Direct Current (Dc) Cardioversion / Defibrillation

A transthoracic electrical direct current (DC) shock of sufficient magnitude to depolarize the entire myocardium and sets the entire cardiac cells in the short term in the refractory period, to repeat the depolarization. After that, the fastest intrinsic pacemaker, usually the sinusatriale node wins back control of the heart rhythm. Therefore, the DC cardioversion / -Defibrillation very effectively ended tachyarrhythmias resulting from a re-entry mechanism. However, it is less effective at opening of tachyarrhythmias resulting from an automaticity, because the rhythm after depolarization probably is the same tachyarrhythmia again. For tachyarrhythmias whose cause no ventricular fibrillation (VF), the DC shock must be QRS complex synchronized (so-called. DC cardioversion) because an electric shock, which issued in the vulnerable period (close to the T-wave maximum) is ventricular fibrillation can cause. In ventricular fibrillation, the QRS complex synchronized cardioversion is neither necessary nor possible. In a DC shock without QRS complex synchronization is a DC defibrillation.

The need to treat an arrhythmia depends on the symptoms and severity, which holds this Arrythmieform in itself. The therapy is based on the reasons behind any particular arrhythmia. If necessary, a direct antiarrhythmic therapy with anti-arrhythmic drugs, cardioversion, defibrillation, implantable cardioverter-defibrillators (ICDs), pacemaker (and a special form of “pacing”, ? cardiac resynchronization therapy ?) or a combination of said forms of treatment may be necessary. A transthoracic electrical direct current (DC) shock of sufficient magnitude to depolarize the entire myocardium and sets the entire cardiac cells in the short term in the refractory period, to repeat the depolarization. After that, the fastest intrinsic pacemaker, usually the sinusatriale node wins back control of the heart rhythm. Therefore, the DC cardioversion / -Defibrillation very effectively ended tachyarrhythmias resulting from a re-entry mechanism. However, it is less effective at opening of tachyarrhythmias resulting from an automaticity, because the rhythm after depolarization probably is the same tachyarrhythmia again. For tachyarrhythmias whose cause no ventricular fibrillation (VF), the DC shock must be QRS complex synchronized (so-called. DC cardioversion) because an electric shock, which issued in the vulnerable period (close to the T-wave maximum) is ventricular fibrillation can cause. In ventricular fibrillation, the QRS complex synchronized cardioversion is neither necessary nor possible. In a DC shock without QRS complex synchronization is a DC defibrillation. Procedures for DC cardioversion When an elective DC cardioversion, the patient should 6-8 h remain sober in order to avoid aspiration. Cardioversion solves the patient fears and is also painful. Therefore, a short general anesthesia or iv Analgesia with sedation (z. B. fentanyl 1 .mu.g / kg, followed by administration of midazolam 1-2 mg every 2 minutes up to a maximum dose of 5 mg) is necessary. Appropriate equipment and trained personnel must guarantee the free attitude of the respiratory tract. The electrodes (pads or paddles) used for cardioversion can anteroposterior (along the left border of the sternum above the 3rd and 4th ICR and below the left shoulder blade) or the anterolateral (between the clavicle and the 2nd ICR along the right boundary of the sternum and be placed on the 5th and 6th ICR in the apex of the heart). Once the QRS synchronization shows on the monitor, the shock can be delivered. The degree of current varies depending on the type of tachyarrhythmia to be treated. Cardioversion is more effective if biphasic shocks are delivered, in which the current polarity is partially reversed by the waveform of the electric shocks. Another possibility is the use of intracardiac electrode catheter. The DC cardioversion / -Defibrillation can be carried out as part of a thoracotomy directly to the heart. In this method, however, much lower currents are required. Complications of DC cardioversion Usually occur only minor complications such as PAC, PVC or muscle pain. Less often, but more often it comes to damage to the myocardial cells and an electromechanical dissociation in patients with low left ventricular function or in the application of multiple shocks.

Health Life Media Team

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