There are few absolute contraindications to cardioversion and defibrillation. Patients with digitalis overdose or electrolyte abnormalities including hypokalemia are at increased risk of developing VF or VT with cardioversion. The procedure should be deferred if possible until these are corrected. Atrial fibrillation of unknown or prolonged duration should not be cardioverted without first taking appropriate steps to reduce risk of thromboembolism. Caution must be taken in patients with severe disease of the cardiac conduction system as a shock may precipitate bradyarrhythmia and temporary pacing capabilities should be on hand. Sinus tachycardia may be a physiologic response to a specific cause such as hypotension and should not be confused with a rhythm treatable with cardioversion.

Patients with implantable cardioverter/defibrillators (ICD) or pacemakers can undergo DC cardioversion but the electric charge may disrupt computer programming or damage the device. If cardioversion is performed interrogation must be completed afterward. Pregnancy also is not a contraindication to cardioversion or defibrillation but fetal heart rate should be monitored during the procedure.

External cardioversion and defibrillation normally employ pads or paddles that are pressed to the skin and connected by cables to a case housing the computer, energy source, and cardiac monitor (Fig. 27.1). Devices manufactured prior to 2000 normally use monophasic waveforms and those made after use biphasic waveforms. Electrode types include handheld paddles that use electrically conductive gel and self-adhesive pads which stick to the patient’s skin [2].

Equipment for monitoring heart rhythm and vital signs should be available along with supplies needed for an emergency response including a code cart for advanced cardiac life support, temporary pacing, and airway equipment. Supplemental oxygen should be present. Clippers for removing excess hair may be necessary for application of adhesive pads and to reduce electrical impedance. If procedural sedation is to be performed the appropriate sedative and analgesic agents must be available.

Intravenous access, cardiac telemetry, and vital signs monitoring must be present throughout the procedure. A 12-lead electrocardiogram should be done prior to and following cardioversion. To reduce the risk of aspiration patients should not eat or drink for at least 6 h before elective cardioversion. Supplemental oxygen should be removed prior to discharge of any electrical energy due to the risk of fire.

Procedural sedation is commonly performed as cardioversion may cause pain, anxiety, and unpleasant memories. Commonly used agents with initial dose in mg/kg include midazolam (0.02–0.03), fentanyl (0.5–1.0), etomidate (0.1–0.15), ketamine (1.0–2.0), and propofol (0.5–1.0).

Proper electrode placement is important for successful cardioversion as this determines the pathway of current [3]. Pads are primarily placed in two positions, antero-lateral and antero-posterior (Fig. 27.2). If an ICD or pacemaker is present pads or paddles should not be placed directly over the device and the antero-posterior position may be favored. Pad placement should also avoid breast tissue.