Michael S. Mitchell
Assistant Professor of Emergency Medicine
Section of Pediatric Emergency Medicine
Wake Forest University School of Medicine
Winston Salem, NC 27157
“In this world nothing can be said to be certain, except death and taxes.” –Benjamin Franklin
Death, taxes, and bronchiolitis.
Providers of pediatric patients know all too well that the winter season is characterized by colder weather, shorter days, and an abundance of children with bronchiolitis. Bronchiolitis is a dynamic disease and thus can have a varied presentation. It is within this variety of symptoms that overlapping medical conditions can hide, masquerading as bronchiolitis, especially as providers quickly become numb to the disease due to the overwhelming volume of patients presenting with similar symptoms. Myocarditis is one such disease with the potential for significant morbidity. Although it is rare, its symptoms significantly overlap those of bronchiolitis. It is the intent of this article to highlight these two disease states in helping pediatric providers identify myocarditis, essentially finding the proverbial needle in the haystack.
Bronchiolitis is a disease process caused by a viral lower respiratory tract infection. Viral invasion of airways causes a robust inflammatory cascade that leads to increased mucus production. The most common symptoms of bronchiolitis are rhinorrhea, cough, tachypnea, wheezing, and respiratory distress. Exam findings can consist of tachypnea, retractions at various sites, wheezes, crackles, and rhonchi that are generally found diffusely in all lung fields. Recent guidelines (2014) from the American Academy of Pediatrics1 promote the use of supportive care to assist in recovery and specifically suggest the avoidance of routine bronchodilators and chest radiography.
While bronchiolitis is a respiratory tract disease, myocarditis, in contrast, is a disease process characterized by inflammation of the myocardium. It is caused by a variety of insults: infectious, toxin-induced, and immune mediated; however, an infectious etiology, specifically viral, is the most important cause of myocarditis in North America and Europe. Common viral genomes found to cause myocarditis include enterovirus, adenovirus, influenza, human herpes virus-6, and parvovirus B19.2
Much like bronchiolitis, myocarditis can have a variety of presentations.
Some children will be asymptomatic while others can present in cardiogenic shock. Several studies3-4 have attempted to elucidate the most common presenting symptoms of pediatric patients with myocarditis. In general, the most common symptom category of these patients was respiratory in nature with around 70% of patients in both studies presenting in this manner. The most common exam findings were respiratory distress/tachypnea and tachycardia; however, these findings were not as uniform. Respiratory distress and tachypnea were found between 60-68% of the time and tachycardia was found between 32-58% of the time, though in patients under 10, Freedman et al. found tachycardia in 73% of patients.4 Unfortunately a consistent abnormality by history or exam could not be found. Providers should note the expansive overlap of respiratory and cardiac symptoms and exam findings with bronchiolitis.
Diagnostics haven’t proven to be the magic bullet either. The most consistent abnormality found on diagnostics is an abnormal electrocardiogram (ECG); however, any abnormality could be found including sinus tachycardia (most common in one study at 46%4), ST wave abnormalities (between 32-67% of patients), and QT prolongation. Chest radiographs can be helpful, but they are widely variable in sensitivity (55-90% of patients had an abnormal chest x-ray). Laboratory evaluations including white blood cell count, c-reactive protein, erythrocyte sedimentation rate, and troponin have been met with various sensitivities.
The diagnosis of myocarditis is elusive.
In two pediatric studies that were previously discussed, alternate diagnoses (notably respiratory) were given at the first visit 57-84% of the time. In order to make the diagnosis, it must remain on the differential diagnosis list, especially during the bronchiolitis season.
There may be subtle nuances which could assist in differentiating bronchiolitis and myocarditis. Bronchiolitis has a rather well-defined time course, with worsening symptoms peaking around day 3-4; myocarditis does not. Consider myocarditis when the apparent bronchiolitic patient is worsening outside of the expected time window. While tachycardia is not a consistent finding in myocarditis in the aforementioned studies, providers should nonetheless respect tachycardia. Bronchiolitis often causes tachycardia, but it’s usually secondary to fever, bronchodilator use, or dehydration. These patients should be monitored for improvement in heart rate, and myocarditis should be considered in those patients without heart rate reduction. Finally, while the heart and lung exam can be similar in these two disease states, bronchiolitis should not cause hepatomegaly. Providers should be mindful of the possible presence of hepatomegaly when examining a patient with presumed bronchiolitis. Hepatomegaly was found in 36-50% of pediatric patients with myocarditis, and while this is not a large percentage, it is much higher than would be expected in bronchiolitis.
Ultimately, the challenge is great.
Myocarditis mimics other respiratory illnesses in both presenting symptoms and in exam findings. There is no consistent abnormality within the physical exam to rely on making the diagnosis. Further frustrating to ED practitioners is that diagnostics can have varied results. Despite these setbacks, pediatric ED providers must remain vigilant to diagnose this disease. Much is at stake; myocarditis is the most common cause of dilated cardiomyopathy and has been associated with up to 50% of cases.5-6 Furthermore, myocarditis has been implicated as a cause of up to 12% of all cases of sudden death in young adults.7 Pediatric providers need to be mindful of myocarditis during the peak bronchiolitis season. Further research is needed to help elucidate more specific symptoms, exam findings, or diagnostics to more clearly identify myocarditis and differentiate it from other illnesses like bronchiolitis. Until that is accomplished, clinical suspicion remains paramount. Ultimately, myocarditis is a bronchiolitis masquerade, and a scary one at that. Remain diligent to find it.
- Ralston SL, Lieberthal AS, Meissner HC, et al. Clinical practice guideline: the diagnosis, management, and prevention of bronchiolitis. Pediatrics 2014;134:e1474-e1502.
- Caforio AL, Pankuweit S, Arbustini E et al. Current state of knowledge on aetiology, diagnosis, management, and therapy of myocarditis: a position statement of the European society of cardiology working group on myocardial and pericardial diseases. European Heart Journal 2013;34:2636-2648.
- Durani Y, Egan M, Baffa J, Selbst SM, and Nager AL. Pediatric myocarditis: presenting clinical characteristics. Am J Emerg Med.2009;27:942-947.
- Freedman SB, Haladyn JK, Floh A, Kirsh JA, Taylor G, and Thull-Freedman J. Pediatric myocarditis: emergency department clinical findings and diagnostic evaluation. Pediatrics 2007;120:1278-1285.
- Kindermann I, Barth C, Mahfoud F, et al. Update on myocarditis. J Am Coll Cardiol 2012;59:779-792.
- Towbin JA, Lowe AM, Colan SD, et al. Incidence, causes, and outcomes of dilated cardiomyopathy in children. JAMA 2006;296:1867-1876.
- Magnani JW and Dec GW. Myocarditis: current trends in diagnosis and treatment. Circulation 2006;113:876-890.