Research Article: What Is the Significance of Unrecognized Non-Q-Wave Myocardial Infarction?

Date Published: April 21, 2009

Publisher: Public Library of Science

Author(s): Clara Kayei Chow

Abstract: Clara Kayei Chow discusses the clinical implications of a new study that sought to examine the frequency and prognosis of unrecognized non-Q-wave myocardial infarction.

Partial Text: Myocardial infarction (MI) that has no clinical symptoms (“silent MI”) or atypical symptoms is usually categorized as unrecognized MI (UMI). The mechanism underlying UMI is unclear, but given that silent MI is more common in people with diabetes, one hypothesis is that it may be related to autonomic neuropathy [1], [2]. UMI, which accounts for about one in four MIs in populations that are screened for events both clinically and with electrocardiogram (ECG), is a high-risk clinical condition associated with similar morbidity and mortality to clinically recognized MI [3], [4].

In this issue of PLoS Medicine, Han Kim and colleagues report findings from a study that sought to examine the frequency and prognosis of non-Q-wave UMI [8]. The researchers prospectively recruited 185 patients with suspected coronary disease, but no clinical history of MI, who had been referred for invasive angiography. Patients who had a medical record of prior clinical MI, previous coronary revascularization procedure, or history of non-ischemic myocardial disorders that could cause myocardial scarring were excluded. Patients with serious intercurrent illness (e.g., cancer) that could shorten their lifespan to less than two years or who had a contraindication to CMR were also excluded.

In Kim and colleagues’ study, 16 deaths occurred in about two years of follow up: 13 in patients with non-Q-wave UMI (26%), one in a patient with Q-wave UMI (7%), and two in patients without MI (2%). Given that the numbers of patients with Q-wave UMI was low, it is probably incorrect to draw any conclusions from the apparent difference in mortality between the non-Q-wave and Q-wave UMI groups. However, patients with non-Q-wave UMI appeared to have more established cardiovascular risk factors and more severe angiographic findings of coronary artery disease (in terms of the extent and the proportion with obstructive disease).

This important new study has two key clinical implications. First, previous non-Q-wave UMI is potentially being missed in patients with suspected coronary artery disease. Second, non-Q-wave UMI is important because it is significantly associated with increased mortality.



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