Changes in Myocardial Native T1 and T2 After Exercise Stress A Noncontrast CMR Pilot Study

OBJECTIVES This study assessed changes in myocardial native T-1 and T-2 values after supine exercise stress in healthy subjects and in patients with suspected ischemia as potential imaging markers of ischemia. BACKGROUND With emerging data on the long-term retention of gadolinium in the body and brain, there is a need for an alternative noncontrast cardiovascular magnetic resonance (CMR)-based myocardial ischemia assessment. METHODS Twenty-eight healthy adult subjects and 14 patients with coronary artery disease (CAD) referred for exercise stress and/or rest single-photon emission computed tomography/myocardial perfusion imaging (SPECT/MPI) for evaluation of chest pain were prospectively enrolled. Free-breathing myocardial native T-1 and T-2 mapping were performed before and after supine bicycle exercise stress using a CMR-compatible supine ergometer positioned on the MR table. Differences in T-1 (rest), T-2 (rest) and T-1 (post-exercise), T-2 (post-exercise) values were calculated as T-1 and T-2 reactivity, respectively. RESULTS The mean exercise intensity was 104 W, with exercise duration of 6 to 12 min. After exercise, native T-1 was increased in healthy subjects (p < 0.001). T-1 reactivity, but not T-2 reactivity, correlated with the rate-pressure product as the index of myocardial blood flow during exercise (r = 0.62; p < 0.001). In patients with CAD, T-1 reactivity was associated with the severity of myocardial perfusion abnormality on SPECT/MPI (normal: 4.9%; quartiles: 3.7% to 6.3%, mild defect: 1.2%, quartiles: 0.08% to 2.5%; moderate defect: 0.45%, quartiles: -0.35% to 1.4%; severe defect: 0.35%, quartiles: -0.44% to 0.8%) and had similar potential as SPECT/MPI to detect significant CAD (>50% diameter stenosis on coronary angiography). The area under the receiver-operating characteristic curve was 0.80 versus 0.72 (p = 0.40). The optimum cutoff value of T-1 reactivity for predicting flow-limiting stenosis was 2.5%, with a sensitivity of 83% and a specificity of 92%, a negative predictive value of 96%, a positive predictive value of 71%, and an area under the curve of 0.86. CONCLUSIONS Free-breathing stress/rest native T-1 mapping, but not T-2 mapping, can detect physiological changes in the myocardium during exercise. Our feasibility study in patients shows the potential of this technique as a method for detecting myocardial ischemia in patients with CAD without using a pharmacological stress agent. (C) 2020 Published by Elsevier on behalf of the American College of Cardiology Foundation.