title: Unrecognized non-Q-wave myocardial infarction: prevalence and prognostic significance in patients with suspected coronary disease.
abstract: BACKGROUND
  Unrecognized myocardial infarction (UMI) is known to constitute a substantial portion of potentially lethal coronary heart disease. However, the diagnosis of UMI is based on the appearance of incidental Q-waves on 12-lead electrocardiography. Thus, the syndrome of non-Q-wave UMI has not been investigated. Delayed-enhancement cardiovascular magnetic resonance (DE-CMR) can identify MI, even when small, subendocardial, or without associated Q-waves. The aim of this study was to investigate the prevalence and prognosis associated with non-Q-wave UMI identified by DE-CMR.
  
  
  RESULTS
  We conducted a prospective study of 185 patients with suspected coronary disease and without history of clinical myocardial infarction who were scheduled for invasive coronary angiography. Q-wave UMI was determined by electrocardiography (Minnesota Code). Non-Q-wave UMI was identified by DE-CMR in the absence of electrocardiographic Q-waves. Patients were followed to determine the prognostic significance of non-Q-wave UMI. The primary endpoint was all-cause mortality. The prevalence of non-Q-wave UMI was 27% (50/185), compared with 8% (15/185) for Q-wave UMI. Patients with non-Q-wave UMI were older, were more likely to have diabetes, and had higher Framingham risk than those without MI, but were similar to those with Q-wave UMI. Infarct size in non-Q-wave UMI was modest (8%+/-7% of left ventricular mass), and left ventricular ejection fraction (LVEF) by cine-CMR was usually preserved (52%+/-18%). The prevalence of non-Q-wave UMI increased with the extent and severity of coronary disease on angiography (p<0.0001 for both). Over 2.2 y (interquartile range 1.8-2.7), 16 deaths occurred: 13 in non-Q-wave UMI patients (26%), one in Q-wave UMI (7%), and two in patients without MI (2%). Multivariable analysis including New York Heart Association class and LVEF demonstrated that non-Q-wave UMI was an independent predictor of all-cause mortality (hazard ratio [HR] 11.4, 95% confidence interval [CI] 2.5-51.1) and cardiac mortality (HR 17.4, 95% CI 2.2-137.4).
  
  
  CONCLUSIONS
  In patients with suspected coronary disease, the prevalence of non-Q-wave UMI is more than 3-fold higher than Q-wave UMI. The presence of non-Q-wave UMI predicts subsequent mortality, and is incremental to LVEF.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT00493168.
authors.affiliation: Duke Cardiovascular Magnetic Resonance Center, Division of Cardiology, Duke University, Durham, North Carolina, USA.
authors.forename: Han W
authors.initials: HW
authors.lastname: Kim
authors.forename: Igor
authors.initials: I
authors.lastname: Klem
authors.forename: Dipan J
authors.initials: DJ
authors.lastname: Shah
authors.forename: Edwin
authors.initials: E
authors.lastname: Wu
authors.forename: Sheridan N
authors.initials: SN
authors.lastname: Meyers
authors.forename: Michele A
authors.initials: MA
authors.lastname: Parker
authors.forename: Anna Lisa
authors.initials: AL
authors.lastname: Crowley
authors.forename: Robert O
authors.initials: RO
authors.lastname: Bonow
authors.forename: Robert M
authors.initials: RM
authors.lastname: Judd
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Kim
mesh_terms: D000368:Aged; D002423:Cause of Death; D017023:Coronary Angiography; D003327:Coronary Disease / Q000150:complications / Q000175:diagnosis* / Q000401:mortality; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology*; D015995:Prevalence; D011379:Prognosis; D011446:Prospective Studies