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[Intermittent atrio-ventricular block induced by exertion. Description of 3 cases]
Insights
Exercise can trigger severe atrioventricular block in some individuals. This condition indicates His-Purkinje system disease, not atrioventricular node issues, and may necessitate permanent cardiac pacing.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Electrophysiology
Background:
- Atrioventricular (AV) conduction at rest is typically normal in affected individuals.
- Exercise stress testing can unmask underlying cardiac conduction abnormalities.
Observation:
- Three patients presented with 1:1 atrioventricular conduction at rest.
- During exercise testing, these patients developed fixed 2nd or 3rd-degree atrioventricular block.
Findings:
- Electrophysiologic studies confirmed the block was distal to the atrioventricular node, specifically within the His-Purkinje system.
- Increased atrial rate during exercise likely exacerbated abnormal refractoriness in the His-Purkinje system, leading to block.
Implications:
- Exercise-induced high-degree atrioventricular block suggests His-Purkinje system disease, even without bundle branch block.
- These patients may benefit from evaluation for permanent cardiac pacing.
- Understanding the location of the block is crucial for appropriate patient management.
Abstract:
Three patients with 1:1 atrio-ventricular conduction at rest developed fixed 2nd or 3rd degree atrio-ventricular block during exercise testing. In all patients electrophysiologic study documented block distal to the atrioventricular node. The exercise induced block probably occurred because of increased atrial rate and abnormal refractoriness of the His-Purkinje conduction system. These findings suggest that high degree atrioventricular block appearing during exercise reflects conduction disease of the His-Purkinje system rather than of the atrio-ventricular node, even in absence of bundle branch block. These patients should be considered for permanent cardiac pacing.