AIMS: Recent-onset dilated cardiomyopathy (RODCM) is characterized by heterogeneous aetiology and diverse clinical outcomes, with scarce data on genotype-phenotype correlates. Our aim was to correlate individual RODCM genotypes with left ventricular reverse remodelling (LVRR) and clinical outcomes. METHODS AND RESULTS: In this prospective study, a total of 386 Czech RODCM patients with symptom duration ≤6 months underwent genetic counselling and whole-exome sequencing (WES). The presence of pathogenic (class 5) or likely pathogenic (class 4) variants in a set of 72 cardiomyopathy-related genes was correlated with the occurrence of all-cause death, heart transplantation, or implantation of a ventricular assist device (primary outcome) and/or ventricular arrhythmia event (secondary outcome). LVRR was defined as an improvement of left ventricular ejection fraction to >50% or ≥10% absolute increase, with a left ventricular end-diastolic diameter ≤33 mm/m2 or ≥10% relative decrease. Median follow-up was 41 months. RODCM was familial in 98 (25%) individuals. Class 4-5 variants of interest (VOIs) were identified in 125 (32%) cases, with 69 (18%) having a single titin-truncating variant (TTNtv) and 56 (14%) having non-titin (non-TTN) VOIs. The presence of class 4-5 non-TTN VOIs, but not of TTNtv, heralded a lower probability of 12-month LVRR and proved to be an independent baseline predictor both of the primary and the secondary outcome. The negative result of genetic testing was a strong protective baseline variable against occurrence of life-threatening ventricular arrhythmias. Detection of class 4-5 VOIs in genes coding nuclear envelope proteins was another independent predictor of both study outcomes at baseline and also of life-threatening ventricular arrhythmias after 12 months. Class 4-5 VOIs of genes coding cytoskeleton were associated with an increased risk of life-threatening ventricular arrhythmias after baseline assessment. A positive family history of dilated cardiomyopathy alone only related to a lower probability of LVRR at 12 months and at the final follow-up. CONCLUSIONS: RODCM patients harbouring class 4-5 non-TTN VOIs are at higher risk of progressive heart failure and life-threatening ventricular arrhythmias. Genotyping may improve their early risk stratification at baseline assessment.

1st Internal Clinic of Cardio Angiology St Anne's University Hospital and Medical School of Masaryk University Brno Czech Republic

Department of Cardiology Institute for Clinical and Experimental Medicine Prague Czech Republic

Department of Cardiovascular Medicine 2nd Department of Medicine 1st Faculty of Medicine Charles University and General University Hospital Prague Czech Republic

Department of Internal Medicine 1 Cardiology University Hospital Olomouc Olomouc Czech Republic

Department of Pathological Physiology Faculty of Medicine and Dentistry Palacky University Olomouc Olomouc Czech Republic

Department of Pediatrics and Adolescent Medicine 1st Faculty of Medicine Research Unit for Rare Diseases Charles University Prague Czech Republic

European Reference Network for Rare Low Prevalence and Complex Diseases of the Heart ERN GUARD Heart IKEM Prague Czech Republic

Institute of Physiology 1st Faculty of Medicine Charles University Prague Czech Republic

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