Pacemaker Rhythms and Artifact Recognition

What Is a Pacemaker?

A cardiac pacemaker is an implanted device that delivers a small electrical impulse to the heart when the heart's own conduction system fails to do so reliably. Pacemakers are used when patients have symptomatic bradycardia, heart block, or other conditions in which the natural rate or rhythm is dangerously slow or irregular. As an EKG technician, you will frequently record rhythms from patients who have pacemakers. You must recognize pacemaker activity, confirm that it is working correctly, and know when something looks wrong — so the appropriate clinician can be notified promptly.

The Pacemaker Spike

Every pacemaker stimulus produces a sharp, narrow vertical mark on the rhythm strip called a pacemaker spike (also called a pacing artifact). This spike is the electrical footprint of the device firing. Spikes are thin and vertical and stand out clearly from the surrounding waveforms. Your first task on any strip is to locate these spikes.

• Atrial pacing: The spike appears just before a P wave. The QRS that follows should be narrow and normal-looking because ventricular conduction continues through the natural pathway.
• Ventricular pacing: The spike appears just before a QRS complex. Because the impulse bypasses the normal conduction pathway, the resulting QRS is wide and has an abnormal, bundle-branch-block-like appearance. There may be no visible P wave before the spike, or the P wave is unrelated to the paced beat.
• Dual-chamber (AV) pacing: Two spikes appear per cycle — one before the P wave (atrial spike) and one before the QRS (ventricular spike). This mimics the heart's natural sequential contraction of atria then ventricles.

Determining Capture

Capture means the pacemaker's stimulus actually caused the heart muscle to depolarize. Look for a waveform immediately after every spike:

• Atrial capture: A P wave follows the atrial spike.
• Ventricular capture: A wide QRS follows the ventricular spike.
• Failure to capture: A spike appears but NO waveform follows. This is a malfunction that must be reported to the nurse or supervising clinician immediately because the patient may not be getting the pacing support they need.
• Failure to pace (failure to fire): Expected spikes are absent. Also a malfunction requiring immediate escalation.

Note: in a patient who is fully pacemaker-dependent, failure to capture or failure to pace can be life-threatening. Never delay reporting these findings.

Understanding Sensing

Most pacemakers are programmed to sense the patient's own heartbeats. When the device detects a native beat, it resets its timer and holds off firing — this is called inhibition. You may see a mix of native beats and paced beats on the same strip. A paced beat that fires when it should be inhibited (competes with a native beat) is called pacemaker competition or failure to sense, and it should also be reported.

Common EKG Artifacts and How to Recognize Them

Artifacts are signals on the strip that come from sources other than the heart. They can mimic dysrhythmias or obscure real rhythms. Recognizing them protects patients from misdiagnosis and unnecessary treatment.

Somatic Tremor (Muscle Tremor)

Caused by patient movement, shivering, Parkinson's disease, or anxiety. Produces an irregular, chaotic, high-frequency baseline that can look like atrial fibrillation or even ventricular fibrillation. Key clue: you can still find regular R waves marching through the noise if you look carefully.

AC (Alternating Current) Interference

Caused by nearby electrical equipment, poor grounding, or a lead wire touching a metal bed rail. Produces a perfectly regular, fine-tooth-comb waveform at 60 cycles per second (60 Hz in the US). The baseline thickens into a uniform fuzzy band. Correction: move or turn off nearby electrical equipment; check lead wire routing; ensure the machine is grounded.

Baseline Wander (Baseline Drift)

The baseline rolls up and down in a slow wave, often caused by patient breathing, patient movement, or electrode gel drying out. Correction: ask the patient to breathe quietly and avoid talking; replace dried electrodes; ensure lead wires are not pulling on electrodes.

Loose or Detached Electrode (Lead-Off Artifact)

Produces a straight flat line or wildly erratic signal in one lead. Other leads on the same strip often look normal — a key clue that the problem is mechanical, not cardiac. Correction: check and reattach the electrode; clean and dry the skin; replace the electrode if needed.

Safety and Scope of Practice

• Never interpret a rhythm strip as a diagnosis or tell a patient they are having a heart attack or that their pacemaker is broken. Your role is to acquire and document the tracing and report abnormalities to the supervising clinician.
• Always report suspected failure to capture or failure to pace immediately — do not wait until end of shift.
• If a strip shows what could be ventricular fibrillation, confirm all leads are attached before concluding it is artifact. Patient safety depends on ruling out true life-threatening rhythms first.
• Wash hands and follow facility infection-control policy when placing and removing electrodes.
• Document what you observe on the strip (e.g., "pacemaker spikes present, capture noted") and any corrective actions you took for artifacts.