Atrioventricular (AV) and Ventriculoatrial (VA) Conduction Pattern in Patients with Short P — R Interval and Normal QRS Complex

Gaps in anterograde conduction in patients with the short PR interval, normal QRS complex syndrome.

“…Such discontinuous anterograde conduction plots were evident in 3 of the 8 patients with the short PR interval, normal QRS complex syndrome studied recently in our laboratory and reported here. Others have found similar results in this syndrome (Denes et al, 1974b;Neuss et al, 1975;Aranda et al, 1976;Seipel et al, 1976). The discontinuity of the conduction curves in the present cases is emphasised by the gap in anterograde conduction which separates slow and fast pathway conduction (Fig.…”

“…Gap phenomena have been previously encountered in the short PR interval, normal QRS complex syndrome (Coumel et al, 1972;Aranda et al, 1976;Seipel et al, 1976). Aranda and his col-leagues found anterograde gaps in 2 of 4 cases reported and resumption of anterograde conduction was not related to refractoriness of the fast pathway.…”

“…Such a tract of tissue has been histologically verified in one patient with the short PR interval, normal QRS complex syndrome (Brechenmacher et al, 1974). Nevertheless, the alternative explanation of a rapidly conducting intranodal pathway (Caracta (Bisset et al, 1973;Neuss et al, 1975), premature atrial stimulation (Castellanos et al, 1971;Aranda et al, 1976), and intravenous verapamil (Both et al, 1975;Seipel et al, 1976) is typical of the short PR interval, narrow QRS complex syndrome and more consistent with an extranodal bypass tract than an intranodal fast pathway. In the cases reported here, anatomical dissociation of the fast pathway from the AV node is very likely because conduction anterogradely through the slow AH pathway results in atrial echo beats with earliest activation on the proximal coronary sinus electrode (Narula, 1974;Agha et al, 1976;Amat-y-Leon et al, 1976).…”

“…The syndrome of short PR interval, normal QRS complex associated with paroxysms of tachycardia (Clerc et al, 1938;Lown et al, 1952) provides an example of dual conduction pathways at AV nodal level (Denes et al, 1974b) which is often associated with gaps in anterograde conduction (Seipel et al, 1976). In this study the interplay between dual proximal conduction and distal conduction failure in 3 patients with the short PR interval, normal QRS complex syndrome is defined.…”

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“…In the presence of partial or complete A-V nodal bypass tracts (Brechenmacher et al .. 1974) or enhanced A-V nodal conduction, the normal A-V nodal delay is considerably attenuated (Aranda et al, 1976;Castellanos et al, 1971;Hope et a/., 1977) with a correspondingly short A-V nodal FRP (Bissett et al .. 1975;Camm et al, 1978;Seipel et al, 1976). This naturally occurring model may allow the delivery of sufficiently closely coupled H 1 -H2 impulses to result in infra nodal delay or block (Aranda et al, 1976;Camm et al .. 1978).…”