Abstract

National Survey of Influenza Myocarditis in Japanese Children in Three Seasons

Akira Ukimura, Kanta Kishi, Tomoyuki Yamada, Yuriko Shibata, Yukimasa Ooi, Yumiko Kanzaki and Hiroshi Tamai

An Influenza pandemic occurred in 2009. A nationwide, retrospective survey of Influenza myocarditis in Japanese children in 3 consecutive Influenza seasons was performed to compare Influenza myocarditis in the 2009/2010 season (the pandemic season), the 2010/2011 season, and the 2011/2012 season, by mailing questionnaires to 514 hospitals in Japan that have pediatric departments and collecting data from 285 hospitals. A questionnaire-based survey related to Influenza myocarditis was also conducted to evaluate the attitudes of Japanese pediatricians concerning the diagnosis of Influenza myocarditis. Fifteen Influenza myocarditis patients were reported, with 8 (H1N1pdm:6, type A:1, type B:1) from the 2009/10 season, 4 (type A:1, type B:3) from the 2010/11 season, and 3 (type B:3) from the 2011/12 season. Only 8 patients with Influenza A virus myocarditis were reported, with 7 patients from the 2009/2010 season, one from the 2010/2011 season, and none in the 2011/2012 season. Mortality was 33.3% (5/15) among the myocarditis patients. Twelve patients (12/15, 80%) were diagnosed with fulminant myocarditis with fatal arrhythmias and/or cardiogenic shock. In the pediatricians’ attitude survey, only 3.3% of pediatricians routinely examined the electrocardiograms of children hospitalized with Influenza infection in Japan. The number of Japanese children with myocarditis associated with Influenza A virus seemed to increase in the pandemic season. Increased awareness of Influenza myocarditis in children is needed during future Influenza pandemics.