A comparison between transthoracic impedance and body mass index as indicators of the energy for cardioversion

It has been reported that transthoracic impedance (Z_t) influences the final value of energy supplied to the patient during defibrillation. At present it is used as a parameter allowing to automatically correct the value of charge stored in the discharge capacitor, so the patient receives precisely the energy selected, thus "personalizing" the discharge. Recently, the relation between body mass index (BMl) and the energy necessary for cardioversion has been investigated. In this paper the authors have investigated for a possible relation between BMI and Z_t that would allow using transthoracic impedance as an indicator to select the energy for cardioversion. Z_t was measured and BMI calculated in 593 apparently healthy subjects, who had previously agreed to take part in the investigation. No reasonable dependence was found between them, and it is concluded that it is not adequate to use transthoracic impedance as a parameter to correct the energy stored for a cardioversion discharge.