Comparison of cardiac troponin I and creatine kinase ratios in the detection of myocardial injury after aortic surgery

Background: Perioperative myocardial infarction may not be diagnosed correctly because World Health Organization criteria are often not met and creatinine kinase myocardial fraction (creatinine kinase/ creatinine kinase MB isoenzyme; CK/CK-MB) ratios can be difficult to interpret. Cardiac troponin (cTn) I and cTnT are the most sensitive and specific markers of myocardial cell necrosis currently available but are not widely used in surgical practice. The aim was to compare cTnl and CK/CK-MB ratios in the detection of myocardial injury following aortic surgery. Methods: This was a prospective study of 59 patients undergoing elective (n = 28) or ruptured (n = 24) abdominal aortic aneurysm repair or elective aortofemoral bypass (n = 7). cTnI level was measured before operation and at 6, 24 and 48 h after surgery. The CK/CK-MB ratio was measured where cTnI was detectable. Results: Some 14 of 24 emergency and ten of 35 elective patients had detectable cTnl (greater than 0.5 ng/ml) at one or more time-points. The CK/CK-MB ratio was greater than 5 per cent in only four of 24 patients having an emergency operation and in none of the elective patients with detectable cTnI. Conclusion: Over half of patients undergoing emergency operation and more than a quarter of those having elective aortic surgery suffered myocardial necrosis as determined by detectable cTnl levels. This was accompanied by a raised CK/CK-MB ratio in less than one-fifth of patients.