The new definition of myocardial infarction: diagnostic and prognostic implications in patients with acute coronary syndromes.
BACKGROUND
The clinical implications of the recently revised criteria for diagnosis of acute myocardial infarction (AMI) in patients with suspected acute coronary syndromes are unknown.


METHODS
To evaluate the prognostic implications of the new diagnostic criteria for AMI, we studied 493 consecutive patients with suspected acute coronary syndromes admitted to University of Michigan, Ann Arbor, between May 1, 1999, and January 1, 2000. Patients with positive cardiac enzymes and symptoms suggestive of coronary ischemia (n = 275) were divided into 2 groups: group A, with elevated peak creatine kinase-MB fraction and/or new electrocardiographic changes suggestive of AMI regardless of troponin status (diagnosed as AMI by old criteria), and group B, with normal peak creatine kinase-MB fraction but elevated troponin I level (additional patients diagnosed as having AMI by new criteria).


RESULTS
As compared with group A (n = 224), patients in group B (n = 51) were older women, with increased comorbidities such as previous stroke or aortic stenosis, and had fewer in-hospital procedures. In-hospital adverse events (reinfarction, heart failure, shock, and mortality) were similar between the groups, whereas 6-month mortality was higher among group B patients (16.3% vs 5.8%; P =.03). This difference was not statistically significant after adjustment for differences in baseline characteristics between the groups (odds ratio, 1.6; 95% confidence interval, 0.5-5.9).


CONCLUSIONS
The new criteria result in a substantial increase in the diagnosis of AMI. Furthermore, they help to identify patients with acute coronary syndromes who have greater comorbidities and worse 6-month outcomes who are otherwise missed by the old criteria. Additional studies are needed to confirm these preliminary findings and to determine the financial implications of the new criteria.
Division of Cardiology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48105, USA.
Mark A
MA
Meier
Wisam H
WH
Al-Badr
Jeanna V
JV
Cooper
Eva M
EM
Kline-Rogers
Dean E
DE
Smith
Kim A
KA
Eagle
Rajendra H
RH
Mehta
D000208:Acute Disease; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use; D015415:Biomarkers / Q000097:blood; D003327:Coronary Disease / Q000175:diagnosis / Q000453:epidemiology / Q000401:mortality; D003402:Creatine Kinase / Q000097:blood; D052279:Creatine Kinase, MB Form; D023381:Endpoint Determination; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization; D006801:Humans; D007527:Isoenzymes / Q000097:blood; D007902:Length of Stay; D008297:Male; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000453:epidemiology / Q000401:mortality; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors / Q000627:therapeutic use; D011379:Prognosis; D012307:Risk Factors; D016019:Survival Analysis; D013577:Syndrome
D000319:Adrenergic beta-Antagonists; D000925:Anticoagulants; D015415:Biomarkers; D007527:Isoenzymes; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D003402:Creatine Kinase; D052279:Creatine Kinase, MB Form