Author + information
- Received March 6, 1992
- Revision received July 20, 1992
- Accepted July 23, 1992
- Published online February 1, 1993.
- Laszlo Littmann, MD, FACCa,∗,
- Robert H. Svenson, MD, FACCa,
- Saroja Bharati, MD, FACC∗,
- Maurice Lev, MD, FACC∗,
- Chi Hui Chuang, MDa,
- Pal Kempler, MDa,
- Robert Splinter, MSa,
- Jan R. Tuntelder, BSa and
- George P. Tatsis, MSa
- ↵∗Address for correspondence: Laszio Littmann, MD, Laser and Applied Technologies Laboratory, Carolinas Heart Institute, P. O. Box 32861, Charlotte, N.C. 28232.
Objectives. The purpose of this study was to test the feasibility of selective elimination of ventriculoatrial (VA) conduction by limited laser photocoagulation of the atrioventricular (AV) node, and to analyze the histologic substrate of unidirectional retrograde block.
Background. Atrioventricular node reentry requires intact retrograde conduction.
Methods. Neodymium:yttrium-aluminum-garnet laser photocoagulation was performed during cardiopulmonary bypass through a right atriotomy in 15 dogs that had intact retrograde conduction before operation. Short laser pulses were delivered to an area between the coronary sinus orifice and the proximal His bundle. The end point of lasing was second-degree AV node block at a paced atrial cycle length of 250 ms.
Results. Complete retrograde block developed immediately in 11 of the 15 dogs (group I), while AV conduction persisted in all 11. In 4 of the 15 dogs (group II), both AV and VA conduction remained intact. During a 3-month follow-up period, retrograde conduction remained absent in all group I dogs. Retrograde block was not reversed by isoproterenol. Anterograde AV node characteristics (WencKebach cycle length, functional refractory period, ventricular rate during atrial fibrillation) were unchanged in five dogs and modified in six. Complete AV block did not develop. In four control dogs (group III, sham operation), anterograde and retrograde AV node characteristics were unchanged. The anterograde Wenckebach cycle lengths in groups I, II and III at 3 months measured 192 ± 15 ms, 195 ± 6 ms and 170 ± 22 ms, respectively, whereas the retrograde Wenckebach cycle lengths in groups II and III measured 345 ± 62 ms and 278 ± 25 ms, respectively. Histologic study at 3 months in cases with unidirectional VA block showed the compact part of the AV node intact with destruction of the atrial approaches and the superificial layers of the proximal end of the node on the right side.
Conclusions. 1) With limited laser photocoagulation of the proximal node area, VA conduction can be eliminated and anterograde AV node transmission maintained. 2) Destruction of the atrial approaches on the right side with preservation of the compact part of the AV node may result in unidirectional retrograde block.
☆ This study was presented in part at the 40th Annual Scientific Session of the American College of Cardiology, Atlanta, Georgia, March 1991. It was supported by Grant OTKA 1/3-1081 from the Hungarian Academy of Sciences, Budapest, Hungary.
- Received March 6, 1992.
- Revision received July 20, 1992.
- Accepted July 23, 1992.