DC cardioversion procedure treatment for arrhythmias is determined by the symptoms and severity of the arrhythmia. The treatment focuses on the root of the problem. Antiarrhythmic medicines, direct current (DC) cardioversion-defibrillation, implantable cardioverter-defibrillators (ICDs), pacemakers (including a special type of pacing, cardiac resynchronization treatment), catheter ablation, surgery, or a combination of these are employed if necessary.
DC cardioversion procedure
When elective DC cardioversion is performed, patients should fast for 6 to 8 hours to avoid aspiration. Brief general anesthesia or IV analgesia and sedation (eg, fentanyl 1 mcg/kg, then midazolam 1 to 2 mg every 2 minutes to a maximum of 5 mg) is required because the procedure is terrifying and unpleasant. Airway maintenance equipment and employees must be present.
The electrodes (pads or paddles) used for cardioversion can be placed anteroposteriorly (along the left sternal border, over the 3rd and 4th intercostal spaces, and in the left infrascapular region or anterolaterally along the left sternal border, over the 3rd and 4th intercostal spaces, and in the left infrascapular region) (between the clavicle and the 2nd intercostal space along the right sternal border and over the 5th and 6th intercostal spaces at the apex of the heart). A shock is provided after synchronization to the QRS complex is confirmed on the monitor.
The best energy level depends on the type of tachyarrhythmia being treated. Biphasic shocks, in which the current polarity is reversed partway through the shock waveform, improve cardioversion and defibrillation efficacy.
The energy level for the first shock in defibrillation of ventricular fibrillation or pulseless ventricular tachycardia is
For biphasic devices, 120 to 200 joules (or as specified by the manufacturer), while many practitioners use the maximum device output in this setting.
360 joules for monophasic devices or as specified by the manufacturer.
The energy level for the first shock in synchronized cardioversion of atrial fibrillation is
For biphasic devices, the joules range from 100 to 200, depending on the manufacturer’s specifications.
For monophasic devices, 200 joules (or as specified by the manufacturer).
Both biphasic and monophasic devices have subsequent shocks with the same or higher energy levels.
During a thoracotomy or with the use of an intracardiac electrode catheter, DC cardioversion-defibrillation can also be administered directly to the heart; in this case, substantially lower energy levels are necessary.
DC cardioversion complications
Premature atrial and ventricular beats, as well as muscle discomfort, are common complications. Cardioversion causes myocyte destruction and electromechanical dissociation less frequently, but more frequently if patients have a marginal left ventricular function or repeated shocks are applied.