Unique Scar in RVOT May Trigger Ventricular Tachycardia Seen in High-Level Endurance Athletes

High-level endurance athletes with ventricular tachycardia (VT) may have unique scarring in the right ventricular outflow tract (RVOT) that acts as a substrate for the arrhythmia, a new study shows.

Investigators caution that the analysis included just a small sample of athletes who developed scarring in the RVOT. Moreover, this particular scar pattern—restricted to the subepicardial anterior RVOT below the pulmonary valve—was observed in high-level athletes, including five professional and six competitive athletes.

“There are a lot of people who exercise at very high levels, such as professional cyclists or runners, and for the total population of people who do a lot of exercise, these arrhythmias are a very rare situation,” senior investigator Katja Zeppenfeld, MD (Leiden University Medical Center, the Netherlands), told TCTMD. “We don’t want to raise any impression that these [high-level] athletes are now at risk. It might be that there is something else that we haven’t yet identified that makes them develop this substrate.”

While the underlying mechanism for scar formation is not clear, investigators say the scar pattern can help “distinguish exercise-induced arrhythmogenic remodeling from arrhythmogenic right ventricular cardiomyopathy (ARVC) and other postinflammatory cardiomyopathies.”

The study, led by Jeroen Venlet, MD (Leiden University Medical Center), and published online January 30, 2017, in the Journal of the American College of Cardiology, included 57 consecutive patients undergoing catheter ablation for scar-related right ventricle VT. Using electroanatomic mapping, the researchers identified two distinct scar patterns in the right ventricle: dominant scarring located near the subtricuspid RV inflow tract in 46 patients (group A) and scarring restricted to subepicardial anterior RVOT in 11 patients (group B).

All 11 patients in group B were high-level endurance athletes who spent 15 hours per week, on average, training for 13 years. Group A patients, on the other hand, exercised for 4 hours per week for 18 years. Nearly a third of the group A patients had a family history of ARVC and 64% had a genetic mutation in ARVC-associated genes. In group B, none of the athletes had a family history of ARVC or any of the pathogenic or likely pathogenic mutations for the condition.

Following catheter ablation, complete procedural success—defined as not being able to induce any sustained monomorphic VT—was achieved in 10 of the 11 group B athletes and 26 of the 46 group A subjects (91% vs 57%, P = 0.034). After 27 months of follow-up, VT recurred in 50% of the group A subjects but in none of the group B athletes. 

Speaking with TCTMD, Zeppenfeld said previous studies have shown that high-level endurance activity, such as cycling or long-distance running, can increase the volume of the right ventricle. If such high-level endurance training is maintained, this can lead to right ventricular (RV) remodeling in some individuals.

“It’s always a question of whether this is the athlete’s heart—is it just both ventricles getting larger?—or is there something else happening, something pathological?” she said. “We think that if you do a certain amount of exercise over a prolonged period, there probably is some irreversible scarring in the right ventricle.”

Constant training of long duration, say investigators, might lead to “repetitive and cumulative injury,” which may result in pathological remodeling and the development of the arrhythmogenic scar. Previous imaging studies have shown an enlargement of the right ventricle in high-level athletes but not a substrate for the arrhythmia, said Zeppenfeld.

‘Interesting’ but Not Definitive     

Speaking with TCTMD, Mark Link, MD (University of Texas Southwestern Medical Center, Dallas), agreed that “there is something about the right ventricle in high-level athletes,” with a number of previous studies showing that these athletes have some degree of remodeling. The epicardial scar in the RVOT has been described in other conditions, such as Brugada syndrome, but “whether it is completely unique and secondary to the endurance [sport] is not clear,” he said.

For Link, who was not involved in the analysis, the identification of a distinctive substrate for VT in high-level endurance athletes is “interesting,” but the research does have limitations. One of the biggest issues is the potential for selection bias, said Link. The investigators started with 371 patients with ventricular arrhythmias from the right ventricle but included just 57 patients in their analysis (overall, 229 patients were excluded with idiopathic ventricular arrhythmia, 15 with ischemic cardiomyopathy, 65 with congenital heart disease, and 5 with abnormal left ventricles).

“There’s certainly a hint there’s something going on in the right ventricle, and mechanistically it makes sense that it could cause scarring in the outflow tract, but it’s not the definitive answer,” said Link. “The real problem is how many of these high-level athletes could have had a predisposition to idiopathic VT, which is the main condition this would be difficult to sort out from, and whether they got their VT because they were stretching their right ventricle.” 

If a high-level athlete presented with VT that appeared to originate from the RVOT, most times this could be ablated from the endocardium, Link said, adding, “However, if they were a high-level athlete, you would have think about giving an epicardial ablation.” He noted that these patients all failed endocardial ablation, making this a very select group.

Zeppenfeld stressed that while VT in high-level endurance athletes is rare, if identified in symptomatic patients, it means these individuals should undergo invasive electroanatomic mapping as a diagnostic test. Their results suggest that, unlike the progressive arrhythmia ARVC, the VT in athletes with this distinctive scar pattern can be cured by ablation, she said.

In an editorial, Harikrishna Tandri, MD (Johns Hopkins University School of Medicine, Baltimore, MD), and Mathew Hutchinson, MD (University of Arizona College of Medicine, Tucson), said there are a number of questions raised by the research. One question, they note, is exactly when a physician should consider epicardial mapping to rule out occult substrate in athletes presenting with ventricular arrhythmias. Also important to address is how exercise contributes to development of scarring in the RVOT and whether other environment/genetic factors play a role.

From a practical standpoint, the editorialists ask, what recommendations should be made regarding exercise in a patient with VT stemming from the RVOT scar who are successfully ablated? Link said many physicians would be “uncomfortable” telling such athletes they could return to high-level sport. Zeppenfeld agreed, stating they might be allow to participate in recreational physical activity, but that she would advise against high-level exercise.