Diagnosis and management
Cardiac MRI increasingly has been replacing endomyocardial biopsy for diagnosis, with MRI exceeding biopsy use between 2009 and 2010, Dr. Butts said. The advantage of endomyocardial biopsy is that it’s specific, if not very sensitive. The test is invasive, however, requiring sedation and carrying the risk of tricuspid injury. The most common finding on cardiac MRI is late gadolinium enhancement (80%) while early gadolinium enhancement is less common (55%).
Although Dr. Butts mentioned the Dallas diagnostic criteria from 1987, he advocated for the more recent Lake Louise Criteria, which require clinical suspicion of myocarditis and at least two of three findings on MRI: T2-weighted myocardial abnormalities, T1 early or late gadolinium enhancement, or regional wall motion abnormalities or evidence of pericarditis
Point-of-care ultrasound can be useful for detecting myocarditis, but its success depends on whether the user can pick up on the subtle changes in ventricular function. “Just because someone has a point-of-care ultrasound that’s normal or thought to be normal, it shouldn’t rule out the diagnosis,” he said.
Learning the etiology of viral myocarditis often is difficult, and etiology doesn’t affect management of the condition, Dr. Butts said. Even in cases of myocarditis confirmed by biopsy, the virus may be identified in only about 60%-70% of cases with myocardial polymerase chain reaction. In clinical cases, the virus can be determined only about 25%-30% of the time with serum PCR.
Prognosis is usually good, with 80%-90% of children and teens going home transplant free despite most arriving critically ill and 50%-80% initially being admitted to ICU. Two-thirds of those discharged go home with heart failure medications, but only one in six are readmitted within a year.
The strongest risk factors for poor prognosis are younger age and being critically ill at presentation but other risk factors include female sex, poor ventricular function, poor perfusion on exam, increased dilation on echocardiogram, and a need for ECMO or inotropes or mechanical ventilation.
That said, Dr. Butts cautioned attendees not to ignore normal function. In one study of 171 patients, among 75 who presented with normal function, 15% went home with inotropes, 12% required mechanical ventilation, 9% had arrhythmia, and 5% needed extracorporeal membrane oxygenation.
A big question in treatment is whether to give IVIG or not and the evidence is murky, Dr. Butts said. He reviewed a couple studies on IVIG, including one that suggested better ventricular functional recovery with the treatment but those who received IVIG were also more likely to be on an ACE inhibitor.
“Was it the ACE inhibitor or was it IVIG? We don’t know,” he said. Different cardiologists may give different opinions on IVIG. “It has nothing to do with the actual evidence behind it.”
IVIG has drawbacks: It’s very expensive and it involves risks that include serum sickness and interstitial nephritis.
“Pediatricians typically aren’t going to directly decide on giving or not giving IVIG,” Dr. Han said. “Typically, the ultimate choice comes from a group discussion between the hospital cardiologist – perhaps the hospitalist pediatrician if they are involved – and the family. We acknowledge the ambiguity of the evidence and decide based upon the severity of the initial disease process.”