Also consider administering an analgesic either with sedation or shortly following cardioversion. Sedatives have no pain control properties, thus using a sedative alone may sedate patients, but they will still experience the pain associated with cardioversion. Since analgesics are not routinely administered with cardioversion, consult your medical director before initiating this practice.
Synchronized cardioversion is an advanced cardiac life support skill that cannot be performed by basic EMTs or with an automated external defibrillator. Before each cardioversion attempt, be sure to press the cardiac monitor's synchronization button to synchronize energy delivery at the appropriate point during QRS complex. Failure to synchronize cardioversion can result in energy delivery during the heart's relative refractory stage, which is likely to result in ventricular fibrillation. You will know the heart monitor is synchronized by the presence of a dot on the top of each QRS complex. Press the synchronization button before each attempted cardioversion.
Patients with polymorphic ventricular tachycardia can also present with instability; however, it is often impossible to perform synchronized cardioversion in these patients. The American Heart Association states, as a general rule, if you cannot synchronize the QRS complexes with your eye, the defibrillator also will not be able to synchronize them. In these instances, and if allowed by protocol, perform unsynchronized cardioversion at high energy levels: 360 joules for monophasic defibrillators; 150–200 joules for biphasic defibrillators.
ENERGY LEVEL SELECTION
When performing synchronized cardioversion with a monophasic defibrillator, use stepped increases in energy levels, delivering the first cardioversion at 100 joules. If additional cardioversion attempts are necessary, deliver the energy at 200, then 300 and finally 360 joules.
When using a biphasic defibrillator, use the manufacturer's recommended energy level, which is normally between 120–200 joules. There is no need to increase the amount of energy with each cardioversion attempt when using a biphasic defibrillator.4
Once the ventricular tachycardia has converted, recheck the patient's airway, breathing and circulation, determine the level of consciousness and perform a neuro exam as necessary. Begin an IV infusion of an antiarrhythmic to decrease the chances of a recurring dysrhythmia.
Ventricular tachycardia represents ectopic cells within the ventricles stimulating the heart to contract. Many conditions cause ventricular tachycardia, including myocardial muscle deterioration and drug stimulation. The symptom most suggestive of unstable ventricular tachycardia is a change in mental status or loss of consciousness. Stable ventricular tachycardia is managed with antiarrhythmic medications, while unstable ventricular tachycardia requires immediate cardioversion. After converting ventricular tachycardia to a sinus rhythm, administer an antiarrhythmic infusion.
1. Compton S. Ventricular Tachycardia. Emedicine.com. www.emedicine.com/med/topic2367.htm.
2. Ernoehazy W. Ventricular Tachycardia. Emedicine.com. www.emedicine.com/emerg/topic634.htm.
3. The American Heart Association. Part 5: Electrical Therapies: Automated External Defibrillators, Defibrillation, Cardioversion, and Pacing. Circulation 112: IV-35–46, 2005.
4. The American Heart Association. Part 7.3: Management of Symptomatic Bradycardia and Tachycardia. Circulation 112: IV-67–77, 2005.
5. Tomlinson DR, et al. Emerg Med J 25(1):15, Jan 2008.
6. Marill KA, et al. Ann Emerg Med 47(3):217, March 2006.
7. The American Heart Association. Part 7.2: Management of Cardiac Arrest. Circulation 112: IV-58–66, 2005.
Kevin Thomas Collopy, BA, CCEMT-P, NREMT-P, WEMT, is a flight paramedic for Spirit Medical Transportation Service in central Wisconsin. He is the author of numerous magazine articles, textbook chapters, and flash-based CE lessons. He is an adjunct EMS faculty member for Mid-State Technical College, a consultant with Emergency Preparedness Systems, LLC, and a lead instructor for Wilderness Medical Associates. You can contact him at email@example.com.