Author + information
- Received January 26, 1996
- Revision received May 28, 1996
- Accepted September 9, 1996
- Published online December 1, 1996.
- K. Ching Man, DO⁎,
- Karin Brinkman, BS,
- Frank Bogun, MD,
- Bradley Knight, MD,
- Marwan Bahu, MD,
- Raul Weiss, MD,
- Rajiva Goyal, MD,
- Mark Harvey, MD,
- Emile G. Daoud, MD,
- S. Adam Strickberger, MD and
- Fred Morady, MD, FACC⁎
- ↵⁎Address for correspondence: Dr. K. Ching Man, University of Michigan Hospital, Division of Cardiology; B1-F245, 1500 East Medical Center Drive, Ann Arbor, Michigan 48109-0022.
Objectives The purpose of this study was to determine the incidence and to clarify the mechanism of 2:1 atrioventricular (AV) block during AV node reentrant tachycardia induced in the electrophysiology laboratory.
Background In patients with 2:1 AV block during AV node reentrant tachycardia, the absence of a His bundle potential in the blocked beats has been considered evidence of intranodal, lower common pathway block.
Methods In consecutive patients with AV node reentrant tachycardia, the incidence of 2:1 AV block and the response to atropine and a single ventricular extrastimulus was observed.
Results Persistent 2:1 AV block occurred in 13 of 139 patients with AV node reentrant tachycardia. A His bundle deflection was present in the blocked beats in eight patients and absent in five. Patients with 2:1 AV block had a shorter tachycardia cycle length than did patients without such block (mean ± SD 312 ± 32 vs. 353 ± 55 ms, p < 0.01). Atropine did not alter the 2:1 block in any patient. In every patient, a single ventricular extrastimulus introduced during the tachycardia converted the 2:1 block to 1:1 conduction.
Conclusions The incidence of induced 2:1 AV block during AV node reentrant tachycardia is ~ 10%. The lack of a response to atropine and the consistent conversion of 2:1 block to 1:1 conduction by a ventricular extrastimulus indicate that, regardless of the presence or absence of a His bundle potential in blocked beats, 2:1 block during AV node reentrant tachycardia is due to functional infranodal block.
(J Am Coll Cardiol 1996;28:1770–4)
- Received January 26, 1996.
- Revision received May 28, 1996.
- Accepted September 9, 1996.
- American College of Cardiology