Endocardial extent by contrast enhanced cardiac magnetic resonance imaging is not an accurate method for assessing myocardium at risk; validation with T2-weighted cardiac magnetic resonance imaging

Introduction

In the situation of acute coronary occlusion, the myocardium supplied by the occluded vessel is subject to ischemia and is referred to as the myocardium at risk (MaR). It has previously been shown that cardiac magnetic resonance (CMR) imaging can be used for the assessment of MaR employing a T2-weighted edema sequence. Recently, it has been suggested that the endocardial extent of hyperenhancement as assessed by contrast enhanced CMR can also be used to quantify the MaR.

Purpose

We sought to assess the ability of endocardial extent by contrast enhanced CMR to quantify MaR in relation to T2-weighted edema imaging.

Methods

Thirty-six patients with early reperfused first-time ST-segment elevation myocardial infarction underwent CMR imaging within 7 days after percutaneous coronary intervention. The MaR was determined by contrast enhanced endocardial extent and compared to the MaR as determined by T2-weighted edema imaging.

Results

The MaR was 34 ± 10% (range 16-59) and 24 ± 12% (range 0-66) of the left ventricle by T2-weighted edema imaging and contrast enhanced endocardial extent, respectively. Comparison of the two methods yielded a weak correlation (r2 = 0.26, p = 0.002) with a bias of -10 ± 11% (Figure 1). The MaR was consistently larger than the final infarct size (14 ± 10%, range 0-47), which resulted in a myocardial salvage of 57 ± 21% (range 12-100).

Figure 1

Agreement between contrast enhanced endocardial extent and T2-weighted CMR. (A) The MaR determined by contrast enhanced endocardial extent versus the MaR as determind by T2-weighted CMR. Solid line+ of identity; dashed line = regression line. (B) Bland-Altman graph showing the difference between contrast enhanced endocardial extent and T2-weighted CMR. Soldid line = mean difference; dashed lines = ± 2SD. Patients with an aborted infraction of myocardial salvage over 90% are presented as encircled dots.

Conclusion

This study demonstrated that the endocardial extent as assessed by contrast enhanced CMR is not an accurate method for the assessment of MaR in patients with early reperfusion, using T2-weighted edema imaging as reference method.