2425Evaluation of myocardial gene expression profiling for superior diagnosis of idiopathic giant cell myocarditis in a large cohort of patients with acute cardiac decompensation

Background Idiopathic giant cell myocarditis (IGCM) diagnostics is based on differential patterns of inflammatory cell infiltration, and multinucleated giant cells (GCs) in histological sections of endomyocardial biopsies (EMBs). However, the sampling error is high for the detection of focally GCs by histopathology. We report on a clinical evaluation of a recently published method for improved differential diagnosis of this frequently fatal disease by myocardial gene expression profiling. Objective This is to improve the diagnostics of IGCM by gene expression profiling, and to demonstrate the feasibility of this method in clinical practice in a large cohort of patients. Methods In this multicenter study, EMBs of n=427 patients with clinically acute cardiac decompensation and suspected acute myocarditis were screened (mean age 47.03±15.69 years). In each patient, EMBs were analyzed by histology, immunohistology, molecular virology, and gene expression profiling. Results Out of the total of n=427 patient samples examined, GCs could be detected in 26 cases (6.0%) by histology. An established myocardial gene profile – consisting of 27 genes – was revealed resulting in a specified profile of 5 genes (chemokine receptor 5 (CCR5), chemokine receptor 6 (CCR6); carnitine palmitoyltransferase I (CPT1), toll-like receptor 8 (TLR8), and chemokine (C-C motif) ligand 20 (CCL20)) which identified histologically proven IGCM with high specificity in 25 of the 26 patients (96.2%). Applying this newly established profiling on the remaining patient samples, additional n=31 (7.3%) patients were identified for IGCM without any histological proof of myocardial GCs. Conclusions Myocardial gene expression profiling is a reliable method in clinical practice to predict IGCM even without direct histological proof of GCs in EMB section. The gene profiling is of high clinical relevance to overcome the sampling error of purely histological examination, and to control the effectiveness of the therapy. The data clearly show the importance to take EMB in unexplained acute decompensation to get a diagnosis and improve the prognosis.