The Case
A 71-year-old man presses a small device card into the triage nurse’s hand while the smell of burned toast clings to his jacket. He felt three sharp shocks in his chest over 20 minutes, followed by lightheadedness but no loss of consciousness. The monitor shows a wide-complex rhythm, and his implanted device is quietly blinking beneath the skin of his left chest. Whether the shocks were appropriate, harmful, or already too late is not yet known.
Before You Read
- What must be done before the device representative arrives?
- When is a shock “appropriate,” and when does it signal lead or rhythm failure?
- What does a magnet do to an ICD versus a pacemaker?
Why It Matters
Device patients can deteriorate from ventricular arrhythmia, lead failure, pacing failure, oversensing, or unrelated disease. Interrogation is valuable, but unstable patients require immediate resuscitation rather than waiting for a printout.
When to Think of It
Interrogate for syncope, palpitations, shocks, suspected device malfunction, bradycardia, unexplained arrest, chest trauma, electrocautery exposure, or recurrent VT/VF. Obtain the device type, manufacturer, indication, implant date, last interrogation, and patient’s device card; examine the pocket for infection or erosion and obtain a 12-lead ECG.
Sick or Not Sick
The key call is unstable arrhythmia or pacing failure versus stable device evaluation. Hypotension, ischemia, pulmonary edema, altered mental status, ongoing VT/VF, recurrent shocks, or pacemaker-dependent bradycardia mandates immediate resuscitation, external pads, and specialist involvement.
The First Fifteen Minutes
- Place defibrillation/pacing pads in an anteroposterior or lateral position away from the generator, attach continuous monitoring, obtain IV access, and perform a 12-lead ECG; external therapy takes priority over interrogation.
- If pulseless VT/VF → unsynchronized biphasic defibrillation 200 J, escalating per device; defibrillation terminates fibrillation when the myocardium is electrically reset.
- If unstable monomorphic VT with a pulse → synchronized cardioversion 100 J biphasic, escalating as needed; synchronization avoids delivering energy on the vulnerable T wave.
- If stable regular monomorphic wide-complex tachycardia → amiodarone 150 mg IV over 10 minutes, repeat if needed, then 1 mg/min infusion for 6 hours, because it prolongs refractoriness and suppresses ventricular reentry. Dose and rhythm-specific treatment should follow local ACLS protocol.
- If a patient with an ICD is receiving repeated inappropriate shocks from oversensing and is otherwise stable → place a magnet directly over the ICD, which generally suspends tachyarrhythmia detection/therapy while leaving brady-pacing active. Confirm device-specific behavior with the manufacturer; do not use this as a substitute for defibrillator pads or expert evaluation.
- If pacemaker-dependent bradycardia with poor perfusion → begin transcutaneous pacing, typically 60–80/min with current increased until capture, because external pacing bypasses failed or inhibited implanted pacing. Provide analgesia/sedation only if blood pressure permits; if needed, fentanyl 25–50 mcg IV cautiously.
- If symptomatic bradycardia without immediate pacing access and no contraindication → atropine 1 mg IV every 3–5 minutes, maximum 3 mg, because vagolysis can improve nodal conduction; it may fail in infranodal block or a pacemaker-dependent patient.
Definitive Care & Disposition
Interrogate the device for stored electrograms, lead impedance, sensing/capture thresholds, battery status, therapies delivered, and programming. Treat the underlying trigger: ischemia, electrolyte abnormality, hypoxia, medication toxicity, infection, or lead fracture/dislodgment. Recurrent appropriate ICD therapies, any ventricular arrhythmia, suspected lead failure, pacemaker dependence with malfunction, pocket infection, or syncope generally requires admission and electrophysiology consultation. Stable patients with a normal interrogation and a clear benign explanation may be discharged only with reliable device follow-up and explicit return precautions.
How This One Kills
The dangerous failure is assuming every shock is therapeutic and simply discharging the patient; recurrent shocks may reflect lead fracture or T-wave oversensing, while failure to recognize pacemaker noncapture can progress to arrest.
The Atypical Presentation
Older patients may report “trembling,” falls, weakness, or vague chest discomfort rather than shocks. A patient may be unaware of repeated nocturnal therapies, and device malfunction may present only as syncope or bradycardia. A normal surface ECG does not exclude intermittent failure; stored electrograms and lead trends are often decisive.
Back to Our Patient
The 71-year-old man is immediately recognized as high risk because of recurrent shocks, lightheadedness, and a wide-complex rhythm. Pads, monitoring, IV access, and ECG are placed before waiting for interrogation; he remains perfusing but has sustained monomorphic VT, so synchronized cardioversion is prepared and amiodarone is given per protocol. A magnet is available if inappropriate recurrent ICD shocks occur, but it does not replace external rescue capability. Interrogation reveals appropriate therapies for VT with no lead fracture; after rhythm stabilization and correction of a low potassium level, he is admitted to telemetry/ICU with electrophysiology consultation.
Patient Presentation to Attending
“This is a 71-year-old man with an ICD who experienced three shocks and lightheadedness over 20 minutes, without syncope. He is currently perfusing but has a regular wide-complex tachycardia; he has no fever, pocket erythema, or recent chest trauma, and his ECG shows monomorphic VT. I have placed external pads away from the generator, started monitoring and IV access, and obtained a 12-lead ECG. My assessment is recurrent ventricular tachycardia with potentially appropriate ICD therapies; I’m giving IV amiodarone, preparing synchronized cardioversion if he becomes unstable, and requesting immediate device interrogation and electrophysiology admission.”
Study Directive
- Memorize the difference between magnet effects on pacemakers and ICDs, then verify manufacturer-specific exceptions.
- Review one sample interrogation report and identify battery longevity, lead impedance, sensing, capture thresholds, therapies, and stored electrograms.
- Practice an unstable-device algorithm: pads, ECG, pacing/defibrillation, antiarrhythmic therapy, magnet when indicated, interrogation, and disposition.
- Perform a focused device exam on three patients: generator location, pocket infection, erosion, trauma, and pacemaker dependence.
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