PMC5771922_01
ECG shows atrial and ventricular pacing artifacts, each followed by a ventricular depolarization, constantly coupled but with a latency of 600 ms. Atrial depolarizations are indiscernible. The QRS complex is widened, with a QRS duration of 240 ms, and a Brugada-like pattern with ST-segment elevation and T-wave inversion in leads V1 and V2.
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ECG (Fig. 1) was judged to be exit block of the ventricular pacing lead, and after discharge from the nuclear medicine ward, the patient was referred for lead revision.
ECG during device interrogation (AAI pacing 60 bpm, atrial exit block) shows intrinsic heart rate of <25 bpm also with signs of hyperkalemia, but a different QRS morphology when compared to ECG 1.
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The atrial lead showed complete exit-block, intrinsic heart rate during device interrogation was <25 bpm with a different QRS morphology (Fig. 2).
Electrogram upon device interrogation shows, from top to bottom, marker annotation, lead I of the surface ECG, and atrial (A) and ventricular (V) electrograms. Atrial and ventricular pacing is delivered, followed by a constantly coupled, but delayed ventricular sensing. In the atrial electrogram, no depolarization can be detected. From ventricular sensing, the next ventricular pacing is delivered after 1000 ms, corresponding to the programmed stimulation rate of 60 bpm.
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Sensing of the delayed ventricular depolarization resulted in reduction in the effective pacing rate to 35 bpm (Fig. 3).