Internal atrial defibrillation: the importance of lead location, waveform morphology, and shock synchronization

Atrial fibrillation (AF) remains the most common arrhythmia encountered in clinical medicine and is associated with significant morbidity and mortality. Electrical cardioversion remains a very effective method for the acute termination of AF. However, the standard method for atrial cardioversion requires shock strengths of 50 to 400 joules delivered across transthoracic cutaneous electrodes. These shocks strengths can be detrimental to the heart as well as painful to the patient. Until recently, there was little available information concerning the technique of internal atrial defibrillation in either animal models or humans. Current research effort have shown that this method usually requires much lower energies, in the 1-5 joule range and requires only sedation and not anesthesia in humans. Over the past 5-6 years the interest in internal atrial defibrillation has greatly grown and now the feasibility of an implantable atrial defibrillator appears soon to be a reality. This manuscript discusses some of the more recent animal and human studies which have looked at the efficacy as well as the safety of internal atrial defibrillation of AF