| Abstrakt: |
The timing of entrainment onset has been shown to correlate with the conduction time to critical elements of a tachycardia circuit in a pacemaker model of reentrant ventricular tachycardia (VT). The utility of this method in evaluating clinical reentrant tachycardias was therefore evaluated in 24 patients with symptomatic Wolff-Parkinson- White syndrome and single bypass tracts (left free wall in 17, posteroseptal in 5, anteroseptal in 1, and right free wall in 1). Bight ventricular apex (RVA) pacing during orthodromic atrioventricular reentrant tachycardia (oAVRT) at 10-70 msec less than tachycardia cycle length demonstrated concealed entrainment of the tachycardia in all patients studied. An entrainment index (EI), defined as the minimal prematurity of the ventricular stimulus that first resulted in atrial reset, was calculated from multiple entrainments in each patient. The EI was 121 ± 25, 83 ± 29, and 55 msec for left free wall, septal, and right free-wall bypass tracts, respectively (P = 0.004 for difference between left free wall and septal). A corrected El, derived by subtracting the amount of atrial reset from the EI, gave values of 108 ± 22 and 71 ± 17 msec for left free wall and septal bypass tracts (P = 0.001). These values were compared to the preexcitation index (PI) by linear regression analysis in these patients. The PI correlated closely with both the EI and the corrected EI (r 0.90 and 0.93, respectively), but the PI could only be derived in 12/2 7 (71%) left free-wall tachycardias versus the EI in 17/17 (100%) (P < 0.05). Thus, the timing of entrainment onset can be used to calculate a relative conduction time to the tachycardia circuit in oAVRT, thus localizing the bypass tract. This may prove useful in localizing critical components of the reentrant circuit in other clinical tachycardias. [ABSTRACT FROM AUTHOR] |
Plný text