Noninvasive evaluation of pacemaker circus movement tachycardias.

Ventriculoatrial (VA) conduction was studied in 11 patients before DDD pacemaker implantation by incremental right ventricular pacing while recording right atrial endocavitary signals. After implantation and at 3-month outpatient visits, VA conduction and ability to initiate and sustain pacemaker circus movement tachycardia (PCMT) were systematically assessed noninvasively by testing the response of the pacemaker to asynchronous and single synchronized chest wall stimuli, muscle signals, and programmer pertubations. VA conduction was demonstrated in 3 of 11 patients before implantation as well as by noninvasive techniques after implantation with induction of PCMT. VA conduction became apparent in 2 additional patients after implantation. One of the 2 patients presented clinically with PCMT. In both patients, PCMT could be induced noninvasively. The presence or absence of VA conduction was variable, as was the rate of right ventricular pacing at which VA block occurred. In conclusion, (1) noninvasive testing techniques were effective in inducing PCMT in all patients with VA conduction and helpful in determining control of PCMTs, and (2) thorough preimplantation and repeated postimplantation assessment is needed to control and prevent PCMT.