Cardiac and Respiratory Complications of Necrotizing Autoimmune Myopathy

Objective: To characterize the cardiorespiratory abnormalities in patients with necrotizing autoimmune myopathy (NAM). Patients and Methods: Cardiopulmonary features of patients with NAM evaluated in our neuromuscular clinic (January 1, 2004, to September 20, 2018) were reviewed retrospectively with respect to autoantibody status and history of cardiac disease. Clinical characteristics and laboratory findings were compared among patient subgroups. Results: We identified 109 patients with NAM: 36 anti–3-hydroxy-3-methylglutaryl coenzyme A reductase autoantibody (anti-HMGCR Ab)–positive, 18 anti–signal recognition particle antibody (anti-SRP Ab)–positive (3 dual anti-HMGCR/anti–SRP Ab–positive), and 58 seronegative. Median age at diagnosis was 60 years (range, 18-86 years). Forty-three patients had dyspnea at presentation and 32 patients had preexisting risk for cardiac disease (10 coronary artery disease and 28 hypertension). The electrocardiogram was abnormal in 55 of 86 patients (33 without cardiac risk factors), including prolonged corrected QT interval (QTc) (n=31), conduction blocks (n=19), and atrial or ventricular ectopic beats (n=10). Echocardiography was abnormal in 34 of 72 patients, including 19 of 45 without preexisting cardiac disease risks. Echocardiographic abnormalities included left ventricular diastolic dysfunction (n=31) and systolic dysfunction (n=8). The left ventricular diastolic dysfunction improved in 4 of 11 patients after treatment. Pulmonary function testing showed changes suggestive of neuromuscular respiratory muscle weakness in 51 of 66 patients and reduced carbon monoxide diffusing capacity in 11 of 35 patients. However, only 6 patients had radiographic evidence of interstitial lung disease (2 anti-HMGCR Ab–positive and 4 seronegative). Overnight oximetry revealed desaturations in 24 of 38 patients. Six patients required mechanical ventilation and 7 required noninvasive ventilatory support. Conclusion: Most patients with NAM exhibited cardiac and respiratory muscle dysfunction. Immunotherapy can improve echocardiographic abnormalities. Interstitial lung disease was rarely identified. Formal evaluation of cardiac and respiratory status should be integral in assessment of patients with NAM.