Used to treat tachyarrhythmias, synchronized cardioversion delivers an electrical charge to the myocardium at the peak of the R wave. This charge causes immediate depolarization, interrupting reentry circuits and allowing the sinoatrial node to resume control. Synchronizing the electrical charge with the R wave ensures that the current won’t be delivered on the vulnerable T wave, which would disrupt repolarization and possibly lead to ventricular fibrillation.

Synchronized cardioversion is the treatment of choice for arrhythmias that don’t respond to vagal maneuvers or drug therapy, such as unstable supraventricular tachycardia resulting from reentry, unstable atrial flutter, unstable atrial fibrillation, and unstable monomorphic ventricular tachycardia with a pulse.¹ It may be performed as an elective or urgent procedure, depending on how well the patient tolerates the arrhythmia.¹ If a patient is hemodynamically unstable, for instance, he may require urgent cardioversion. When preparing for synchronized cardioversion with any patient, keep in mind that a patient’s condition can deteriorate quickly, requiring immediate defibrillation.

Synchronized cardioversion should be performed according to the 2010 American Heart Association (AHA) guidelines and should follow an assessment of the patient’s cardiac and metabolic status.¹ Assessment should include electrolyte levels, particularly potassium levels, which should be in the normal range; creatinine levels to determine renal function, which helps guide the dosage of adjunctive medications; and serum digoxin levels, which should be in the nontoxic range. If the patient has chronic lung disease, arterial blood gas (ABG) analysis may also be helpful.

When possible, the patient should be in optimal functional status at the time of the procedure. The doctor should discuss the procedure with the patient beforehand and obtain written informed consent. A general anesthetic or sedative agent as well as cardiopulmonary resuscitation equipment should be available during the procedure.

The AHA recommends immediate synchronized cardioversion for treatment of symptomatic (unstable) tachycardia. Signs and symptoms of unstable tachycardia include altered mental status, shock or hypotension, and ongoing chest pain.¹ If the patient is stable, he’ll need a 12-lead electrocardiogram (ECG) to further classify the tachycardia.