Defining cardiac involvement in idiopathic inflammatory myopathies: a systematic review

Objective: Recent advances in cardiac MRI (CMR) and other diagnostic techniques have made it easier to identify subclinical cardiac inflammation and dysfunction in the idiopathic inflammatory myopathies (IIM). Herein, we systematically review the literature regarding cardiac involvement in IIM. Methods: We searched Medline and EMBASE from 1990 to 2020 using keywords related to IIM and cardiac disease. We included English language studies in adults with any immune-mediated, inflammatory muscle pathology. Results: We identified 10 425 potentially relevant abstracts, of which 29 were included. Most frequently these included patients with PM or DM without symptomatic myocarditis. Five categories of cardiac investigation were used in these patients: cardiac enzyme testing, ECG, transthoracic echocardiography, CMR and nuclear medicine testing. Patients with clinical myocarditis had universally abnormal cardiac troponin levels and ECG. Elevated cardiac troponin T was more common than cardiac troponin I and may correlate with disease activity, whereas cardiac troponin I was more specific for cardiac involvement. Non-specific ECG changes were common. The major finding on transthoracic echocardiography was abnormal ejection fraction. Gross systolic dysfunction was unusual, but subclinical systolic dysfunction was reported in several studies. Abnormal diastolic function was common and may be associated with disease duration. Late gadolinium enhancement (reflecting regional necrosis or scarring) and abnormal myocardial mapping parameters (reflecting myocardial inflammation, fibrosis and oedema) were frequently identified on CMR, suggesting significant subclinical myocardial pathology (despite typically normal ejection fraction). Conclusion: Abnormal cardiac investigations are commonly found in asymptomatic IIM patients, which has potential prognostic and treatment implications.