title: Influenza myocarditis and myositis: case presentation and review of the literature.
abstract: Myocarditis, a general inflammatory condition of the heart muscle, can result from a variety of etiologies, the most common being viral. Despite common pathogens, concomitant myocarditis and myositis remains a rare event. Although a common cause of respiratory illness, extrapulmonary infections with influenza are infrequent. We describe the case of a patient who presented to our centre with concomitant "seasonal" H1N1 influenza A myocarditis further complicated by pan-myositis. The patient's condition rapidly declined, eventually requiring biventricular mechanical support, in addition to multilimb fasciotomies. The cardiac support required was progressive, from a percutaneous left ventricular assist device, to extracorporeal membrane oxygenation, to eventual biventricular assist device support for bridge-to-transplantation. This case motivated a detailed review of the literature (a total of 29 cases were identified), in which we found that patients with influenza myocarditis/myositis were predominantly female (63%) and young (mean age 33.2 years) and continue to have a high incidence of morbidity and mortality (27%). As a result of its atypical pattern, the 2009 H1N1 pandemic strain has gained attention. From our review, we found 7 patients with of 2009 H1N1 pandemic influenza myocarditis. Serial serum cytokine analysis did not demonstrate a "cytokine storm," which has been associated with other virulent influenza strains. The PB1-F2 marker in particular has been associated with a vigorous cytokine response. The 2009 H1N1 and "seasonal" influenza strains lack this marker. In those patients with community-acquired influenza, interleukin-6 has been shown to correlate with symptoms. For patients with myocarditis resulting in shock, mechanical circulatory support has gained acceptance as a means to recovery or transplantation.
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface Research Centre, Winnipeg, Manitoba, Canada.
authors.forename: Kanwal
authors.initials: K
authors.lastname: Kumar
authors.forename: Mina
authors.initials: M
authors.lastname: Guirgis
authors.forename: Shelley
authors.initials: S
authors.lastname: Zieroth
authors.forename: Evelyn
authors.initials: E
authors.lastname: Lo
authors.forename: Alan H
authors.initials: AH
authors.lastname: Menkis
authors.forename: Rakesh C
authors.initials: RC
authors.lastname: Arora
authors.forename: Darren H
authors.initials: DH
authors.lastname: Freed
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006353:Heart-Assist Devices; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology / Q000821:virology; D008297:Male; D008875:Middle Aged; D009205:Myocarditis / Q000175:diagnosis / Q000276:immunology / Q000628:therapy* / Q000821:virology; D009220:Myositis / Q000175:diagnosis / Q000276:immunology / Q000628:therapy* / Q000821:virology; D058873:Pandemics; D055815:Young Adult