Method for simultaneous epicardial and endocardial mapping of in vivo canine heart: Application to atrial conduction properties and arrhythmia mechanisms

Endocardial/Epicardial Mapping of AF. Introduction: It has been suggested t hat the three-dimensional structure of the atria may be crucial in arrhythm ogenesis; however, previous in vivo atrial activation mapping studies have been limited to either endocardial or epicardial approaches. Methods and Results: To investigate the role of endocardial and epicardial structures and their interaction in atrial conduction and arrhythmias, we u sed five epicardial plaques and two intra-atrial balloon arrays to record a total of 368 unipolar electrograms from the entire epicardial and endocard ial surface of both atria, During regular 1:1 pacing from the right atrial appendage, right atrial endocardial activation spread considerably faster t han epicardial (total activation time 45 +/- 12 msec vs 60 +/- 19 msec, res pectively [mean +/- SD]; P < 0.05), pointing to preferential conduction ove r structures like the crista terminalis and pectinate muscles, No such diff erences were noted in the left atrium, Transseptal spread occurred via disc rete anterior and posterior pathways, causing separate breakthroughs in ant erior and posterior atrial regions, respectively. Dissociation between sept al pathways played a role in reentry during vagal atrial fibrillation, In 2 of 4 dogs with atrial fibrillation associated with congestive heart failur e, single macroreentrant circuits involving endocardial and epicardial comp onents were revealed during the arrhythmia, Conclusion We conclude that activation mapping using simultaneous recording from both epicardial and endocardial surfaces provides potentially importa nt insights into the mechanisms of atrial conduction and arrhythmogenesis.