Author + information
- Received March 3, 1986
- Revision received April 30, 1986
- Accepted May 14, 1986
- Published online November 1, 1986.
- Rehan Mahmud, MD, FACC*,1,
- Patrick J. Tchou, MD1,
- Stephen T. Denker, MD, FACC1,
- Michael H. Lehmann, MD, FACC1 and
- Masood Akhtar, MD, FACC1
- ↵*Address for reprints: Rehan Mahmud, MD, Section of Cardiology, East Carolina University School of Medicine, Pitt County Memorial Hospital, Greenville, North Carolina 27834.
The effect of improved conduction in areas of delay was tested during macro-reentry within the His-Purkinje system, in an attempt to separate the role of conduction delay from that of prematurity of the extrastimulus as the key determinant of reentry. Using the right ventricular extrastimulus technique (S1S2method), both the critical His-Purkinje system delays and the zone of S1S2intervals causing His-Purkinje system reentry were determined. Then, using a previously described technique of atrioventricular (AV) sequential pacing during the basic drive, the potential site of His-Purkinje system conduction delay was (anterogradely) excited earlier (preexcitation), as compared with the control S1S2method. This produced a decrease in retrograde His-Purkinje system delay (S2H2), as compared with the same S1S2interval during the control method. Changing the degree of pre-excitation at each S1S2interval allowed for determination of the critical (or shortest) S2H2delay necessary for His-Purkinje system reentry at each coupling interval. Of importance was the observation that the critical delay was not specific for each case but varied with the prematurity of S2. For example, the critical S2H2delay required for reentry was actually less at shorter S1S2intervals as compared with longer S1S2intervals (from 206 ± 25 to 187 ± 20 ms, p < 0.01).
These data suggest that manifestation of reentry is a complex interplay between degree of prematurity and conduction delay. The so-called critical conduction delay can be readily modified by altering the site of block, which in turn may be dependent on prematurity of the extrastimulus.
- Received March 3, 1986.
- Revision received April 30, 1986.
- Accepted May 14, 1986.
- American College of Cardiology Foundation