human
***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Introduction Pulmonary vein isolation ( PVI ) is an effective therapy for paroxysmal atrial fibrillation ( AF ) , but it has limitations . The two most significant recent advances have centred on the integration of real-time quantitative assessment of catheter contact force into focal radio frequency ( RF ) ablation catheters and the development of dedicated ablation tools capable of achieving PVI with a single ablation lesion ( A rct ic Front cryoballoon , Medtronic , Minneapolis , MN , USA ) . Although each of these holds promise for improving the clinical success of catheter ablation of AF , there has not been a rigorous comparison of these advanced ablation technologies . Moreover , the optimal duration of cryoablation ( freezing time ) has not been determined . Methods and analysis Patients undergoing an initial PVI procedure for paroxysmal AF will be recruited . Patients will be r and omised 1:1:1 between contact-force irrigated RF ablation , short duration cryoballoon ablation ( 2 min applications ) and st and ard duration cryoballoon ablation ( 4 min applications ) . The primary outcome is time to first documented AF recurrence on implantable loop recorder . With a sample size of 111 per group and a two-sided 0.025 significance level ( to account for the two main comparisons ) , the study will have 80 % power ( using a log-rank test ) to detect a difference of 20 % between contact force RF catheter ablation and either of the two cryoballoon ablation groups . Factoring in a 4 % loss to follow-up , 116 patients per group should be r and omised and followed for a year ( total study population of 348 ) . Ethics and dissemination The study was approved by the University of British Columbia Office of Research ( Services ) Ethics Clinical Research Ethics Board . Results of the study will be su bmi tted for publication in a peer- review ed journal . Trial registration number NCT01913522 ; Pre- Aims Contact force ( CF ) catheters provide catheter-tissue contact information to improve outcome of  pulmonary vein isolation ( PVI ) in paroxysmal atrial fibrillation ( PAF ) . We evaluated different target-CF values for achievement of the additional endpoint of an unexcitable ablation line . Methods A total of 106 patients undergoing PVI  were r and omized into three groups ( G ) ( G1 : target-CF 15 g , G2 : target-CF 10 g , G3 : CF concealed from operator ) . The PVI encircling line was divided into predefined sections . Excitable tissue along the PVI-line identified by high output pacing ( 10 V , 2 ms ) was targeted for further ablation . Results Mean average CF was 17.4 ± 4.7 g ( G1 ) vs. 12.3 ± 6.0 g ( G2 ) vs. 11.1 ± 6.5 g ( G 3 ) ( p < 0.001 ) . Primary unexcitable ablation lines were found in 38.6 , 19.4 and 5.7 % ( G1 , G2 , G3 respectively ; G1 vs. G2 p < 0.05 , G1 vs. G3 p < 0.001 , G2 vs. G3 ns ) . Additional radiofrequency (RF)-energy to achieve unexcitability was lowest in G1 ( 3.6 ± 3.1 kJ vs. 8.6 ± 7.2 kJ ( G2 ) and 10.4 ± 6.7 ( G3 ) , p ≤ 0.001 , G2 vs. G3 ns ) with accordingly lowest additional RF applications in G1 ( 3.0 ± 2.6 vs. 7.0 ± 5.4 in G2 and 8.4 ± 4.0 in G3 ; G1 vs. G2 and G3 , p < 0.001 , G 2 vs. G 3 ns ) . Sections along ablation lines with low initial CF were most likely to reveal excitability . Single procedure success was 81.9 vs. 73.5 vs. 71.4 % ( G 1 , 2 and 3 , p = 0.6 ) during 437 ± 254 day follow-up . Conclusion Higher tip-to-tissue CF during PVI facilitates the achievement of an unexcitable ablation line , requiring less additional RF-energy BACKGROUND Pulmonary vein isolation ( PVI ) is a well-established treatment of atrial fibrillation ( AF ) , with contact force (CF)-sensing catheters joining 3-dimensional mapping systems and image integration as technological advancements over the last decade . OBJECTIVE The purpose of this study was to analyze trends in radiation exposure for AF ablation over the last 12 years at our center . METHODS We review ed prospect ively collected data of 2344 consecutive PVI procedures for either paroxysmal or persistent AF between January 2004 and December 2015 . During this period , all cases used 3-dimensional mapping systems , with 8 software and 2 hardware up grade s. Primary endpoints were fluoroscopy time , absorbed dose ( Air Kerma in mGy ) , and effective dose ( mSv ) . RESULTS In total , 1914 patients underwent initial PVI , and 430 patients underwent redo PVI using radiofrequency energy . Fluoroscopy time , and absorbed and effective doses significantly and progressively decreased over the 12-year period for initial PVI as follows : 2004 - 2006 : 61 ± 27 minutes ; 2007 - 2009 : 46 ± 14 minutes , 1365 ± 1369 mGy , 11.3 ± 12.5 mSv ; 2010 - 2012 : 31 ± 11 , 464 ± 339 mGy , 9.0 ± 10.4 mSv ; and 2013 - 2015 : 17 ± 9 minutes , 304 ± 758 mGy , 5.5 ± 6.7 mSv . CF-sensing catheters were used for 357/508 PVI only cases between 2014 and 2015 . Fluoroscopy times ( 11 ± 5 vs 21 ± 8 minutes ; P < .001 ) and absorbed dose ( 200 ± 524 vs 470 ± 1326 mGy ; P = .004 ) were significantly shorter with this catheter . CONCLUSION Radiation exposure has dramatically decreased over the last decade for PVI and is related to operator experience , annual case volume , technology evolution , and more recently CF-sensing catheters . This has significant implication s for both patient and operator long-term risk BACKGROUND Contact force ( CF ) information may improve the safety and efficacy of ablation for paroxysmal atrial fibrillation ( PAF ) . OBJECTIVE The purpose of this study was to assess the impact of CF data on ablation for PAF . METHODS Patients undergoing first-time PAF ablation were r and omized at 7 UK centers to ablation with ( CF-on ) or without ( CF-off ) CF data available to the operator , using the same ablation catheter and mapping system . An ablation CF of 5 - 40 g was targeted . Pulmonary vein ( PV ) reconnection was assessed with adenosine at 60 minutes . Follow-up for arrhythmia recurrence was for 1 year with 7-day Holter recordings at 6 and 12 months . RESULTS One hundred seventeen patients were studied ( 59 CF-on , 58 CF-off ) . In the CF-on group , a reduction in acute PV reconnection rates ( 22 % vs 32 % , P = .03 ) but no significant difference in 1-year success rates off antiarrhythmic drugs ( 49 % vs 52 % , P = .9 ) was observed . There was no difference in major complication rates : 2 of 59 ( 3 % ) CF-on , 3 of 58 ( 5 % ) CF-off ( P = .7 ) . Procedural and fluoroscopy times were not significantly different ( P>.5 ) . Overall mean CFs per ablation were not different between groups ( 13.4 [9.1 - 19.6]g CF-on , 13.4 [7.4 - 22.4]g CF-off , P = .5 ) , but a greater proportion of readings in the CF-on group were in the target range ( 80 % vs 68 % , P<.001 ) . CONCLUSION This r and omized multicenter study demonstrated that CF data availability was associated with reduced acute PV reconnection but not improved 1-year success rates , procedural and fluoroscopy times , or complication rates . There was a reduction in extremes of CF , above and below the study target range , suggesting greater CF control during ablation BACKGROUND Contact force ( CF ) monitoring could be useful in accomplishing circumferential pulmonary vein ( PV ) isolation ( CPVI ) for atrial fibrillation ( AF ) . OBJECTIVE The purpose of this study was to compare procedure parameters and outcomes between CF-guided and non-guided CPVI . METHODS Thirty-eight consecutive AF patients ( mean age 60 ± 11 years , 28 paroxysmal AF ) undergoing CPVI were r and omized to non-CF-guided ( n = 19 ) and CF-guided ( n = 19 ) groups .  CPVI was performed with the ThermoCool SmartTouch catheter in both groups . The end-point was bidirectional block between the left atrium ( LA ) and PV . In the CF group , CF was kept between 10 and 20 g during CPVI , whereas in the non-CF group , all CF information was blanked . Radiofrequency energy at 30 W in the anterior and 25 W in the posterior LA wall was applied for 20 - 25 seconds at each point . RESULTS CPVI was successfully accomplished without any major complications in both groups . Mean CF in the non-CF and CF groups were 5.9 ± 4.5 g and 11.1 ± 4.3 g , respectively , for left-side CPVI , and 9.8 ± 6.6 g and 12.1 ± 4.8 g , respectively , for right-side CPVI ( both P < .001 ) . The procedure and fluoroscopy times  for CPVI in the non-CF and CF groups were 96 ± 39 minutes and 59 ± 16 minutes , respectively ( P < .001 ) , and 22 ± 63 seconds and 9 ± 20 seconds ( P = NS ) , respectively . Total number of residual conduction gaps was 6.3 ± 3.0 in the non-CF group and 2.8 ± 1.9 in the CF group ( P < .001 ) . During 6-month follow-up , 84.2 % of patients in the non-CF group and 94.7 % in the CF group were free from any atrial tachyarrhythmias ( P = .34 ) . CONCLUSION CF-guided CPVI  is effective in reducing procedure time and additional touch-up ablation and may improve long-term outcome Background The aim of this study was to evaluate the impact of contact force ( CF ) visualization on the incidence of low and high CF during left atrial ( LA ) mapping and pulmonary vein isolation ( PVI ) . Methods CF was assessed in 70 patients who underwent PVI .  Three highly experienced operators performed all procedures . The operators were blinded to CF in group A ( 35 patients ) , and CF was displayed in group B ( 35 patients ) . In group B , optimal CF was defined as mean CF between 10 and 39 g , and operators attempted to acquire points and ablate within this range . Results A total of 8401 mapping points were analyzed during LA mapping ( group A : 4104 , group B : 4297 ) . Low CF < 10 g and high CF ≥40 g were noted in a significantly larger number of points in group A ( 37.7 vs. 12.0 % , P < 0.001 ; 11.5 vs. 1.5 % , P < 0.001 ) . At the mitral isthmus and ridge areas , CF was significantly lower ( 7.7 vs. 12.2 g , P < 0.001 ; 5.3 vs. 11.7 g , P < 0.001 ) in group A than in group B. PVI was successfully achieved in all patients . There were significant site-dependent CF differences between the two groups . Optimal CF was achieved in significantly more applications in group B ( P < 0.001 ) . There was no significant difference in atrial fibrillation ( AF ) recurrence rates after a minimum follow-up of 1 year between the two groups in this cohort ( P = 0.24 ) . No significant peri-procedural complications occurred in either group . Conclusions CF visualization can assist in avoiding both low and high CF , which may have the potential to improve lesion formation and patient safety profile . In this study , CF-guided ablation did not affect AF recurrence Purpose We prospect ively investigated the differences in pulmonary vein reconnections ( PVRs ) and clinical outcomes between contact force (CF)-guided and conventional circumferential PV isolation ( CPVI ) of atrial fibrillation ( AF ) . Methods One hundred twenty consecutive AF patients ( 63 ± 10 years ; 88 males ) undergoing an initial CPVI were r and omized to ablation with a target CF of 20 g ( CF group ; n = 60 ) or that with operators blinded to the CF information ( blind group ; n = 60 ) . Results The CF group had fewer PVRs ( 0.67 ± 0.91/patient vs. 1.16 ±  
    Output:
    
agent
Conclusion Meta- analysis of r and omized data demonstrated that CF guidance does not improve the safety or efficacy of AF ablation , despite initial observational data showing dramatic improvement .
***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Introduction Pulmonary vein isolation ( PVI ) is an effective therapy for paroxysmal atrial fibrillation ( AF ) , but it has limitations . The two most significant recent advances have centred on the integration of real-time quantitative assessment of catheter contact force into focal radio frequency ( RF ) ablation catheters and the development of dedicated ablation tools capable of achieving PVI with a single ablation lesion ( A rct ic Front cryoballoon , Medtronic , Minneapolis , MN , USA ) . Although each of these holds promise for improving the clinical success of catheter ablation of AF , there has not been a rigorous comparison of these advanced ablation technologies . Moreover , the optimal duration of cryoablation ( freezing time ) has not been determined . Methods and analysis Patients undergoing an initial PVI procedure for paroxysmal AF will be recruited . Patients will be r and omised 1:1:1 between contact-force irrigated RF ablation , short duration cryoballoon ablation ( 2 min applications ) and st and ard duration cryoballoon ablation ( 4 min applications ) . The primary outcome is time to first documented AF recurrence on implantable loop recorder . With a sample size of 111 per group and a two-sided 0.025 significance level ( to account for the two main comparisons ) , the study will have 80 % power ( using a log-rank test ) to detect a difference of 20 % between contact force RF catheter ablation and either of the two cryoballoon ablation groups . Factoring in a 4 % loss to follow-up , 116 patients per group should be r and omised and followed for a year ( total study population of 348 ) . Ethics and dissemination The study was approved by the University of British Columbia Office of Research ( Services ) Ethics Clinical Research Ethics Board . Results of the study will be su bmi tted for publication in a peer- review ed journal . Trial registration number NCT01913522 ; Pre- Aims Contact force ( CF ) catheters provide catheter-tissue contact information to improve outcome of  pulmonary vein isolation ( PVI ) in paroxysmal atrial fibrillation ( PAF ) . We evaluated different target-CF values for achievement of the additional endpoint of an unexcitable ablation line . Methods A total of 106 patients undergoing PVI  were r and omized into three groups ( G ) ( G1 : target-CF 15 g , G2 : target-CF 10 g , G3 : CF concealed from operator ) . The PVI encircling line was divided into predefined sections . Excitable tissue along the PVI-line identified by high output pacing ( 10 V , 2 ms ) was targeted for further ablation . Results Mean average CF was 17.4 ± 4.7 g ( G1 ) vs. 12.3 ± 6.0 g ( G2 ) vs. 11.1 ± 6.5 g ( G 3 ) ( p < 0.001 ) . Primary unexcitable ablation lines were found in 38.6 , 19.4 and 5.7 % ( G1 , G2 , G3 respectively ; G1 vs. G2 p < 0.05 , G1 vs. G3 p < 0.001 , G2 vs. G3 ns ) . Additional radiofrequency (RF)-energy to achieve unexcitability was lowest in G1 ( 3.6 ± 3.1 kJ vs. 8.6 ± 7.2 kJ ( G2 ) and 10.4 ± 6.7 ( G3 ) , p ≤ 0.001 , G2 vs. G3 ns ) with accordingly lowest additional RF applications in G1 ( 3.0 ± 2.6 vs. 7.0 ± 5.4 in G2 and 8.4 ± 4.0 in G3 ; G1 vs. G2 and G3 , p < 0.001 , G 2 vs. G 3 ns ) . Sections along ablation lines with low initial CF were most likely to reveal excitability . Single procedure success was 81.9 vs. 73.5 vs. 71.4 % ( G 1 , 2 and 3 , p = 0.6 ) during 437 ± 254 day follow-up . Conclusion Higher tip-to-tissue CF during PVI facilitates the achievement of an unexcitable ablation line , requiring less additional RF-energy BACKGROUND Pulmonary vein isolation ( PVI ) is a well-established treatment of atrial fibrillation ( AF ) , with contact force (CF)-sensing catheters joining 3-dimensional mapping systems and image integration as technological advancements over the last decade . OBJECTIVE The purpose of this study was to analyze trends in radiation exposure for AF ablation over the last 12 years at our center . METHODS We review ed prospect ively collected data of 2344 consecutive PVI procedures for either paroxysmal or persistent AF between January 2004 and December 2015 . During this period , all cases used 3-dimensional mapping systems , with 8 software and 2 hardware up grade s. Primary endpoints were fluoroscopy time , absorbed dose ( Air Kerma in mGy ) , and effective dose ( mSv ) . RESULTS In total , 1914 patients underwent initial PVI , and 430 patients underwent redo PVI using radiofrequency energy . Fluoroscopy time , and absorbed and effective doses significantly and progressively decreased over the 12-year period for initial PVI as follows : 2004 - 2006 : 61 ± 27 minutes ; 2007 - 2009 : 46 ± 14 minutes , 1365 ± 1369 mGy , 11.3 ± 12.5 mSv ; 2010 - 2012 : 31 ± 11 , 464 ± 339 mGy , 9.0 ± 10.4 mSv ; and 2013 - 2015 : 17 ± 9 minutes , 304 ± 758 mGy , 5.5 ± 6.7 mSv . CF-sensing catheters were used for 357/508 PVI only cases between 2014 and 2015 . Fluoroscopy times ( 11 ± 5 vs 21 ± 8 minutes ; P < .001 ) and absorbed dose ( 200 ± 524 vs 470 ± 1326 mGy ; P = .004 ) were significantly shorter with this catheter . CONCLUSION Radiation exposure has dramatically decreased over the last decade for PVI and is related to operator experience , annual case volume , technology evolution , and more recently CF-sensing catheters . This has significant implication s for both patient and operator long-term risk BACKGROUND Contact force ( CF ) information may improve the safety and efficacy of ablation for paroxysmal atrial fibrillation ( PAF ) . OBJECTIVE The purpose of this study was to assess the impact of CF data on ablation for PAF . METHODS Patients undergoing first-time PAF ablation were r and omized at 7 UK centers to ablation with ( CF-on ) or without ( CF-off ) CF data available to the operator , using the same ablation catheter and mapping system . An ablation CF of 5 - 40 g was targeted . Pulmonary vein ( PV ) reconnection was assessed with adenosine at 60 minutes . Follow-up for arrhythmia recurrence was for 1 year with 7-day Holter recordings at 6 and 12 months . RESULTS One hundred seventeen patients were studied ( 59 CF-on , 58 CF-off ) . In the CF-on group , a reduction in acute PV reconnection rates ( 22 % vs 32 % , P = .03 ) but no significant difference in 1-year success rates off antiarrhythmic drugs ( 49 % vs 52 % , P = .9 ) was observed . There was no difference in major complication rates : 2 of 59 ( 3 % ) CF-on , 3 of 58 ( 5 % ) CF-off ( P = .7 ) . Procedural and fluoroscopy times were not significantly different ( P>.5 ) . Overall mean CFs per ablation were not different between groups ( 13.4 [9.1 - 19.6]g CF-on , 13.4 [7.4 - 22.4]g CF-off , P = .5 ) , but a greater proportion of readings in the CF-on group were in the target range ( 80 % vs 68 % , P<.001 ) . CONCLUSION This r and omized multicenter study demonstrated that CF data availability was associated with reduced acute PV reconnection but not improved 1-year success rates , procedural and fluoroscopy times , or complication rates . There was a reduction in extremes of CF , above and below the study target range , suggesting greater CF control during ablation BACKGROUND Contact force ( CF ) monitoring could be useful in accomplishing circumferential pulmonary vein ( PV ) isolation ( CPVI ) for atrial fibrillation ( AF ) . OBJECTIVE The purpose of this study was to compare procedure parameters and outcomes between CF-guided and non-guided CPVI . METHODS Thirty-eight consecutive AF patients ( mean age 60 ± 11 years , 28 paroxysmal AF ) undergoing CPVI were r and omized to non-CF-guided ( n = 19 ) and CF-guided ( n = 19 ) groups .  CPVI was performed with the ThermoCool SmartTouch catheter in both groups . The end-point was bidirectional block between the left atrium ( LA ) and PV . In the CF group , CF was kept between 10 and 20 g during CPVI , whereas in the non-CF group , all CF information was blanked . Radiofrequency energy at 30 W in the anterior and 25 W in the posterior LA wall was applied for 20 - 25 seconds at each point . RESULTS CPVI was successfully accomplished without any major complications in both groups . Mean CF in the non-CF and CF groups were 5.9 ± 4.5 g and 11.1 ± 4.3 g , respectively , for left-side CPVI , and 9.8 ± 6.6 g and 12.1 ± 4.8 g , respectively , for right-side CPVI ( both P < .001 ) . The procedure and fluoroscopy times  for CPVI in the non-CF and CF groups were 96 ± 39 minutes and 59 ± 16 minutes , respectively ( P < .001 ) , and 22 ± 63 seconds and 9 ± 20 seconds ( P = NS ) , respectively . Total number of residual conduction gaps was 6.3 ± 3.0 in the non-CF group and 2.8 ± 1.9 in the CF group ( P < .001 ) . During 6-month follow-up , 84.2 % of patients in the non-CF group and 94.7 % in the CF group were free from any atrial tachyarrhythmias ( P = .34 ) . CONCLUSION CF-guided CPVI  is effective in reducing procedure time and additional touch-up ablation and may improve long-term outcome Background The aim of this study was to evaluate the impact of contact force ( CF ) visualization on the incidence of low and high CF during left atrial ( LA ) mapping and pulmonary vein isolation ( PVI ) . Methods CF was assessed in 70 patients who underwent PVI .  Three highly experienced operators performed all procedures . The operators were blinded to CF in group A ( 35 patients ) , and CF was displayed in group B ( 35 patients ) . In group B , optimal CF was defined as mean CF between 10 and 39 g , and operators attempted to acquire points and ablate within this range . Results A total of 8401 mapping points were analyzed during LA mapping ( group A : 4104 , group B : 4297 ) . Low CF < 10 g and high CF ≥40 g were noted in a significantly larger number of points in group A ( 37.7 vs. 12.0 % , P < 0.001 ; 11.5 vs. 1.5 % , P < 0.001 ) . At the mitral isthmus and ridge areas , CF was significantly lower ( 7.7 vs. 12.2 g , P < 0.001 ; 5.3 vs. 11.7 g , P < 0.001 ) in group A than in group B. PVI was successfully achieved in all patients . There were significant site-dependent CF differences between the two groups . Optimal CF was achieved in significantly more applications in group B ( P < 0.001 ) . There was no significant difference in atrial fibrillation ( AF ) recurrence rates after a minimum follow-up of 1 year between the two groups in this cohort ( P = 0.24 ) . No significant peri-procedural complications occurred in either group . Conclusions CF visualization can assist in avoiding both low and high CF , which may have the potential to improve lesion formation and patient safety profile . In this study , CF-guided ablation did not affect AF recurrence Purpose We prospect ively investigated the differences in pulmonary vein reconnections ( PVRs ) and clinical outcomes between contact force (CF)-guided and conventional circumferential PV isolation ( CPVI ) of atrial fibrillation ( AF ) . Methods One hundred twenty consecutive AF patients ( 63 ± 10 years ; 88 males ) undergoing an initial CPVI were r and omized to ablation with a target CF of 20 g ( CF group ; n = 60 ) or that with operators blinded to the CF information ( blind group ; n = 60 ) . Results The CF group had fewer PVRs ( 0.67 ± 0.91/patient vs. 1.16 ±  
    Output:
    