Superior diagnostic performance of perfusion-cardiovascular magnetic resonance versus SPECT to detect coronary artery disease: The secondary endpoints of the multicenter multivendor MR-IMPACT II (Magnetic Resonance Imaging for Myocardial Perfusion Assessment in Coronary Artery Disease Trial)

Abstract

Background: Perfusion-cardiovascular magnetic resonance (CMR) is generally accepted as an alternative to SPECT to assess myocardial ischemia non-invasively. However its performance vs gated-SPECT and in sub-populations is not fully established. The goal was to compare in a multicenter setting the diagnostic performance of perfusion-CMR and gated-SPECT for the detection of CAD in various populations using conventional x-ray coronary angiography (CXA) as the standard of reference.

Methods: In 33 centers (in US and Europe) 533 patients, eligible for CXA or SPECT, were enrolled in this multivendor trial. SPECT and CXA were performed within 4 weeks before or after CMR in all patients. Prevalence of CAD in the sample was 49% and 515 patients received MR contrast medium. Drop-out rates for CMR and SPECT were 5.6% and 3.7%, respectively (ns). The study was powered for the primary endpoint of non-inferiority of CMR vs SPECT for both, sensitivity and specificity for the detection of CAD (using a single-threshold reading), the results for the primary endpoint were reported elsewhere. In this article secondary endpoints are presented, i.e. the diagnostic performance of CMR versus SPECT in subpopulations such as multi-vessel disease (MVD), in men, in women, and in patients without prior myocardial infarction (MI). For diagnostic performance assessment the area under the receiver-operator-characteristics-curve (AUC) was calculated. Readers were blinded versus clinical data, CXA, and imaging results.

Results: The diagnostic performance (= area under ROC = AUC) of CMR was superior to SPECT (p = 0.0004, n = 425) and to gated-SPECT (p = 0.018, n = 253). CMR performed better than SPECT in MVD (p = 0.003 vs all SPECT, p = 0.04 vs gated-SPECT), in men (p = 0.004, n = 313) and in women (p = 0.03, n = 112) as well as in the non-infarct patients (p = 0.005, n = 186 in 1-3 vessel disease and p = 0.015, n = 140 in MVD).

Conclusion: In this large multicenter, multivendor study the diagnostic performance of perfusion-CMR to detect CAD was superior to perfusion SPECT in the entire population and in sub-groups. Perfusion-CMR can be recommended as an alternative for SPECT imaging.

Trial registration: ClinicalTrials.gov, Identifier: NCT00977093.

Figures

Figure 1

Flow Chart. Flow chart demonstrating the number of eligible patients and drop-outs. CMR: cardiovascular magnetic resonance; CM: contrast medium (Gd-DTPA-BMA); CXA: coronary X-ray angiography; Pats: patients. SPECT: single-photon-emission-computed-tomography.

Figure 2

Diagnostic performance in the entire study population – ROC analyses. Diagnostic performance of perfusion-CMR and SPECT imaging compared by receiver operating characteristics curves (ROC) analyses for detection of CAD (per patient analysis). A). CMR performs superior to all SPECT studies in 1–3 vessel disease (1–3 VD) patients and is also superior to the gated-SPECT and ungated-SPECT groups. Difference in AUC between gated-SPECT and ungated-SPECT did not reach statistical significance. The dots on the ROC curve for CMR indicate the sensitivities and specificities for various thresholds (i.e. at summed gradings of 23 [dot on the left], 21 [middle dot], and 19 [dot on the right]) with + and – indicating superiority and inferiority vs SPECT, respectively, and = indicating non-inferiority versus SPECT for both, sensitivity and specificity, as defined as primary end-point of the study (for details on the definition of the primary endpoint see reference [16]). These dots located at various reading thresholds illustrate that comparisons for sensitivity and specificity depend on the thresholds applied for the 2 tests. Thus, for the same data set, superiority or inferiority can be obtained (for sensitivity or specificity comparisons) depending on the reading thresholds used. Reading CMR studies at a high threshold for perfusion deficits (point on the left on the ROC curve) yields CMR inferiority for sensitivity and CMR non-inferiority for specificity vs SPECT, while the same CMR test read with a low threshold (point on the right of the ROC curve) yields a superior sensitivity for CMR vs SPECT with inferiority for specificity. This dependence of comparisons upon reading thresholds is eliminated by the ROC approach, which assesses test performance over the entire range of reading thresholds. B): Perfusion-CMR is superior to SPECT in multi-vessel disease patients. Sub-group analyses for gated-SPECT and ungated-SPECT yielded superiority for CMR, as well.

Figure 3

Diagnostic performance in men and women – ROC analyses. Perfusion-CMR is superior vs SPECT in both, men (A) and women (B). Numbers indicate mean ± standard error of the AUC.