Po-05-199 association of myocardial interstitial fibrosis with incident arrhythmias in the general population

Myocardial interstitial fibrosis is a common thread in multiple cardiovascular diseases including heart failure, atrial fibrillation, conduction disease and sudden cardiac death. Native myocardial T1 time measured using cardiac magnetic resonance imaging (cMRI) is a histopathologically validated metric for quantifying interstitial fibrosis in the human heart. Examine the prognostic role of native myocardial T1 time in predicting risk of incident arrhythmias in the general population. We examined 41,505 individuals in the United Kingdom Biobank who underwent cardiac MRI with T1 mapping and had long-term clinical outcome data available. Native pre-contrast T1 time was measured using the shortened Modified Look Locker Inversion Recovery Sequence (shMOLLI). Three incident cardiac arrhythmias were examined including incident atrial fibrillation, atrioventricular node/distal conduction disease and ventricular arrhythmias. Incident cardiovascular events were ascertained using International Classification of Diseases, 9th and 10th editions, codes and OPCS Classification of Interventions and Procedures version 4 codes. We stratified the cohort into the upper 20th and lower 80th percentile of native myocardial T1 time. Using a multivariable Cox proportional hazards model adjusted for age at MRI, sex, BMI, MRI scanner, myocardial infarction, diabetes mellitus type 1, diabetes mellitus type 2, chronic kidney disease, beta blocker use, angiotensin converting enzyme inhibitor/angiotensin receptor blocker use, statin use, and mineralocorticoid receptor antagonist use, we examined the association of native myocardial T1 time with incident cardiac arrhythmias. The mean age of study participants was 64.0 ± 7.7 years and 48.1% were men. Mean native myocardial T1 time of the study sample was 918.1 ± 41.5 ms. The median follow-up time following cMRI was 2.54 years, interquartile range 1.63 - 3.88 years. We found that participants in the top 20th percentile of native myocardial T1 time had a higher risk of incident atrial fibrillation (HR 1.62, 99% CI 1.18 - 2.23; p=9.5x10-5), atrioventricular node/distal conduction disease (HR 1.93, 99% CI 1.32 - 2.83; p=8.8x10-6) and ventricular arrhythmia (HR 1.75, 99% CI 0.87 – 3.55; p=4.0 x 10-2) compared to those in the lower 80th percentile. Our findings support the vital role that fibrosis plays in development of cardiac arrhythmias and the prognostic role of native T1 time in screening individuals at risk for arrhythmia in the population.