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Cardiac Pacemakers, Emergency Medicine

Basics

Description

- 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: - 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 syndrome: - Symptoms related to asynchronous chamber contractions (typical with VVI pacer) - Lightheadedness - Dyspnea - Palpitation - Weakness or exercise intolerance - Syncope

  • 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 appliedTemporary 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 yrGenerator:A sophisticated computer with many programmable parametersLeads connected to the RV/RA:Typically sense intrinsic electrical activity of the heart and pace the myocardium as needed
  • Pacemaker magnet:Placed over pacemaker generatorConverts pacer to asynchronous modeUseful if pacer spikes not present on ECGA 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: AtriaV: VentricleD: Dual (both chambers)2nd letter in code indicates chamber that can be paced:A: AtriaV: VentricleD: 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 responseThe most common pacemakers are VVI (single lead) and DDD (two leads).

Etiology

  • Pacemaker-associated infection:Infection of pacemaker components often associated with endocarditisStaphylococcus 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 impulseComponent failure is rare.Battery depletion is rare with routine checks; it is not abrupt.Lead fracture or disconnectionOversensing 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 myocardiumElevated myocardial threshold:Change in cardiac (QRS) morphology
  • Pacemaker-mediated tachycardia:Occurs with dual-chamber pacemakersA re-entry rhythm using generator and intrinsic conduction systemMax. rate typically 140 bpm due to built-in safeguards
  • Runaway pacemaker:Rare; triggered by battery depletion or component failureOften rapid rates (>200 bpm) with hemodynamic compromise

Diagnosis

Signs and Symptoms

  • Pacemaker failure:BradycardiaSyncopeHypotension, progressive to shock and hemodynamic collapseFatigue and weaknessDyspnea on exertion or shortness of breath secondary to CHFIschemic chest painAltered level of consciousness
  • Pacemaker-induced tachycardia:DyspneaIschemic chest painLightheadednessSyncope
  • Pacemaker syndrome:Symptoms related to asynchronous chamber contractions (typical with VVI pacer)LightheadednessDyspneaPalpitationWeakness or exercise intoleranceSyncope

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 spikesThe magnet activates asynchronous pacing mode.Produces pacer spikes at a preprogrammed rate, regardless of the intrinsic rhythmIf 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 septumTip 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 pacemakerTemporary 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 reprogrammingIn 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)