

BACKGROUND/AIMS: There are controversial data about renal function following off-pump coronary artery bypass grafting (CABG). The present study aimed to evaluate renal function changes 24 h after on- and off-pump CABG, as well as renal function correlated with high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor-α (TNF-α). METHODS: Ninety patients with coronary artery disease referred to our center for CABG from July 2006 to November 2007 were enrolled in the study. Patients were equally and randomly divided in two groups, on- and off-pump. Serum levels of creatinine (Cr), blood urea nitrogen, creatinine clearance (CrCl), hs-CRP, and TNF-α were determined immediately before and 24 h after surgery. RESULTS: Cr and CrCl changes after surgery were not significantly different between the two groups; however, blood urea nitrogen levels after surgery were significantly higher in the on-pump group (p = 0.035). No statistically significant difference was noted between the two groups in terms of changes in levels of hs-CRP and TNF-α (p = 0.350 and 0.805, respectively). The changes in CrCl levels had no significant correlation with hs-CRP and TNF-α. CONCLUSIONS: The early Cr and CrCl levels after surgery are not significantly different in on- and off-pump groups. The early renal function after on- or off-pump CABG is not correlated with the levels of inflammatory markers including hs-CRP and TNF-α.

High-sensitivity C-reactive protein (hs-CRP) and tumor necrotizing factor-alpha (TNF-alpha) after on- and off- pump coronary artery bypass grafting

INTRODUCTION

Coronary artery bypass grafting (CABG) is one of the most frequently performed operations around the world. The aim of this study is to evaluate high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor-alpha (TNF-alpha) differences between on-pump and off-pump coronary surgery.

METHODS

In this prospective study, 90 patients with coronary artery disease referred for CABG were enrolled from July 2006-November 2007. Levels of hs-CRP and TNF-alpha were measured by ELISA using commercial kits

RESULTS

hs-CRP levels significantly (p<0.001) increase after CABG. But no difference between off-pump and on-pump groups was noted for hs-CRP and TNF-alpha levels (p=0.4, p=0.8).

CONCLUSIONS

There was no difference in high-sensitivity C-reactive protein (hs-CRP) and TNF-alpha between on-pump and off-pump CABG surgery.

Perfusion preservation of the donor heart: basic science to pre-clinical

As a consequence of technology improvements and refinement, perfusion of the donor heart has moved from the research laboratory to clinical studies. Multiple investigators are currently leading pre-clinical trials of devices using perfusion preservation, and one device is now in European clinical trials. One major problem with the donor heart is the high metabolism relative to other organs, and depletion of ATP leads rapidly to acidosis and necrosis of the myocardium. Two techniques in development to address the issue are normothermic and hypothermic perfusion. This review examines the current issues regarding donor heart preservation and techniques of preclinical evaluation necessary for regulatory approval.

Oxidative stress implication after prolonged storage donor heart with blood versus crystalloid cardioplegia and reperfusion versus static storage

Several factors are known to limit cardiac transplantation, such as number of donors, quality of cardiac graft preservation, and ischemia-reperfusion injury. Some mechanisms of reperfusion injury are now recognized; they include oxygen free radical (OFR), white blood cells activation, changes in calcium influx, alteration of microvascular blood flow, and sympathetic activation. The goal of this study was to assess the effects of two types of cardioplegia with long-term storage, either static or continuous perfusion, in 30 isolated sheep hearts as a model for heart transplantation. We examined myocardial function, histology, ischemic damage, and markers of oxidative stress. Two types of cardioplegia and storage conditions using a Langendorff reperfusion were studied in a combined approach: crystalloid (CP) [groups I and III] or cold oxygenated autologous blood (BC) [groups II and IV], immediate storage during 8h in profound hypothermia (groups I and II), or reperfused with crystalloid (group III), or blood cardioplegia (group IV). All perfusate samples were drawn from the coronary sinus. Lactate levels increased progressively in groups I, II, and IV, but not in group III, as no significant elevation was shown [90 min: 13.6+/-1.7 versus 5.2+/-1.0 mmol/L (P<0.01)]. Arrhythmias were more frequent when using BC (n=5) than CP (n=0). For plasma thiobarbituric acid-reactive substances (TBARS) levels a significant difference was found between group III and the other groups since 15 to 90 min (P<0.05). Vitamin E concentration decreased significantly from 5 min for groups II and IV, 15 min for group I, and 30 min for group III, with a significant difference between groups II and IV (P<0.05) but not between groups I and III. CP followed by a reperfusion with the same solution showed a significantly lower ischemic injury and OFR production, less frequent ventricular arrhythmias while stable hemodynamic parameters carried on. However, this protocol did not act on the early postoperative contractile function.

Early postoperative function of the heart after coronary artery bypass grafting is not predicted by myocardial necrosis and glutathione-associated oxidative stress

BACKGROUND

To investigate whether cardioplegia-related myocardial necrosis, lactate and glutathione release are predictive for early postoperative cardiac function after coronary artery bypass grafting (CABG).

METHODS

Twelve patients with stabile angina scheduled for elective CABG were included. Myocardial release of troponin I (Tn I), creatine kinase MB isoenzyme mass (CK-MB), oxidized glutathione (GSSG) and lactate in blood were measured before cardioplegia, and up to 20 min thereafter. Cardiac function was assessed for 12 postoperative hours.

RESULTS

Release of Tn I and CK-MB peaked at 20 min (-14.5+/-24.1 ng/ml and -23.9+/-30.6 ng/ml, respectively) and lactate at 1 min of reperfusion (-1.5+/-0.6 mmol/l). Significant GSSG release occurred at 5 min, with concomitant increase of glutathione redox ratio. The changes were not correlated to ischemic time. Cardiac index was increased after CPB and remained higher than preoperative value until the first postoperative morning. No correlations between postcardioplegic heart function and markers of tissue injury were found.

CONCLUSIONS

The extent of myocardial reversible and irreversible injury does not predict early postoperative contractile function of the heart.

Intraoperative release of troponin T in coronary venous and arterial blood and its relation to recovery of left ventricular function and oxidative metabolism following coronary artery surgery

OBJECTIVE

To investigate the intraoperative release of troponin T during uncomplicated coronary artery surgery and to determine its relation to ischaemic time and to recovery of left ventricular function and oxidative metabolism.

DESIGN

A prospective observational study.

SETTING

Cardiac surgical unit in a tertiary referral centre.

METHODS

Troponin T, creatine kinase, and lactate were analysed from arterial and coronary sinus samples taken before operation, and 1, 4, 6, 10, 20, 35, and 45 minutes after cross clamp release. Net myocardial troponin T release and lactate extraction were derived from their respective arteriovenous differences. Haemodynamic measurements were made using a thermodilution pulmonary artery catheter.

PATIENTS

45 patients, mean (SD) age 62 (9) years, with two or three vessel coronary artery disease and chronic stable angina undergoing routine coronary artery surgery.

RESULTS

Before operation, troponin T concentrations were not raised, but within one minute of cross clamp release they increased progressively in both coronary sinus and arterial blood for the entire 45 minutes of reperfusion studied. Coronary sinus troponin T concentrations were consistently higher than arterial concentrations at all time points (p < 0.001), indicating net troponin T release by the myocardium. Peak net troponin T release and area under the curve of net troponin T release correlated closely with ischaemic time (r = 0.58 and r = 0.61, p < 0.0001 for both). Area under the curve of arterial troponin T concentration was also significantly correlated with ischaemic time (r = 0.44, p < 0.01). Patients with cross clamp times longer than 72 minutes (upper quartile for ischaemic time) had greater troponin T release, delayed reversion to lactate extraction, and lower left ventricular stroke work index three hours after surgery, compared with patients who had short (< 50 minutes, lower quartile) and intermediate (51-71 minutes, interquartile) cross clamp times. Peak net troponin T release and area under the curve of arterial troponin T concentration were inversely correlated with left ventricular stroke work index three hours after surgery (r = -0.57, r = -0.38, p < 0.01).

CONCLUSIONS

Troponin T concentrations increased in every patient after cross clamp release, and were consistently higher in coronary sinus blood than in arterial blood, indicating net myocardial release of troponin T during the period of reperfusion. Intraoperative net troponin T release has functional significance, as it is closely related to ischaemic time and reflects delayed recovery of left ventricular function and oxidative metabolism; therefore, its measurement may contribute to the perioperative assessment of myocardial injury sustained during coronary artery surgery.