By Anthony J. Hackett, DO
There are several complications that should be considered when pacemakers go bad: lead failure, pocket complications and device complications.
Early post placement complications: pneumothorax, hemothorax and venous thrombosis and air emboli
-Dislodgement: More common in ICD (10%) than in pacers (5%)
-Fracture: occurs where kinks in wire are present (venous entry, pulse generator and at the heart) and can be detected by comparing past X-rays.
-Perforation: ~80% occur early and result in either abberant muscle twitching (diaphragm or intercostal), effusion or tamponade.
-Twiddler’s syndrome: lead dislodgement resulting from patient’s who move pulse generator repeatedly.
Pocket complications: Occurs in about 6% of patients and is usually due to early infection caused by S.Aureus and late infection by S.epidermidis.
Device malfunction: Consists of essentially four classes of failure detailed below
1. Undersensing (Inappropriate pacing): Pacer doesn’t recognize intrinsic rhythm as cardiac activity. You will see a pacer spike after, rather than before a P/QRS complex
2. Oversensing (Inappropriate inhibition): Pacer senses an extrinsic stimulus as an electrical impulse and self inhibits (for example a skeletal muscle contraction) leading to a prolonged pause or new onset symptomatic bradycardia or syncope. The classic example is a patient painting a house who syncopizes as brush strokes are interpreted as cardiac impulses.
3. Failure to pace: May sense but no pacing impulse generated.
4. Failure to capture: Pacing stimulus is generated but doesn’t stimulate the myocardium. Note that the pacer spikes are out of phase with generated contractions
Pacemaker mediated tachycardia:
Rare complication associated with dual chamber pacers. Initiated by PVC’s that travel retrograde and simulate atrial activity which then results in ventricular pacing out of phase with the normal cycle. An essentially runaway rhythm (~100-150 bpm) develops that can be terminated by reverting to the “magnet rate.”
This should be differentiated from “Runaway pacemaker” which is caused by a rapidly firing pulse generator.
Troubleshooting a malfunctioning pacer:
Patients with malfunctioning pacers can have a variety of symptoms but commonly bradycardia and its sequale are seen. Usually most common problems can be determined by looking at the ECG or applying a magnet in certain cases. For more advanced issues, only interrogation of the pacer may reveal the answer.
• ECG: Evaluate for pacer spikes and their relationship to the intrinsic rhythm/complexes
• Magnet: Magnet application turns off the set pace rate and reverts to magnet rate pre-programmed to the pacer manufacturer. This can help work up problems with either the battery or the pacer itself.
-Slow magnet rates (less than factory indicated) represent battery failure
-Lack of pacer spikes following magnet indicates lead fracture
• Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7e. Judith E. Tintinalli et. al
• CURRENT Diagnosis and Treatment Emergency Medicine, Seventh Edition / Edition 7. C. Keith Stone and Roger Humphries
• Special thanks for images uploaded from http://chestdevices.com