Differential electrophysiologic properties of decremental retrograde pathways in long RP' tachycardia.

10 patients with long RP' supraventricular tachycardia (SVT) (RP'/RR, 0.52 to 0.71), including 5 with fast-slow AV nodal reentry and 5 with accessory AV pathways with slow, decremental retrograde conduction properties.

Intravenous adenosine (37.5 to 150 micrograms/kg) and verapamil (0.10 to 0.20 mg/kg iv) administered during SVT.

Termination of SVT and effect on retrograde conductionsurrogate