It’s Shocking! Electricity is Safe and Effective for Treatment of Cardiac Dysrhythmias

You are dispatched for chest pain of a 54-year-old male. You arrive on scene and find your patient sitting in a recliner in the living room of the residence. He appears in obvious distress. He is pale, agitated and is clutching his chest. He tells you that he was watching TV and, suddenly, his heart started beating fast. He tells you that he feels like he’s going to pass out and is having trouble breathing.

You take his pulse and its 180 bpm. His systolic BP is 82 mm Hg. He tells you that he takes medication for high blood pressure and high cholesterol. You connect him to your monitor and recognize the rhythm as supraventricular tachycardia. His SpO2 is 92 % on room air. You administer oxygen and start an IV in his left AC. You administer six milligrams adenosine IV with no conversion followed by twelve milligrams adenosine. Again, with no conversion. What’s next? Synchronized cardioversion should be your next treatment!

Electrical cardioversion has been accepted as a safe and effective procedure to terminate certain cardiac dysrhythmias since the 1950s.¹ Initially used only in the in-hospital setting it is now an accepted treatment for out-of-hospital-providers. The use of synchronized cardioversion in the prehospital setting has been shown to be over 80 percent effective in terminating life-threatening cardiac dysrhythmias.¹ It has also been demonstrated that paramedic-lead electrical cardioversions have efficacy rates similar to those of doctor-administered treatments.²

Initial energy requirements for commonly encountered dysrhythmias using biphasic and monophasic defibrillator cardiac monitor units.

For ventricular fibrillation (Vfib) or pulseless ventricular tachycardia (Vtach) use initial unsynchronized shocks of 120 J biphasic and 200 J monophasic is usually sufficient to convert. If conversion is unsuccessful, subsequent unsynchronized shocks can be delivered at 200 J for biphasic and 360 J for monophasic monitors.³

For polymorphic Vtach with a pulse, unsynchronized shocks of 100 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 200 J biphasic and 360 J monophasic. Monomorphic unstable Vtach with a pulse use synchronized shocks at 100 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 200 J biphasic and 360 J monophasic. It should be noted that synchronized cardioversion can be considered for stable patients with ventricular tachycardia with a pulse and has been proven to be successful and faster than pharmacological cardioversion.⁴ Pharmacological cardioversion will be presented in a separate article.

For hemodynamically unstable atrial fibrillation use an initial synchronized shock is 120 J biphasic and 200 J monophasic. Subsequent shocks can be delivered at 200 J biphasic. Subsequent shocks using a monophasic unit should remain at 200 J. Note that persistent atrial fibrillation with a rate of <150 BPM is infrequently the result of hemodynamic instability. Always consider hypovolemia and hypoxia before using electrical cardioversion.⁵

For unstable atrial flutter, use an initial synchronized shock at 50 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 100 J biphasic and 200 J monophasic.

For supraventricular tachycardia use an initial synchronized shock setting of 50 J biphasic and 100 J monophasic. Subsequent shocks can be delivered at 100 J biphasic and 200 J monophasic.

Remember that electrical cardioversion, whether synchronized or unsynchronized, is only used for hemodynamically unstable patients with the exception noted above for the treatment of stable ventricular tachycardia.⁶ As always, refer to your local protocols for treating cardiac dysrhythmias.

Unstable patients presenting with cardiac dysrhythmias are defined as those patients who present with ischemic chest pain, an altered level of consciousness, dyspnea, and symptomatic hypotension (a systolic blood pressure of less than 90 mm Hg), and fast ventricular rates. Rates close to 300 BPM are seen with polymorphic ventricular tachycardia and atrial fibrillation with pre-excitation. Unstable patients are at serious risk of quick deterioration and organ damage and cardiac arrest.⁷

Since electrical cardioversion is a painful procedure, sedation should always be considered for patients requiring electrical cardioversion.⁴

Remember: Do not synch on the T wave when performing cardioversion! Delivering electrical energy on the T wave during cardioversion can result in electrical destabilization and malignant dysrhythmias. This is referred to as an electrical R-on-T phenomenon, resulting in electrical destabilization.⁹ If a shock is delivered on the T wave (where repolarization occurs), the shock can result in ventricular fibrillation.

The following are suggested procedural guidelines for electrical cardioversion:

1. Identify the arrhythmia
2. Explain the procedure to the patient if they are alert
3. Ensure oxygen availability, ventilate patients if necessary
4. Have an IV established
5. Have suction available
6. Have advanced airway equipment available
7. Apply electrical therapy pads as described below
8. Turn on the synchronize function on your monitor
9. Select the appropriate energy level as shown in the above chart
10. Charge the monitor
11. Make sure all personnel are clear before shock application
12. Depress the shock button. (Refer to the directions for your cardiac monitor as the procedure for cardioversion may differ for specific monitors)

Pad Placement

Place pads in the anterior/posterior positions if possible. One pad is placed on the anterior chest wall lateral to the sternum. The other pad is placed on the back just under the left scapula.⁸ Keep the pads away from implanted devices. If you are unable to place the pads in the anterior/posterior positions, place the pads in the right upper chest and left lateral chest positions.

Conclusion/Summary

When dysrhythmias do not respond to pharmacologic treatments, or the patient is hemodynamically unstable, electrical cardioversion is the most effective treatment. It is highly effective in the treatment of unstable atrial fibrillation, atrial flutter, atrial tachycardia, and supraventricular tachycardia. Electrical cardioversion is a proven safe and highly effective treatment for life-threatening dysrhythmias. Electricity is certainly one of your most powerful therapies in your “drug box.” As always, know and act according to your local protocols.

References

1. Cowley A., Cody D., Nelson M. The Epidemiology and Effectiveness of Synchronized Cardioversion in a UK Prehospital Setting: A Retrospective Cross-Sectional Study. Prehospital and Disaster Medicine 2021; Vol 36, No. 441-444
2. Burton J, Vinson D, Drummond, K, et al. Electrical Cardioversion of Emergency Department Patients with Atrial Fibrillation. Annals of Emergency Medicine 2004; 44:1, 20-30
3. Gupta R, Aldeguer Y. Cardioversion and Defibrillation. Indication for Urgent Cardioversion.  Access Medicine 2022; 3-10
4. Meyers H, Smith S, Marill, K. Tachydysrhythmias. CorePendium EM:RAP 2022: Tachydysrhythmias. https://www.Emrap.org/corependium/corependium/chapter/recGaV7ak0IY2bMIy/Tachydysrhythmias
5. Vinson DR, Hoehn T, Graber DJ, et al. Managing Emergency Department Patients with Recent-onset Atrial Fibrillation. J Emerg Med. 2012;42:139-14
6. Pluymaekers NAHA, Dudink EAMP, Luermans JGLM, Meeder JG, Lenderink T, er al. Early or Delayed cardioversion in recent-onset atrial fibrillation. NEJM 2019; Vol 380, No. 16, 1499-1508
7. Goyal A, Sciammarella J, Chhabra L, Singhal M. NCBI Bookshelf, National Institutes of Health. Jan 2023. https://www.ncbi.nlm.gov/books/NBK482173/
8. Goldberger A. (2006) Clinical Electrocardiography-a Simplified Approach. Mosby Elsevier. 184 p.
9. Mattu A, Zira D, Tabas J, Brady W. ECG of the Month. Annals of Emergency Medicine 2022; vol 79, No. 2, 113-114