VENTricular arrhythmia and cardiac fibrOsis in endUrance eXperienced athletes (The VENTOUX Study)

Introduction Non-ischaemic myocardial fibrosis can be detected by cardiovascular magnetic resonance (CMR) imaging in a significant proportion of lifelong endurance athletes. 1 Similar focal fibrosis is known to be arrhythmogenic in non-ischaemic cardiomyopathy but its significance in asymptomatic athletes is unknown. Purpose To determine whether focal myocardial fibrosis in asymptomatic veteran endurance athletes is associated with incident ventricular arrhythmia by comparing incidence of ventricular arrhythmia detected on implantable loop recorder (ILR) in those with and without fibrosis. Methods 106 healthy amateur competitive cyclists and triathletes aged over 50 years old were prospectively recruited. They underwent resting 12 lead ECG, comprehensive stress-perfusion CMR to detect myocardial fibrosis and maximal effort exercise testing. Each athlete had an ILR implanted 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 logistic regression to investigate which clinical parameters were associated with fibrosis and univariable Cox regression to identify variables associated with VT/NSVT. Log rank testing was also used to compare incidence of ventricular arrhythmia in those with and without myocardial fibrosis. Results 47.2% (50/106) athletes had focal myocardial fibrosis, all of which was a non-ischaemic distribution and predominantly affected the basal inferolateral myocardial segment. 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 1). 18 participants had at least one ventricular arrhythmic event (2 VT, 16 NSVT) during median follow up 542 days (interquartile range 485-576 days). No participants were aware of any episodes of VT/NSVT and all were detected asymptomatically on ILR. 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). This remained significant even after correcting for age (HR 3.20, CI 1.05 – 9.78, P=0.042). Conclusion In asymptomatic lifelong endurance athletes, focal myocardial fibrosis was highly prevalent and associated with the incidence of ventricular arrhythmia. However, despite nearly 100 patient years of follow up in athletes with myocardial fibrosis, there was not a single episode of symptomatic ventricular arrhythmia.