Scenario: This is a routine postoperative 12-lead ECG waveform of a 58-year-old Mexican man status post external and internal carotid bypass repair. He is recovering in the neurointensive care unit.

Interpretation: One hundred percent ventricularly paced at 80 beats per minute.

Unfortunately, without noting the pacemaker spikes (small vertical tick marks best seen in V3), this 12-lead ECG waveform may look pathological because of the wide QRS complexes. However, this is actually a normal functioning ventricular pacemaker. None of the QRS complexes are preceded by a P wave (paced or intrinsic). The ventricular impulses begin with a pacing spike and what follows is strikingly different from a “normal” QRS. Typically, the electrical impulse originates from the right ventricle; thus, excitation spreads aberrantly via nontraditional conduction pathways, much like a premature ventricular contraction.

The nurse should document an ECG to ensure that the pacemaker is sensing, firing, and capturing...

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