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 that the three‐dimensional structure of the atria may be crucial in arrhythmogenesis; 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 used five epicardial plaques and two intra‐atrial balloon arrays to record a total of 368 unipolar electrograms from the entire epicardial and endocardial surface of both atria. During regular 1:1 pacing from the right atrial appendage, right atrial endocardial activation spread considerably faster than epicardial (total activation time 45 ± 12 msec vs 60 ± 19 msec, respectively [mean ± SD]; P < 0.05 ), pointing to preferential conduction over structures like the crista terminalis and pectinate muscles. No such differences were noted in the left atrium. Transseptal spread occurred via discrete anterior and posterior pathways, causing separate breakthroughs in anterior and posterior atrial regions, respectively. Dissociation between septal pathways played a role in reentry during vagal atrial fibrillation. In 2 of 4 dogs with atrial fibrillation associated with congestive heart failure, single macroreentrant circuits involving endocardial and epicardial components were revealed during the arrhythmia. Conclusion: We conclude that activation mapping using simultaneous recording from both epicardial and endocardial surfaces provides potentially important insights into the mechanisms of atrial conduction and arrhythmogenesis.