Circulation, Vol 53, 33-39, Copyright © 1976 by American Heart Association
J Aranda, A Castellanos, F Moleiro and B Befeler
His bundle recordings were studied in four patients with short P-R and A-H
intervals, and narrow QRS complexes, who had experienced several episodes
of supraventricular tachyarrhythmias. The heart was paced from the high
right atrium (HRA) and the coronary sinus (CS). In three patients the A-H
Wenckebach phenomenon occurred at higher rates (greater than 200 pacing
beats/min) when the CS was paced than when pacing was performed from the
HRA. Moreover, CS stimulation produced smaller increments in the A-H
interval than did pacing from HRA. The extrastimulus method of testing was
done. In cases 1 and 2 the functional refractory period of the A-H tissues
was 15 to 25 msec shorter during CS pacing than when pacing from the HRA.
In case 3, the low right atrium (LRA) as well as the other two sites were
paced. A type 1 gap was seen from HRA, a type 2 gap from CS, and both types
appeared when the LRA was paced. Case 4, in which the mid-right atrium
(MRA) was also stimulated, had a double pathway from HRA and CS with
conduction through the accessory pathway late in the cycle and through the
A-V node earlier in the cycle. However, the A-V node could not be
penetrated during MRA stimulation. It appeared that the pacing site
influenced the A-H conduction pattern and refractoriness, possibly by
changing the site and/or mode of entry of the stimulus into the pathways
that are responsible for this syndrome.
ARTICLES
Effects of the pacing site on A-H conduction and refractoriness in patients with short P-R intervals
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