Myocardial T1 and T2 Mapping by Magnetic Resonance in Patients With Immune Checkpoint Inhibitor–Associated Myocarditis

BACKGROUND Myocarditis is a potentially fatal complication of immune checkpoint inhibitor (ICI) therapy. Data on the utility of cardiovascular magnetic resonance (CMR) T1 and T2 mapping in ICI myocarditis are limited.OBJECTIVES This study sought to assess the value of CMR T1 and T2 mapping in patients with ICI myocarditis.METHODS In this retrospective study from an international registry of patients with ICI myocarditis, clinical and CMR findings (including T1 and T2 maps) were collected. Abnormal T1 and T2 were defined as 2 SD above site (vendor/field strength specific) reference values and a z-score was calculated for each patient. Major adverse cardiovascular events (MACE) were a composite of cardiovascular death, cardiogenic shock, cardiac arrest, and complete heart block.RESULTS Of 136 patients with ICI myocarditis with a CMR, 86 (63%) had T1 maps and 79 (58%) also had T2 maps. Among the 86 patients (66.3 +/- 13.1 years of age), 36 (41.9%) had a left ventricular ejection fraction <55%. Across alt patients, mean z-scores for T1 and T2 values were 2.9 +/- 1.9 (p < 0.001) and 2.2 +/- 2.1 (p < 0.001), respectively. On Siemens 1.5-T scanner (n = 67), native T1(1,079.0 +/- 55.5 ms vs. 1,000.3 +/- 221 ms; p < 0.001) and 12 (56.2 +/- 4.9 ms vs. 49.8 +/- 2.2 ms; p < 0.001) values were elevated compared with reference values. Abnormal T1 and T2 values were seen in 78% and 43% of the patients, respectively. Applying the modified Lake Louise Criteria, 95% met the nonischemic myocardial injury criteria and 53% met the myocardial edema criteria. Native T1 values had excellent discriminatory value for subsequent MACE, with an area under the curve of 0.91(95% confidence interval: 0.84 to 0.98). Native T1 values (for every 1-unit increase in z-score, hazard ratio: 1.44; 95% confidence interval: 1.12 to 1.84; p = 0.004) but not T2 values were independently associated with subsequent MACE.CONCLUSIONS The use of T1 mapping and application of the modified Lake Louise Criteria provides important diagnostic value, and T1 mapping provides prognostic value in patients with ICI myocarditis. (C) 2021 by the American College of Cardiology Foundation.