Association between transthoracic impedance and electrical cardioversion success with biphasic defibrillators: An analysis of 1055 shocks for atrial fibrillation and flutter

Abstract

Background The relevance of transthoracic impedance (TTI) to electrical cardioversion (ECV) success for atrial tachyarrhythmias when using biphasic waveform defibrillators is unknown. Hypothesis TTI is predictive of ECV success with contemporary defibrillators. Methods De‐identified data stored in biphasic defibrillator memory cards from ECV attempts for atrial fibrillation (AF) or atrial flutter (AFL) over a 2‐year period at our center were evaluated. ECV success, defined as arrhythmia termination and ≥ 1 sinus beat, was adjudicated by 2 blinded cardiac electrophysiologists. The association between TTI and ECV success was assessed via Cochrane‐Armitage trend and Spearman rank correlation tests, as well as simple and multivariable logistic regression. The influence of TTI on the number of shocks and on cumulative energy delivered per patient was also examined. Results 703 patients (593 with AF, 110 with AFL) receiving 1055 shocks were included. Last shock success was achieved in 88.0% and 98.2% of patients with AF and AFL, respectively. In patients with AF, TTI was positively associated with last shock failure (Ptrend =0.019), the need for multiple shocks (Ptrend <0.001), and cumulative energy delivered (ρ = 0.348; P < 0.001). After adjusting for first shock energy, 10‐Ω increments in TTI were associated with odds ratios of 1.36 (95% CI: 1.24–1.49) and 1.22 (95% CI: 1.09–1.37) for first and last shock failure, respectively (P < 0.001 for both). Conclusions Although contemporary defibrillators are designed to compensate for TTI, this variable continues to be associated with ECV failure in patients with AF. Strategies to lower TTI during ECV for AF may improve procedural success.

The 2020 Canadian Cardiovascular Society/Canadian Heart Rhythm Society Comprehensive Guidelines for the Management of Atrial Fibrillation

“…538,571 In obese patients, using paddles and applying force might improve success rates with DCCV over adhesive pads. 572,573 Pretreatment with antiarrhythmic drugs (eg, ibutilide and amiodarone) has been shown to improve the effectiveness of DCCV. 363,574 Values and preferences.…”

A framework of current based defibrillation improves defibrillation efficacy of biphasic truncated exponential waveform in rabbits

“…An earlier study reported that an optimal biphasic waveform with the first phase duration lasting between 4 and 10 ms, and the second phase duration being shorter than the first one resulted in the lowest energy DFT 43 . In addition to the decreased current, another possible reason for the decreased defibrillation success rate for energy-based defibrillation in higher TTI patients is that the shock duration lasts beyond the optimal duration 23 . Since energy is the product of the square of average current and total shock duration, the energy requirements for waveforms with shorter phase durations will be significantly lower than those for waveforms with prolonged durations.…”

“…Contemporary biphasic defibrillators still use energy in joules to describe the strength of a defibrillation shock but utilize impedance compensation techniques to adjust the defibrillation waveform based on patient TTI measurement prior to shock delivery 22 . Although the use of impedance compensation techniques appears to have promising results, a recent clinical study has reported that higher TTI is still associated with greater prevalence of shock failure 23 . Until now, no studies have been conducted to compare defibrillation efficacy between current-based biphasic defibrillation with impedance compensation and energy-based defibrillation.…”

Atrial fibrillation and flutter – the state of the art. Part 2

“…Thoracic impedance is also dependent on size, position, and distance between defibrillator electrodes, type of defibrillator electrodes, contact pressure on the chest, chemical properties of electrode gels used during cardioversion/defibrillation, and skin reaction [56,[59][60][61]. In AF the effectiveness of DCC ranges from 75% to 94% in restoring sinus rhythm and is inversely related to AF duration and transthoracic impedance [38,46,57,59,[62][63][64][65][66][67]. Moreover, the effectiveness of DCC may be increased after amiodarone (initiating the treatment a few weeks before DCC), sotalol, ibutilide, or vernakalant and probably after flecainide and propafenone [4,51].…”