Acceleration of typical XXXX due to double-wave reentry induced by programmed electrical stimulation.

@entity591 @entity1 @entity956
BACKGROUND: Acceleration of reentrant @entity591 induced by programmed electrical stimulation is a well-documented phenomenon, but the mechanisms remain poorly understood. METHODS AND RESULTS: Twelve @entity1 with typical @entity956 were studied. Activation sequence of the underlying reentrant circuit was recorded by multiple multipolar electrodes placed in the right atrium. In five @entity1 , 27 episodes of @entity956 were induced by single extrastimuli delivered in the isthmus between the tricuspid annulus and eustachian ridge (TA-ER isthmus) and one by rapid overdrive atrial pacing. Analyses of the activation sequences, intracardiac electrograms, and 12-lead surface ECG P-wave morphology indicated that the acceleration was caused by two successive activation wave fronts circulating in the same direction along the same reentrant circuit (double-wave reentry, DWR). DWR was induced only within a narrow range of coupling interval, from 2 to 45 ms beyond the effective refractory period, and was associated with unidirectional antidromic block of the paced impulse. @entity1 with DWR had a shorter effective refractory period (138.8+/-13.4 versus 163.8+/-12.2 ms, P<.015) and larger excitable gap (124.0+/-22.6 versus 83.2+/-13.2 ms, P<.009) compared with @entity1 without inducible DWR. All of the DWR episodes were transient. Most (78.6%) terminated after one of the double wave fronts was blocked in the TA-ER isthmus. CONCLUSIONS: DWR is one of the mechanisms responsible for programmed electrical stimulation-induced @entity956 in @entity1 subjects. Its induction requires a sufficient excitable gap and antidromic unidirectional block of the paced impulse in the TA-ER isthmus. In addition, the TA-ER isthmus is the usual site of DWR termination.
