Comparison of right and left atrial stimulation in demonstration of dual atrioventricular nodal pathways and induction of intranodal reentry.

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Abstract
The role of the atrial stimulation site in demonstration of dual atrioventricular nodal (AVN) pathways and induction of AVN reentry was assessed in 15 patients with clearly discontinuous AVN function curves on atrial extrastimulus testing. Stimulation was performed from the right atrium in all cases. The left atrium was stimulated from the coronary sinus in 13 patients and directly through a patent foramen ovale in 2 patients. Baseline fast-AVN-pathway AH [atrial-His] intervals were significantly shorter with left atrial stimulation. Maximum AH intervals for conduction over the fast or slow AVN pathways were also significantly shorter with left atrial stimulation. Refractory periods of the fast or slow AVN were not significantly altered by the stimulation site. Although failure to induce dual AVN pathways or AVN reentry could occur with use of only 1 atrial stimulation site this was uncommon (4 of 15 patients); the ineffective site was usually the left atrium, and the reason was generally a prolonged atrial functional refractory period at that site. Provided the atrial functional refractory period was not prolonged compared with other sites and several basic cycle lengths were used, the atrial stimulation site did not significnatly affect demonstration of dual AVN pathways and induction of AVN reentry. Variability of most measurements of AVN function and reentry were common. A critical AH interval was not necessary for induction of AVN reentry in 4 cases. Atrial stimulation site influences AH conduction times over both fast and slow AVN pathways without altering refractoriness. The stimulation site does not significantly affect ease of demonstration of dual AVN pathways or induction of AVN reentry.