Chapter 32: Defibrillation and Cardioversion

INTRODUCTION

Defibrillation and cardioversion are procedures that involve giving a controlled electrical shock to the heart through the chest wall and are used for rapid termination of a tachyarrhythmia (a fast, abnormal rhythm originating either in the atrium or ventricle) that is unresponsive to baseline treatment or is causing the patient to have cardiovascular compromise (inadequate systemic perfusion). Baseline treatment consists of correcting metabolic problems, use of vagal maneuvers which work by stimulating the vagal tone that slows the heart rate (eg, diving reflex, bag filled with ice and cold water applied on the whole face for 15–30 seconds without obstructing the airway, rectal stimulation using a thermometer, bending legs and bringing the knees to the chest for 15–30 seconds), use of medications (adenosine, digoxin, propranolol, verapamil, amiodarone, procainamide, lidocaine, or magnesium sulfate), or transesophageal pacing. It is best to try these maneuvers or medical therapy if intravenous access is available. Neonatal arrhythmias are rare, and the majority can be treated with these initial measures.

Current defibrillators can deliver 2 modes of shock: synchronized and unsynchronized. Synchronized shocks are lower dose and used for cardioversion. Unsynchronized shocks are higher dose and used for defibrillation. Pediatric cardiology consultation is recommended for all infants with a tachyarrhythmia.

I. INDICATIONS

1. Cardioversion (synchronized delivery of energy [shock] during the QRS complex)

   1. Unstable patients with tachyarrhythmias who have a perfusing rhythm but evidence of poor perfusion, heart failure, or hypotension (signs of cardiovascular compromise). Tachyarrhythmias appropriate for cardioversion include:

      1. Supraventricular tachycardia or ventricular tachycardia with a pulse and poor perfusion.

      2. Supraventricular tachycardia with shock and no vascular access.

      3. Atrial flutter with shock.

      4. Atrial fibrillation with shock (very rare in infants).

   2. Elective cardioversion in infants with stable supraventricular tachycardia (SVT), ventricular tachycardia (VT), or atrial flutter (good tissue perfusion and pulses) unresponsive to other treatments. This is always done under the close supervision of a pediatric cardiologist. Sedation and a 12-lead electrocardiogram are recommended before cardioversion.

2. Defibrillation (asynchronized, random delivery of energy [shock] during the cardiac cycle). Used in pulseless arrest with a shockable rhythm (VT and ventricular fibrillation) and in between cardiopulmonary resuscitation (CPR) but not in asystole or pulseless electrical activity (PEA). The most common cause of a ventricular arrhythmia in a neonate is electrolyte imbalance. Defibrillation will not stop the arrhythmia in these patients. Defibrillation is recommended and is the most effective treatment for documented ventricular fibrillation and pulseless ventricular tachycardia.

II. EQUIPMENT

1. Manual external defibrillator, (where the operator preselects the energy to be used); two paddle electrodes of the correct sizes, and conductive gel pads. For infants, use the smallest size of paddle (usually measuring 4.5 cm) or hands-free, multifunction, self-adhesive electrode pads (SAEP) can be used instead of paddles for cardioversion, defibrillation, and monitoring. It is important to be familiar with your institution’s equipment because there are many different types and models. Pediatric-capable automated ...