Basics
Description
- A device that uses electrical impulses to contract the heart muscles and provide an adequate pulse
- Methods of cardiac pacing:
- Transcutaneous pacing:
- 2 pads are placed on the chest in the anterior-lateral or anterior-posterior position.
- The pacing current is gradually increased until electrical capture occurs with a pulse.
- Emergency therapy used only until transvenous pacing or another therapy can be applied
- Temporary transvenous pacing:
- A pacemaker wire is placed through central venous access into the right atrium (RA) or right ventricle (RV) and connected to an external generator outside of the body.
- Used as a bridge until a permanent pacemaker can be placed or there is no longer a need for a pacemaker
- Permanent, implanted pacemaker has 3 components:
- A battery-powered energy source:
- Lithium batteries last 7-10 yr
- Generator:
- A sophisticated computer with many programmable parameters
- Leads connected to the RV/RA:
- Typically sense intrinsic electrical activity of the heart and pace the myocardium as needed
- Pacemaker magnet:
- Placed over pacemaker generator
- Converts pacer to asynchronous mode
- Useful if pacer spikes not present on ECG
- A depleted battery will result in decrease in magnet rate by ~10%.
Pacemaker Terminology
- Fixed mode:
- The pacemaker is set to fire at a set rate regardless of patients underlying rhythm.
- Rarely seen
- Demand mode:
- The pacemaker fires only when necessary.
- It senses the underlying rhythm.
- It will only pace if the intrinsic rhythm is absent or less than a set rate.
- Sensing:
- Pacemaker's ability to determine whether the heart has an intrinsic rhythm
- All pacemakers have a 5-letter code to describe their function.
- For ED purposes, only the 1st 3 letters of the code are necessary:
- 1st letter in code indicates chamber being sensed by pacemaker:
- A: Atria
- V: Ventricle
- D: Dual (both chambers)
- 2nd letter in code indicates chamber that can be paced:
- A: Atria
- V: Ventricle
- D: Dual (both chambers)
- 3rd letter in code describes pacemaker's response to sensed intrinsic complex:
- T: Trigger (a sensed beat results in a pacing response as when a sensed atrial beat provokes a subsequent ventricular beat)
- I: Inhibit (a sensed beat precludes pacemaker function)
- D: Dual (a pacemaker is capable of both functions)
- O: No response
- The most common pacemakers are VVI (single lead) and DDD (two leads).
Etiology
- Pacemaker-associated infection:
- Infection of pacemaker components often associated with endocarditis
- Staphylococcus epidermidis and Staphylococcus aureus account for >90% of infections.
- Transesophageal echo is the preferred diagnostic method.
- Venous thrombosis:
- Very common (overall incidence 30-50%)
- Symptomatic, acute obstruction is rare (<3%).
- Pulmonary embolism is rare.
- Pacemaker failure to discharge impulse
- Component failure is rare.
- Battery depletion is rare with routine checks; it is not abrupt.
- Lead fracture or disconnection
- Oversensing of muscular activity or external electrical interference
- Pacemaker failure to capture myocardium:
- Lead dislodgment is common.
- Twiddlers syndrome:
- Unintentional manipulation of pacemaker generator causing lead to be dislodged from myocardium
- Elevated myocardial threshold:
- Change in cardiac (QRS) morphology
- Pacemaker-mediated tachycardia:
- Occurs with dual-chamber pacemakers
- A re-entry rhythm using generator and intrinsic conduction system
- Max. rate typically 140 bpm due to built-in safeguards
- Runaway pacemaker:
- Rare; triggered by battery depletion or component failure
- Often rapid rates (>200 bpm) with hemodynamic compromise
Diagnosis
Signs and Symptoms
- Pacemaker failure:
- Bradycardia
- Syncope
- Hypotension, progressive to shock and hemodynamic collapse
- Fatigue and weakness
- Dyspnea on exertion or shortness of breath secondary to CHF
- Ischemic chest pain
- Altered level of consciousness
- Pacemaker-induced tachycardia:
- Dyspnea
- Ischemic chest pain
- Lightheadedness
- Syncope
- Pacemaker syndrome:
- Symptoms related to asynchronous chamber contractions (typical with VVI pacer)
- Lightheadedness
- Dyspnea
- Palpitation
- Weakness or exercise intolerance
- Syncope
History
- Date of placement pacemaker
- Compliance with follow-up (battery checks)
- Type of pacemaker
Physical Exam
General cardiac exam:
- Heart exam for murmurs
- Lung exam for CHF
- Chest wall exam at generator site
Essential Workup
- 12-lead EKG to assess whether there is any obvious evidence of pacemaker failure
- Metabolic workup to determine whether an acquired medical condition led to an elevated myocardial threshold
- EKG with pacer magnet:
- Assess magnet rate.
- Particularly useful when the baseline EKG does not reveal pacer spikes
- The magnet activates asynchronous pacing mode.
- Produces pacer spikes at a preprogrammed rate, regardless of the intrinsic rhythm
- If the magnet rate equals the preprogrammed rate set at implantation, the pacer is okay.
- If the magnet rate is >10% slower than at implantation, the battery is depleted.
- If there are no pacer spikes, there is significant pacemaker malfunction.
Diagnosis Tests & Interpretation
Lab
- Serum potassium
- ABG
- Serum levels of antidysrhythmic drugs
Imaging
CXR:
- Evaluate integrity of pacer lead(s) and position.
- Fractured lead
- Lead dislodgment:
- Perforation through septum
- Tip of lead moved (e.g., in pulmonary artery)
Treatment
Pre-Hospital
Record rhythm strips for analysis
Initial Stabilization/Therapy
- Oxygen administered via 100% nonrebreather
- Intubation as needed
- IV access
- Advanced cardiac life support drugs as per usual protocol (especially for bradycardia)
- Defibrillation: Avoid placing paddles over generator.
- Transcutaneous pacemaker in hemodynamically unstable patients with pacemaker failure
Ed Treatment/Procedures
- Pacemaker failure:
- Transcutaneous pacemaker
- Temporary transvenous pacemaker:
- Obtain central IV access with a Cordis introducer (right IJ preferred)
- Perform the procedure under fluoroscopy if possible.
- Set the pulse generator to asynchronous mode.
- Turn the output dial all the way up.
- Advance the catheter through the central venous access Cordis until you see a QRS complex on the monitor.
- Check the femoral pulse.
- If you have a pulse and see a QRS complex, the pacer is "capturing."
- Slowly turn the output dial down until you lose the QRS complex (capture threshold).
- Turn the output dial up to 2 or 3 times the capture threshold.
- Continuous EKG monitoring facilitates correct placement.
- Treat hyperkalemia (see "Hyperkalemia").
- Runaway pacemaker:
- AV node blocking or reprogramming
- In extreme situation, may need to disconnect lead from generator surgically
Medication
Adenosine: 6 mg IV bolus
Follow-Up
Disposition
Admission Criteria
- Permanent pacemaker failure or malfunction
- Suspicion of infection involving pacemaker components
Discharge Criteria
- Asymptomatic pacemaker malfunction
- A cardiologist has interrogated the pacemaker
Followup Recommendations
Refer to cardiologist and/or pacemaker clinic
Pearls and Pitfalls
- Always consider pacemaker failure in evaluation of cardiac decompensation, bradycardia, or syncope.
- Utilize pacemaker magnet to evaluate function.
Additional Reading
- Cardall TY, Brady WJ, Chan TC, et al. Permanent cardiac pacemakers: Issues relevant to the emergency physician, parts I and II. J Emerg Med. 1999;17:479-489, 697-709.
- Griffin J, Smithline H, Cook J. Runaway pacemaker: A case report and review. J Emerg Med. 2000;19:177-181.
- McMullan J, Valento M, Attari M, et al. Care of the pacemaker/implantable cardioverter defibrillator patient in the ED. Am J Emerg Med. 2007;25(7):812-822.
- Scher DL. Troubleshooting pacemakers and implantable cardioverter-defibrillators. Curr Opin Cardiol. 2004;19:36-46.
- Stone KR, McPherson CA. Assessment and management of patients with pacemakers and implantable defibrillators. Crit Care Med. 2004;32:155-165.
Codes
ICD9
- V45.01 Cardiac pacemaker in situ
- V53.31 Fitting and adjustment of cardiac pacemaker
- 996.61 Infection and inflammatory reaction due to cardiac device, implant, and graft
ICD10
- T82.7XXA Infect/inflm react d/t oth cardi/vasc dev/implnt/grft, init
- Z45.018 Encounter for adjustment and management of other part of cardiac pacemaker
- Z95.0 Presence of cardiac pacemaker
SNOMED
- 441509002 Cardiac pacemaker in situ
- 233184008 maintenance procedure for cardiac pacemaker system (procedure)
- 473055007 Infection of pacemaker pulse generator site (disorder)