Ambulatory blood pressureandassessmentof pacemaker function

SUMMARY Tenpatients insinus rhythmwithventricular demand(VVI)pacemakers implanted forthesicksinus syndrome underwent 24hourambulatory bloodpressure andelectrocardiographic recording byamodified version oftheOxford system.Fivepatients hadsymptoms ofdizziness orpresyncopeatthetimeofstudy andfive were symptom free. Theonsetofpacing wasassociated with afall inarterial blood pressureinboth groups which was larger inthepatients withsymptoms,andinthese patients theblood pressurerecovery consequenton baroreflex activation was delayed byup tofifteen beats. Inthree ofthepatients withsymptomstheoriginal pacemaker was replaced byan atrioventricular pacing (DVI)device. Thisabolished syrmptoms andtheinitial fall anddelayed recoveryofblood pressure.Thusitappearsthat thedevelopment ofsymptomsofhypotension after theonsetofventricular pacing isdetermined bytherateofthe baroreflex response.Thesesymptomsandthehaemodynamic consequencesmay bealleviated by dualchamber pacing. A patient's electrocardiographic response toan