Scenario: A 68-year-old woman with a ventricular pacemaker was admitted to the telemetry unit for exacerbation of congestive heart failure. The nurse noticed changes in the patient’s cardiac rhythm on telemetry, so she examined a 30-second strip of lead II from the telemetry’s full disclosure software (below). Because the full disclosure does not have an electrocardiogram (ECG) grid on it, the nurse zoomed in on the onset of the rhythm change.

Interpretation: Sinus bradycardia with an intermittent wide QRS rhythm (accelerated ventricular escape rhythm versus ventricular pacing) and a premature junctional contraction (PJC).

The underlying rhythm is normal until the sinus node fails to fire and the heart rate falls below 50/min (after sixth beat). After the pause, the rate is slower, there are no P waves, and the QRS complex widens and changes morphology from Rs to QS with notching. All of these changes suggest either an accelerated ventricular...

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