Related Experiment Videos
Exercise-induced distal atrioventricular block
Insights
Exercise can trigger high-grade atrioventricular (AV) block in some individuals. This block originates in the His-Purkinje system, not the AV node, suggesting a need for pacing consideration.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Background:
- Atrioventricular (AV) conduction normally maintains a 1:1 ratio at rest.
- Treadmill exercise testing is used to assess cardiac function under stress.
Observation:
- Three patients exhibited 1:1 AV conduction at rest.
- During exercise, these patients developed fixed 2:1 or 3:1 AV block.
Findings:
- Electrophysiologic studies revealed AV block distal to the AV node.
- Exercise-induced block was attributed to increased atrial rate and His-Purkinje system abnormalities.
Implications:
- Exercise-induced high-grade AV block indicates His-Purkinje conduction disease, not solely AV nodal disease.
- Patients presenting with these symptoms may benefit from permanent cardiac pacing.
Abstract:
Three patients with 1:1 atrioventricular (AV) conduction at rest developed fixed 2:1 or 3:1 AV block during treadmill exercise testing. Electrophysiologic study documented block distal to the AV node in all three patients, and suggested that the exercise-induced block occurred because of increased atrial rate and abnormal refractoriness of the His-Purkinje conduction system. The findings in these three patients suggest that high grade AV block appearing during exercise reflects conduction disease of the His-Purkinje system rather than of the AV node, even in the absence of bundle branch block. Patients with this diagnosis should be considered for permanent cardiac pacing.