176 Ventricular arrhythmia and cardiac fibrosis in endurance experienced athletes (the ventoux study)

Introduction Myocardial fibrosis on cardiac magnetic resonance (CMR) has increasingly been detected in lifelong endurance athletes, particularly those who are male. In non-ischaemic cardiomyopathy, the presence of myocardial fibrosis on CMR is known to be associated with arrhythmia and adverse outcome. However, the significance of myocardial fibrosis in asymptomatic athletes is unknown. We aimed to prospectively investigate whether focal myocardial fibrosis on CMR in asymptomatic veteran endurance athletes is associated with incident ventricular arrhythmia by comparing the incidence of ventricular arrhythmia detected on implantable loop recorder (ILR) in those with and without myocardial fibrosis on CMR. Methods 106 healthy, asymptomatic, male amateur competitive cyclists and triathletes aged >50 years old were prospectively recruited. They all trained >10 hours per week for >15 years and regularly competed. All athletes underwent baseline assessment, resting 12-lead ECG and comprehensive CMR to detect myocardial fibrosis which included quantitative stress-perfusion, quantitative late gadolinium enhancement (LGE) and parametric tissue characterisation including native T1, ECV and T2 mapping. Each athlete subsequently underwent maximal effort exercise testing to quantify fitness levels before receiving an ILR to detect the presence of arrhythmia. Athletes were followed up for 2 years for the presence of ventricular arrhythmia (ventricular tachycardia (VT)/ non-sustained VT (NSVT)). VT was defined as at least 30 consecutive beats of broad complex tachycardia (BCT) whilst NSVT was defined as at least 3 consecutive beats of BCT. Participants were contacted after every arrhythmic event to establish any associated symptoms. Statistical analysis included unpaired t-test to compare continuous variables and chi-square test to compare categorical variables. Logistic regression was used to investigate which clinical parameters were associated with fibrosis and univariable Cox regression identified variables associated with VT/NSVT. Log rank testing was also utilised to compare incidence of ventricular arrhythmia in those with and without myocardial fibrosis. Results 47.2% (50/106) athletes had focal myocardial fibrosis on CMR, all of which was a non-ischaemic distribution and predominantly affected the basal inferolateral myocardial segment (figure 1). Although athletes with myocardial fibrosis were slightly older than those without fibrosis (61.2 ± 5.7 vs 57.3 ± 4.9, p<0.001), there was no detectable difference in any other demographic characteristic, CMR parameter or training variable including both training history and maximal effort exercise testing (figure 2). 18 participants experienced at least one ventricular arrhythmic event (2 VT, 16 NSVT) during median follow up of 542 days (interquartile range 485–576 days). By Cox regression analysis, the presence of myocardial fibrosis was associated with an increased risk of VT/NSVT (hazard ratio (HR) 3.19, 95% confidence interval (CI) 1.14–8.94, P=0.028) (figure 3). This remained significant even after correcting for age (HR 3.20, CI 1.05 – 9.78, P=0.042). No participants were aware of any episodes of VT/NSVT and all were detected asymptomatically on ILR. There were no episodes of SCD however one participant with myocardial fibrosis was advised to cease competitive sport due to recurrent VT episodes during exercise. Conclusion This prospective cohort study demonstrated focal myocardial fibrosis was highly prevalent and associated with incident ventricular arrhythmia in lifelong endurance athletes. However, despite nearly 100 patient years of follow up in athletes with myocardial fibrosis, there was not a single episode of symptomatic ventricular arrhythmia or SCD. These findings suggest myocardial fibrosis in endurance athletes may be of clinical significance but the mechanism of SCD in athletes may be more complex and requires further investigation. Conflict of Interest Nil