616 patients were included. Prevalence of cardiac involvement varied from 13% to 65% depending on patient selection and method used for detection. Pericarditis was the most common cardiac diagnosis with a prevalence of 30% and 43% in two prospective studies. Non-invasive cardiac tests, including electrocardiogram and echocardiogram, detected subclinical cardiac abnormalities in 6%–38% of patients. These abnormalities included conduction abnormalities, pericardial effusion and mitral valve prolapse. Diastolic dysfunction and accelerated atherosclerosis were well-documented in a case–control study. Three prospective studies revealed an overall mortality of 10.4% over the period of follow-up of 13–15 years. 20% of the mortality was directly attributable to cardiac cause.
Cardiac involvement was common among patients with MCTD though the involvement was often clinically inapparent. Non-invasive cardiac tests might have a role for subclinical disease screening for early diagnosis and timely treatment as cardiac involvement was one of the leading causes of mortality.