Background-Atrial fibrillation ablation has made tremendous progress with respect to innovation, efficacy, and safety.However, limited data exist regarding the burden and trends in adverse outcomes arising from this procedure. The aim of our study was to examine the frequency of adverse events attributable to atrial fibrillation (AF) ablation and the influence of operator and hospital volume on outcomes. Methods and Results-With the use of the Nationwide Inpatient Sample, we identified AF patients treated with catheter ablation. We investigated common complications including cardiac perforation and tamponade, pneumothorax, stroke, transient ischemic attack, vascular access complications (hemorrhage/hematoma, vascular complications requiring surgical repair, and accidental arterial puncture), and in-hospital death described with AF ablation, and we defined these complications by using validated International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes. An estimated 93 801 AF ablations were performed from 2000 to 2010. The overall frequency of complications was 6.29% with combined cardiac complications (2.54%) being the most frequent. Cardiac complications were followed by vascular complications (1.53%), respiratory complications (1.3%), and neurological complications (1.02%). The in-hospital mortality was 0.46%. Annual operator (<25 procedures) and hospital volume (<50 procedures) were significantly associated with adverse outcomes. There was a small (nonsignificant) rise in overall complication rates. Conclusions-The overall complication rate was 6.29% in patients undergoing AF ablation. There was a significant association between operator and hospital volume and adverse outcomes. This suggests a need for future research into identifying the safety measures in AF ablations and instituting appropriate interventions to improve overall AF ablation outcomes.

1 and the 2011 percutaneous coronary intervention (PCI) guidelines recommend (Class IC) that PCIs should be performed by operators with an annual volume (>75 procedures) at high-volume centers (>400 procedures) with on-site cardiac surgery. 2 The last decade has observed a decline in number of PCIs performed, and many interventional cardiologists have experienced a drop in procedural volume. 3,4 As a result, the Background-The relationship between operator or institutional volume and outcomes among patients undergoing percutaneous coronary interventions (PCI) is unclear. Methods and Results-Cross-sectional study based on the Healthcare Cost and Utilization Project's Nationwide Inpatient Sample between 2005 to 2009. Subjects were identified by International Classification of Diseases, 9 th Revision, Clinical Modification procedure code, 36.06 and 36.07. Annual operator and institutional volumes were calculated using unique identification numbers and then divided into quartiles. Three-level hierarchical multivariate mixed models were created. The primary outcome was in-hospital mortality; secondary outcome was a composite of in-hospital mortality and peri-procedural complications. A total of 457 498 PCIs were identified representing a total of 2 243 209 PCIs performed in the United States during the study period. In-hospital, all-cause mortality was 1.08%, and the overall complication rate was 7.10%. ]. Spline analysis also showed significant operator and institutional volume outcome relationship. Similarly operators in the higher quartiles witnessed a significant reduction in length of hospital stay and cost of hospitalization (P<0.001). Conclusions-Overall in-hospital mortality after PCI was low. An increase in operator and institutional volume of PCI was found to be associated with a decrease in adverse outcomes, length of hospital stay, and cost of hospitalization. 5 These recommendations, however, are based on expert opinion derived from the interpretation of data from multiple sources with inherent limitations. Some of these data were derived from state registries and are dated. 5-24The purpose of this study was to determine the association of annual PCI operator and institutional volume with in-hospital mortality, peri-procedural complications, length of hospital stay, and cost of hospitalization using the nation's largest available all-payer insurance inpatient database in a recent era (2005)(2006)(2007)(2008)(2009)) during which procedural techniques and practices have remained relatively stable. Methods Data SourceWe analyzed 5-year data from the 2005 to 2009 from National Inpatient Sample (NIS) database. The NIS is a subset of the Healthcare Cost and Utilization Project sponsored by the Agency for Healthcare Research and Quality (AHRQ). The NIS is the largest publicly available all-payer inpatient care database in the United States; including data on approximately 7 to 8 million discharges per year, it is stratified to sample approximately 20% sample of US community (nonfederal, short-term, general, a...