PMC5412640_01
A: Baseline paced electrocardiogram. Electrocardiogram shows atrial sensed ventricular paced rhythm with a very wide complex tachycardia (QRS duration of 240 milliseconds) at 115 beats per minute with group beating due to intermittent failure to capture. Note, the width of the QRS complex gradually increases such that the last QRS complex before the pause is much wider than the first QRS after the pause. B: Intracardiac electrogram. Atrial sensed ventricular paced rhythm with intermittent failure to capture.
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Her presenting electrocardiogram (ECG) showed a wide complex rhythm with intermittent loss of ventricular capture (Figure 1A). The initial ECG (Figure 1A) showed a very wide complex tachycardia (QRS duration of 240 ms) at 115 bpm with group beating due to intermittent failure to capture. This finding was also demonstrated on the intracardiac electrogram from the pacing device (Figure 1B). The intermittent failure to capture during ventricular pacing is the result of the pacing stimulus occurring during the refractory period of the previous beat, with a very delayed depolarization (Figures 1A and 1B).
A: Baseline nonpaced electrocardiogram shows atrial fibrillation with a wide complex QRS measuring 200 milliseconds. B: Nonpaced electrocardiogram recorded after 48 hours. The electrocardiogram shows atrial fibrillation with QRS measuring 136 milliseconds.
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The nonpaced ECG before and after treatment demonstrated remarkable narrowing of QRS complexes (Figures 2A and 2B).