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BACKGROUND Radiofrequency high-power ablation appears to be a novel concept for atrial fibrillation (AF). The ablation index (AI) value has been associated with durability of pulmonary vein isolation (PVI). OBJECTIVES This study aimed to report the procedural data and initial results of a combined ablation technique using AI-guided high-power (AI-HP; 50 W) ablation for PVI. METHODS Symptomatic AF patients were consecutively enrolled and underwent wide-area contiguous circumferential PVI. Contact-force catheters were used, ablation power was set to 50 W targeting AI values (550 anterior and 400 posterior). Esophageal temperature was monitored during procedure, all patients underwent postablation esophageal endoscopy. RESULTS PVI was achieved in all (n = 50, mean age: 68 ± 9 years, female: 60%) patients, rate of first-round PVI was 92%. A total of N = 2105 AI-guided ablation lesions were analyzed. Comparing left anterior wall vs left posterior wall and right anterior wall vs right posterior wall, mean ablation time (s) per lesion was 20.5 ± 8 vs 8.6 ± 3 and 12.2 ± 4 vs 9.3 ± 3; mean contact force (g): 17.1 ± 12 vs 25.4 ± 14 and 33.7 ± 13 vs 21.0 ± 11; mean AI: 547 ± 48 vs 445 ± 55 and 555 ± 56 vs 440 ± 47 (all P

Background The left atrial appendage (LAA) has been identified as a potential source of atrial fibrillation (AF) and has been described as the "fifth" pulmonary vein (PV). We report our initial experience in LAA isolation (LAAI) using the cryoballoon (CB) and data on durability of CB-LAAI. Methods Patients treated with a CB-LAAI were retrospectively identified. Six weeks after electrical LAAI, patients were scheduled for staged percutaneous LAA closure. During the second procedure, a subset of patients underwent invasive remapping of the LAA. Results A total of 32 patients (21 males, 68 ± 10 years old) were treated with CB-LAAI. Acute LAAI was achieved in 29 of 32 (91%) patients: single-shot LAAI was observed in 18 of 32 (56%) patients. Acute procedural sustained LAAI was related with a significantly shorter time to LAAI (sustained LAAI: 84 ± 50 s vs nonsustained LAAI: 166 ± 76 s, P = 0.004). Mean procedure and fluoroscopy time were 61 ± 29 and 8 ± 6 min, respectively. One left-sided phrenic nerve palsy occurred. In 25 of 32 (78%) patients, a second procedure for percutaneous LAA closure device implantation was performed. In 22 patients, persistency of LAAI was tested: durable LAAI was documented in 16/22 patients (73%). Conclusion In the present report, CB LAA isolation followed by staged LAA closure appeared to be safe and feasible but more data are required. Time to LAAI played a role in predicting acute sustained LAAI rate. CB LAA ablation leads to 73% of durable LAA isolation.

The submembrane cytoskeletal meshwork of the axon contains the scaffolding protein bIV-spectrin. It provides mechanical support for the axon and anchors membrane proteins. Quivering (qv 3j ) mice lack functional bIV-spectrin and have reduced voltage-gated so- dium channel (VGSC) immunoreactivity at the axon initial segment and nodes of Ranvier. Because VGSCs are critically involved in action poten- tial generation and conduction, we hypothesized that qv 3j mice should also show functional deficits at the network level. To test this hypothe- sis, we investigated granule cell function in the dentate gyrus of anes- thetized qv 3j mice after electrical stimulation of the perforant path in vivo. This revealed an impaired input-output relationship between stimulus intensity and granule cell population spikes and an enhanced paired-pulse inhibition of population spikes, indicating a reduced ability of granule cells to generate action potentials and decreased network excitability. In contrast, the input-output curve for evoked field excita- tory postsynaptic potentials (fEPSPs) and paired-pulse facilitation of fEPSPs were unchanged, suggesting normal excitatory synaptic transmis- sion at perforant path-granule cell synapses in qv 3j mutants. To corrobo- rate our findings, we analyzed the influence of VGSC density reduction on dentate network activity using an established computational model of the dentate gyrus network. This in silico approach confirmed that the loss of VGSCs is sufficient to explain the electrophysiological changes observed in qv 3j mice. Taken together, our findings demonstrate that bIV-spectrin is required for normal granule cell firing and for physio- logical levels of network excitability in the mouse dentate gyrus in vivo. V C 2009 Wiley-Liss, Inc.