Transvenous Low Energy Internal Cardioversion for Atrial Fibrillation: A Review of Clinical Applications and Future Developments

Abstract

BORIANI, G., et al.: Transvenous Low Energy Internal Cardioversion for Atrial Fibrillation: A Review of Clinical Applications and Future Developments. Low energy internal atrial cardioversion can be performed by delivering biphasic shocks between transvenous catheters positioned within the cardiac chambers or great vessels. Delivery of shocks results in effective cardioversion at energies < 6–10 J and the procedure can be effective even when external cardioversion has failed. Shock induced discomfort varies from patient to patient, but the procedure can be usually performed without general anesthesia and eventually under mild sedation. Nevertheless, tolerability has to be improved by obtaining a substantial reduction in defibrillating thresholds. With regard to safety, delivery of shocks for defibrillating the atria implies a potential risk of inducing ventricular fibrillation; to minimize this risk, shock delivery must be synchronous to the QRS and should be avoided during rapid RR cycles (< 300 ms). Presently, transvenous low energy cardioversion is an investigational procedure, but a widening of indications is expected in the near future. The cost of the procedure, which remains invasive and requires a brief hospital stay, must be balanced with the benefit of restoring sinus rhythm and the possibility of maintaining sinus rhythm for the medium‐ to long‐term. Experimental and clinical investigations of low energy internal cardioversion have resulted in the development of devices for atrial defibrillation whose clinical role and cost‐benefit ratio is currently under evaluation.

Increase in QT/QTc dispersion after low energy cardioversion of chronic persistent atrial fibrillation

“…Its efficacy ranges between 65% and 95% [3] and improves markedly with the use of biphasic shocks [4]. Recently, use of antiarrhythmic drugs immediately before cardioversion was proposed in order to enhance the effectiveness of the procedure.…”

“…Internal cardioversion is effective in 95 -100% of cases of atrial fibrillation. Its effectiveness extends to patients who are refractory to external cardioversion [3].…”

Efficacy of internal cardioversion for chronic atrial fibrillation in patients with and without left ventricular dysfunction

“…An alternative strategy is low-energy transvenous internal cardioversion. This technique, which is still under evaluation [8], allows cardioversion with energies as low as 6 -10 J and general anaesthesia can most often be avoided. Few data are available regarding its suitability for patients with left ventricular dysfunction.…”

Simultaneous Double External DC Shock Technique for Refractory Atrial Fibrillation in Concomitant Heart Disease

“…Some authors have advocated peri-procedural discontinuation of anticoagulation, but this may increase the risk of left atrial clot formation and systemic embolisation, especially in organic heart disease. [8][9][10] As little as 4% of the current from the external shock effectively penetrates cardiac tissue, while the majority follows haphazard pathways through the chest. 11) In addition, atrial fibrillation thresholds determined from defibrillation electrodes placed in the high right atrium and the coronary sinus in terms of mean energy have varied from as low as 1.5 to as high as 8.9 using biphasic shocks.…”