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Abstract

Objectives: Giant cell myocarditis is a rare and often fatal disorder. According to the American Heart Association, the American College of Cardiology Foundation, and the European Society of Cardiology scientific statements, an endomyocardial biopsy should be done to exclude giant cell myocarditis in unexplained new-onset heart failure of 2 weeks to 3 months duration associated with dilated left ventricle and new ventricular arrhythmias, or Mobitz type II second-degree, or third-degree atrioventricular heart block. Case Presentations: Two hundred thirty-five heart transplants were performed since May 1993 at the Institut universitaire de cardiologie et de pneumologie de Quebec, Canada. Giant cell myocarditis was found in the explanted hearts of 5 patients. The preoperative diagnosis of giant cell myocarditis was done by endomyocardial biopsy or at the installation of a left ventricular-assisted device. Patients had symptoms of progressive heart failure of subacute onset. Patients consulted at a mean 32 days after the onset of symptoms. Two patients neither had ventricular arrhythmia nor heart block. Two patients had ventricular arrhythmias and heart block; the other patient had symptomatic heart block. All patients had at least 2 echocardiographies. Two patients had an increase in left ventricular size, enough to reach the criteria of left ventricular dilatation according to the American Society of Echocardiography. During this time, left ventricular ejection fraction showed a rapid decline (mean 37% to 16%). Conclusions: Ventricular arrhythmia, heart block, and left ventricular dilatation initially can be absent in many patients having giant cell myocarditis with symptoms of progressive heart failure. Endomyocardial biopsy should be quickly considered in patients with a rapid and dramatic decline of left ventricular ejection fraction, even in the absence of classic clinical and echocardiographic features of giant cell myocarditis to rapidly obtain the diagnosis of this rare but lethal disease.

A Case of Incidental Giant Cell Myocarditis Presenting After COVID-19 mRNA Vaccination

“… 1 However, studies have shown that high-degree atrioventricular block and ventricular arrhythmias may be absent up to 50% of the time. 1 , 7 Therefore, a rapid decline in LVEF over several days, with subacute CHF of 2 weeks' to 3 months’ duration that is refractory to 1 to 2 weeks of standard treatment, should raise suspicion for GCM. An endomyocardial biopsy should be considered—including early transfer to specialized centres when necessary—in these circumstances, irrespective of vaccination status, and even in the absence of arrhythmia and classic echocardiographic features of GCM.…”

Immunomodulatory Therapy for Giant Cell Myocarditis: A Narrative Review

“…In later stages, the Th2 response may dominate, leading to the fibrosis of affected areas. The eosinophils in the infiltrate also increase cytokine production and release cytotoxic substances from their granules, like major basic proteins and eosinophil peroxidase [ 17 ].…”