P5560Assessing etiology in a cohort of patients with myocarditis presenting with complex ventricular arrhythmias: can the percutaneous endomyocardial biopsy help?
Authors: Dello Russo A , Casella M , Gasperetti A , Basso C , Bianchini L , Zanchi S , Catto V , Della Rocca D , Moltrasio M , Fassini G , Andreini D , Natale A , Tondo C 
Published: October 2019

Abstract

Background
Myocarditis represents a common but often under-diagnosed disease, with a wide range of clinical presentations; diagnosis is often presumptive and a clear etiology leading to a specific therapeutic approach is usually not identified.

Purpose
To describe and assess disease etiology in a cohort of myocarditis patients (pts) with arrhythmic presentation undergoing an invasive diagnostic work-up.

Methods
All pts with myocarditis presenting with ventricular arrhythmias undergoing an electro-anatomical mapping (EAM) guided endo-myocardial biopsy (EMB) at our institution were enrolled. All enrolled pts also underwent cardiac magnetic resonance imaging (MRI) and an electrophysiological study (EPS). Demographics, arrhythmic presentation, MRI data, arrhythmic inducibility at EPS, EAM and EMB biopsy data were retrieved and analyzed. Molecular biology testing for cardio-tropic virus genome as well as leukocyte immunohistochemical typization were routinely performed on all EMB samples.

Results
Twenty-six pts were enrolled (85% male, 39±6 y.o.). Clinical presentation was an organized ventricular arrhythmia in 16 (62%) pts (n=3 non-sustained ventricular arrhythmia; n=9 sustained ventricular arrhythmia; n=4 ventricular fibrillation) while frequent (>10.000) premature ventricular complexes (PVCs) in the remaining 10 (38%) pts.
MRI showed a late gadolinium enhancement (LGE) pattern consistent with myocarditis in all pts (35% left LGE; 65% right LGE). At the EPS, 10 (38%) pts showed inducibility for SVTs and underwent an intra-cardiac defibrillator (ICD) implant, while 4 (16%) more were implanted for secondary arrhythmic prevention.
EAM was performed in 18 (70%), 6 (22%) and 2 (8%) pts in the right, left and in both ventricle respectively; in all cases, abnormal myocardial voltages were retrieved in the area showing LGE at MRI. Extensive myocardial scarring was detected in 7 (27%) pts.
All EMB were performed without peri-procedural complications; inflammatory infiltrate and substrate alteration consistent with myocarditis were retrieved in 100% of the bioptic samples. Viral genome was identified in 13 (50%) samples (n=5 Human Herpes Virus 6; n=2 Parvovirus B 19; n=3 Adenovirus; n=1 Ebstein Barr Virus; n=1 Cytomegalovirus; n=1 Rhinovirus) and specific human immunoglobulin treatment was undergone by a single pt; eosinophilic infiltration was found in 2 (8%) patients; lymphocite invasion and auto-antibodies consistent with auto-immune myocarditis were detected in 2 (8%) patients and appropriate immunosuppressive therapy was started, while a myocardial band contraction pattern typical of toxic myocarditis was found in a single (4%) patient [Figure 1].
Different Myocarditis Etiology Rates

Conclusion
In our myocarditis cohort, EMB confirmed viruses to represented the first myocarditis etiological agent. Despite an invasive work-out, 31% of the cohort etiology still remains unclear.