Transesophageal defibrillation: animal studies and preliminary clinical observations

Safety and Feasibility of Transesophageal Pacing in a Dog

This study investigated the feasibility of using a modified transesophageal atrial pacing system for dogs requiring temporary ventricular pacing. Atrial pacing was readily achieved in the one dog studied, but it caused considerable diaphragmatic movement. Ventricular pacing could not be achieved at any lead configuration or energy stimulation. While transesophageal cardiac pacing was a safe procedure, the large variation in the chest anatomy of dogs requires further study to explore this model as a substitute for transvenous or transthoracic ventricular pacing.

Potential benefit of transesophageal defibrillation: an experimental evaluation

INTRODUCTION

Because of the proximity of the esophagus to the heart, transesophageal defibrillation might increase defibrillation success. We assessed the defibrillation threshold (DFT) of transesophageal defibrillation compared with standard transthoracic defibrillation.

METHODS

Defibrillation success and DFTs were determined in 22 female pigs with high (68+/-4 kg, n=12) or low body weight (39+/-1 kg, n=10). After induction of ventricular fibrillation, biphasic shocks were delivered between two cutaneous patch electrodes (sternal and apical position) or between an esophageal and two cutaneous patch electrodes in a sternal and apical position. The esophageal electrode was integrated into a latex sheath covering a standard transesophageal echocardiography probe.

RESULTS

In 5 of 12 pigs with high body weight, external defibrillation failed despite 3 consecutive 200-J shocks, whereas subsequent transesophageal defibrillation was successful with the first shock. In the remaining 7 pigs, a more than 50% reduction in DFT was obtained with transesophageal defibrillation compared with standard biphasic external defibrillation (67+/-27 vs 164+/-23 J, P<.001). Pigs with lower body weight were successfully defibrillated by both transthoracic and transesophageal shocks. The DFT in pigs with low body weight was significantly lower using transesophageal defibrillation compared with transthoracic shocks (65+/-15 vs 99+/-38 J, P<.05).

CONCLUSIONS

In this animal model, nonresponders to standard external defibrillation could successfully be defibrillated via an esophageal-cutaneous electrode configuration. Overall, an almost 50% DFT reduction was achieved by transesophageal defibrillation. Transesophageal defibrillation may provide an additional tool for terminating VF, which is refractory to external defibrillation, eg, in patients with very high body weight.

Does the change of the polarity of electrodes influence the results of transoesophageal bidirectional DC cardioversion?

The aim of the study was to compare the bidirectional transoesophageal DC cardioversion (BOC) with unidirectional transoesophageal DC cardioversion (UOC) and to evaluate, if the reversion of the polarity of electrodes alters the effectiveness and the amount of energy during BOC. UOC was attempted in 300 patients (pts) with atrial fibrillation (AF) and BOC in 241 pts with AF. In UOC mode shocks were delivered between the 4-ring oesophageal electrode (cathode) and the chest pad (anode) positioned in the precordial region. In BOC shocks were delivered between the same oesophageal electrode and two chest pads joined with each other, positioned on both sides of the sternum. First 147 pts were cardioverted with the oesophageal electrode as a cathode, next 94 with an anode in oesophageal position. The effectiveness of both modes (UOC and BOC) was very high, however in pts with chronic AF success rate was better in BOC approach (82% vs 100%). BOC, compared with UOC, allowed to decrease the threshold defibrillation significantly: in pts with recent onset of AF from 61.5 J to 33.3 J and in pts with chronic AF from 99.8 J to 75.2 J. In pts with long standing AF the reduction of the defibrillation threshold was statistically not significant (from 68.6 J to 50.6 J). The effectiveness of BOC was also very high independently of the polarity of electrodes. The change of the polarity did not affect the minimal and total successful energy of shocks, too. In pts with oesophageal electrode as a cathode defibrillation threshold was 48.4 J and in pts with the anodal electrode 43.7 J. In conclusions we found BOC as a very effective method in pts with AF. Defibrillation threshold in BOC is lower than in UOC and the polarity of electrodes does not influence the success rate and successful energy.

Current concepts in electrical defibrillation

The electrical defibrillator has been proven to be a life-saving device in the treatment of cardiac arrest due to ventricular tachycardia or ventricular fibrillation. An understanding of the physiology and technology behind this device is useful for providers of emergency care. In this article, we review the current concepts in electrical defibrillation and briefly discuss the developmental history. The physiology and the technical considerations will make up the bulk of the discussion. The latest developments in electrical defibrillation also will be reviewed.

Innovative emergency defibrillation methods for refractory ventricular fibrillation in a variety of hospital settings

This article reviews the ability of innovative rescue defibrillation techniques for the treatment of refractory ventricular fibrillation. These data were obtained in a variety of hospital settings at the University of California, San Francisco, from 1986 to 1992. Innovative rescue defibrillation techniques were applied to 15 patients with refractory ventricular fibrillation having failed > or = 2 high-energy transthoracic shocks in a variety of hospital settings. Intracardiac defibrillation was performed from a right ventricular catheter to a posterior patch in nine patients who had refractory ventricular fibrillation in the course of invasive electrophysiologic testing. Emergency simultaneous transthoracic and epicardial defibrillation was successfully performed with standard paddles placed over the thorax in contact with epicardial patch or pacing lead connectors in two patients in the operating room who underwent implantable cardioverter-defibrillator insertion and failed standard rescue defibrillations. Transesophageal defibrillation was performed in four patients in the emergency department who had a refractory ventricular fibrillation in the field. Intracardiac defibrillation successfully terminated refractory ventricular fibrillation in 9 of 9 patients in the electrophysiology laboratory. Similarly, emergency simultaneous transthoracic and epicardial defibrillation restored sinus rhythm in two patients in the operating room. Transesophageal defibrillation performed after 50 minutes of cardiac arrest successfully terminated ventricular fibrillation in each patient. Thus alternative methods now exist that permit rescue defibrillation in a variety of hospital emergency settings. These techniques are performed with simple-to-use equipment that is compatible with standard defibrillators.