- Of 1.1% of 964 patients who developed myocarditis, close to half (46%) developed a major adverse cardiac event, or MACE.
- Myocarditis occurred within a median of 34 days during the use of immune checkpoint inhibitors (ICI) and was detectable through an abnormal electrocardiogram (EKG) and elevated troponin.
- 94% of myocarditis patients at clinical presentation had elevated troponin levels, 89% had abnormal electrocardiograms and 66% had abnormal natriuretic peptides, while 51% had a normal left ventricular ejection fraction, or LVEF.
- 89% of myocarditis patients received steroids as the initial therapy with a higher initial steroid dose associated with a lower rate of major adverse cardiac events.
Myocarditis is an uncommon but potential fatal side effect of the immune checkpoint inhibitors (ICI), medications that are being increasingly used to treat cancer. Before ICI, determining who might develop myocarditis is challenging because patients often have a normal baseline left ventricular ejection fraction (LVEF) and EKG. To fill in this knowledge gap, researchers led by Tomas G. Neilan, MD, MPH, director of the Cardio-Oncology Program at Massachusetts General Hospital, set up a study to identify the prevalence of myocarditis as well as its typical presentation and clinical course. They found a prevalence rate of 1.1% and close to half (46%) of those patients went on to experience a major adverse cardiac event (MACE).
Further investigation revealed that routine tests—namely, an EKG and troponin test— may help identify patients with myocarditis relatively early and allow doctors to intervene with high-dose steroid treatment.
Using an eight-center registry study, researchers identified patients with ICI myocarditis. Results, published in the Journal of the American College of Cardiology, revealed that the rate of myocarditis was relatively low and that the median time to onset of myocarditis was 34 days. Researchers found that once patients on ICI present with myocarditis, an EKG and troponin test can typically identify the condition. Specifically, they found that 94% of myocarditis patients at clinical presentation had elevated troponin levels, 89% had abnormal ECGs, and 66% had abnormal natriuretic peptides, while 51% had a normal LVEF. In fact, troponin levels at final/discharge troponin T of ≥1.5 ng/ml turned out to indicate a 4-fold increased risk of a MACE.
Once clinicians identified myocarditis, 89% of patients received steroids with a higher initial steroid dose associated with a lower rate of MACE (cardiovascular death, cardiogenic shock, cardiac arrest or complete heart block).
The team also looked at differences that might exist between myocarditis cases and controls in terms of other ICI-related side effects. The only variation found was that those with myocarditis who had an additional previous immune-related side effect also had higher rates of hepatitis.