ABSTRACTS Heart, Lung and Circulation Abstracts S105 2011;20S:S1–S155 CSANZ Abstracts 2011 symptomatic AF (135 paroxysmal [61%], 85 persistent/ longstanding persistent [39%]) to undergo either SRI or WAI, with or without additional left lateral MIL ablation. Patients who had recurrences beyond the three month blanking period were offered a repeat procedure. They were followed clinically and with seven-day Holter studies for 2.4 ± 0.9 years. Results: After the first procedure, AF recurred in 41 patients (19%), OAT in 47 (21%) and both in 23 (10%). Of them, 96 (50 SRI, 46 WAI; p = 0.59) had a repeat pro- cedure. Patients who had recurrent OAT after the first procedure had superior survival free of atrial arrhythmias or drugs two years after their second procedure than those who only had recurrent AF (71 ± 7% vs. 54 ± 9%, p = 0.04). Adjusting for treatment allocation, recurrent OAT still predicted fewer recurrences after the repeat procedure (HR = 0.48, p = 0.046). SRI patients tended towards better survival two years after the second procedure than WAI patients (71 ± 8% vs. 55 ± 8%, p = 0.06), but MIL ablation had no effect on survival rates. Conclusions: OAT recurrences predict better outcomes after a repeat procedure than AF recurrences. There may be fewer overall recurrences after SRI. doi:10.1016/j.hlc.2011.05.260 258 Presence of Abnormal Atrial Substrate in New Onset Atrial Fibrillation G. Rangnekar ∗ , A. Brooks, P. Sanders The University of Adelaide, Australia New onset AF is often interpreted as the beginning of a disease process. This study assessed for the first time, the baseline degree of abnormal atrial substrate in new onset AF patients compared with established disease. Seven day Holter monitoring was used to obtain ambulatory electrocardiography characteristics of nine new onset atrial fibrillation patients and 12 established paroxysmal AF patients. The ectopy burden, relative pre- maturity (ratio of ectopic beat coupling to the previous 3 sinus beats) and left atrial size via transthoracic echocar- diography were recorded for all patients. Age (p = 0.7) and risk factor burden were not differ- ent between new onset and established AF. In contrast, new onset AF patients had a median disease history of 3 [2–3] compared with 24 [12–90] for established patients. LA diameter was not different in any dimension between the groups (p > 0.05). The bimodal pattern of atrial coupling and atrial ectopy burden (p = 0.7) were also equivalent in both groups (figure). These data suggest that new AF already has the electro- cardiographic and substrate characteristics of established paroxysmal arrhythmia, suggesting that new onset AF may represent a critical threshold in an established disease process. doi:10.1016/j.hlc.2011.05.261 259 Pulmonary Vein Isolation with the Cryoballoon Tech- nique N. Jackson ∗ , M. Barlow, J. Leitch John Hunter Hospital, NSW, Australia Background: Cryoballoon ablation (CBA) is becoming a popular technique for pulmonary vein isolation. It has the potential to improve operator usability, to decrease proce- dural times, and decrease risk of serious complications. Method: 200 consecutive patients underwent CBA with 15 months mean follow-up. Results: Of 772 veins attempted, 94.8% were isolated with the cryoballoon alone and 97.7% were isolated with the addition of a radiofrequency catheter. The 28 mm cry- oballoon was used in 562 veins, with an isolation rate of 94.3% (1.6% phrenic nerve palsy (PNP) rate) and the 23 mm cryoballoon in 210 veins with an isolation rate of 96.7% (2.8% PNP rate). The average number of freezes per pro- cedure was 9.6 (LSPV 2.6, LIPV 2.5, RSPV 2.1 and RIPV 2.4). Procedure times fell as illustrated: During 228 procedures minor complications included: nine (3.9%) transient PNPs (recovery during the proce- dure) and six (2.6%) PNPs persisting beyond the procedure