Assessment of advanced coronary artery disease: advantages of quantitative cardiac magnetic resonance perfusion analysis

Abstract

Objectives: The purpose of this paper was to compare quantitative cardiac magnetic resonance (CMR) first-pass contrast-enhanced perfusion imaging to qualitative interpretation for determining the presence and severity of coronary artery disease (CAD).

Background: Adenosine CMR can detect CAD by measuring perfusion reserve (PR) or by qualitative interpretation (QI).

Methods: Forty-one patients with an abnormal nuclear stress scheduled for X-ray angiography underwent dual-bolus adenosine CMR. Segmental myocardial perfusion analyzed using both QI and PR by Fermi function deconvolution was compared to quantitative coronary angiography.

Results: In the 30 patients with complete quantitative data, PR (mean +/- SD) decreased stepwise as coronary artery stenosis (CAS) severity increased: 2.42 +/- 0.94 for <50%, 2.14 +/- 0.87 for 50% to 70%, and 1.85 +/- 0.77 for >70% (p < 0.001). The PR and QI had similar diagnostic accuracies for detection of CAS >50% (83% vs. 80%), and CAS >70% (77% vs. 67%). Agreement between observers was higher for quantitative analysis than for qualitative analysis. Using PR, patients with triple-vessel CAD had a higher burden of detectable ischemia than patients with single-vessel CAD (60% vs. 25%; p = 0.02), whereas no difference was detected by QI (31% vs. 21%; p = 0.26). In segments with myocardial scar (n = 64), PR was 3.10 +/- 1.34 for patients with CAS <50% (n = 18) and 1.91 +/- 0.96 for CAS >50% (p < 0.0001).

Conclusions: Quantitative PR by CMR differentiates moderate from severe stenoses in patients with known or suspected CAD. The PR analysis differentiates triple- from single-vessel CAD, whereas QI does not, and determines the severity of CAS subtending myocardial scar. This has important implications for assessment of prognosis and therapeutic decision making.

Figure 1. Qualitative Interpretation of Perfusion CMR Imaging

First-pass perfusion images obtained during peak contrast enhancement cardiac magnetic resonance (CMR) imaging of the basal left ventricular (left column), mid-ventricular (middle column), and apical (right column) slices are shown during hyperemic (top row) and resting (bottom row) conditions. The white arrows point to a large perfusion defect extending from the basal to the apical slice.

Figure 2. Perfusion Time Intensity Curves

Representative time intensity curves used for Fermi function deconvolution are shown. The red line and circles represent a typical arterial input function (AIF). The top blue line and Xs represent the tissue function (TF) in a segment supplied by a coronary artery without a stenosis. The bottom blue line and triangles represent the tissue function in a segment supplied by a stenosed coronary artery.

Figure 3. Relationship Between Perfusion Reserve and Percent Stenosis

Segmental perfusion reserve (mean ± SE) decreases in a stepwise manner as the severity of coronary stenosis increases.

Figure 4. Comparison of Qualitative Interpretation and Perfusion Reserve Analysis, Example 1

(A) No perfusion defects are visually appreciated on first-pass perfusion images obtained during peak contrast enhancement of the basal left ventricular (left column), the mid-ventricular (middle column), and the apical (right column) slices during hyperemic (top row) or resting (bottom row) conditions. (B) Measured perfusion reserve for each of the 16 segments is plotted using a bulls-eye graph with the color scale shown on the right. Fifty-six percent of the left ventricle had a perfusion reserve <1.55. (C) Based on quantitative coronary angiography, each of the 16 segments was determined to be supplied by a stenosis <50% (yellow), >50% (orange), or >70% (red). Despite the absence of a visually appreciable perfusion defect, an abnormal perfusion reserve was present in this patient with multivessel coronary artery disease.

Figure 5. Assessment of LV Ischemic Burden

Comparison of qualitative interpretation and perfusion reserve analysis: unlike perfusion reserve analysis, qualitative interpretation cannot detect the difference in ischemic burden (percent left ventricular [LV] ischemia [mean ± SE]) that is present in patients with single-vessel (1V) coronary artery disease (CAD) (blue bars) or triple-vessel (3V) CAD (gold bars).

Figure 6. Comparison of Qualitative Interpretation and Perfusion Reserve Analysis, Example 2

(A) First-pass perfusion images obtained during peak contrast enhancement of the basal left ventricular slice (left column), the mid-ventricular slice (middle column), and the apical slice (right column) are shown during hyperemic (top row) and resting (bottom row) conditions. The white arrows point to a small perfusion defect in the inferolateral wall. (B) Perfusion reserve for each of the 16 segments is plotted using a bulls-eye graph with the color scale shown on the right. Fifty-six percent of the left ventricle had a perfusion reserve <1.55. (C) Based on quantitative coronary angiography, each of the 16 segments was determined to be supplied by a stenosis <50% (yellow), >50% (orange), or >70% (red). Qualitative interpretation significantly underestimated the ischemic burden in this patient with multivessel coronary artery disease.