Elsevier

The Lancet

Volume 361, Issue 9355, 1 February 2003, Pages 374-379
The Lancet

Articles
Contrast-enhanced MRI and routine single photon emission computed tomography (SPECT) perfusion imaging for detection of subendocardial myocardial infarcts: an imaging study

https://doi.org/10.1016/S0140-6736(03)12389-6Get rights and content

Summary

Background

Myocardial infarcts are routinely detected by nuclear imaging techniques such as single photon emission computed tomography (SPECT) myocardial perfusion imaging. A newly developed technique for infarct detection based on contrast-enhanced cardiovascular magnetic resonance (CMR) has higher spatial resolution than SPECT. We postulated that this technique would detect infarcts missed by SPECT.

Methods

We did contrast-enhanced CMR and SPECT examinations in 91 patients with suspected or known coronary artery disease. All CMR and SPECT images were scored, using a 14-segment model, for the presence, location, and spatial extent of infarction. To compare each imaging modality to a gold standard, we also acquired contrast-enhanced CMR and SPECT images in 12 dogs with, and three dogs without, myocardial infarction as defined by histochemical staining.

Findings

In animals, contrast-enhanced CMR and SPECT detected all segments with nearly transmural infarction (>75% transmural extent of the left-ventricular wall). CMR also identified 100 of the 109 segments (92%) with subendocardial infarction (<50% transmural extent of the left-ventricular wall), whereas SPECT identified only 31 (28%). SPECT and CMR showed high specificity for the detection of infarction (97% and 98%, respectively). In patients, all segments with nearly transmural infarction, as defined by contrast-enhanced CMR, were detected by SPECT. However, of the 181 segments with subendocardial infarction, 85 (47%) were not detected by SPECT. On a per patient basis, six (13%) individuals with subendocardial infarcts visible by CMR had no evidence of infarction by SPECT.

Interpretation

SPECT and CMR detect transmural myocardial infarcts at similar rates. However, CMR systematically detects subendocardial infarcts that are missed by SPECT.

Introduction

The frequency of non-Q-wave myocardial infarction has increased in the past two decades,1, 2, 3 partly because of changes in treatment strategies—eg, increasing rate of early reperfusion1, 3—and partly as a result of the availability of more sensitive methods of diagnosis of acute myocardial infarction.4 Non-Q-wave infarcts probably represent small infarcts, which are associated with a morbidity and mortality comparable to that of larger infarcts.5, 6, 7, 8, 9

In the absence of biochemical and electrocardiographic evidence of infarction, myocardial infarcts can be detected by cardiac imaging techniques. Single-photon emission computed tomography (SPECT) myocardial perfusion imaging is an established procedure used for diagnosis of infarcts. However, results of studies10, 11, 12 suggest that SPECT misses small infarcts. One reason that infarcts might not be identified by SPECT is the fairly poor spatial resolution of about 10×10×10 mm full width half maximum,13, 14 suggesting that infarcts smaller than this size are difficult to see. Contrast-enhanced cardiovascular magnetic resonance (CMR) is a new technique that allows visualisation of transmural and subendocardial myocardial infarcts.15, 16, 17 A potential advantage of contrast-enhanced CMR is its high spatial resolution of about 1·4×1·9×6·0 mm—ie, about 60-fold greater than SPECT. We postulated, therefore, that CMR would be able to detect subendocardial infarcts missed by SPECT.

Section snippets

Patients

Between Jan 28, 1999, and Sept 2, 2001, we consecutively enrolled patients who underwent clinically indicated stress-rest SPECT perfusion imaging for known or suspected coronary artery disease at Northwestern Memorial Hospital or Veterans Affairs Lakeside Hospital, and studied them by contrast-enhanced CMR. We defined known coronary artery disease as a 50% or greater stenosis in one or more of the coronary arteries at cardiac catheterisation or a history of myocardial infarction, or both. The

Results

We enrolled 91 patients (24 women and 67 men, mean age 57 years [SD 13]) who had known (n=35) or suspected (n=56) coronary artery disease. All patients had CMR and SPECT within 2 months (mean 10 days, SD 17) of each other. No patient had a clinically recognised myocardial infarction within the 3 months before CMR or between the CMR and SPECT scans. We also studied 15 dogs, in which we produced myocardial infarction by occlusion of the left anterior descending coronary artery (n=9) or the left

Discussion

Our findings show that although SPECT and CMR detect transmural myocardial infarcts at similar rates, CMR systematically detects subendocardial infarcts that are missed by SPECT. A comparison of the CMR findings in animals confirmed that the subendocardial infarcts detected by CMR corresponded to infarcts defined histologically.

The general idea that SPECT misses small infarcts has been previously suggested.10, 11, 12 A possible reason for this lack of sensitivity is that the spatial resolution

References (26)

  • BeharS et al.

    Long-term prognosis of patients after a Q wave compared with a non-Q wave first acute myocardial infarction: data from the SPRINT registry

    Eur Heart J

    (1996)
  • ChidaK et al.

    A clinicopathologic correlation study of thallium-201 myocardial scintigraphy in diagnosis of myocardial infarction

    Jpn Heart J

    (1987)
  • MillerTD et al.

    Infarct size after acute myocardial infarction measured by quantitative tomographic 99mTc sestamibi imaging predicts subsequent mortality

    Circulation

    (1995)
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