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Evidence for free-radical mediated injury during coronary artery bypass surgery
A Movahed1, K G Nair, T F Ashavaid
1PD Hinduja National Hospital & Medical Research Centre, Bombay.
Insights
Coronary artery bypass graft surgery causes oxygen free-radical bursts, leading to myocardial impairment. This study shows increased malondialdehyde and cardiac damage markers during reperfusion, indicating free-radical mediated cardiac membrane damage.
Area of Science:
- Cardiology
- Biochemistry
- Free Radical Biology
Background:
- Coronary artery bypass graft (CABG) surgery involves ischemia and reperfusion, which can cause myocardial damage.
- Oxygen free-radical generation increases during reperfusion following CABG.
- This oxidative stress may lead to cardiac membrane damage and impaired heart function.
Purpose of the Study:
- To investigate the role of oxygen free radicals in myocardial impairment during CABG surgery.
- To measure free-radical activity and cardiac damage markers at different reperfusion times.
- To correlate these markers with the duration of ischemia.
Main Methods:
- Blood samples were collected from 55 patients undergoing CABG surgery.
- Thiobarbituric acid reactive species (TBARS), primarily malondialdehyde (MDA), were measured to assess free-radical activity.
- Creatine phosphokinase (CPK), CPK-MB, and Troponin-T levels were measured to indicate myocardial damage.
Main Results:
- MDA levels significantly increased at 1 and 10 minutes post-reperfusion (p < 0.001), correlating with aortic cross-clamp time.
- CPK and CPK-MB activities doubled post-reperfusion (p < 0.001).
- Plasma Troponin-T levels significantly increased at 1 and 10 minutes post-reperfusion (p < 0.01), correlating with ischemia severity.
Conclusions:
- The study demonstrates a significant increase in free-radical activity and cardiac damage markers during reperfusion after CABG surgery.
- The findings suggest that free radicals mediate cardiac membrane damage during CABG.
- This highlights the potential for therapeutic interventions targeting oxidative stress in CABG patients.
Abstract:
Prolonged global ischemia followed by reperfusion during coronary artery bypass graft (CABG) surgery leads to a burst of oxygen free-radical generation and subsequent myocardial impairment. Blood samples were collected at different time periods from the right atrium of patients (n = 55) who underwent CABG surgery. Free-radical activity was measured by assays for thiobarbituric acid reactive species (TBARS), mainly malondialdehyde (MDA), at zero minute (before aortic cross-clamp), one minute and 10 minutes after declamping i.e. reperfusion. There was a significant increase (p < 0.001) in the level of MDA at one minute of reperfusion which continued to be elevated up to 10 minutes. This increase was significantly correlated with aortic cross-clamp time (r = 0.525, p < 0.05). The activity of CPK and CPK-MB was raised by two fold (p < 0.001) after release of the clamp. Plasma Troponin-T level was estimated in 10 patients during CABG surgery and a significant increase (p < 0.01) was observed at one minute as well as 10 minutes of reperfusion which correlated well (r = 0.81, p < 0.01) with the severity of ischemia. The concomitant rise in TBARS (marker of free-radical activity), CPK, CPK-MB and Troponin-T (indicators of myocardial damage) on reperfusion implies that there is free-radical mediated damage to the cardiac membrane during CABG surgery.