Genetic architecture of acute myocarditis and the overlap with inherited cardiomyopathy

Abstract

Background: Acute myocarditis is an inflammatory condition that may herald the onset of dilated (DCM) or arrhythmogenic cardiomyopathy (ACM). We investigated the frequency and clinical consequences of DCM and ACM genetic variants in a population-based cohort of patients with acute myocarditis. Methods: Population-based cohort of 336 consecutive patients with acute myocarditis enrolled in London and Maastricht. All participants underwent targeted DNA-sequencing for well-characterised cardiomyopathy-associated genes with comparison to healthy controls (n=1053) sequenced on the same platform. Case ascertainment in England was assessed against national hospital admission data. The primary outcome was all-cause mortality. Results: Variants that would be considered pathogenic if found in a patient with DCM or ACM were identified in 8% of myocarditis cases compared to <1% of healthy controls (p=0.0097). In the London cohort (n=230; median age 33years; 84% men), patients were representative of national myocarditis admissions (median age 32years; 71% men; 66% case ascertainment), and there was enrichment of rare truncating variants (tv) in ACM-associated genes (3.1% cases vs 0.4% controls; odds ratio 8.2; p=0.001). This was driven predominantly by desmoplakin (DSP)-tv in patients with normal LV ejection fraction and ventricular arrhythmia. In Maastricht (n=106; median age 54years; 61% men), there was enrichment of rare truncating variants in DCM-associated genes, particularly TTN-tv found in 7% (all with LVEF<50%) compared to 1% in controls (OR 3.6; p=0.0116). Across both cohorts over a median of 5.0 years (IQR 3.9-7.8), all-cause mortality was 5.4%. Two thirds of deaths were cardiovascular, due to worsening heart failure (92%) or sudden cardiac death (8%). The 5-year mortality risk was 3.3% in genotype negative patients versus 11.1% for genotype positive patients (Padjusted=0.08). Conclusions: We identified DCM- or ACM-associated genetic variants in 8% of patients with acute myocarditis. This was dominated by the identification of DSP-tv in those with normal LVEF, and TTN-tv in those with reduced LVEF. Despite difference between cohorts, these variants have clinical implications for treatment, risk stratification and family screening. Genetic counselling and testing should be considered in patients with acute myocarditis to help reassure the majority whilst improving the management of those with an underlying genetic variant.