Diagnostic and prognostic role of cardiac troponins – reply

Dear Sir, This letter will answer the objections to our article on cardiac Troponins (cTns) [1] that were posed by Drs Riga and Shenenberger in the February 2003 issue of this journal [2]. The first comment regarding the prognostic power of cTns elevation in the postoperative period. We agree that the independent prognostic power of cTns elevation is related to its high specificity and sensitivity as a marker of myocardial injury [3]. Unfortunately, cTns can't be compared with a ‘gold standard’ tool in the diagnosis of myocardial injury in surgical patients. This is due to the low sensitivity and specificity of traditional markers of myocardial necrosis in peri-operative setting. Moreover, some rare spurious cTns elevations have been reported [4] so that, peri-operative cTns elevation could be misinterpreted as a false positive result. As a consequence of what has been stated before, we think that the demonstration of cTns-negative and positive predictive power can provide relevant information: it further supports the evidence that peri-operative cTns elevation is not a false positive result; it demonstrates that cTns may influence prognosis even after hospital discharge, it demonstrates that negative cTns patients may be safely discharged from the hospital [5, 6]. This last issue is particularly relevant because serial negative cTns determinations don't necessarily exclude transient ischaemic episodes. Before these findings, it was unclear whether negative cTns patients suffering peri-operative myocardial ischaemia were at such high risk for future cardiac complications as positive cTns patients. Whether postoperative cTns elevation may predict future cardiovascular events even in a low-risk population is still to be proved. In a group of women undergoing elective caesarean section, an unexpected 7.69% cTnT elevation has been demonstrated but, unfortunately, no follow-up data have been reported [7]. Due to the limited length of the follow-up in the surgery studies (maximum 6 months), we still lack data about the prognostic power of cTns elevation in the long term. This would provide crucial information to the clinicians who plan the future management of such patients. About the second comment: the correlation between cTns elevation and severity of coronary artery disease in noncardiac surgery patients has not been demonstrated yet. We can only assume that this correlation (observed in patients with acute coronary syndromes [8]) might explain the independent prognostic power of cTns in the postsurgery setting. Given the complex metabolic alterations accompanying and following surgery, we cannot exclude the influence of other mechanisms in the determination of myocardial injury (i.e. inflammation, activation of the coagulation cascade, endothelial damage in a coronary vascular bed &without severe stenosis).