In 7 patients with triple atrioventricular nodal pathways out of 165 p
atients with paroxysmal supraventricular tachycardia, we determined th
e effects of cycle length on the refractoriness of the triple nodal pa
thways. Cycle length modulated the dispersion in the refractoriness of
the triple nodal pathways by causing greater changes in the slower pa
thways, and thus determined the feasibility of their apparent manifest
ation.