Cardioversion

Lauren M. Yorek, MD
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Subject: Cardioversion

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Introduction

Cardioversion is the use of electric shock to alter the cardiac rhythm of a patient. The energy is measured in joules and is delivered to the patient via paddles or adhesive pads designed for this purpose. 
Cardioversion is implemented in many cardiac rhythm disturbances and can be delivered either as synchronized or unsynchronized. When the cardiac rhythm has its origin in the atria, then synchronized cardioversion is performed to prevent deterioration to a less stable rhythm originating in the ventricle (see Table 13-1). Synchronized cardioversion can also be performed for ventricular tachycardia with a pulse. 
When the patient’s abnormal rhythm is not of atrial origin and the patient does not have a palpable pulse, then unsynchronized cardioversion is performed. The amount of energy or joules used for cardioversion varies upon the particular situation. 
An antiarrhythmic medication is often begun on patients with atrial fibrillation or atrial flutter to increase the chances of success with electric cardioversion. If patients are placed on antiarrythmic medications, they may require a longer period of observation and continuation of medication if the cardioversion is successful. Procedural sedation can be achieved with intravenous (IV) sedatives such as diazepam, midazolam, or propofol (see Procedural (Conscious) Sedation). Analgesics may also be added for patient comfort such as IV fentanyl or meperidine. Medical staff experienced in conscious sedation techniques should be present. 
A recent study in the American Heart Journal demonstrated a better outcome with biphasic shock than monophasic shock for patients undergoing cardioversion for atrial fibrillation. Successful cardioversion with biphasic current also required less energy delivery to the patient (fewer joules required). Patients who underwent cardioversion with biphasic current reported less pain at 1 and 24 hours postprocedure. Life Pack cardioversion models produced within the past few years are designed to deliver biphasic shocks. 
Atrial flutter does have good response rates to monphasic cardioversion. However, cardioversion at lower energy levels has been successful with atrial flutter. In addition, cardioversion of atrial flutter with biphasic current has been shown to require less antiarrythmic medication to sustain sinus rhythm. The risk of skin burns is also decreased with decreased energy requirements. 
 
Table 13-1.
Recommended Energy Settings for Cardioversion
The electrodes may be placed anteroposterior (AP) or anterolateral (AL) in biphasic conversion for atrial fibrillation. The number of shocks required and needed energy delivery is comparable with both electrode configurations. 

Equipment

  • An automatic external defibrillator (AED) device with or without manual control option is useful in smaller clinics and urgent care centers where the cost and maintenance of a larger fully manual device may be prohibitive.

  • A manual defibrillator device, which usually has manual control options, may have the option to also function automatically as an AED.

  • The newer defibrillator devices (such as Life Pack 12) include pads rather than paddles, which may also be used for cardiac pacing.

Indications

Synchronized Cardioversion

  • Unstable supraventricular tachycardia with a pulse. In the absence of a pulse, unsynchronized cardioversion is performed.

  • Patient with serious signs or symptoms due to arrhythmia including

    • Acute coronary syndrome.

    • Decreased level of consciousness.

    • Chest pain.

    • Dyspnea.

    • Pulmonary edema.

    • Hypotension.

  • Unstable atrial fibrillation with acute presentation.

  • New onset atrial fibrillation, if known to have begun within the past 48 hours:

    • Note that when attempting to restore sinus rhythm in a patient with atrial fibrillation, the presence or absence of an atrial clot must be determined. It is often recommended that patients undergo cardiac echo to determine the absence of an atrial clot, which may embolize after conversion to sinus rhythm.

  • Ventricular tachycardia with a pulse that is not responsive to pharmacologic therapy.

Unsynchronized Cardioversion

  • Used in cardiac arrhythmias of ventricular origin without a palpable pulse:

    • Ventricular tachycardia.

    • Ventricular fibrillation.

Contraindications: Synchronous Cardioversion

Elective Cardioversion

  • Electrolyte disturbances

  • Atrial tachycardias that do not respond to cardioversion: [comp: nested

    • Multifocal atrial tachycardia, which is usually a supraventricular tachycardia with an irregular rhythm and is not usually responsive to cardioversion

    • Sinus tachycardia, which is a response to underlying pathology (shock, pulmonary embolus, etc.) and not a primary rhythm disturbance

  • Digitalis toxicity

  • Patients with little proven symptomatic improvement with sinus rhythm

  • Left atrial diameter >4.5 cm (relative)

  • Patients who have a low probability of maintaining sinus rhythm and readily return to atrial fibrillation (relative)

  • Patients who require a pacemaker for maintenance of stable rhythm after cardioversion such as patients with sick sinus syndrome or sinoatrial (SA) nodal blockade

Urgent Cardioversion

  • Absence of electrocardiographic wave (QRS) complex on electrocardiogram (EKG) monitor

  • Absent pulse

The Procedure

Step 1

For elective procedures, the anticoagulant therapy must be at therapeutic levels for patients in atrial fibrillation at risk or producing emboli from an atrial thrombus. Also evaluate the electrolyte and serum digoxin levels. The patient should be held on nothing by mouth (NPO) status for 8 hours. Informed consent must be obtained and documented if the procedure is elective. Insert an IV line for sedation and necessary medication in the event that the patient decompensates. 
  • Pearl: A general procedure form with the benefits and risks of the procedure described is acceptable and must be signed by the patient or guardian, the provider, and a witness.

Step 2

Place the patient under full cardiac and respiratory monitoring, lying flat on a dry surface. Supplemental oxygen should be given with ventilatory support available in the event of respiratory suppression. IV sedation should be given prior to the procedure. Electrode pads or paddles should be applied. Defibrillator pads are placed on the sternum and the skin over the apex of the heart. 
  • PITFALL: Skin burns can occur if inadequate gel is applied to the patient’s skin.

  • Pearl: Urgent cardioversion in the unstable patient may not allow time for sedation. If possible in the conscious patient, adequate sedation should be administered.

Step 3

Turn on the defibrillator and select the appropriate energy level (see Table 13-1). Ensure that synchronization mode is selected if necessary. Check for proper electrode placement. Synchronization will be indicated by markers above R-waves on the EKG monitor. 

Step 4

Call “all clear,” and ensure all personnel are clear before discharging electrodes. Deliver shock with approximately 25 pounds of pressure if paddles are applied. Evaluate cardiac rhythm after the shock is delivered. Start with the lower end of the recommended range and increase as needed to obtain a response. 

Step 5

Cardioversion may need to be repeated at a higher energy level if it is unsuccessful on the first attempt. Ensure that the defibrillator is in synchronization mode before each shock is delivered. The patient should be monitored for several hours after the procedure until the following discharge criteria are met: 
  • Return of oxygen saturation to baseline

  • Normal vital signs

  • Return of level of consiousness to baseline

  • Return of baseline ambulatory capacity

Complications

Bradycardia may be noted in patients with previous inferior myocardial infarction. 
Patients with digitalis toxicity or electrolyte disturbances such as hyperkalemia may have an increased risk of complications. 
Ectopy of the atria or ventricles may be observed in the first 30 minutes after successful cardioversion. 
Deterioration to a more unstable rhythm may occur with cardioversion. 
Skin burns can occur if adequate gel is not applied to the patient’s skin. Commercially available electrode pads have gel incorporated into the pads. 
Patients without adequate anticoagulation may experience embolization of an atrial clot with return to sinus rhythm. 

Pediatric Considerations

Supraventricular tachycardia (SVT) can present in children. Infants usually have a heart rate of >220 bpm, whereas children have heart rates of >180 bpm. Sinus tachycardia can be confused with SVT. Children can have a high heart rate due to sinus tachycardia, and this must be differentiated from SVT. (SVT should not have P-waves; sinus tachycardia will have P-waves visible.) 
If SVT is unresponsive to adenosine, then synchronized cardioversion may be performed at a dose of 0.5 to 1 J/kg. If initial cardioversion is unsuccessful, the energy dose is increased to 2 J/kg for subsequent attempts. Expert consultation is advised in this situation. 
Wide complex tachycardia of ventricular origin can also be seen in children (QRS >0.08 seconds). Energy levels used in cardioversion are the same as in narrow complex tachycardia (0.5 to 1 J/kg initially with repeat dose of 2 J/kg if needed). 

Postprocedure Instructions

The patient should be monitored in a controlled setting capable of resuscitation for several hours postprocedure. If the patient is receiving an antiarrythmic medication, prolonged monitoring may be necessary for dosage adjustment. If anticoagulation therapy is indicated, it will need to be continued for at least 3 months postprocedure and should ideally be delivered 3 weeks prior to cardioversion. 

Coding Information and Supply Sources

ICD-9 Codes

Suppliers

Bibliography

Gurevitz OT, Ammash NM, Malouf JF, et al Comparative efficacy of monophasic and biphasic waveforms for transthoracic cardioversion of atrial fibrillation and atrial flutter. Am Heart J.  2005;149(2):316–321.  [View Abstract]
Koster RW, Dorian P, Chapman FW, et al A randomized trial comparing monophasic and biphasic waveform shocks for external cardioversion of atrial fibrillation. Am Heart J.  2004:147(5):e1–e7.
Minczac BM, Krim JR Defibrilation and cardioversion. In: Joberts JR, Hedges JR, eds. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia: Saunders;  2004;226–256.
Siaplaouras S, Buob A, Rötter C A randomized comparison of anterolateral versus anteroposterior electrode position for biphasic external cardioversion of atrial fibrillation. Am Heart J.  2005;150(1):150–152.  [View Abstract]
2008 MAG Mutual Healthcare Solutions, Inc.’s Physicians’ Fee and Coding Guide. Duluth, Georgia. MAG Mutual Healthcare Solutions, Inc. 2007.
 
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