rate-dependent bundle branch block
Pronunciation: rayt-dih-PEN-dent BUN-dul branch blok
Bundle branch block that appears only at certain heart rates, typically at faster rates. Also known as phase 3 or tachycardia-dependent block.
Full Definition
Rate-dependent bundle branch block is a conduction abnormality where bundle branch block appears only when the heart rate exceeds a certain threshold, typically during faster rates or exercise. This phenomenon occurs due to the prolonged refractory period of one of the bundle branches, which fails to conduct when the cycle length becomes shorter than its refractory period. Also termed phase 3 block or tachycardia-dependent block, this condition contrasts with bradycardia-dependent or phase 4 block, where conduction abnormalities appear at slower rates. Rate-dependent bundle branch block is often functional rather than structural and may indicate underlying conduction system disease. Recognition is important in exercise testing and ambulatory monitoring interpretation.
Usage
Usage note: Use hyphens in 'rate-dependent' when functioning as a compound adjective.
In Context
- "Exercise testing revealed rate-dependent bundle branch block at heart rates above 120 bpm." — Stress test report
- "The rate-dependent bundle branch block resolved when the patient's heart rate decreased below 90 bpm." — Telemetry monitoring note