Cardioversion and Defibrillation

W6 Cardioversion and Defibrillation



Raúl J. Gazmuri



image Before Procedure



Indications



• Emergency reestablishment of an organized electrical rhythm (defibrillation):
• Ventricular fibrillation

• Pulseless ventricular tachycardia

• Narrow or wide QRS complex tachycardia (ventricular rate >150) associated with hemodynamic instability, chest pain, or pulmonary edema

• Hemodynamically unstable polymorphic ventricular tachy-cardia

• Elective reestablishment of sinus rhythm:
• Atrial fibrillation

• Atrial flutter

• Hemodynamically stable ventricular tachycardia unresponsive to medical treatment

• Others


Contraindications



• Specific advance directives (e.g., do not attempt resuscitation for cases of ventricular fibrillation)

• Digitalis toxicity–associated tachycardia

• Sinus tachycardia caused by various clinical conditions

• Rhythms not responsive to electric shocks (e.g., multifocal atrial tachycardia)

• Atrial fibrillation or atrial flutter without proper anticoagulation or exclusion of atrial thrombi


Equipment



• Automated external defibrillator or manual defibrillator

• Proper age-adjusted pads or paddles


image Anatomy


The heart is located behind the sternum. Its base is at the level of the third intercostal space immediately to the right of the sternum, and its apex is at the level of the fifth intercostal space inferior and usually just medial to the nipple. External cardioversion or defibrillation is attempted by delivering one or more electric shocks through the chest cavity for the purpose of passing an electric current of sufficient energy through the heart muscle to fully depolarize the atria (e.g., atrial fibrillation or atrial flutter) or the ventricles (e.g., ventricular fibrillation or ventricular tachycardia). Cardioversion should enable the natural or artificial cardiac pacemaker to resume control of the cardiac rhythm. Electrodes (paddles or pads) can be positioned on the anterior chest wall with one electrode below the right clavicle lateral to the sternum and the other electrode below the breast tissue along the midaxillary line. Electrodes (pads; paddles more difficult) can also be positioned in an anteroposterior position, with the anterior electrode placed over the precordium and the posterior electrode at the right infrascapular location. For internal cardioversion or defibrillation, specially designed paddles are applied directly to the epicardial surface of the ventricles.

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Jul 7, 2016 | Posted by in CRITICAL CARE | Comments Off on Cardioversion and Defibrillation

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