Automated Pixel-Wise Quantitative Myocardial Perfusion Mapping by CMR to Detect Obstructive Coronary Artery Disease and Coronary Microvascular Dysfunction: Validation Against Invasive Coronary Physiology

Abstract

Objectives: This study sought to assess the performance of cardiovascular magnetic resonance (CMR) myocardial perfusion mapping against invasive coronary physiology reference standards for detecting coronary artery disease (CAD, defined by fractional flow reserve [FFR] ≤0.80), microvascular dysfunction (MVD) (defined by index of microcirculatory resistance [IMR] ≥25) and the ability to differentiate between the two.

Background: Differentiation of epicardial (CAD) and MVD in patients with stable angina remains challenging. Automated in-line CMR perfusion mapping enables quantification of myocardial blood flow (MBF) to be performed rapidly within a clinical workflow.

Methods: Fifty patients with stable angina and 15 healthy volunteers underwent adenosine stress CMR at 1.5T with quantification of MBF and myocardial perfusion reserve (MPR). FFR and IMR were measured in 101 coronary arteries during subsequent angiography.

Results: Twenty-seven patients had obstructive CAD and 23 had nonobstructed arteries (7 normal IMR, 16 abnormal IMR). FFR positive (epicardial stenosis) areas had significantly lower stress MBF (1.47 ± 0.48 ml/g/min) and MPR (1.75 ± 0.60) than FFR-negative IMR-positive (MVD) areas (stress MBF: 2.10 ± 0.35 ml/g/min; MPR: 2.41 ± 0.79) and normal areas (stress MBF: 2.47 ± 0.50 ml/g/min; MPR: 2.94 ± 0.81). Stress MBF ≤1.94 ml/g/min accurately detected obstructive CAD on a regional basis (area under the curve: 0.90; p < 0.001). In patients without regional perfusion defects, global stress MBF <1.82 ml/g/min accurately discriminated between obstructive 3-vessel disease and MVD (area under the curve: 0.94; p < 0.001).

Conclusions: This novel automated pixel-wise perfusion mapping technique can be used to detect physiologically significant CAD defined by FFR, MVD defined by IMR, and to differentiate MVD from multivessel coronary disease. A CMR-based diagnostic algorithm using perfusion mapping for detection of epicardial disease and MVD warrants further clinical validation.

Keywords: CMR; cardiovascular magnetic resonance; coronary artery disease; index of microcirculatory resistance; microvascular dysfunction; myocardial blood flow.

Copyright © 2019. Published by Elsevier Inc.

Figures

Figure 1:. Myocardial blood flow and FFR.

Scatter plots showing distribution of stress MBF and MPR according to FFR.

Figure 2:. Perfusion maps in single vessel disease.

Stress perfusion maps, first pass perfusion images and corresponding coronary angiogram of a 54-year old male with severe stenosis in the mid-LAD. (Cx: circumflex artery; LAD: left anterior descending artery; RCA: right coronary artery)

Figure 3:. Stress MBF and FFR.

Relationship between stress MBF and FFR in vessels with physiologically significant stenosis (FFR≤0.80).

Figure 4:. Diagnostic performance of stress MBF and MPR.

ROC curves for prediction of positive FFR on per-territory analysis.

Figure 5:. Global stress MBF and disease type.

Scatter plots showing distribution of global stress MBF according to disease type.

Figure 6:. Perfusion maps in three-vessel disease, MVD and unobstructed coronaries.

Examples of stress perfusion maps and corresponding coronary angiograms of three patients: normal coronary physiology in all vessels, MVD and severe three-vessel coronary disease. Lower panel shows stress perfusion maps of a control subject (Cx: circumflex artery; LAD: left anterior descending artery; RCA: right coronary artery)

Figure 7:. Differentiation of microvascular dysfunction from 3-vessel disease and normal.

Confusion matrix for detection of normal coronary physiology, microvascular dysfunction (MVD) and 3 vessel disease using global stress myocardial blood flow and visual analysis of first-pass perfusion.

Figure 8:. Proposed diagnostic algorithm for detection of obstructive epicardial disease and coronary microvascular dysfunction using CMR myocardial perfusion mapping.

Pathway for the detection of obstructive CAD and MVD based on regional and global stress MBF. Patients with a regional perfusion defect and regional stress MBF ≤1.94ml/g/min are likely to have obstructive one or two-vessel disease. Global stress MBF ≤2.25ml/g/min with visual perfusion defects is likely to be obstructive 3-vessel disease and global stress MBF