Elsevier

The Lancet

Volume 357, Issue 9249, 6 January 2001, Pages 21-28
The Lancet

Articles
Visualisation of presence, location, and transmural extent of healed Q-wave and non-Q-wave myocardial infarction

https://doi.org/10.1016/S0140-6736(00)03567-4Get rights and content

Summary

Background

A technical advance in contrast-enhanced magnetic resonance imaging (MRI) has significantly improved image quality. We investigated whether healed myocardial infarction can be visualised as hyperenhanced regions with this new technique, and whether assessment of the transmural extent of infarction yields new physiological data.

Methods

82 MRI examinations were carried out in three groups: patients with healed myocardial infarction; patients with non-ischaemic cardiomyopathy; and healthy volunteers. Patients with healed myocardial infarction were prospectively enrolled after enyzmatically proven necrosis and imaged 3 months (SD 1) or 14 months (7) later. The MRI procedure used a segmented inversion-recovery gradient-echo sequence after gadolinium administration. Findings were compared with those of coronary angiography, electrocardiography, cine MRI, and creatine kinase measurements.

Findings

29 (91%) of 32 patients with infarcts imaged at 3 months (13 non-Q-wave) and all of 19 imaged at 14 months (eight non-Q-wave) showed hyperenhancement. In patients in whom the infarct-related-artery was identified by angiography, 24 of 25 imaged at 3 months and all of 14 imaged at 14 months had hyperenhancement in the appropriate territory. None of the 20 patients with non ischaemic cardiomyopathy or the 11 healthy volunteers showed hyperenhancement. Irrespective of the presence or absence of Q waves, the majority of patients with hyperenhancement had only non-transmural involvement. Normal left-ventricular contraction was shown in seven patients examined at 3 months and three examined at 14 months, but in these cases hyperenhancement was limited to the subendocardium.

Interpretation

The presence, location, and transmural extent of healed Q-wave and non-Q-wave myocardial infarction can be accurately determined by contrastenhanced MRI.

Introduction

The diagnosis of previous myocardial infarction is clinically important. Population surveys have shown that survivors of myocardial infarction have a mortality rate three to 14 times that of the general population.1 The mortality rate is increased whether the index myocardial infarction is symptomatic or asymptomatic1, 2 or is classified electrocardiographically as Q-wave or non-Q-wave.3, 4 The diagnosis can, however, be difficult to confirm if infarction was not documented at the time of the acute event. There is a limited period in which biochemical evidence of infarction is present, and for many people the electrocardiogram will be non diagnostic, because the majority of acute myocardial infarctions are not associated with the formation of Q waves.3

Current non-invasive imaging methods have inherent limitations that reduce the accuracy of diagnosis. For example, if a patient has a healed myocardial infarct that is subendocardial, regional wall motion by echocardiography, regional perfusion by nuclear scintigraphy, and regional metabolism by positron emission tomography may all be normal because subendocardial defects cannot be detected by these techniques. Contrast-media-enhanced magnetic resonance imaging (MRI) has high spatial resolution and can detect myocardial infarction in human beings.5 Limited differences in image intensities between hyperenhanced and non-hyperenhanced regions, however, have restricted use of this technique to the study of acute myocardial infarction, and uncertainty remains over whether chronic, healed infarcts can be detected.

A recent technical advance in contrast-enhanced MRI has led to significant improvement in image quality.6 Our study of acute myocardial infarction with this technique showed typical differences in image intensity between infarcted and non-infarcted regions of 500% compared with about 50% for previously reported MRI approaches.6 Studies in dogs with this new technique showed clear distinction of infarcted from non-infarcted tissue whatever the time since infarction, with excellent correlation of hyperenhancement by MRI with infarct size by histopathology.7, 8 So far, data on the sensitivity and specificity of this new technique in patients with healed myocardial infarction are lacking.

The aim of our study was to test whether contrastenhanced MRI can detect healed myocardial infarction. We postulated that both transmural and non-transmural healed infarction could be visualised. Patients were identified at the time of the acute event, solely on the basis of abnormal creatine kinase release. MRI was done several months later. In all patients, findings on contrast-enhanced MRI were compared with the results of coronary angiography, electrocardiography, cine MRI, and creatine kinase measurements. To assess the specificity of the findings, contrast-enhanced MRI was also done in patients with non-ischaemic cardiomyopathy and in healthy volunteers.

Section snippets

Patients

82 cardiac MRI examinations were done in the three groups. We did not recruit patients with unstable angina, New York Heart Association class IV heart failure, or contraindications to MRI (eg, pacemaker). All participants gave informed consent to the study protocol, which was approved by the Northwestern University Institutional Review Board.

44 patients admitted to Northwestern Memorial Hospital or the Veterans Administration-Lakeside Hospital with enzymatically proven myocardial necrosis (peak

Results

Of the 32 patients studied 3 months after myocardial infarction, 17 had peak activities of creatine kinase and its MB isoenzyme that were less than five times the upper limit of normal (ie, they had small infarcts, which are typically difficult to detect). The median peak creatine kinase activity was 533 IU/L (range 176–5912), and the median peak MB isoenzyme concentration was 35 μg/L (range 12–792). 19 patients had electrocardiographic Q waves: six in anterior leads, 13 in inferior leads, and

Discussion

There have been conflicting findings on whether MRI with routine gadolinium-based contrast agents can be used to detect healed myocardial infarction. Some researchers have observed gadolinium hyperenhancement in patients with acute myocardial infarction but found no hyperenhancement in patients with healed infarction.13, 14, 15 Others have described hyperenhancement in patients with chronic coronary-artery disease and high clinical likelihood of remote infarction,16, 17 but biochemical evidence

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