Dual chamber pacemakers are programmed to allow for AV synchrony. Whenever a patient with a dual chamber pacemaker with underlying sinus rhythm presents with AV dissociation, the lack of AV synchrony should be questioned. The authors present a case of new onset dyspnea diagnosed as pacemaker syndrome. The diagnosis was initially delayed due to underlying ventricular paced rhythm as misidentified as normal pacemaker behavior.

A 69-year-old female with a past medical history of 2:1 atrioventricular block status post dual-chamber pacemaker implant presented with complaints of new onset shortness of breath and dyspnea. The ECG showed a ventricular rate of 66 beats per minute. Pacing spikes were prior to each QRS complex indicating ventricular-paced rhythm with left bundle branch morphology. There were p waves from sinus origin which were completely dissociated from the ventricular paced rhythm. Overall, there was ventricular paced rhythm with underlying AV dissociation. This was initially suspected to be normal pacemaker behavior as there was appropriate ventricular pacing and ventricular capture. Review of the tracing noted AV dissociation, which would be unusual in a patient with underlying sinus rhythm and dual chamber device. Device interrogation noted that device was at end of life and atrial lead was powered down to allow for ventricular pacing. It is important to always question the lack of AV synchrony if patients have dual chamber pacemaker as lack of AV synchrony can cause pacemaker syndrome.

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12-Lead Electrocardiogram

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Post-operative ECG