This 74-year-old woman underwent implantation of an Adapta dual chamber pacemaker for syncopal episodes caused by complete AV block due to degenerative disease of the conduction system; she was seen in follow-up 3 months after device implantation for palpitation and signs of moderate left heart insufficiency.
Tracing 2a: the first channel is lead III of the surface ECG with the markers superimposed, the second is the ventricular EGM, and the third is lead II with the time intervals superimposed;
Tracing 2b: interrogation of the device revealed that mode switch was not programmed; tracings recorded before and after programming of mode switch;
Mode switch is programmed as a nominal setting and should not be turned off, even in patients who have no history of atrial arrhythmia.
In this patient in complete AV block, the absence of fallback was associated with prolonged, rapid ventricular pacing at the maximum tracking rate. A combined loss of atrial systole and runaway ventricular pacing was responsible for the manifestations of cardiac decompensation observed in this patient. Programming of mode switch restored a more physiologic heart rate. To prevent a sudden fall in ventricular rate, the return to the backup or the sensor-driven rate is progressive.
Along with the reprogramming of her pacemaker, the patient management included 1) the introduction of anticoagulation, 2) a conversation regarding the merits of converting her atrial arrhythmia. No rate slowing medication was needed for this patient who was in complete AV block. The recent onset of the arrhythmia and the absence of prominent dilatation of the atria on echocardiogram suggested that an attempt at pharmacologic or transthoracic DC shock cardioversion might be worthwhile.
