Cycle length change during reciprocating tachycardia in patients with Wolff-Parkinson-White syndrome.
Cycle Length (CL) changes during reciprocating tachycardia (RT) were examined in 82 consecutive patients with Wolff-Parkinson-White syndrome (WPW) during electrophysiological studies. The significant CL changes (sudden and greater than 30 msec.) were found in 21 of 82 patients (26%). Thirteen patients had a manifest WPW and eight had a concealed WPW. An accessory pathway (AP) was located in the left side in 14 patients, the right side in four patients and the septum in two patients. One patient had multiple AP's. The development of ipsilateral bundle branch block during RT was responsible for CL changes in 11 patients. The sudden shift between fast and slow pathways in atrioventricular node (AVN) during RT was responsible for CL changes in two patients. Alternating CL changes during RT were found in eight patients. In five of them, alternating CL changes could be explained by physiological properties of a single AVN pathway. In the remaining three patients, the onset of 2:1 block in a fast pathway with 1:1 conduction in a slow pathway of the AVN may be responsible for CL changes. In one patient with multiple AP's the shift from one re-entrant circuit to the other was responsible for CL changes.


CONCLUSIONS
1) CL changes during RT are not uncommon in patients with WPW. 2) Several different mechanisms are responsible for CL changes.
D000293:Adolescent; D000328:Adult; D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology*; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D013610:Tachycardia / Q000175:diagnosis / Q000503:physiopathology*; D014927:Wolff-Parkinson-White Syndrome / Q000175:diagnosis / Q000503:physiopathology*