Myocarditis with Pandemic H1N1 Influenza A in Children

Abstract & commentary

By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor, Stanford University School of Medicine, is Associate Editor for Infectious Disease Alert.

Synopsis: During a 30-day period in October 2009, 80 children were admitted to Rady Children's Hospital with confirmed H1N1 infection. Of those, four children were diagnosed with fulminant myocarditis, including one child who died.

Source: Bratinecsak A, et al. Fulminant myocarditis associated with pandemic H1N1 influenza A virus in children. J Am Coll Cardiol. 2010; 55: epub Feb 10.

Eighty children with PCR-documented pandemic H1N1 influenza A virus infection were admitted to Rady Children's Hospital in San Diego during a 30-day period in October 2009. Serum troponin I and creatine-kinase MB band levels were obtained in 11 children; eight underwent echocardiography. Four of these H1N1-infected children were diagnosed with myocarditis based on elevated cardiac enzymes (n = 2), significant decrease in left ventricular systolic function on echocardiogram (n = 3), or histologic evidence of severe myocarditis (n = 1). The children ranged in age from three months to nine years old. The five-year-old child who died had evidence of extensive myocardial damage at autopsy, including myocyte necrosis and lymphocytic infiltration of the interventricular septum and the AV node. This child experienced third-degree AV block antemortum. The three-month-old and nine-month-old patients required ECMO support and sustained intracranial hemorrhage and ischemic encephalopathy, although they recovered LV systolic function over 5-7 days.


While thankfully the numbers of new cases of pandemic H1N1 influenza A appear to be decreasing over the peak seen in the fall of 2009 in the United States and Canada, we are still seeing sporadic cases of critically ill adults and children with pandemic H1N1 requiring admission to our intensive care units at our county hospital. These case reports highlight the severity of clinical manifestations associated with infection in many cases of pandemic H1N1 influenza A seen over the last year. Influenza A virus-associated myocarditis has been exceedingly rare in the past, with only a handful of cases reported previously in the literature.1-3 Clinicians need to maintain a high index of suspicion for myocarditis in influenza A patients admitted to the intensive care unit with respiratory distress, since supportive treatment of acute congestive heart failure (possibly associated with conduction system abnormalities) will require other modalities in addition to ventilatory support.


  1. Mamas MA, et al. Cardiovascular manifestations associated with influenza virus infection. Int J Cardiol. 2008; 130:304-309.
  2. Guarner J, et al. Histopathologic and immunohistochemical features of fatal influenza virus infection in children during the 2003-2004 season. Clin Infect Dis. 2006;43:132-140.
  3. Onitsuka H, et al. Clinical manifestations of influenza A myocarditis during the influenza pandemic of winter 1998-1999. J Cardiol. 2001;37:315-323.