Author + information
- Received March 7, 1983
- Revision received May 23, 1983
- Accepted May 27, 1983
- Published online January 1, 1984.
- Arthur S. Pickoff, MD*,
- Sharanjeet Singh, MD,
- Celia J. Flinn, MD,
- Edda Torres, MD,
- Alan M. Ezrin, PhD and
- Henry Gelband, MD, FACC
- ↵*Address for reprints: Arthur S. Pickoff, MD, Pediatric Cardiology, Department of Pediatrics, University of Miami School of Medicine, P.O. Box 016820, Miami, Florida 33101.
This study reports on the changes in ventriculoatrial (VA) conduction that occur with maturation. Programmed atrial and ventricular premature extra-stimulation (coupled to a fixed paced cycle length) and rapid atrial pacing were performed in three groups of dogs: Group 1 = 8 neonates aged 5 to 14 days, Group II = 9 young dogs aged 6 to 9 weeks and Group III = 10 adult dogs. High right atrial, His bundle and right ventricular electrograms were recorded. There were no differences in the AH intervals at rest. In all but five animals, atrioventricular conduction was limited by the atrial functional refractory period (Group I, 109 ± 12 ms; Group II, 152 ± 22 ms; Group III, 167 ± 19 ms). As expected, with rapid atrial pacing, Wenckebach conduction developed at a shorter cycle length in the younger animals (Group I,145 ± 20 ms; Group II, 153 ± 15 ms; Group III, 200 ± 25 ms, p < 0.01).
Ventriculoatrial conduction was documented in 87% of Group I puppies and 100% of Group II, but only 40% of Group III dogs. The effective and functional refractory periods of the VA conduction system were significantly shorter in the more immature groups of dogs (effective/functional: Group I, 124 ± 27/168 ± 22 ms; Group II, 139 ± 23/202 ± 13 ms; Group III, 270 ± 28/326 ± 25 ms; p < 0.01).
Relative to the adult dog, the immature heart showed a greater incidence of VA conduction and shorter VA refractory periods. This enhanced VA conduction may be of physiologic importance in the initiation and perpetuation of certain supraventricular arrhythmias.
with the technical assistance of Carlos A. Flores, Judith Kassner
This study was supported by Clinical Investigator Award HL00881 (Dr. Pickoff) and Research Training Grand HL07436 from the National Heart, Lung, and Blood Institute, Bethesda, Maryland and a grant from the American Heart Association of Greater Miami, Florida.
- Received March 7, 1983.
- Revision received May 23, 1983.
- Accepted May 27, 1983.
- American College of Cardiology Foundation