Myocardial injury in abdominal aortic surgery
Background: Peri-operative myocardial infarction (PMI) may be under- and/or mis-diagnosed because WHO criteria are often not met and creatinine kinase (CK/CK-MB) ratios can be difficult to interpret. Cardiac troponin (cTn) I is the most sensitive and specific marker of myocardial cell necrosis but is not yet widely available. Aims: 1. To examine the use of pre-operative risk indices, including ASA score, POSSUM score and Goldman’s cardiac risk index and compare these with peri-operative cTnI rise. 2. To compare cTnI levels with CK/CK-MB levels peri-operatively in the diagnosis of MI. 3. To explore the role of the fibrinolytic system in patients undergoing emergency surgery for ruptured aneurysm and relate this to cTnI levels. 4. To examine the use of the polymerase chain reaction (PCR) in the identification of bacteraemia and to relate this to systemic endotoxin levels and septic episodes. Methods: Prospective observational study of 67 patients undergoing aortic surgery (29 elective AAA, 31 emergency AAA, 7 aorto-occlusive). cTnI and endotoxin were measured pre-operatively and at 6, 24, 48, 72 and 96 hours postoperatively. Blood for PCR was also collected at these time points. CK and CK-MB were measured where cTnI was detectable. Fibrinolytic markers were measured up to 24 hours post operatively. Clinical, septic, ECG and cardiac events were prospectively documented. Results: ASA score was correlated with perioperative cTnI rise. Over 50% of patients undergoing emergency, and more than a quarter undergoing elective, aortic surgery will suffer myocardial injury as determined by cTnI rise. This is accompanied by CK/ CK-MB ratio in less than a fifth of cases. eTnI rise is associated with inhibition of fibrinolysis with emergency AAA repair. No relationships were observed with the presence of bacterial DNA, endotoxin response and sepsis.