Successful management of fulminant influenza A subtype H1N1 myocarditis

Fulminant Influenza a Myocarditis Complicated by Transient Ventricular Wall Thickening and Cardiac Tamponade

Myocarditis is an infrequent complication of influenza infection that is most often diagnosed clinically in the setting of confirmed influenza infection and elevated cardiac enzymes. Pericarditis can also occur in cases of influenza myocarditis and may require pericardiocentesis for tamponade. Patients with fulminant myocarditis have cardiogenic shock; however, echocardiographic findings may be subtle, showing a preserved ejection fraction and diffuse left ventricular wall thickening (compared to baseline) due to inflammatory edema. Recognizing these echocardiographic findings in the appropriate clinical setting facilitates the early recognition of fulminant myocarditis. Therefore, we report a case of fulminant influenza A myocarditis in healthy 37-year-old women complicated by transient left ventricular wall thickening and tamponade, highlighting the importance of early diagnosis and supportive management for a successful outcome.

Influenza Myopericarditis and Pericarditis: A Literature Review

Myopericarditis is a rare complication of influenza infection. The presentation may range from mild and frequently unrecognized, to fulminant and potentially complicated by cardiogenic and/or obstructive shock (tamponade), which is associated with high mortality. We performed a review of literature on all influenza pericarditis and myopericarditis cases according to PRISMA guidelines using the PubMed search engine of the Medline database. Seventy-five cases of influenza myopericarditis and isolated pericarditis were identified from 1951 to 2021. Influenza A was reported twice as often as influenza B; however, influenza type did not correlate with outcome. Men and elderly patients were more likely to have isolated pericarditis, while women and younger patients were more likely to have myopericarditis. All included patients had pericardial effusion, while 36% had tamponade. Tamponade was more common in those with isolated pericarditis (41.2%) than myopericarditis (13.8%). Cardiogenic shock was more common in patients with myopericarditis (64%), with an overall mortality rate of 14.7%. Nearly 88% of the recovered patients remained without long-term complications reported. Conclusion: Influenza A appears a more common cause of pericarditis and myopericarditis. Isolated pericarditis was more commonly associated with tamponade but without reported deaths, whereas myopericarditis was more commonly associated with cardiogenic shock and death (19%).

Human influenza A virus causes myocardial and cardiac-specific conduction system infections associated with early inflammation and premature death

AIMS

Human influenza A virus (hIAV) infection is associated with important cardiovascular complications, although cardiac infection pathophysiology is poorly understood. We aimed to study the ability of hIAV of different pathogenicity to infect the mouse heart, and establish the relationship between the infective capacity and the associated in vivo, cellular and molecular alterations.

METHODS AND RESULTS

We evaluated lung and heart viral titres in mice infected with either one of several hIAV strains inoculated intranasally. 3D reconstructions of infected cardiac tissue were used to identify viral proteins inside mouse cardiomyocytes, Purkinje cells, and cardiac vessels. Viral replication was measured in mouse cultured cardiomyocytes. Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used to confirm infection and study underlying molecular alterations associated with the in vivo electrophysiological phenotype. Pathogenic and attenuated hIAV strains infected and replicated in cardiomyocytes, Purkinje cells, and hiPSC-CMs. The infection was also present in cardiac endothelial cells. Remarkably, lung viral titres did not statistically correlate with viral titres in the mouse heart. The highly pathogenic human recombinant virus PAmut showed faster replication, higher level of inflammatory cytokines in cardiac tissue and higher viral titres in cardiac HL-1 mouse cells and hiPSC-CMs compared with PB2mut-attenuated virus. Correspondingly, cardiac conduction alterations were especially pronounced in PAmut-infected mice, associated with high mortality rates, compared with PB2mut-infected animals. Consistently, connexin43 and NaV1.5 expression decreased acutely in hiPSC-CMs infected with PAmut virus. YEM1L protease also decreased more rapidly and to lower levels in PAmut-infected hiPSC-CMs compared with PB2mut-infected cells, consistent with mitochondrial dysfunction. Human IAV infection did not increase myocardial fibrosis at 4-day post-infection, although PAmut-infected mice showed an early increase in mRNAs expression of lysyl oxidase.

CONCLUSION

Human IAV can infect the heart and cardiac-specific conduction system, which may contribute to cardiac complications and premature death.

The hidden burden of influenza: A review of the extra-pulmonary complications of influenza infection

Severe influenza infection represents a leading cause of global morbidity and mortality. Although influenza is primarily considered a viral infection that results in pathology limited to the respiratory system, clinical reports suggest that influenza infection is frequently associated with a number of clinical syndromes that involve organ systems outside the respiratory tract. A comprehensive MEDLINE literature review of articles pertaining to extra‐pulmonary complications of influenza infection, using organ‐specific search terms, yielded 218 articles including case reports, epidemiologic investigations, and autopsy studies that were reviewed to determine the clinical involvement of other organs. The most frequently described clinical entities were viral myocarditis and viral encephalitis. Recognition of these extra‐pulmonary complications is critical to determining the true burden of influenza infection and initiating organ‐specific supportive care.

Emerging pharmacologic targets and treatments for myocarditis

Myocarditis is a heterogeneous group of disorders defined by inflammation of the heart muscle. The primary clinical manifestations of myocarditis are heart failure and sudden death in children and young adults. Numerous interventions have been investigated for the treatment of myocarditis, including broad spectrum alteration of the immune response and antiviral treatments; however, success has been limited. Since the myocarditis treatment trials in the 1990s there has been an improved understanding of disease progression and new facets of the immune response have been discovered. This new information provides fresh opportunities to develop therapeutics to treat myocarditis. This review analyzes previous pharmacologic approaches including immunosuppression, high dose intravenous immunoglobulin treatment, immunoadsorption and antiviral treatments, and looks forward toward recently identified immune factors that can be exploited as targets for new treatments. Such strategies include bolstering beneficial regulatory T cells or mitigating the detrimental Th17 T cells which can drive autoimmunity in the heart. The surging interest of the application of humanized monoclonal antibodies makes targeting deleterious arms of the immune response like Th17 cells a tangible goal in the near future. Promising constituents of herbal remedies have also been identified that may hold potential as new pharmacological treatments for myocarditis, however, significant work remains to elucidate the pharmacokinetics and side-effects of these compounds. Finally, advances in our understanding of the function of Matrix Metalloproteinases yield another target for altering disease progression given their role in the development of fibrosis during Dilated Cardiomyopathy. In bringing to light the various new targets and treatments available since the last myocarditis treatment trials, the aim of this review is to explore the new treatments that are possible in new myocarditis treatment trials.

A Case of Influenza Associated Fulminant Myocarditis Successfully Treated with Intravenous Peramivir

We report the case of a patient with fulminant myocarditis caused by influenza A virus, who presented with acute-onset heart failure and cardiogenic shock and was treated successfully with single dose of intravenous peramivir and with pharmacologic hemodynamic support. A 45-year-old Korean woman presented to our emergency department (ED) with shortness of breath and an episode of seizure that developed abruptly 5 hours before she arrived in the ED. She had a history of recurrent epileptic seizure 25 years ago, but denied other specific medical illnesses. In the ED, she was hypoxemic (arterial partial pressure of oxygen, 59.8 mmHg on room air) and chest radiography revealed bilateral alveolar infiltrates. A rapid antigen test for influenza A virus was positive, and she was administered a single dose of peramivir (300 mg) intravenously. Five hours later, the patient's dyspnea had worsened and she was hypotensive (blood pressure, 86/53 mmHg), requiring norepinephrine infusion. Further evaluation disclosed an increased cardiac troponin I level of 1.36 ng/mL and a depressed left ventricular ejection fraction of 30%. Under the diagnosis of influenza A-associated myocarditis and cardiogenic shock, she was managed with continuous critical care in the intensive care unit. On day 3, the patient's dyspnea began to resolve and her ventricular function returned to normal. Real-time polymerase chain reaction assays for influenza viruses in serial nasopharyngeal aspirates were positive for influenza A (hH3N2) with a threshold cycle value of 27.39 on day 2, but these became negative by day 4. The patient recovered and was discharged on day 9 after admission. In conclusion, this case indicates that intravenous peramivir might be an effective antiviral agent for the treatment of severe influenza A virus infection.