Influenza-associated myocarditis: a case series and structured narrative review

Area of Science:

• Cardiology
• Infectious Diseases
• Internal Medicine

Background:

• Influenza is a major global health concern, primarily affecting the respiratory system.
• Influenza can lead to serious extra-pulmonary complications, including myocarditis and myopericarditis.
• The incidence and scope of influenza-associated myocarditis are not well-established, particularly in the Middle East.

Purpose of the Study:

• To investigate influenza-associated myocarditis in Saudi Arabia.
• To describe the clinical presentation, management, and outcomes of this condition.
• To contextualize findings with a review of existing literature.

Main Methods:

• Retrospective case series of adult patients diagnosed with influenza-associated myocarditis at King Abdulaziz Medical City, Riyadh (September 2024 - July 2025).
• Diagnosis based on 2024 ACC Expert Consensus Decision Pathway criteria and positive influenza PCR.
• Data collection from electronic medical records, supplemented by a structured literature review of published cases.

Main Results:

• Four adult patients (ages 37-79) presented with influenza-associated myocarditis.
• Clinical presentations varied from mild myopericarditis to fulminant myocarditis with cardiogenic shock requiring advanced mechanical support (ECMO, Impella).
• Three patients recovered fully; one died despite aggressive treatment. Literature review identified 24 cases, with a 20.8% mortality rate, often due to rapid deterioration.

Conclusions:

• Influenza-associated myocarditis is a rare, potentially lethal complication in healthy adults.
• Early identification, prompt antiviral treatment (oseltamivir), and mechanical circulatory support are vital.
• This study provides crucial insights into this underrecognized condition in Saudi Arabia and globally.