Determinants of atrioventricular reentrant paroxysmal tachycardia in patients with Wolff-Parkinson-White syndrome.

Normal and anomalous pathway properties were evaluated in 50 patients with preexcitation to discover determinants of paroxysmal supraventricular tachycardia (PSVT). Twenty-eight patients had inducible PSVT and 22 had no inducible PSVT. Patients with inducible PSVT had: 1) ability for retrograde anomalous pathway conduction demonstrated with ventricular pacing at short paced cycle lengths (< 429 msec) and close coupling intervals (< 400 msec); and 2) antegrade AV nodal refractoriness less than anomalous pathway refractoriness during rapid and/or coupled atrial pacing with ability for exclusive normal pathway conduction for at least one beat at short atrial paced cycle lengths (< 375 msec) or close coupling intervals (< 320 msec). Failure to induce PSVT was accounted for by one of the following: 1) absent or poor retrograde anomalous pathway conduction alone (six patients); 2) inadequate antegrade AV nodal properties alone (eight patients); 3) both inadequate antegrade AV nodal and retrograde anomalous pathway properties (seven patients); and 4) prolonged atrial refractoriness (one patient). There were no significant differences in anomalous pathway antegrade refractory periods between the patients with and without PSVT. We conclude that the occurrence of PSVT in Wolff-Parkinson-White syndrome depends on the ability for retrograde anomalous pathway conduction and adequate antegrade AV nodal conduction. The inability to induce PSVT usually reflects inadequate retrograde anomalous and/or antegrade normal pathway properties. The ability to induce PSVT is independent of antegrade anomalous pathway properties.