exit block
Conduction disturbance preventing electrical impulses from leaving their site of origin, such as the sinus node or an ectopic focus.
Full Definition
Exit block refers to a conduction abnormality where electrical impulses generated at their site of origin (such as the sinus node, atrial ectopic focus, or ventricular focus) fail to propagate to surrounding myocardial tissue due to localized conduction failure. This results in missed beats or pauses without affecting the underlying rhythm generator itself. Sinoatrial exit block is the most common form, where sinus node impulses fail to activate the atria, creating pauses that are multiples of the basic sinus cycle length. Exit block can be classified as first-degree (prolonged conduction time), second-degree (intermittent failure), or third-degree (complete failure). The mechanism involves dysfunction in the specialized conducting tissue surrounding the impulse generator, often due to fibrosis, ischemia, or drug effects.
Usage
Usage note: Specify the location (SA exit block, ventricular exit block) for clarity.
In Context
- "The patient's Holter monitor revealed intermittent sinoatrial exit block with pauses up to 3.2 seconds." — Holter monitor report
- "Second-degree SA exit block was suspected based on the regular pattern of dropped P waves." — ECG interpretation report