Good Agreement Between CMR, FFR for Evaluating Nonculprit STEMI Lesions

Cardiac magnetic resonance (CMR) imaging and invasive measurements of fractional flow reserve (FFR) have moderate-to-good agreement in evaluating nonculprit lesions in patients with ST-segment elevation myocardial infarction (STEMI) with multivessel disease, according to a study published in JACC: Cardiovascular Imaging. Moreover, fully quantitative analysis of myocardial perfusion yields similar diagnostic performance as semiquantitative and visual analysis yield.

This substudy of data from the REDUCE-MVI trial at the Vrije Universiteit Amsterdam University Medical Center was designed to determine the agreement between CMR imaging and invasive measurements of FFR for evaluating nonculprit lesions after STEMI, as well as to investigate whether fully quantitative analysis of myocardial perfusion is superior to semiquantitative and visual analysis. Participants in the larger study were enrolled if they had a first STEMI with at least 1 intermediate lesion in a nonculprit vessel after the successful revascularization of the culprit (N=77).

An intermediate lesion was defined as stenosis 50% to 90% in diameter. Exclusion criteria included decompensated heart failure, cardiogenic shock, chronic total occlusion, and left main disease. Follow-up CMR, invasive coronary angiography, and FFR measurements were scheduled for 1-month post-index event, with CMR always preceding invasive testing. Hemodynamically obstructive nonculprit lesions were defined as FFR 0.80 or lower.

Stress perfusion CMR was successfully performed on 77 of the 90 patients. Among the 77 total participants, 94 nonculprit vessels with 50% or greater diameter stenosis were found and used for analysis. Hemodynamically obstructive nonculprit lesions were found in 36 vessels (38%) of 31 patients (40%). Visual analysis showed an area under the curve (AUC) of 0.74 (95% CI, 0.62-0.83) for detecting nonculprit lesions with an optimal cutoff of at least 1 at a per-patient level, resulting in 73% sensitivity and 70% specificity.

For semiquantitative analysis, the relative upslope of the stress signal intensity time curve (stress rel upslope) and relative upslope-derived flow reserve (MFR rel upslope) had respective AUCs of 0.66 (95% CI, 0.54-0.77) and 0.71 (95% CI, 0.59-0.81) for diagnosing nonculprit vessels on a per-patient basis with FFR 0.80 or lower.

Using cutoff values of 9.1% for stress rel upslope, per-patient sensitivity was 76% and specificity was 65%. Using a 1.4% cutoff value for MFR rel upslope, there was a similar diagnostic performance of 61% sensitivity and 83% specificity (P =.50).

Stress myocardial blood flow showed an AUC of 0.76 (95% CI, 0.64-0.85), with 69% sensitivity and 77% specificity using a cutoff value for 1.98 mL/min/g. MFR similarly displayed an AUC of 0.82 (95% CI, 0.71-0.90), with 82% sensitivity and 71% specificity using a cutoff value of 2.10 mL/min/g. Similar diagnostic performances were yielded from visual, semi-quantitative, and fully quantitative analyses (P >.05 for all).

This study had several limitations. The sample size was small, so the study could have been underpowered. The results should be interpreted with caution because FFR has not been established as the gold standard for managing nonculprit lesions after STEMI the way it has been for guiding revascularization in cases of stable coronary artery disease. Furthermore, FFR measurements could have been influenced by collateral connections to/from stenotic nonculprit vessels. Nevertheless, the investigators concluded that when evaluating nonculprit lesions in patients with STEMI with multivessel disease who have been reperfused, CMR and FFR have moderate-to-good agreement, and fully quantitative analysis is not superior to semi-quantitative analysis or visual analysis of myocardial perfusion.

Disclosure

Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Everaars H, van der Hoeven NW, Janssens GN, et al. Cardiac magnetic resonance for evaluating nonculprit lesions after myocardial infarction: Comparison with fractional flow reserve [published online September 12, 2019]. JACC Cardiovasc Imaging. doi:10.1016/j.jcmg.2019.07.019