April 17, 2009Open Access

Unrecognized Non-Q-Wave Myocardial Infarction: Prevalence and Prognostic Significance in Patients with Suspected Coronary Disease

Q: What is the clinical evidence from this study?

Study design: Cohort. Population: Suspected coronary disease (n=185). Intervention: Presence of non-Q-wave unrecognized myocardial infarction (UMI) vs. Absence of myocardial infarction. Primary outcome: All-cause mortality (HR 11.4, 95% CI 2.5-51.1, p=0.002).

Key Result

Unrecognized non-Q-wave myocardial infarction identified by DE-CMR independently predicted an 11.4-fold increased risk of all-cause mortality compared to patients without myocardial infarction.

Study Design

Type

Cohort (n=185)

Multicenter

Yes

PICO

Population

Suspected coronary disease (n=185)

Intervention / Comparator

Presence of non-Q-wave unrecognized myocardial infarction (UMI) vs Absence of myocardial infarction

Primary Outcome

All-cause mortality — HR 11.4 (2.5-51.1), p=0.002

Main Result

Effect estimate: HR 11.4 (95% CI 2.5-51.1)

Absolute Event Rate: 26% vs 2%

p-value: p=0.002

Limitations

Small number of events in the study limited the ability to evaluate the incremental prognostic value of infarct size.
Findings may not be applicable to entirely asymptomatic cohorts since many patients had symptoms like chest pain and dyspnea.
Lack of data on the number of patients screened, declined, or excluded over the recruitment period.

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. METHODS AND FINDINGS: 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. TRIAL REGISTRATION: Clinicaltrials.gov NCT00493168.

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