***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    ***EXAMPLES*** 
    Input: Background : The novel oral anticoagulants ( NOACs ) are used for stroke prevention in atrial fibrillation ( AF ) , but their safety and efficacy in the periablation period are not well established . Additionally , no st and ard procedure for managing periprocedural and intraprocedural anticoagulation has been established . Objective : To evaluate the frequency of hemorrhagic and thrombotic events as well as periprocedural management strategies of NOACs compared with warfarin as anticoagulation therapy for AF ablation . Methods : This was a retrospective cohort study from a prospect i ve AF ablation registry maintained at a large , academic medical center . Results : A total of 374 cases ( 173 warfarin , 123 dabigatran , 61 rivaroxaban , and 17 apixaban ) were included in the analysis . The overall hemorrhagic/thrombotic event rate was 14.2 % ( major hemorrhage 2.7 % , minor hemorrhage 11.2 % , thrombotic stroke 0.5 % ) . The frequency of minor hemorrhage was significantly higher with warfarin compared with dabigatran ( 15 % vs 5.7 % , P = 0.012 ) . The average heparin dose required to reach the goal activated clotting time ( ACT ) was 5600 units for warfarin , 12 900 units for dabigatran ( P < 0.001 ) , 15 100 units for rivaroxaban ( P < 0.001 ) , and 14 700 units for apixaban ( P < 0.001 ) . The average time in minutes to reach the goal ACT was significantly longer , compared with warfarin , for dabigatran ( 57 vs 28 , P < 0.001 ) , rivaroxaban ( 63 vs 28 , P < 0.001 ) , and apixaban ( 72 vs 28 , P < 0.001 ) . Conclusions : Compared with warfarin , periprocedural anticoagulation with dabigatran result ed in fewer minor hemorrhages and total adverse events after AF ablation . Patients anticoagulated with NOACs required larger doses of heparin and took longer to reach the goal ACT compared with patients anticoagulated with warfarin OBJECTIVES The purpose of this study was to evaluate the feasibility and safety of periprocedural dabigatran during atrial fibrillation ( AF ) ablation . BACKGROUND AF ablation requires optimal periprocedural anticoagulation for minimizing bleeding and thromboembolic complications . The safety and efficacy of dabigatran as a periprocedural anticoagulant for AF ablation are unknown . METHODS We performed a multicenter , observational study from a prospect i ve registry including all consecutive patients undergoing AF ablation in 8 high-volume centers in the United States . All patients receiving dabigatran therapy who underwent AF ablation on periprocedural dabigatran , with the dose held on the morning of the procedure , were matched by age , sex , and type of AF with an equal number of patients undergoing AF ablation with uninterrupted warfarin therapy over the same period . RESULTS A total of 290 patients , including 145 taking periprocedural dabigatran and an equal number of matched patients taking uninterrupted periprocedural warfarin , were included in the study . The mean age was 60 years with 79 % being male and 57 % having paroxysmal AF . Both groups had a similar CHADS(2 ) score , left atrial size , and left ventricular ejection fraction . Three thromboembolic complications ( 2.1 % ) occurred in the dabigatran group compared with none in the warfarin group ( p = 0.25 ) . The dabigatran group had a significantly higher major bleeding rate ( 6 % vs. 1 % ; p = 0.019 ) , total bleeding rate ( 14 % vs. 6 % ; p = 0.031 ) , and composite of bleeding and thromboembolic complications ( 16 % vs. 6 % ; p = 0.009 ) compared with the warfarin group . Dabigatran use was confirmed as an independent predictor of bleeding or thromboembolic complications ( odds ratio : 2.76 , 95 % confidence interval : 1.22 to 6.25 ; p = 0.01 ) on multivariate regression analysis . CONCLUSIONS In patients undergoing AF ablation , periprocedural dabigatran use significantly increases the risk of bleeding or thromboembolic complications compared with uninterrupted warfarin therapy BACKGROUND We aim ed to evaluate the feasibility of an oral direct thrombin inhibitor , dabigatran , as a periprocedural anticoagulant for use with ablation of atrial fibrillation ( AF ) . METHODS Consecutive patients scheduled to undergo an AF ablation were r and omly assigned to receive dabigatran ( n = 45 ) or warfarin ( n = 45 ) to compare their clinical feasibility . Both of those oral anticoagulants were discontinued the day before the ablation and were resumed after confirming hemostasis of the venipuncture site . A bridging therapy with heparin was not used in either of the patient groups . RESULTS Dabigatran was switched to warfarin before the ablation because of dyspepsia in three patients . An occurrence of rebleeding from the venipuncture site was less common in dabigatran-allocated patients than in warfarin-allocated patients ( 20 % vs 44 % ; P = 0.013 ) . The reduction in the D-dimer level after the initiation of oral anticoagulants was greater in the dabigatran-allocated patients than in the warfarin-allocated patients . The time from the initiation of the anticoagulants to the ablation was significantly shorter in the dabigatran-allocated patients than in the warfarin-allocated patients ( 43 ± 7 vs 63 ± 13 days ; P < 0.0001 ) . There was only one fatal periprocedural complication in a patient receiving warfarin , who had a mesenteric arterial thrombosis after the ablation . CONCLUSIONS An anticoagulation strategy with dabigatran may surpass that with warfarin in reducing both the periprocedural risk of minor bleeding and a hypercoagulable state , and the time to ablation in patients undergoing ablation of AF Background and Objectives Two new oral anticoagulants , rivaroxaban and dabigatran , with no need for anticoagulation monitoring , are available for patients with atrial fibrillation ( AF ) . We aim ed to compare their anticoagulant effects and safety when used during the AF ablation periprocedural period . Methods Patients undergoing AF ablation were r and omly assigned to receive rivaroxaban 15 mg once daily ( N = 30 ) or dabigatran 110 mg twice daily ( N = 30 ) . Rivaroxaban was withheld on the morning of the day before the ablation , and dabigatran was discontinued from the evening of the day before the procedure . Both anticoagulants were then resumed after haemostasis of the access site . D-dimer levels were measured just before the ablation , at the end of the ablation , and at 24 h and 48 h after the procedure . Results The baseline D-dimer levels were identical in both groups . However , D-dimer levels increased more markedly following the ablation procedure in patients receiving rivaroxaban than in those receiving dabigatran ( mean ± st and ard deviation from 0.62 ± 0.16 to 1.09 ± 0.38 μg/mL vs from 0.59 ± 0.08 to 0.75 ± 0.17 μg/mL ; p < 0.0001 ) . The rate of rebleeding from the access site was similar in patients receiving rivaroxaban and those receiving dabigatran ( 33 vs 27 % ; p = 0.78 ) . Conclusion As compared with dabigatran , rivaroxaban may increase the risk of hypercoagulability when used during the periprocedural period of AF ablation , suggesting a potential rebound effect of rivaroxaban or a mismatch between its half-life and dose regimen Background Systemic thromboembolism and bleeding remain the two most common and serious complications of catheter ablation of atrial fibrillation . A variety of periprocedure anticoagulation strategies have been proposed to mitigate these risks . Although operators are now routinely administering dabigatran for anticoagulation in this setting , its relative safety and effectiveness compared to warfarin are unknown . Methods and results A total of 202 patients received dabigatran  as part of their periprocedural anticoagulation regimen at the time of initial or redo catheter ablation for symptomatic atrial fibrillation . A comparison group of 202 patients treated with warfarin was r and omly selected from patients undergoing atrial fibrillation ( AF ) ablation during the same time period . AF types were paroxysmal in 223 patients , persistent in 158 patients , and longst and ing persistent in 13 patients . Mean age was 60.0 ± 10.5 years , 55 % had a history of hypertension , and mean CHADS-VASc score was 1.7 ± 1.3 . “ Continuous ” warfarin or dabigatran was administered in 80 and 32 % of patients , respectively . Time to first dose  of dabigatran post-procedure was 12.2 ± 10.3 h. Two dabigatran and no warfarin-treated patients had systemic thromboembolism ( p = NS ) ; five dabigatran and three warfarin-treated patients had bleeding complications ( p = NS , combined endpoint p = 0.116 ) . One dabigatran patient had severe pericardial bleeding ( 3 L blood loss ) . Conclusions In a retrospective pilot trial comparing the risks of systemic thromboembolism or bleeding complications in patients treated  with warfarin or dabigatran anticoagulation , the outcomes were similar . A prospect i ve trial is warranted BACKGROUND Periprocedural anticoagulation using uninterrupted warfarin could reduce the risk of thromboembolic complications of atrial fibrillation ( AF ) ablation . Few studies , however , have evaluated the efficacy and safety of periprocedural dabigatran in AF ablation . METHODS AND RESULTS A total of 211 consecutive patients who underwent AF ablation , including 110 patients who received 110 mg dabigatran twice daily ( group D ) and 101 patients who received dose-adjusted warfarin ( international normalized ratio , 2.0 - 3.0 ; group W ) , were evaluated .  Dabigatran was discontinued on the morning of the procedure , and resumed on the next morning . Warfarin was continued throughout the procedure . During the procedure , heparin infusion was maintained to achieve an activated clotting time of > 300s . Postprocedural cerebral magnetic  resonance imaging ( MRI ) was performed in 60 patients ( group D , n=31 ; group W , n=29 ) . No periprocedural deaths or symptomatic thromboembolic complications were observed in either group . MRI indicated a silent cerebral infa rct ion in 1 patient in each group . Five patients in group D and 11 in group W had minor bleeding ( P=0.12 ) . Cardiac tamponade occurred in 2 patients in group W , but in none in group D. Total bleeding complications occurred less frequently in group D ( 4.5 % ) than in group W ( 12.9 % ; P<0.05 ) . CONCLUSIONS Dabigatran at a dose of 110 mg twice daily was safe for AF ablation in patients with a relatively low risk of thromboemboli , suggesting that it may become an alternative to warfarin in those patients AIMS Experiences with novel oral anticoagulants ( NOACs )  early after atrial fibrillation ( AF ) catheter ablation are limited and show controversial results . We aim ed to assess the longer-term safety , efficacy , and acceptance of NOACs in a large real-world cohort of patients presenting for AF catheter ablation . METHODS AND RESULTS From July 2010 until June 2012 , 259 patients undergoing AF catheter ablation were prospect ively included .  Novel oral anticoagulants were given for at least 3 months post-ablation . Clinical outcome ( stroke , thromboembolic events , major bleeding ) , adverse effects , and drug adherence were assessed at discharge and follow-up . On admission patients were presented with a variety of  anticoagulants  including 54 patients ( 21 % ) already on NOACs prior ablation . After ablation 38 % of patients received dabigatran 110 mg , 56 % 150 mg , and 6 % received rivaroxaban 20 mg . There were four periprocedural thromboembolic and major bleeding complications ( 1.5 % ) , all in patients without NOACs prior ablation ( two on warfarin and two on heparin ) . During long-term follow-up [ 311 ( 199 ; 418 ) days ] no stroke , systemic embolism , or major haemorrhage could be observed . Uneventful electrical cardioversions and reablation procedures were performed in 27 and 12 patients on dab 
    Output:
    
With respect to total bleeding risk , no significant difference was observed between dabigatran , rivaroxaban , apixaban , and vitamin K antagonists ( VKAs ) by mixed-treatment comparison .
The similar results were seen in the direct comparison .
Conclusions Risks of bleeding  with dabigatran , rivaroxaban , apixaban , and VKAs were similar in peri-procedural period of CA for AF