Antidromic reentrant tachycardia(ART), in which an accessory atrioventricular pathway is used as the anterograde limb of an atrioventricular reentrant tachycardia, has been documented clinically in less than 10% of patients with the Wolff-Parkinson-White(WPW) syndrome. The wide QRS complex makes the distinction between antidromic AV reentrant tachycardia and ventricular tachycardia somewhat difficult. The purpose of this study is to evaluate the clinical and eoectrophysiologic characteristics of the antidromic reentrant tachycardia.

During the electrophysiologic study of 355 patients, from December 1986 to April 1995, referred for evaluation of Wolff-Parkinson-White syndrome, 18(5.1%) patients had preexcited reciprocating tachycardia. 1) The age of the antidromic reentrant rnchycardia patients ranged from 15 to 53 years(28±12) and the mean age was younger than that of orthodromic reentrant tachycardia(ORT)patients(p<0.05). 2) Thirteen were male patients, five were females. 3) There were associated heart diseases in 3 cases. Two patients had Egstein's anomaly and ond had valvular heart disease. 4) The locations of accessory pathways(APs) documented on surface ECG were 7 left side(39%), 9 right side(50%)< 1 posteroseptal side(5.5%), and 1 anteroseptal side. 5) Nultiple bypass tracts were documented by electrophysiologic study in 7/18(38.9%) cases with ART, more common than cases with ORT(20/337(5.9%))(p<0.05). 6) 25 accessory pathways were documented by EPS in 18 patients(10 ;eft side, 11 right side, 2 posteroseptal side and 2 anteroseptal side). ART patients had more right sided AP(11/25,44%) than those with ORT(98/357, 27.5%), but ART patients had less posteroseptal AP(2/25, 8%)than those with ORT(63/357, 17.6%). 7) The types of ECG patterns naturally occurred were LBBB(11 cases), RBBB(6cases), and atrial fibrillation(4 cases). 8) The types of induced tachycardia in electrophysiologic study were 11 antidronic reentrant tachycardia, 10 orthodromic reentrant tachycardia, 7 reentrant tachycardia using two accessory bypass tracts, 3 AVnodal reentrant tachycardia, and 5 atrial fibrillations.

ART patients were younger and had more multiple tracts than those with ORT. ART patients had less posteroseptal AP than ORT patients and more right sided AP than ORT patients. The posteroseptal AP was used as retrograde limb only.