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    Cardioversion: Indications, Process, Troubleshooting

    Cardiovascular

    Last Updated Jan 18, 2022
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    By Willem De Vynck, Adele van Wyk

    Context

    • As the conduction system wears out over time in the heart the incidence of arrhythmias increase. These include atrial fibrillation, atrial flutter, atrioventricular tachycardias (AVNRT), and ventricular tachycardia.
    • Cardioversion is the conversion of these non-sinus rhythms to sinus rhythm. This can be done chemically with medications or with electricity.
    • Delivery of electricity is synced to the QRS complexes in cardioversion, whereas it is not in defibrillation.
    • The indications for cardioversion are based on the history, characteristics, patient preference and current condition.
    • There is a high rate of success in new onset AFib or AFlutter with no underlying structural heart disease such as atrial dilation or valve prolapse.
    • The success rate decreases in cases where the Atrial fibrillation is chronic, or there is underlying structural heart disease or valve prolapse.
    • Clinical starting point is identification of symptomatic arrhythmia on ECG.
    • Clinical endpoint is return to sustained sinus rhythm.

    Indications

    • Arrhythmias:
      • New onset Afib
      • New onset Aflutter
      • SVTs
      • VT
    • Patient Characteristics for Afib & Aflutter:
      • CHADS 65 <2
      • Onset <12 hours in absence of recent stroke or TIA (in last 6 months) OR anticoagulated therapeutically for preceding 3 weeks.
      • Symptomatic or hemodynamically unstable.

    Contraindications

    • Absolute Contraindications
      • Unable to be anticoagulated (unless certain onset in <12hours, or hemodynamically unstable).
      • Comorbidities cause the risk of chemical or electrical cardioversion to be more hazardous than remaining in a non-sinus rhythm.
      • Those in whom the cardioversion has significant risks due to patient comorbidities AND due to patient characteristics cardioversion is unlikely to last (ie., left atrial dilation, significant hyperthyroidism).
      • Known left atrial thrombus.
      • Failed previous cardioversion.
    • Relative contraindications:
      • Sustained AF for the preceding year.
      • AF recurrence while on appropriate anti-arrhythmic that patient has been compliant with (likely to revert to AF even if converted to Sinus).

    Process

    • Preparation:
      • Monitoring (SP02, BP cuff, telemetry).
      • IV access for procedural sedation.
      • Supplemental O2 and end tidal CO2 monitoring.
      • Place leads: for AF, anterior posterior. For unstable arrhythmias/urgent situations anterior lateral pad placement is acceptable.
      • Consider padding railings or hard surfaces patient could strike due to involuntary jerks from electricity delivery.
      • Appropriate equipment available and checked. Should include Suction, intubation equipment, Code cart with ACLS protocol medications.
    • Procedure:
      • Select energy level: this will differ based on whether your machine is biphasic of monophasic, and what arrhythmia you are attempting to cardiovert. Biphasic is the preferred energy delivery and allows for lower energy electricity delivery with greater efficacy. The below energy suggestions are for biphasic machines.
      • Atrial Fibrillation: 120-200J.
      • Atrial Flutter: 50-100J.
      • Ventricular Tachycardia with pulse: 100J.
      • Ventricular Fibrillation or Ventricular Tachycardia without pulse or: 200J.
    • Considerations:
      • Previously with monophonic electricity delivery supplemental oxygen would be turned off at the wall as electricity and oxygen together are a fire hazard. However with the vast majority of cardioversions being done with biphasic electricity delivery this is no longer such a great concern and oxygen can be left on during the procedure.
      • Pregnant patients – cardioversion is safe in pregnancy, but the fetal heart rate should be monitored during the procedure.
      • Patients with pacemakers – a few precautions need to be taken. The pads should be place at leads 12cm from the impulse generator, and the lowest possible energy selection to cardiovert the arrhythmia should be used. A-P pad placement is recommended and the pacemaker should be interrogated after the cardioversion. In some cases an electrophysiologist may be able to assist by using the ICD to carry out the cardioversion.
      • Patients with Digoxin toxicity – digoxin toxicity causes increased susceptibility to arrhythmias and increases the chances that cardioversion will trigger ventricular fibrillation or tachycardia (especially if electrolyte abnormalities such as hypokalemia are also present).
      • If these patients have a supraventricular arrhythmia cardioversion should be withheld until digoxin levels are in normal range, and their toxidrome has resolved. If electrolyte abnormalities are present these should ideally be corrected first as well. If they are hemodynamically unstable cardioversion should be performed with the lowest possible energy level likely to attain cardioversion. Rapid atrial pacing can also be considered for indications such as atrial flutter, and maybe be safer than cardioversion in these circumstances.
      • If they are in ventricular fibrillation or ventricular tachycardia, cardioversion must be carried out as these are life threatening arrhythmias. Patients should be loaded with a push dose of 1mg/kg lidocaine up to 100mg for prophylactic stabilization of the cardiac membrane.

    Complications and Troubleshooting

    • Skin burns:
      • This has become a less common problem with use of biphasic waveform cardioversion.
      • Steroid cream, topical ibuprofen, or silver sulfadiazine cream can be used to manage inflammation.
    • Transient Hypotension:
      • Can persist for a few hours after cardioversion. Unclear what the mechanism is,. usually responds to fluids.
    • ST changes:
      • Following shock delivery transient ST elevation, ST depression or increased T wave amplitude are common.
      • This appears to be more common with monophasic than biphasic waveforms.
      • These changes usually normalize within 5 minutes.
      • These changes should not be the impetus for considering the patient to have an ACS.
    • Myocardial Stunning:
      • May occurs after reperfusion of ischemic tissue (such as in MI), or after cardioversion.
      • When occurring after cardioversion most often results in transient dysfunction of left atrium and atrial appendage commonly termed “atrial stunning”.
      • Not a function of the mode of cardioversion as it has been observed after every cardioversion method (spontaneous, chemical, overpacing, internal and transthoracic).
      • Right atrial stunning does occur, but less severely, and resolves more quickly.
      • Decreased left atrial contractility may lead to de novo thromboembolism after cardioversion.
      • Transient in nature. Most severe right after cardioversion. Resolves anywhere from a few minutes after cardioversion to 4-6 weeks post cardioversion.
      • If cardiac output and contractility don’t improve after cardioversion consider possibility that myocardial stunning may be at play, and continue/initiate anticoagulation if not already in place until output and contractility improve.
    • Thromboembolism:
    • Myocardial necrosis:
      • A small amount of necrosis mostly of the epicardium may occur with higher energy electricity deliver. This is almost always asymptomatic, and therefore it is not recommended to monitor troponin levels after cardioversion unless there’re underlying/concomitant ACS symptoms occurring.
    • Arrhythmias:
      • Arrhythmias after cardioversion are not uncommon.
      • Most are transient and relatively benign such as sinus tachycardia or nonsustained VT.
      • Supraventricular tachycardias (including sinus tachycardia and atrial flutter) and AVNRT are more common after cardioversion of longstanding or chronic AF.
      • Clinically significant/hemodynamically threatening arrhythmias such as VF and sustained VT can occur as well.
      • VF is usually due to a non-synchronized shock delivery.
      • Bradycardias are uncommon but can occur. They are slightly more common in patients taking antiarrhythmics.
      • Bradycardias can result from transient LBBB, but are more commonly due to AV dissociation.
      • When cardioverting a patient on an anti-arrhythmic external pacing should be available.

    Helpful Resources

    Quality Of Evidence?

    Justification

    Recommendations are based on small-medium observational trials, some of which were based on monophonic waveform cardioversion while some were based on biphasic waveform cardioversion.

    Moderate

    Anticoagulation recommendations from CCS are low quality as stated on their website.

    Low

    Related Information

    Reference List

    1. Andrade, Jason G. et al. 2018 Focused Update of the CCS Guidelines for the Management of Atrial Fibrillation. Can J Cardiol, 2018;34: 1371 – 1392


    2. Knight, B. (2021, September 9). Cardioversion for specific arrhythmias. Uptodate.


    3. Tintinalli, J., Stapczynski, J. S., Ma, J., Cline, D., Cydulka, R., & Meckler, G. (2011). Cardiac Rhythm Disturbances. Tintinalli’s Emergency Medicine (7th ed., pp. 131–153). McGraw Hill.


    4. Khan, I. A. (2003). Atrial stunning: basics and clinical considerations. International Journal of Cardiology, 92, 113-28.

       


    Print Summary

    RESOURCE AUTHOR(S)

    Dr Willem De Vynck

    DISCLAIMER

    The purpose of this document is to provide health care professionals with key facts and recommendations for the diagnosis and treatment of patients in the emergency department. This summary was produced by Emergency Care BC (formerly the BC Emergency Medicine Network) and uses the best available knowledge at the time of publication. However, healthcare professionals should continue to use their own judgment and take into consideration context, resources and other relevant factors. Emergency Care BC is not liable for any damages, claims, liabilities, costs or obligations arising from the use of this document including loss or damages arising from any claims made by a third party. Emergency Care BC also assumes no responsibility or liability for changes made to this document without its consent.

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