The Influence of Transthoracic Impedance on Electrical Cardioversion and Defibrillation: Current Data

Sudden cardiac death (SCD) is a leading cause of death globally, often caused by malignant ventricular arrhythmias. Rapid termination by direct current defibrillation (DF) is the best way to treat pulseless ventricular tachycardia and ventricular fibrillation. Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice. External cardioversion (ECV) is an immediate, effective, and safe procedure for the treatment of arrhythmias with high ventricular rate, for example, AF. The success of both ECV and DF is dependent on the delivery of sufficient current, influenced by energy and transthoracic impedance (TTI). TTI depends on patient characteristics, and the exact factors affecting it are still a matter of debate. Influencing factors such as respiration phase, contact pressure, coupling agent, and total energy delivered are commonly identified. However, there are multiple studies with controversial results concerning the effect of age, gender, body mass index, hemoglobin concentration, the presence of chronic heart failure, and fluid accumulation as independent predictors of TTI. The review emphasizes refining energy dosage during ECV and while minimizing complications caused by an unnecessarily high energy delivery. The value of TTI should be predicted to optimize the energy dosage and the number of shocks for successful ECV and DF