Working Diagnosis:
Vagally-mediated complete atrioventricular (AV) block

Treatment:
N/A

Outcome:
The exercise stress echocardiogram demonstrated normalization of AV conduction with exertion, confirming an appropriate chronotropic and conduction response despite complete AV block at rest. Cardiac structure and function were normal, and no ischemia or exercise-induced arrhythmias were identified. Given his lack of symptoms, structurally normal heart, and physiologic improvement in conduction during exercise, the AV block was determined to be vagally mediated rather than pathologic. The athlete was cleared for unrestricted participation and returned to professional basketball without complications.

Author's Comments:
Resting sinus bradycardia, ectopic atrial, junctional rhythm, 1° AV block, and Mobitz I AV block are common benign adaptations in highly trained athletes due to increased parasympathetic tone. Complete AV block, however, is distinctly uncommon and warrants thorough evaluation to exclude intrinsic conduction system disease or structural heart disease. Vagally mediated complete AV block is characterized by transient AV nodal block occurring during periods of heightened parasympathetic activity while demonstrating restoration of normal conduction with sympathetic stimulation, such as exercise. Dynamic testing is therefore critical in distinguishing physiologic adaptations from pathologic conduction abnormalities. In asymptomatic athletes with normal cardiac structure and appropriate normalization of AV conduction during exercise, conservative management and return to play are appropriate after comprehensive cardiovascular evaluation.

Editor's Comments:
Complete atrioventricular block identified during pre-participation screening should never be assumed to represent a benign athletic adaptation based solely on the absence of symptoms. Current sports cardiology guidelines recommend further evaluation of high-grade conduction abnormalities with imaging and dynamic testing to determine whether AV block improves appropriately with exercise. Improvement to normal 1:1 AV conduction during exertion strongly supports a vagally mediated process occurring at the AV node, whereas persistent or worsening block with exercise raises concern for infranodal conduction disease and warrants additional investigation with a cardiac electrophysiology study. This case illustrates the importance of integrating ECG findings with exercise physiology and highlights why collaboration with a sports cardiologist is essential before determining athletic eligibility.

References:
Zipes DP, et al. Eligibility and Disqualification Recommendations for Competitive Athletes With Cardiovascular Abnormalities: Task Force 9: Arrhythmias and Conduction Defects. J Am Coll Cardiol. 2015;66(21):2412-2423.

Lampert R, et al. 2024 HRS expert consensus statement on arrhythmias in the athlete: Evaluation, treatment, and return to play. Heart Rhythm. 2024;21(10):e151-e252.

Drezner JA, et al. International criteria for electrocardiographic interpretation in athletes: Consensus statement. Br J Sports Med. 2017;51(9):704-731.

Alboni P, Holz A, Brignole M. Vagally mediated atrioventricular block: Pathophysiology and diagnosis. Heart. 2013;99:904-908.

Abela M, Bonello J, Sammut MA. A case report of profound atrioventricular block in an endurance athlete: how far do you go? Eur Heart J Case Rep. 2022;6(5):ytac190.

Braga F, Bessa T, Cunha M, Bueno Paiva R, Stein R. Exercise-induced complete atrioventricular block resulting in cardiac arrest: a case report and review of diagnostic strategies. Eur Heart J Case Rep. 2024;8(7):ytae316.

Mesirca P, et al. Intrinsic electrical remodeling underlies atrioventricular block in athletes. Circ Res. 2021;129(1):e1-e20.

Return To The Case Studies List.