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Troponin-based MI diagnosis supported
9 May 2008
MedWire News: The additional patients diagnosed with myocardial infarction (MI) rather than unstable angina since the definition of MI was redefined have even higher long-term mortality than patients diagnosed according to the older definition, reports a team from Switzerland.
There has been a substantial increase in the number of patients diagnosed with MI since the European Society of Cardiology and American College of Cardiology classified cardiac troponin as a major criterion in redefining MI in the year 2000.
Cardiac troponin is recognized as a more sensitive marker for myocardial necrosis than creatinine phosphokinase, elevations of which were previously needed to diagnose MI according to the World Health Organization (WHO) definition. But the increase in patients being transferred to coronary care units and catheter laboratories since the newer definition was introduced sparked controversy over whether these patients were appropriately labeled as having MI.
In an attempt to settle this controversy, Christian Mueller (University Hospital Basel, Switzerland) and colleagues examined long-term mortality in 1024 consecutive non-ST-elevation acute coronary syndrome (NSTE-ACS) patients treated by early invasive therapy.
They report in the American Journal of Medicine that 67 patients died during the median 16-month follow-up period.
By Kaplan-Meier analysis, patients classified as having unstable angina had a cumulative 3-year mortality rate of 5.6%. This compared with 9.1% in the 184 patients identified as having NSTEMI by the former WHO definition and 17.5% in the further 262 patients identified as having NSTEMI by the newer definition (p<0.001 for three-way comparison).
Univariate Cox regression analysis confirmed the additional criteria significantly predicted mortality, at a hazard ratio of 3.1 (p<0.001).
The team concludes: "The additional cohort of patients with NSTEMI not meeting the older WHO criteria are appropriately labeled as MI by the new definition, as they have a significantly increased risk of death despite most contemporary early invasive therapy.
"In fact, long-term mortality in 'additional criteria' patients is higher than in 'WHO criteria' patients."
