Inflammation of Conduction Tissue in Patients with Arrhythmic Phenotype of Myocarditis.

BACKGROUND

Myocarditis can manifest with lone ventricular tachyarrhythmias (LVT). Elective inflammation of conduction tissue (CT) is supposed but unproved.

METHODS

Forty-two of 420 patients with biopsy proven myocarditis presented with LVT. Twelve of them included CT sections in endomyocardial biopsies. Real-time polymerase chain reaction (PCR) for viral genomes, immunohistochemistry for viral antigens and Toll like receptor 4 (TLR4) were performed. Twelve myocarditis patients with infarct-like or cardiomyopathic phenotype and CT included in tissue section were used as controls.

RESULTS

Four of the 12 patients presented non-sustained ventricular tachycardia (nsVT), six with sustained ventricular tachycardia (sVT), two with ventricular fibrillation. CT was inflamed in all LVT patients and not in controls (p < 0.001). PCR was positive for influenza-A virus in two, herpes simplex virus type 2 (HSV2) in one and adenovirus in one with positive CT immunostaining for viral antigens. In eight patients, negative PCR and TLR4 overexpression suggested an immune-mediated pathway. Patients with influenza-A myocarditis and CT infection responded to oseltamivir, those with HSV2 (Herpes Virus 2) and adenovirus infection died. The eight patients with immune-mediated myocarditis were treated with steroids and azathioprine. Seven of them had no more VT(ventricular tachyarrhythmias)during six-month follow-up.

CONCLUSIONS

Arrhythmic phenotype of myocarditis is associated with CT inflammation/infection. Molecular characterization of CT damage may lead to pharmacologic control of arrhythmias in 75% of cases.