Author + information
- Received February 18, 1986
- Revision received June 11, 1986
- Accepted July 7, 1986
- Published online February 1, 1987.
- ↵*Address for reprints: Pablo Denes, MD, Professor of Medicine, Rush-Presbyterian-St. Lukes Medical Center, 1750 West Harrison Street, Chicago, Illinois 60612.
A case of paroxysmal bradycardia- and tachycardia-dependent atrioventricular (AV) block is described in a patient with right bundle branch block. The His bundle recordings demonstrated the site of the AV block to be distal to the His bundle recording site (probably in the left bundle branch). Whereas AV block distal to the His bundle occurred at an atrial paced cycle length of 700 ms, intact ventriculoatrial (VA) conduction was present up to a ventricular paced cycle length of 400 ms. Resumption of AV conduction was dependent on a critical HH or RH (in case of escapes) interval.
These findings suggest that the bradycardia-dependent block is related to a time-dependent decrease in the amplitude of the current intensity of the proximal segment during late diastole. Spontaneous diastolic depolarization during late diastole resulted in impaired anterograde (AV) conduction but facilitated retrograde (VA) conduction. These findings are consistent with experimental “in vitro” observation in the sucrose gap model of AV block.
- Received February 18, 1986.
- Revision received June 11, 1986.
- Accepted July 7, 1986.
- American College of Cardiology Foundation