Paris, France - A group of Swiss researchers has developed a simple algorithm for those presenting to the emergency room with acute chest pain that they believe will help doctors to differentiate exactly who has suffered an MI. The method incorporates testing of high-sensitivity cardiac troponin (hs-T); the team found that absolute change in this parameter in the first hour after presentation was most helpful in determining an accurate diagnosis.
Dr Philip Haaf
Dr Philip Haaf (University Hospital, Basel, Switzerland) presented the findings, from an analysis of the Advantageous Predictors of Acute Coronary Syndrome Evaluation (APACE) study, here at the European Society of Cardiology (ESC) 2011 Congress today.
Haaf explained that the gradual implementation of hs-T tests in clinical practice—while helping doctors to detect and treat acute MI earlier than with conventional assays—has also caused considerable confusion, particularly with regard to the interpretation of minor elevations. This is because it is difficult to accurately distinguish between those with cardiac, but noncoronary, disease—such as arrhythmias, heart failure, hypertensive emergency, and myocarditis—and those having an MI, with coronary obstruction.
The new algorithm he and his colleagues developed incorporates the presence of ST elevation in the ECG together with presentation values and changes of hs-T in the first hour. Asked to comment on the new findings, Dr Christian Hamm (Kerckhoff Heart Center, Bad Nauheim, Germany) said: "I think this is an important study."
New guidelines stipulate three-hour rule-out period; study contributes
Haaf said APACE is an ongoing study, with roughly 2000 patients enrolled so far, in whom a meticulous patient history, ECG analysis, and measurement of biomarkers are taken, with the primary goal being the fast detection or exclusion of AMI. In this analysis, data from the first 887 patients were computed. Haaf told heartwire : "We wanted to contribute to the clinical application of hs-T.
"The first idea was, is the absolute value of hs-T more important than relative change? And the second was, what presentation cutoff might be relevant to risk-stratify patients? Is it AMI or maybe something else, since now many, many patients appear with positive hs-T values and they don't have MI?"
Haaf and colleagues found that absolute changes in hs-T in the first hour were much more discriminatory than relative changes. Absolute changes of high-sensitivity cardiac troponin T as low as 0.005 µg/L had the best discriminatory power in the differential diagnosis of AMI and cardiac, noncoronary, disease.
Of patients with AMI, 98.4% had presentation values of hs-T above 0.028 µg/L or absolute changes of >0.005 µg/L in the first hour. Of note, considering changes of hs-T after the first hour did not seem to generate much further benefit, Haaf said.
Hamm says these findings are particularly important on the background of new guidelines on non-ST-elevation ACS, on which he was first author[1].
He adds that with these, "For the first time, we introduce a three-hour rule-out protocol, so we need studies like this to define what is a significant rise in troponins in this rule-out period. This is a major contribution, although we need more trials like this."
Asked whether it will eventually be possible to know, based on an initial hs-T, whether a patient has had an AMI or not, Haaf said: "This question is not yet answered. Currently, we have this six-hour period that we need to wait until we can clearly exclude the diagnosis of AMI, and now it may be limited to three hours, but this is not yet clearly defined."
Heartwire from Medscape © 2011
Cite this: Absolute changes in high-sensitivity troponin in first hour help pinpoint AMI - Medscape - Aug 31, 2011.
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