Rosen & Barkin's 5-Minute Emergency Medicine Consult (126 page)

None

May consider referral to regional cardiac arrest center

Admission to ICU

• Provide targeted temperature management in comatose post arrest patients.
  
• Expect recurrent cardiac arrest and provide close monitoring and appropriate postresuscitative treatment, which may consist of fluids and vasopressors.
  
• Get a cardiology consultation to determine if patient is candidate for cardiac catheterization.
  

• Field JM, Hazinski MF, Vanden Hoek TL, et al. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science.
  Circulation.
  2010; 122:S640--S656.
  
• Hallstrom AP, Ornato JP, Weisfeldt M, et al. Public-access defibrillation and survival after out-of-hospital cardiac arrest.
  N Engl J Med
  . 2004;351:637–646.
  
• Neumar RW, Otto CW, Link MS, et al. Part 8: Adult advanced cardiovascular life support: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care.
  Circulation
  . 2010;122:S729--S767.
  
• Peberdy MA, Callaway CW, Neumar RW, et al. Part 9: Post-Cardiac Arrest Care: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascula care.
  Circulation
  . 2010;122:S768--S786.
  
• Wik L, Hansen TB, Fylling F, et al. Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation: A randomized trial.
  JAMA
  . 2003;289:1389–1395.
  

CODES

427.5 Cardiac arrest

BASICS

• 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%.
    

• Fixed mode:
  
  • The pacemaker is set to fire at a set rate regardless of patient’s 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: A
      tria
      
    • V: V
      entricle
      
    • D: D
      ual (both chambers)
      
  • 2nd letter in code indicates chamber that can be paced:
    
    • A: A
      tria
      
    • V: V
      entricle
      
    • D
      :
      D
      ual (both chambers)
      
  • 3rd letter in code describes pacemaker’s response to sensed intrinsic complex:
    
    • T: T
      rigger (a sensed beat results in a pacing response as when a sensed atrial beat provokes a subsequent ventricular beat)
      
    • I: I
      nhibit (a sensed beat precludes pacemaker function)
      
    • D: D
      ual (a pacemaker is capable of both functions)
      
    • O: N
      o response
      
  • The most common pacemakers are VVI (single lead) and DDD (two leads).
    

• 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.
    
  • Twiddler’s syndrome:
    
    • Unintentional manipulation of pacemaker generator causing lead to be dislodged from myocardium
      
  • Elevated myocardial threshold:
    
    • Hyperkalemia
      
    • Ischemia
      
  • 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

• 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
    

• Date of placement pacemaker
  
• Compliance with follow-up (battery checks)
  
• Type of pacemaker
  

General cardiac exam:

• Heart exam for murmurs
  
• Lung exam for CHF
  
• Chest wall exam at generator site
  

• 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.
    

• Serum potassium
  
• ABG
  
• Serum levels of antidysrhythmic drugs
  

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