cardiovascular disorders
Direct Current (DC) Cardioversion Defibrillation
Introduction
The need for treatment of Overview of Arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including A transthoracic DC shock of sufficient magnitude Electrophysiology , rendering the entire heart momentarily refractory to repeat depolarization. Thereafter, the most rapid intrinsic pacemaker, usually the sinoatrial (SA) node, reassumes control of heart rhythm. Thus, DC cardioversion-defibrillation very effectively terminates tachyarrhythmias that result from reentry. However, it is less effective for terminating tachyarrhythmias that result from automaticity because the return rhythm is likely to be the automatic tachyarrhythmia. For tachyarrhythmias other than ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT), the DC shock must be synchronized to the QRS complex (called DC cardioversion) because a shock that falls during the vulnerable period (near the peak of the T wave) can induce VF. In VF, synchronization of a shock to the QRS complex is neither necessary nor possible. A DC shock applied without synchronization to a QRS complex is DC defibrillation. Direct current (DC) cardioversion or defibrillation can be delivered as Monophasic current Biphasic current Monophasic current travels in one direction between the two electrodes. In biphasic devices, the current reverses direction part way through the shock waveform. The biphasic device requires lower energy and has been shown to lead to higher rates of return of spontaneous circulation (ROSC). However, survival outcomes are similar in both devices ( General reference ). Most manual and automated external defibrillators (AEDs) are now biphasic because of increased efficiency at restoring sinus rhythm. Biphasic devices are also smaller in size (making the devices more portable). 