T2 mapping of the heart: correlation with measures of cardiopulmonary MRI in COVID-19 convalescents.

PURPOSE: Alterations in myocardial and blood pool relaxation times may be due to physiologic change or pathological factors. Blood T2 relaxation time is sensitive to oxygenation changes. We aimed to assess the association between indices of cardiopulmonary circulation and cardiac parametric mapping. METHODS: 213 adults recovered from COVID-19 infection (96 men, mean age 55 ± 14 years) were scanned at a 3 T MRI. Left and right ventricular (LV and RV) function and structure were measured in the cine images. Normalized pulmonary transit time (nPTT), pulmonary and aortic full width half maximum (PA and AO FWHM) were assessed in the lung perfusion images. Linear regression slope between myocardial and LV blood T2 was used to normalize myocardial T2 to the mean blood T2 of the study population. Same concept was adapted to normalize LV blood T2 by heart rate. RESULTS: After normalization to LV blood T2, myocardial T2 demonstrated positive associations with RV volumes and AO FWHM. Lower nPTT, larger ventricular volumes, and higher stroke volumes were associated with higher RV blood T2. AO FWHM, LV volumes and mass were positively, and LV EF negatively, associated with LV blood T2. Similar results were found following T2 correction for heart rate. CONCLUSIONS: Myocardial and ventricular blood T2 values are associated with ventricular structure and function. Lower LV function is associated with higher LV blood T2 values. Ventricular blood T2 is a promising index to provide a clinically feasible measure of cardiac performance.