Myositis & the Heart: New Perspectives on the Pathogenesis & Management of Cardiac Involvement in Myositis

For the prevalence of myocarditis in myositis, which is largely unknown, Dr. Diederichsen said non-controlled case series using traditional cardiac MRI criteria have found changes consistent with subclinical myocarditis in 56–75% of myositis patients.⁴ In a similar study using T1 mapping in 25 PM/DM patients without cardiovascular symptoms, compared with 25 healthy controls, myocardial fibrosis was identified in 19% of PM/DM patients.⁵

“This indicates T1 mapping of cardiac MRI [may] be a valuable tool to detect subclinical myocardial involvement in asymptomatic myositis patients,” she said.

Further, although cardiac MRI cannot distinguish between different myocardial diseases by their magnetic properties alone, adding skeletal muscle measurements may help differentiate the conditions, as demonstrated by past research. A study from Huber et al. found MRI changes in the pectoralis muscle differentiated patients with idiopathic inflammatory myopathies from patients with acute viral myocarditis and healthy controls.⁶ In addition to detection, Dr. Diederichsen highlighted a 2020 study by Xu et al. suggesting T1 and T2 mapping of cardiac MRI may be valuable in monitoring subclinical myocardial involvement in myositis.⁷

In discussing recent studies on severe myocarditis in myositis patients, which are rare, Dr. Diederichsen said, “It’s quite striking that there is a lack of uniformity regarding subsets of myositis. These cases present various subsets of myositis with different autoantibody profiling.”

She next discussed the different autoantibodies that have been identified in patients with myositis and cardiac involvement, including myositis-specific autoantibodies, such as anti-signal recognition particle autoantibodies, and myositis-associated autoantibodies, such as anti-mitochondrial antibodies.

‘T1 mapping of cardiac MRI [may] be a valuable tool to detect subclinical myocardial involvement in asymptomatic myositis patients.’ —Louise P. Diederichsen, MD, PhD

Looking toward further research in this area, Dr. Diederichsen mentioned several unmet needs, including prospective cardiovascular studies on larger cohorts of myositis patients to identify cardiac biomarkers in myositis and international standardized cardiovascular screening recommendations for myositis.

Dr. Zakaria

Cardiologist’s Perspective
Dr. Zakaria, an associate professor of medicine at the Johns Hopkins University School of Medicine, Baltimore, who specializes in cardiac intensive care, discussed his experiences and treatment approaches for patients with cardiac manifestations of rheumatic disease.

He began by introducing the cardiologist’s general approach to evaluating heart involvement in patients with immune-mediated disease, as described in a position statement of the European Society of Cardiology Working Group on Myocardial and Pericardial Disease.⁸

Dr. Zakaria said a cardiologist’s diagnostic approach for identifying myocarditis begins with two questions: Does this patient with myositis have associated myocarditis or myopericarditis? Does the patient have clinical evidence of organ damage, such as heart failure or arrhythmias?