Background-Catheter ablation of ventricular tachycardia (VT) is effective and particularly useful in patients with frequent defibrillator interventions. Various substrate modification techniques have been described for unmappable or hemodynamically intolerable VT. Noninducibility is the most frequently used end point but is associated with significant limitations, so the optimal end point remains unclear. We hypothesized that elimination of local abnormal ventricular activities (LAVAs) during sinus rhythm or ventricular pacing would be a useful and effective end point for substrate-based VT ablation. As an adjunct to this strategy, we used a new high-density mapping catheter and frequently used epicardial mapping. Methods and Results-Seventy patients (age, 67Ϯ11 years; 7 female) with VT and structurally abnormal ventricle(s) were prospectively enrolled. Conventional mapping was performed in sinus rhythm in all, and a high-density Pentaray mapping catheter was used in the endocardium (nϭ35)

Atrial fibrosis as defined by DE MRI is associated with slower and more organized electrical activity but with lower voltage than healthy atrial areas. Ninety percent of continuous CFAE sites occur at non-DE and patchy DE LA sites. These findings are important when choosing the ablation strategy in persistent AF.

BACKGROUND Complex fractionated electrograms (CFAEs) detected during substrate mapping for atrial fibrillation (AF) reflect etiologies that are difficult to separate. Without knowledge of local refractoriness and activation sequence, CFAEs may represent rapid localized activity, disorganized wave collisions, or far-field electrograms. OBJECTIVE The purpose of this study was to separate CFAE types in human AF, using monophasic action potentials (MAPs) to map local refractoriness in AF and multipolar catheters to map activation sequence. METHODS MAP and adjacent activation sequences at 124 biatrial sites were studied in 18 patients prior to AF ablation (age 57 ± 13 years, left atrial diameter 45 ± 8 mm). AF cycle length, bipolar voltage, and spectral dominant frequency were measured to characterize types of CFAE. RESULTS CFAE were observed at 91 sites, most of which showed discrete MAPs and (1) pansystolic local activity (8%); (2) CFAE after AF acceleration, often with MAP alternans (8%); or (3) nonlocal (far-field) signals (67%). A fourth CFAE pattern lacked discrete MAPs (17%), consistent with spatial disorganization. CFAE with discrete MAPs and pansystolic activation (consistent with rapid localized AF sites) had shorter cycle length (P <.05) and lower voltage (P <.05) and trended to have higher dominant frequency than other CFAE sites. Many CFAEs, particularly at the septa and coronary sinus, represented far-field signals. CONCLUSION CFAEs in human AF represent distinct functional types that may be separated using MAPs and activation sequence. In a minority of cases, CFAEs indicate localized rapid AF sites. The majority of CFAEs reflect far-field signals, AF acceleration, or disorganization. These results may help to interpret CFAE during AF substrate mapping.

Background Complex fractionated electrograms (CFAE) are targets of atrial fibrillation (AF) ablation. Serial high density maps were evaluated to understand the impact of activation direction and rate on electrogram (EGM) fractionation. Methods and Results 18 patients (9 persistent) underwent high density, 3D, left atrial mapping (>400 points/map) during AF, Sinus (SR) and CS-paced (CSp) rhythms. In SR and CSp, fractionation was defined as EGM with ≥4 deflections, while in AF CFEmean <80ms was considered as continuous CFAE. The anatomic distribution of CFAE sites was assessed, quantified and correlated between rhythms. Mechanisms underlying fractionation were investigated by analysis of voltage, activation and propagation maps. A minority of continuous CFAE sites displayed EGM fractionation in SR (15+/−4%) and CSp (12+/(12+/−8%). EGM fractionation did not match between SR and CSp at 70+/−10% sites. Activation maps in SR and CSp showed that wave collision (71%) and regional slow conduction (24%) caused EGM fractionation. EGM voltage during AF (0.59+/−0.58mV) was lower than during SR and CSp (>1.0mV) at all sites. During AF, the EGM voltage was higher at continuous CFAE sites than at non-CFAE sites (0.53mV (Q1, Q3: 0.33–0.83) vs. 0.30 mV (Q1, Q3: 0.18–0.515), p<0.00001). Global LA voltage in AF was lower in persistent vs. paroxysmal AF patients (0.6+/−0.59mV vs. 1.12+/−1.32mV, p<0.01). Conclusions The distribution of fractionated EGMs is highly variable, depending on direction and rate of activation (SR vs. CSp vs. AF). Fractionation in sinus and CSp rhythms mostly resulted from wave collision. All sites with continuous fractionation in AF displayed normal voltage in SR suggesting absence of structural scar. Thus, many fractionated EGMs are functional in nature and their sites dynamic.

Objectives To assess whether additional ablation in the right atrium(RA) improves termination rate in long-lasting persistent atrial fibrillation(PsAF). Background Prolongation of atrial fibrillation(AF) cycle length(CL) measured from the left atrial appendage predicts favorable outcome during catheter ablation of PsAF. However, in some patients despite prolongation of AFCL in the left atrium(LA) with ablation, AF persists. We hypothesized that this is due to RA drivers and these patients may benefit from RA ablation. Methods 148 consecutive patients undergoing catheter ablation of PsAF(duration 25±32 months) were studied. AFCL was monitored in both atria during stepwise ablation commencing in the LA. Ablation was performed in the RA when all LA sources in AF had been ablated and a RA-LA gradient existed. The procedural endpoint was AF termination. Results Two distinct patterns of AFCL change emerged during LA ablation. In 104patients(70%), there was parallel increase of AFCL in LA and RA culminating in AF termination (baseline: LA 153ms[140,170], RA 155ms[143,171]; after ablation: LA 181ms[170,200], RA 186ms[175,202]). In 24 patients(19%), RA AFCL did not prolong, creating a right-to-left frequency gradient, (baseline: LA 142ms[143,153], RA 145 ms[139,162]; after ablation: LA 177 ms[165–185], RA 152ms[147,175]). These patients had a longer AF history (23versus12 months, p=0.001), and larger RA diameter (42versus39mm, p=0.005) and RA ablation terminated AF in 55%. In the remaining 20 patients, biatrial ablation failed to terminate AF. Conclusions A divergent pattern of AFCL prolongation after LA ablation resulting in a right-to-left gradient demonstrating that the right atrium is driving AF in about 20 % of PsAF.