High-density activation mapping of fractionated electrograms in the atria of patients with paroxysmal atrial fibrillation

BACKGROUND Areas of complex fractionated atrial electrograms (CFAEs) have been implicated in the atrial substrate of atrial fibrillation (AF). The mechanisms underlying CFAE in humans are not well investigated. OBJECTIVES The purpose of this study was to investigate the regional activation pattern associated with CFAE using a high-density contact mapping catheter. METHODS Twenty patients with paroxysmal AF were mapped using a high-density multielectrode catheter. CFAE were mapped at 10 different sites (left atrium [LA]: inferior, posterior, roof, septum, anterior, lateral; right atrium [RA]: anterior, lateral, posterior, septum). Local atrial fibrillation cycle length (AFCL) was measured immediately before and after the occurrence of CFAE, and the longest electrogram duration (CFAE(max)) was assessed. RESULTS Longer electrogram durations were recorded in the LA compared with the RA (CFAE(max) 118 +/- 21 ms vs 104 +/- 23 ms, P = .001). AFCL significantly shortened before the occurrence of CFAE(max) compared with baseline (LA: 174 +/- 32 ms vs 186 +/- 32 ms, P = .0001; RA: 177 +/- 31 ms vs 188 +/- 31 ms, P = .0001) and returned to baseline afterwards. AFCL shortened by >= 10 ms in 91% of mapped sites. Two different local activation patterns were associated with occurrence of CFAE(max): a nearly simultaneous activation in all spines in 84% indicating passive activation, and a nonsimultaneous activation sequence suggesting local complex activation or reentry. CONCLUSION Fractionated atrial electrograms during AF demonstrate dynamic changes that are dependent on regional AFCL. Shortening of AFCL precedes the development of CFAE; thus, cycle length is a major determinant of fractionation during AF. High-density mapping in AF may help to differentiate passive activation of CFAE from CFAE associated with an active component of the AF process.