Differentiating ischemic from healthy myocardium using cardiovascular magnetic resonance dipyridamole rest and stress T1 mapping

Cardiovascular magnetic resonance (CMR) stress T1 mapping using adenosine and regadenoson can differentiate ischemic, infarcted, and healthy myocardium. However, the effect of dipyridamole remains unclear. This study evaluates whether dipyridamole-induced stress T1-mapping can distinguish myocardial tissue types. Twenty-five healthy controls and 20 patients with coronary artery disease (CAD) underwent rest and dipyridamole stress T1-mapping (ShMOLLI), followed by gadolinium-based quantitative perfusion imaging at 1.5T. Native T1 values and stress T1 reactivity (dT1) were assessed across different myocardial tissues. Correlations between dT1 and myocardial blood flow (MBF) were examined. In healthy controls, global rest T1 was 934 ± 26ms, with a stress-induced increase of 6.5 ± 0.6% (p < 0.0001). Infarcted myocardium showed elevated resting T1 (1146 ± 71 ms) with an absent stress response (dT1 = -0.9%±1.8%). Ischemic myocardium had mildly elevated rest T1 (965 ± 26 ms; p < 0.001) and blunted reactivity (dT1 = 1.3 ± 0.6%) compared to healthy myocardium. Remote myocardium had rest T1 similar to normal tissue (936 ± 19 ms; p > 0.05) but reduced stress reactivity (dT1 = 4.5 ± 1.1%; p < 0.0001) compared to norm. dT1 strongly correlated with stress MBF (r = 0.80) and myocardial perfusion reserve (r = 0.70) (both p < 0.0001). Dipyridamole-induced stress T1-mapping can differentiate infarcted, ischemic, and healthy myocardium, supporting its use in non-contrast CMR for myocardial tissue characterization.