We report a case of a 56-year-old endurance athlete with frequent resting dizziness. His electrocardiogram documented a Mobitz 2 atrioventricular (AV) block alternating with a third-degree AV block with an escape rhythm of 30/min with a normal QRS duration. After excluding several complete AV block differential diagnosis namely Lyme disease, the patient underwent an exercise treadmill testing that documented the early resolution of the AV block. He maintained a first-degree AV block with a PR interval from 400 to 270 ms, at peak exercise capacity (Panel A). At electrophysiological study (EPS), we localized the AV block at the node (Panel B) with normal infra-hisian conduction (AH interval of 290 ms and HV of 40 ms; Wenckebach point of 80/min).
We implanted a double-chamber pacemaker after considering (i) the symptomatic paroxystic complete AV block with a slow junctional escape rhythm; (ii) the AV pathological findings at peak exercise and after atropinization at EPS, and (iii) the patient refusal to deconditioning.
Our case is noteworthy because it shows that the pathological phenotypic expression can be dependent on the combination of concomitant intrinsic pathological changes and the remarkable autonomic modification induced by exercise. The increasing prevalence of endurance senior athletes will challenge cardiologists to define the subtle boundary between physiological and pathological rhythm disorders.
The full-length version of this report can be viewed at: http://www.escardio.org/communities/EHRA/publications/ep-case-reports/Documents/bradycardia-in-the-athlete.pdf.
