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: Background —Circumferential radiofrequency ablation around pulmonary vein ( PV ) ostia has recently been described as a new anatomic approach for atrial fibrillation ( AF ) . Methods and Results —We treated 251 consecutive patients with paroxysmal ( n=179 ) or permanent ( n=72 ) AF .  Circular PV lesions were deployed transseptally during sinus rhythm ( n=124 ) or AF ( n=127 ) using 3D electroanatomic guidance . Procedures lasted 148±26 minutes . Among 980 lesions surrounding individual PVs ( n=956 ) or 2 ipsilateral veins with close openings or common ostium ( n=24 ) , 75 % were defined as complete by a bipolar electrogram amplitude < 0.1 mV inside the lesion and a delay > 30 ms across the line . The amount of low-voltage encircled area was 3594±449 mm2 , which accounted for 23±9 % of the total left atrial ( LA ) map surface . Major complications ( cardiac tamponade ) occurred in 2 patients ( 0.8 % ) . No PV stenoses were detected by transesophageal echocardiography . After 10.4±4.5 months , 152 patients with paroxysmal AF ( 85 % ) and 49 with permanent AF ( 68 % ) were AF-free . Patients with and without AF recurrence did not differ in age , AF duration , prevalence of heart disease , or ejection fraction , but the LA diameter was significantly higher ( P < 0.001 ) in permanent AF patients with recurrence . The proportion of PVs with complete lesions was similar between patients with and without recurrence , but the latter had larger low-voltage encircled areas after radiofrequency ( expressed as percent of LA surface area;P < 0.001 ) . Conclusions —Circumferential PV ablation is a safe and effective treatment for AF . Its success is likely due to both PV trigger isolation and electroanatomic remodeling of the area encompassing the PV ostia AIMS This study examined the difference in autonomic modification ( AM ) and its effect on paroxysmal atrial fibrillation ( PAF ) recurrence between segmental pulmonary vein isolation ( S-PVI ) and circumferential PVI ( C-PVI ) . METHODS AND RESULTS Successful S-PVI or C-PVI with a basket catheter was achieved in 120 consecutive PAF patients . Serial 24 Holter-recordings were obtained before , immediately , and 1 , 3 , 6 , 12 months after the PVI to analyse the heart rate variability ( HRV ) .  Nineteen patients were excluded from analysis because of additional ablation for recurrent PAF after successful PVI . Among the residual 101 patients , 33 had PAF recurrences ( S-PVI = 44.0 % , C-PVI = 21.6 % ) at 1 year of follow-up . The root mean square of successive differences and high-frequency power reflecting parasympathetic nervous activity were significantly lower in patients with and without PAF recurrences after C-PVI and patients without PAF recurrences after S-PVI than patients with PAF recurrences after S-PVI ( P < 0.005 - 0.0001 ) . However , there were no significant differences in any HRV parameters in the immediate aftermath of PVI among the patients without PAF recurrences after S-PVI and those with and without PAF recurrences after C-PVI . CONCLUSION Although additional radiofrequency ablation for AM may be recommended after S-PVI to reduce PAF recurrences , it should be carefully determined after C-PVI Background — Pulmonary vein ( PV ) isolation is a promising new treatment for  atrial fibrillation ( AF ) . We hypothesized that isolation of large areas around both ipsilateral PVs with verification of conduction block is more effective than the isolation of each individual PV . Methods and Results — A total of 110 patients , 67 with paroxysmal AF and 43 with persistent AF , were r and omly assigned to undergo either isolation of each individual PV or isolation of large areas around both ipsilateral PVs . The isolation of each individual PV was an electrophysiologically guided , ostial segmental ablation with a 64-pole basket catheter or a 20-pole circular mapping catheter ( group I ) . Isolation of large areas was performed around the 2 ipsilateral veins with a nonfluoroscopic navigation system and a circular 20-pole mapping catheter for verification of conduction block ( group II ) . In both groups , an irrigated-tip ablation catheter ( 25 to 35 W ) was used to achieve complete isolation . Procedure and ablation times were longer in group II , whereas fluoroscopic time was significantly shorter ( P≤0.001 ) . After a follow-up period of 15±4 months , 27 patients in group I ( 49 % ) and 37 patients in group II ( 67 % ) remained free of symptoms of AF and had no AF or atrial flutter during repetitive Holter monitoring without antiarrhythmic drug treatment after a single procedure ( P≤0.05 ) . Conclusions — The rate of success was significantly higher and fluoroscopy times were significantly lower in the group with large isolation areas around both ipsilateral PVs than in those who underwent individual PV isolation Background —The pulmonary veins ( PVs ) and surrounding ostial areas frequently house focal triggers or reentrant circuits critical to the genesis of atrial fibrillation ( AF ) . We developed an anatomic approach aim ed at isolating each PV from the left atrium ( LA ) by circumferential radiofrequency ( RF ) lesions around their ostia . Methods and Results —We selected 26 patients with resistant AF , either paroxysmal ( n=14 ) or permanent ( n=12 ) . A nonfluoroscopic mapping system was used to generate 3D electroanatomic LA maps and deliver RF energy . Two maps were acquired during coronary sinus and right atrial pacing to vali date the lateral and septal PV lesions , respectively . Patients were followed up closely for ≥6 months . Procedures lasted 290±58 minutes , including 80±22 minutes for acquisition of all maps , and 118±16 RF pulses were deployed . Among 14 patients in AF at the beginning of the procedure , 64 % had sinus rhythm restoration during ablation . PV isolation was demonstrated in 76 % of 104 PVs treated by low peak-to-peak electrogram amplitude ( 0.08±0.02 mV ) inside the circular line and by disparity in activation times ( 58±11 ms ) across the lesion . After 9±3 months , 22 patients ( 85 % ) were AF-free , including 62 % not taking and 23 % taking antiarrhythmic drugs , with no difference ( P = NS ) between paroxysmal and permanent AF . No thromboembolic events or PV stenoses were observed by transesophageal echocardiography . Conclusions —Radiofrequency PV isolation with electroanatomic guidance is safe and effective in either paroxysmal or permanent AF Background —Atrial fibrillation ( AF ) is frequently initiated from pulmonary veins ( PVs ) , but little is known of the electrophysiological properties of PVs . Methods and Results —Two groups were studied : 28 patients ( 49±13 years old ) with paroxysmal AF and 20 control patients ( 49±14 years old ) without AF . Effective and functional refractory period and conduction time from PV to left atrium ( LA ) were compared in the 2 groups by use of programmed stimulation with a single extrastimulus in the PVs and LA . In the AF group , the venous effective refractory periods ( ERPs ) were shorter than that of the LA : 185±71 versus 253±21 ms , P < 0.001 , whereas in the control group , they were longer ( 282±45 versus 253±41 ms , P = 0.009 ) . The venous ERPs and functional refractory periods in patients with AF were also shorter than that observed in control subjects ( 185±71 versus 282±45 ms and 210±77 versus 315±43 ms , respectively , P < 0.001 ) , whereas LA ERPs were not significantly different . Decremental conduction in PVs was more frequent ( 93 % versus 56 % , P = 0.01 ) and had a greater increment ( 102±65 versus 42±40 ms , P < 0.001 ) in patients with AF . Finally , AF was more frequently induced when pacing was performed in PVs ( 22 of 90 ) versus LA ( 1 of 81 ) in patients with AF ( P < 0.001 ) . Conclusions —The PVs of patients with AF exhibited distinctive electrophysiological properties , which were strikingly different from those of patients devoid of AF , potentially explaining their arrhythmogenicity Background —Segmental ostial catheter ablation ( SOCA ) to isolate the pulmonary veins ( PVs ) and left atrial catheter ablation ( LACA ) to encircle the PVs both may eliminate paroxysmal atrial fibrillation ( PAF ) .  The relative efficacy of these 2 techniques has not been directly compared . Methods and Results —Of 80 consecutive patients with symptomatic PAF ( age , 52±10 years ) , 40 patients underwent  PV isolation by SOCA and 40 patients underwent LACA to encircle the PVs . During SOCA , ostial PV potentials recorded with a ring catheter were targeted . LACA was performed by encircling the left- and right-sided PVs 1 to 2 cm from the ostia and was guided by an electroanatomic mapping system ; ablation lines also were created in the mitral isthmus and posterior left atrium . The mean procedure and fluoroscopy times were 156±45 and 50±17 minutes for SOCA and 149±33 and 39±12 minutes for LACA , respectively . At 6 months , 67 % of patients who underwent SOCA and 88 % of patients who underwent LACA  were free of symptomatic PAF when not taking antiarrhythmic drug therapy ( P = 0.02 ) . Among the variables of age , sex , duration and frequency of PAF , ejection fraction , left atrial size , structural heart disease , and the ablation technique , only an increased left atrial size and the SOCA  technique were independent predictors of recurrent PAF . The only complication was left atrial flutter in a patient who underwent LACA . Conclusions —In patients undergoing catheter ablation for PAF  , LACA to encircle the PVs is more effective than SOCA BACKGROUND Stepwise segmental pulmonary vein isolation ( SPVI ) and circumferential pulmonary vein isolation ( CPVI ) have been developed to treat patients with atrial fibrillation ( AF ) , but the preferable approach for paroxysmal AF ( PAF ) has not been established . METHODS AND RESULTS One hundred and ten patients with symptomatic PAF were r and omized into a stepwise SPVI group ( n=55 ) or CPVI group ( n=55 ) . Systemic SPVI combined with left atrial linear ablation tailored by inducibility of AF was performed in the stepwise SPVI group . Circumferential linear ablation around the left and right-sided pulmonary veins ( PVs ) guided by 3-dimensional electroanatomic mapping was performed in the CPVI group . The endpoints of ablation are non-induciblity of AF in the stepwise SPVI group and continuity of circular lesions combined with PV isolation in the CPVI group . After the initial procedures , atrial tachyarrhythmis ( ATa ) recurred within the first 3 months in 23 of the 55 patients ( 41.8 % ) who underwent stepwise SPVI and in 20 of the 55 patients ( 36.4 % ) who had CPVI ( p=0.69 ) . Repeat procedures were performed in 7 patients from the stepwise SPVI group and 5 from the CPVI group ( p=0.76 ) . During the 3 - 9 months after the last procedure , 46 patients ( 83.6 % ) from the CPVI group and 43 ( 78.2 % ) from the stepwise SPVI group did not have symptomatic ATa while not taking anti-arrhythmic drugs ( p=0.63 ) . Severe subcutaneous hematoma or PV stenosis occurred in 3 patients . CONCLUSIONS The efficacy of stepwise SPVI is comparable to that of CPVI for patients with PAF Aims Previous studies have analyzed the efficacy of atrial fibrillation (  AF )  ablation in series of consecutive patients or comparing methods in a r and omized way , without taking account individual patient characteristics . The purpose of this study was to evaluate the results of a strategy based on selecting the ablation method according to patient clinical features in drug-refractory paroxysmal or persistent AF . Methods and results Patients with left atrial diameter ≤40 mm and runs of atrial tachycardia of more than ten beats during Holter recording were selected for selective segmental ostial ablation ( SSOA ) in order to disconnect only those pulmonary veins with electrical potentials . The remaining patients underwent circumferential pulmonary veins ablation ( CPVA ) to modify left atrial substrate by extensive linear lesions . A group of 131 consecutive patients were included . Mean follow-up was 21.5 ± 15.2 months . In paroxysmal AF , 44 and 55 patients were selected for SSOA and CPVA , respectively , and the efficacy of the procedure was similar in the two groups ( 77 vs 74 % ; log 
    Output:
    
agent
Our primary finding is that PVI performed with a wide antral approach is more effective than ostial PVI in achieving freedom from total atrial tachyarrhythmia recurrence at long-term follow-up
***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: Background —Circumferential radiofrequency ablation around pulmonary vein ( PV ) ostia has recently been described as a new anatomic approach for atrial fibrillation ( AF ) . Methods and Results —We treated 251 consecutive patients with paroxysmal ( n=179 ) or permanent ( n=72 ) AF .  Circular PV lesions were deployed transseptally during sinus rhythm ( n=124 ) or AF ( n=127 ) using 3D electroanatomic guidance . Procedures lasted 148±26 minutes . Among 980 lesions surrounding individual PVs ( n=956 ) or 2 ipsilateral veins with close openings or common ostium ( n=24 ) , 75 % were defined as complete by a bipolar electrogram amplitude < 0.1 mV inside the lesion and a delay > 30 ms across the line . The amount of low-voltage encircled area was 3594±449 mm2 , which accounted for 23±9 % of the total left atrial ( LA ) map surface . Major complications ( cardiac tamponade ) occurred in 2 patients ( 0.8 % ) . No PV stenoses were detected by transesophageal echocardiography . After 10.4±4.5 months , 152 patients with paroxysmal AF ( 85 % ) and 49 with permanent AF ( 68 % ) were AF-free . Patients with and without AF recurrence did not differ in age , AF duration , prevalence of heart disease , or ejection fraction , but the LA diameter was significantly higher ( P < 0.001 ) in permanent AF patients with recurrence . The proportion of PVs with complete lesions was similar between patients with and without recurrence , but the latter had larger low-voltage encircled areas after radiofrequency ( expressed as percent of LA surface area;P < 0.001 ) . Conclusions —Circumferential PV ablation is a safe and effective treatment for AF . Its success is likely due to both PV trigger isolation and electroanatomic remodeling of the area encompassing the PV ostia AIMS This study examined the difference in autonomic modification ( AM ) and its effect on paroxysmal atrial fibrillation ( PAF ) recurrence between segmental pulmonary vein isolation ( S-PVI ) and circumferential PVI ( C-PVI ) . METHODS AND RESULTS Successful S-PVI or C-PVI with a basket catheter was achieved in 120 consecutive PAF patients . Serial 24 Holter-recordings were obtained before , immediately , and 1 , 3 , 6 , 12 months after the PVI to analyse the heart rate variability ( HRV ) .  Nineteen patients were excluded from analysis because of additional ablation for recurrent PAF after successful PVI . Among the residual 101 patients , 33 had PAF recurrences ( S-PVI = 44.0 % , C-PVI = 21.6 % ) at 1 year of follow-up . The root mean square of successive differences and high-frequency power reflecting parasympathetic nervous activity were significantly lower in patients with and without PAF recurrences after C-PVI and patients without PAF recurrences after S-PVI than patients with PAF recurrences after S-PVI ( P < 0.005 - 0.0001 ) . However , there were no significant differences in any HRV parameters in the immediate aftermath of PVI among the patients without PAF recurrences after S-PVI and those with and without PAF recurrences after C-PVI . CONCLUSION Although additional radiofrequency ablation for AM may be recommended after S-PVI to reduce PAF recurrences , it should be carefully determined after C-PVI Background — Pulmonary vein ( PV ) isolation is a promising new treatment for  atrial fibrillation ( AF ) . We hypothesized that isolation of large areas around both ipsilateral PVs with verification of conduction block is more effective than the isolation of each individual PV . Methods and Results — A total of 110 patients , 67 with paroxysmal AF and 43 with persistent AF , were r and omly assigned to undergo either isolation of each individual PV or isolation of large areas around both ipsilateral PVs . The isolation of each individual PV was an electrophysiologically guided , ostial segmental ablation with a 64-pole basket catheter or a 20-pole circular mapping catheter ( group I ) . Isolation of large areas was performed around the 2 ipsilateral veins with a nonfluoroscopic navigation system and a circular 20-pole mapping catheter for verification of conduction block ( group II ) . In both groups , an irrigated-tip ablation catheter ( 25 to 35 W ) was used to achieve complete isolation . Procedure and ablation times were longer in group II , whereas fluoroscopic time was significantly shorter ( P≤0.001 ) . After a follow-up period of 15±4 months , 27 patients in group I ( 49 % ) and 37 patients in group II ( 67 % ) remained free of symptoms of AF and had no AF or atrial flutter during repetitive Holter monitoring without antiarrhythmic drug treatment after a single procedure ( P≤0.05 ) . Conclusions — The rate of success was significantly higher and fluoroscopy times were significantly lower in the group with large isolation areas around both ipsilateral PVs than in those who underwent individual PV isolation Background —The pulmonary veins ( PVs ) and surrounding ostial areas frequently house focal triggers or reentrant circuits critical to the genesis of atrial fibrillation ( AF ) . We developed an anatomic approach aim ed at isolating each PV from the left atrium ( LA ) by circumferential radiofrequency ( RF ) lesions around their ostia . Methods and Results —We selected 26 patients with resistant AF , either paroxysmal ( n=14 ) or permanent ( n=12 ) . A nonfluoroscopic mapping system was used to generate 3D electroanatomic LA maps and deliver RF energy . Two maps were acquired during coronary sinus and right atrial pacing to vali date the lateral and septal PV lesions , respectively . Patients were followed up closely for ≥6 months . Procedures lasted 290±58 minutes , including 80±22 minutes for acquisition of all maps , and 118±16 RF pulses were deployed . Among 14 patients in AF at the beginning of the procedure , 64 % had sinus rhythm restoration during ablation . PV isolation was demonstrated in 76 % of 104 PVs treated by low peak-to-peak electrogram amplitude ( 0.08±0.02 mV ) inside the circular line and by disparity in activation times ( 58±11 ms ) across the lesion . After 9±3 months , 22 patients ( 85 % ) were AF-free , including 62 % not taking and 23 % taking antiarrhythmic drugs , with no difference ( P = NS ) between paroxysmal and permanent AF . No thromboembolic events or PV stenoses were observed by transesophageal echocardiography . Conclusions —Radiofrequency PV isolation with electroanatomic guidance is safe and effective in either paroxysmal or permanent AF Background —Atrial fibrillation ( AF ) is frequently initiated from pulmonary veins ( PVs ) , but little is known of the electrophysiological properties of PVs . Methods and Results —Two groups were studied : 28 patients ( 49±13 years old ) with paroxysmal AF and 20 control patients ( 49±14 years old ) without AF . Effective and functional refractory period and conduction time from PV to left atrium ( LA ) were compared in the 2 groups by use of programmed stimulation with a single extrastimulus in the PVs and LA . In the AF group , the venous effective refractory periods ( ERPs ) were shorter than that of the LA : 185±71 versus 253±21 ms , P < 0.001 , whereas in the control group , they were longer ( 282±45 versus 253±41 ms , P = 0.009 ) . The venous ERPs and functional refractory periods in patients with AF were also shorter than that observed in control subjects ( 185±71 versus 282±45 ms and 210±77 versus 315±43 ms , respectively , P < 0.001 ) , whereas LA ERPs were not significantly different . Decremental conduction in PVs was more frequent ( 93 % versus 56 % , P = 0.01 ) and had a greater increment ( 102±65 versus 42±40 ms , P < 0.001 ) in patients with AF . Finally , AF was more frequently induced when pacing was performed in PVs ( 22 of 90 ) versus LA ( 1 of 81 ) in patients with AF ( P < 0.001 ) . Conclusions —The PVs of patients with AF exhibited distinctive electrophysiological properties , which were strikingly different from those of patients devoid of AF , potentially explaining their arrhythmogenicity Background —Segmental ostial catheter ablation ( SOCA ) to isolate the pulmonary veins ( PVs ) and left atrial catheter ablation ( LACA ) to encircle the PVs both may eliminate paroxysmal atrial fibrillation ( PAF ) .  The relative efficacy of these 2 techniques has not been directly compared . Methods and Results —Of 80 consecutive patients with symptomatic PAF ( age , 52±10 years ) , 40 patients underwent  PV isolation by SOCA and 40 patients underwent LACA to encircle the PVs . During SOCA , ostial PV potentials recorded with a ring catheter were targeted . LACA was performed by encircling the left- and right-sided PVs 1 to 2 cm from the ostia and was guided by an electroanatomic mapping system ; ablation lines also were created in the mitral isthmus and posterior left atrium . The mean procedure and fluoroscopy times were 156±45 and 50±17 minutes for SOCA and 149±33 and 39±12 minutes for LACA , respectively . At 6 months , 67 % of patients who underwent SOCA and 88 % of patients who underwent LACA  were free of symptomatic PAF when not taking antiarrhythmic drug therapy ( P = 0.02 ) . Among the variables of age , sex , duration and frequency of PAF , ejection fraction , left atrial size , structural heart disease , and the ablation technique , only an increased left atrial size and the SOCA  technique were independent predictors of recurrent PAF . The only complication was left atrial flutter in a patient who underwent LACA . Conclusions —In patients undergoing catheter ablation for PAF  , LACA to encircle the PVs is more effective than SOCA BACKGROUND Stepwise segmental pulmonary vein isolation ( SPVI ) and circumferential pulmonary vein isolation ( CPVI ) have been developed to treat patients with atrial fibrillation ( AF ) , but the preferable approach for paroxysmal AF ( PAF ) has not been established . METHODS AND RESULTS One hundred and ten patients with symptomatic PAF were r and omized into a stepwise SPVI group ( n=55 ) or CPVI group ( n=55 ) . Systemic SPVI combined with left atrial linear ablation tailored by inducibility of AF was performed in the stepwise SPVI group . Circumferential linear ablation around the left and right-sided pulmonary veins ( PVs ) guided by 3-dimensional electroanatomic mapping was performed in the CPVI group . The endpoints of ablation are non-induciblity of AF in the stepwise SPVI group and continuity of circular lesions combined with PV isolation in the CPVI group . After the initial procedures , atrial tachyarrhythmis ( ATa ) recurred within the first 3 months in 23 of the 55 patients ( 41.8 % ) who underwent stepwise SPVI and in 20 of the 55 patients ( 36.4 % ) who had CPVI ( p=0.69 ) . Repeat procedures were performed in 7 patients from the stepwise SPVI group and 5 from the CPVI group ( p=0.76 ) . During the 3 - 9 months after the last procedure , 46 patients ( 83.6 % ) from the CPVI group and 43 ( 78.2 % ) from the stepwise SPVI group did not have symptomatic ATa while not taking anti-arrhythmic drugs ( p=0.63 ) . Severe subcutaneous hematoma or PV stenosis occurred in 3 patients . CONCLUSIONS The efficacy of stepwise SPVI is comparable to that of CPVI for patients with PAF Aims Previous studies have analyzed the efficacy of atrial fibrillation (  AF )  ablation in series of consecutive patients or comparing methods in a r and omized way , without taking account individual patient characteristics . The purpose of this study was to evaluate the results of a strategy based on selecting the ablation method according to patient clinical features in drug-refractory paroxysmal or persistent AF . Methods and results Patients with left atrial diameter ≤40 mm and runs of atrial tachycardia of more than ten beats during Holter recording were selected for selective segmental ostial ablation ( SSOA ) in order to disconnect only those pulmonary veins with electrical potentials . The remaining patients underwent circumferential pulmonary veins ablation ( CPVA ) to modify left atrial substrate by extensive linear lesions . A group of 131 consecutive patients were included . Mean follow-up was 21.5 ± 15.2 months . In paroxysmal AF , 44 and 55 patients were selected for SSOA and CPVA , respectively , and the efficacy of the procedure was similar in the two groups ( 77 vs 74 % ; log 
    Output:
    