Myocardial fibrosis as an early manifestation of hypertrophic cardiomyopathy

BACKGROUND: Myocardial fibrosis is a hallmark of hypertrophic cardiomyopathy and a proposed substrate for arrhythmias and heart failure. In animal models, profibrotic genetic pathways are activated early, before hypertrophic remodeling. Data showing early profibrotic responses to sarcomere-gene mutations in patients with hypertrophic cardiomyopathy are lacking. METHODS: We used echocardiography, cardiac magnetic resonance imaging (MRI), and serum biomarkers of collagen metabolism, hemodynamic stress, and myocardial injury to evaluate subjects with hypertrophic cardiomyopathy and a confirmed genotype. RESULTS: The study involved 38 subjects with pathogenic sarcomere mutations and overt hypertrophic cardiomyopathy, 39 subjects with mutations but no left ventricular hypertrophy, and 30 controls who did not have mutations. Levels of serum C-terminal propeptide of type I procollagen (PICP) were significantly higher in mutation carriers without left ventricular hypertrophy and in subjects with overt hypertrophic cardiomyopathy than in controls (31% and 69% higher, respectively; P<0.001). The ratio of PICP to C-terminal telopeptide of type I collagen was increased only in subjects with overt hypertrophic cardiomyopathy, suggesting that collagen synthesis exceeds degradation. Cardiac MRI studies showed late gadolinium enhancement, indicating myocardial fibrosis, in 71% of subjects with overt hypertrophic cardiomyopathy but in none of the mutation carriers without left ventricular hypertrophy. CONCLUSIONS: Elevated levels of serum PICP indicated increased myocardial collagen synthesis in sarcomere-mutation carriers without overt disease. This profibrotic state preceded the development of left ventricular hypertrophy or fibrosis visible on MRI. (Funded by the National Institutes of Health and others.

Global circumferential and radial strain among patients with immune checkpoint inhibitor myocarditis

BACKGROUND Global circumferential strain (GCS) and global radial strain (GRS) are reduced with cytotoxic chemotherapy. There are limited data on the effect of immune checkpoint inhibitor (ICI) myocarditis on GCS and GRS. OBJECTIVES This study aimed to detail the role of GCS and GRS in ICI myocarditis. METHODS In this retrospective study, GCS and GRS from 75 cases of patients with ICI myocarditis and 50 ICI-treated patients without myocarditis (controls) were compared. Pre-ICI GCS and GRS were available for 12 cases and 50 controls. Measurements were performed in a core laboratory blinded to group and time. Major adverse cardiovascular events (MACEs) were defined as a composite of cardiogenic shock, cardiac arrest, complete heart block, and cardiac death. RESULTS Cases and controls were similar in age (66 15 years vs 63 12 years; P ¼ 0.20), sex (male: 73% vs 61%; P ¼ 0.20) and cancer type (P ¼ 0.08). Pre-ICI GCS and GRS were also similar (GCS: 22.6% 3.4% vs 23.5% 3.8%; P ¼ 0.14; GRS: 45.5% 6.2% vs 43.6% 8.8%; P ¼ 0.24). Overall, 56% (n ¼ 42) of patients with myocarditis presented with preserved left ventricular ejection fraction (LVEF). GCS and GRS were lower in myocarditis compared with on-ICI controls (GCS: 17.5% 4.2% vs 23.6% 3.0%; P < 0.001; GRS: 28.6% 6.7% vs 47.0% 7.4%; P < 0.001). Over a median follow-up of 30 days, 28 cardiovascular events occurred. A GCS (HR: 4.9 [95% CI: 1.6-15.0]; P ¼ 0.005) and GRS (HR: 3.9 [95% CI: 1.4-10.8]; P ¼ 0.008) below the median was associated with an increased event rate. In receiveroperating characteristic (ROC) curves, GCS (AUC: 0.80 [95% CI: 0.70-0.91]) and GRS (AUC: 0.76 [95% CI: 0.64-0.88]) showed better performance than cardiac troponin T (cTnT) (AUC: 0.70 [95% CI: 0.58-0.82]), LVEF (AUC: 0.69 [95% CI: 0.56-0.81]), and age (AUC: 0.54 [95% CI: 0.40-0.68]). Net reclassification index and integrated discrimination improvement demonstrated incremental prognostic utility of GRS over LVEF (P ¼ 0.04) and GCS over cTnT (P ¼ 0.002). CONCLUSIONS GCS and GRS are lower in ICI myocarditis, and the magnitude of reduction has prognostic significance. (J Am Coll Cardiol Img 2022;15:1883–1896) © 2022 the American College of Cardiology Foundation. Published by Elsevier. All rights reserved

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 all 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 ¼ 67), native T1 (1,079.0 55.5 ms vs. 1,000.3 22.1 ms; p < 0.001) and T2 (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 ¼ 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. (J Am Coll Cardiol 2021;77:1503–16) © 2021 by the American College of Cardiology Foundation