Early T1 shortening (eT1sh): a new CMR parameter to detect myocardial hyperemia in acute myocarditis

Purpose: To evaluate T1-mapping based approaches for the quantification of hyperemia in patients with acute myocarditis. Methods and materials: 55 subjects (40 patients with acute myocarditis [AM]; 15 age- and sex-matched healthy control subjects [HC]) underwent 1.5T CMR. T1 mapping was acquired before (native T1) and 2 minutes after gadoliunium administration (early-enhanced T1). 3 different T1 mapping-based parameters were calculated: early enhanced T1-rt (eT1), early T1-rt shortening (eT1sh), and early relative T1-rt shortening (erT1sh). Optimal cut-off values and their diagnostic performances in the identification of AM were calculated. Results: In AM patients, median eT1 was 275.6 ms [252-297], eT1sh was 75% [73%-78%], and erT1sh was 2.15 [1.83-2.59], all being significantly higher with respect to HC (p=0.0014, p<0.0001, and p<0.0001, respectively). eT1sh showed the best diagnostic performance with excellent AUC (97%, 95% confidence interval, CI: [93%-100%]). A reduction of eT1sh ≥69.5% identified AM with very high sensitivity (93%), specificity (100%), NPV (83%), PPV (100%), and accuracy (95%). eT1 had a good AUC (92.5%, 95% CI: [86%-99%]), slightly worse than eT1sh. eT1≤331 ms identified AM with 93% sensitivity, 87% specificity, 81% NPV, 95% PPV, and 91% accuracy. erT1sh showed the worst diagnostic performance with 78% AUC (95% CI: [66%-91%]). erT1sh>1.9 identified AM with 68% sensitivity, 87% specificity, 50% NPV, 93% PPV, and 73% accuracy. Conclusion: eT1sh showed the best diagnostic performance in the identification of AM. It can be a promising alternative method for the detection of hyperemia in AM. Limitations: A relatively small sample size. Ethics committee approval: The study was approved by the Institutional Review Board. Written informed consent was obtained. Funding: The study was partially granted by the Italian Ministery