Elsevier

American Heart Journal

Volume 152, Issue 4, October 2006, Pages 742-748
American Heart Journal

Clinical Investigation
Imaging and Diagnostic Testing
Lack of sensitivity of the electrocardiogram for detection of old myocardial infarction: A cardiac magnetic resonance imaging study

https://doi.org/10.1016/j.ahj.2006.02.037Get rights and content

Background

The presence of Q waves in the electrocardiogram (ECG) has been used as a marker of prior myocardial infarction (MI). Its accuracy, however, is uncertain. The purpose of this study is to determine the accuracy of an ECG to detect prior MI compared with a novel criterion standard.

Methods

This study conducted retrospective inclusion with de novo analysis of ECG and cardiac magnetic resonance (CMR) by independent blinded readers in a single-institution setting. The population consisted of a consecutive sample of 146 patients referred for CMR for evaluation of myocardial viability and necrosis. Q/QS waves on ECG were defined as per Minnesota Code criteria. Myocardial scar was quantified and localized by CMR delayed contrast hyperenhancement and assumed as criterion standard. Sensitivity, specificity, and predictive values of ECG were calculated for different scar sizes (>1%, >15%, and >30% of the myocardium) and location (global, anterior, inferior, and lateral walls).

Results

Sensitivity was 48.4%; specificity, 83.5; positive predictive accuracy, 72.0%; and negative predictive accuracy, 64.2%. Sensitivity improved when only large infarcts were considered (64.2%), but specificity decreased to 72.7%. Sensitivity for detecting isolated anterior or inferior wall scars was similar, but isolated lateral wall scar was rarely identified (14.3%). When all 3 walls were involved, sensitivity was still low at 57.9%.

Conclusions

The lack of sensitivity and the resulting low negative predictive value of Q/QS criteria seriously limit its accuracy as a marker of prior MI.

Section snippets

Methods

The institutional review board of the Medstar Research Institute (Washington, DC) approved the protocol as a review of an existing database. All patient identifiers were removed before analysis.

Results

One hundred forty-six consecutive patients were reviewed. Seven were excluded because of left bundle branch block. The remaining 139 patients were analyzed. Sixty-six (47.5%) patients had a myocardial scar. Forty-four (31.7%) had MC Q/QS criteria. Baseline characteristics are shown in Table I. The mean time between CMR and ECG was 2.8 days. In 13 (20%) of the 66 patients with myocardial scar, CMR was performed within 7 days of MI. In the remaining 53 (80%), the age of the MI was greater than 7

Discussion

Electrocardiogram is accepted in clinical practice as a screening tool for detecting patients with prior MI. Despite its widespread clinical use, only a limited number of studies are available comparing ECG findings with the presence of myocardial necrosis or scar. The major finding of this study was the low sensitivity of MC Q/QS criteria for detecting myocardial scar represented by DCHE on CMR. One third of the largest scars, those involving more than 30% of the total ventricular volume, were

Conclusions

We conclude that the use of MC criteria for pathologic Q and QS waves to detect prior MI is importantly limited by a relatively low sensitivity. Moreover, these findings are in keeping with the long-held understanding that lateral wall MI is often unrecognized by the ECG.

References (24)

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