When looking for historical clues, the cardiologist wants to see if the patient has any evidence of unexplained dyspnea, which may indicate heart failure; palpitations or syncope, which may indicate the patient has had arrythmias; and chest pain, which may be a sign of heart failure, myopericarditis or accelerated coronary artery disease.
“We have to remember that patients with autoimmune myositis actually have higher rates of macrovascular and microvascular coronary artery disease,” he said.
The next diagnostic approach is a physical examination for heart failure, which looks for important signs, such as a third heart sound, abdominojugular reflux, jugular venous distension or rales.9
Next, a cardiologist will order a battery of tests, including laboratory studies and imaging. Lab tests include—but are not limited to—a blood draw to identify elevated levels of troponin and disease-related biomarkers. However, Dr. Zakaria noted, myocarditis can be found in patients with and without myositis-related antibodies.
Imaging studies can include electrocardiogram, in which 85% of patients with myocarditis show an abnormality, and echocardiogram, in which 65% of myocarditis patients show abnormality. Cardiac MRI is the best way to evaluate myocarditis non-invasively, he said, citing a study by Sharma et al.10
“Patients with myocarditis have a characteristic pattern of myocardial involvement. It tends to occur in the subepicardial or mid-myocardial regions, which are different [from] what you see in patients with coronary artery disease,” Dr. Zakaria said.
Cardiac computed tomography has the added benefit of evaluating the coronary artery to look for obstructive disease.
Endomyocardial biopsy is still the gold standard to diagnose myocarditis and guide changes in disease management. However, it’s an invasive procedure with adverse events. Dr. Zakaria said, “I tend to consider it if a patient has clear evidence of non-ischemic heart failure and we need to confirm a diagnosis of myocarditis.”
After myocarditis is diagnosed, Dr. Zakaria works closely with the referring rheumatologist to plan care management. “When I’m thinking of treating a patient’s myocarditis, it’s hard for me to do that in isolation from rheumatologic treatments, because myocardial involvement is secondary to the underlying myositis,” he said.
In this case, he tends to follow the lead of the rheumatologist, because the patient is often on multiple immunosuppressants and immunomodulators. One caveat to this approach is if the patient has severe decompensation in cardiac status, which usually indicates the need for more intensive therapy. Dr. Zakaria also looks for side effects of therapies, such as complications to the heart from high doses of steroids.
