Stress T1 mapping for the detection of obstructive coronary artery disease: a prospective diagnostic accuracy study

BACKGROUND: In the assessment of patients with suspected coronary artery disease (CAD), the diagnostic role of stress-perfusion cardiovascular magnetic resonance (CMR) is well established. However, its reliance on gadolinium-based contrast agents may restrict its application in certain populations. T1 mapping during vasodilatory stress has been proposed as a contrast-free alternative for detecting CAD. This study sought to compare the diagnostic accuracy of adenosine-stress T1 reactivity (ΔT1) with that of stress-perfusion CMR for identifying hemodynamically significant CAD. METHODS: Patients with suspected angina referred for diagnostic invasive coronary angiography underwent 3-Tesla CMR consisting of the following: (1) T1 mapping at rest and following intravenous adenosine using a modified Look-Locker inversion recovery sequence, (2) stress and rest perfusion, and (3) late-gadolinium enhancement. Significant CAD was defined invasively as fractional flow reserve ≤0.80 in epicardial vessels ≥2 mm diameter (or quantitative flow ratio ≤0.80 if unavailable). A ΔT1 vessel threshold (% increase in T1 from rest to stress) was derived from receiver operating characteristic analysis, using invasive coronary angiography as the reference standard. Stress-perfusion CMR was assessed qualitatively with CAD determined by the presence of ischemia and/or infarction, (A) per-vessel (as determined by two independent readers) and (B) per-patient (following consensus read). RESULTS: Of 121 prospectively recruited patients, 115 had paired T1 mapping and coronary angiography data (mean age 66 ± 9 years, 72% [83/115] male, CAD prevalence 51% [59/115]). ΔT1 demonstrated poor diagnostic performance for detecting significant CAD (area under the curve 0.59 [95% CI: 0.52, 0.65], p = 0.011), with an optimal vessel threshold ≤4.36% giving accuracy 54.9%, sensitivity 68.3%, and specificity 49.2%. Stress-perfusion CMR demonstrated superior diagnostic accuracy compared to ΔT1: (A) per-vessel (for the two independent reads, +26.2% [19.4%, 32.6%] and +26.7% [19.9%, 33.3%], both p<0.001) and (B) per-patient (for consensus read, +21.7% [10.2%, 32.6%], p<0.001). CONCLUSION: In patients with suspected angina, ΔT1 demonstrates limited diagnostic accuracy for the detection of obstructive CAD. Future efforts should be directed toward alternative contrast-free methods for the reliable detection of CAD in this population.