In the latest article in our Clinical Problem-Solving series, a 20-year-old female college student presented in the winter with a 2-week history of fatigue, cough, sinus congestion, and rhinorrhea, followed by 2 days of vomiting, diarrhea, and abdominal pain.
Clinically, influenza remains very difficult to distinguish from “influenza-like illnesses,” but the distinction is important. Among hospitalized patients, mortality from seasonal influenza and pandemic H1N1 influenza has been estimated to be as high as 8% and 14%, respectively, rates of death that are much higher than those from other respiratory viral infections. Complications from influenza must be considered when fever or respiratory symptoms persist, or if they recur soon after the initial syndrome resolves.
• What is the primary long-term complication of Kawasaki’s disease?
The primary long-term complication of Kawasaki’s disease is the development of stenosis at the site of the earlier coronary-artery aneurysm, which may lead to ischemic heart disease. In rare instances, visceral arterial aneurysms develop and lead to ischemic disease in adulthood.
• What are the most likely infectious causes of myocarditis?
Most cases of infectious myocarditis are due to common viruses, such as coxsackievirus, which are difficult to identify; nonetheless, nucleic acid tests for community-acquired respiratory viruses, such as influenza virus, should be performed, especially since such tests may remain positive for a prolonged period. Molecular and serologic assays for cytomegalovirus, Epstein-Barr virus, parvovirus, and HIV should also be performed. Less common infectious causes of myocarditis include Chagas’ disease, toxoplasmosis, trichinosis, and Lyme disease.
Morning Report Questions
Q: How common is myocarditis as a complication of influenza, and how is it diagnosed?
A: Myocarditis is an uncommon complication of influenza, with an overall incidence of up to 11%, although it is unknown whether the incidence varies according to the viral strain. Initially, symptoms can be subtle, but presentations with syncope, arrhythmia, and sudden death have been reported. Myocarditis is diagnosed on the basis of clinical, serologic, pathological, and imaging findings. The clinical hallmark of fulminant influenza-associated myocarditis is rapid hemodynamic decompensation within 2 weeks after the onset of influenza symptoms. Electrocardiography remains a sensitive test for most cardiac diseases, including myocarditis. Although almost any ECG [electrocardiogram] abnormality can be found in myocarditis, including QT prolongation and low voltage, some findings have prognostic significance. For example, a pseudoinfarction pattern – a Q wave with ST-segment elevation — has been correlated with a fulminant course. Myocarditis can be diagnosed with the use of endomyocardial biopsy, but false negative results are common. Since in most human cases and animal models of influenza-associated myocarditis, influenza viral replication has not been confirmed in myocardial tissue, biopsy will rarely prove that influenza is the cause of myocarditis.
Q: What is the prognosis for patients with fulminant influenza-associated myocarditis?
A: Patients with fulminant influenza-associated myocarditis usually require circulatory support. Intraaortic balloon pumps, percutaneous cardiopulmonary support, surgical left ventricular assist devices, and arteriovenous ECMO [extracorporeal membrane oxygenation] have all been used as bridges to myocardial recovery. Even with circulatory support, however, the short-term risk of death remains high; a recent review of 2009 cases of H1N1 influenza-associated myocarditis worldwide reported an in-hospital mortality of 24%. Patients who require prolonged mechanical support should be evaluated for cardiac transplantation. Patients with fulminant viral myocarditis who survive tend to recover completely within a few weeks and to have excellent long-term outcomes, with 1-year and 11-year survival rates estimated at 95% and 93%, respectively.