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Inflammation of Conduction Tissue in Patients with Arrhythmic Phenotype of Myocarditis

Andrea Frustaci1,2, Romina Verardo2, Maria Alfarano1

  • 1Department of Clinical, Internal, Anesthesiologist and Cardiovascular Sciences, Sapienza University, 00161 Rome, Italy.

Journal of Clinical Medicine
|November 3, 2020
PubMed

Insights

Myocarditis causing ventricular arrhythmias is linked to inflammation of the conduction tissue (CT). Identifying the cause, whether viral infection or immune response, allows for targeted treatment, improving outcomes in most patients.

Area of Science:

  • Cardiology
  • Infectious Diseases
  • Pathology

Background:

  • Myocarditis, an inflammation of the heart muscle, can present with lone ventricular tachyarrhythmias (LVT).
  • The role of conduction tissue (CT) inflammation in LVT associated with myocarditis has been hypothesized but not definitively proven.

Purpose of the Study:

  • To investigate the association between conduction tissue (CT) inflammation and lone ventricular tachyarrhythmias (LVT) in patients with myocarditis.
  • To determine the etiological factors (viral vs. immune-mediated) contributing to CT inflammation in these patients.
  • To evaluate the efficacy of targeted therapies based on the identified cause of myocarditis.

Main Methods:

  • Analysis of endomyocardial biopsies from 420 patients with myocarditis, focusing on 42 presenting with LVT.
  • Histopathological examination of CT in biopsies, alongside real-time polymerase chain reaction (PCR) for viral genomes and immunohistochemistry for viral antigens and Toll like receptor 4 (TLR4).
  • Comparison with 12 control myocarditis patients without LVT but with CT involvement in biopsies.

Main Results:

  • Conduction tissue (CT) inflammation was present in all 12 LVT patients but absent in controls (p < 0.001).
  • Viral genomes (influenza-A, HSV2, adenovirus) were detected in 4 patients; 8 patients showed TLR4 overexpression, suggesting an immune-mediated pathway.
  • Influenza-A and HSV2 (Herpes Virus 2) myocarditis patients responded differently to treatment; immune-mediated cases treated with steroids and azathioprine showed significant reduction in ventricular arrhythmias (VT).

Conclusions:

  • The arrhythmic phenotype of myocarditis is strongly associated with conduction tissue (CT) inflammation or infection.
  • Molecular characterization of CT damage in myocarditis is crucial for guiding pharmacologic control of arrhythmias.
  • Targeted treatment strategies based on etiology can lead to successful arrhythmia management in approximately 75% of cases.
Abstract

Keywords:
arrhythmic phenotypeconduction tissuemyocarditis

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