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: CONTEXT Treatment with antiarrhythmic drugs and anticoagulation is considered first-line therapy in patients with symptomatic atrial fibrillation ( AF ) .  Pulmonary vein isolation ( PVI ) with radiofrequency ablation may cure AF , obviating the need for antiarrhythmic drugs and anticoagulation . OBJECTIVE To determine whether PVI is feasible as first-line therapy for treating patients with symptomatic AF . DESIGN , SETTING , AND PARTICIPANTS A multicenter prospect i ve r and omized study conducted from December 31 , 2001 , to July 1 , 2002 , of 70 patients aged 18 to 75 years who experienced monthly symptomatic AF episodes for at least 3 months and had not been treated with antiarrhythmic drugs . INTERVENTION Patients were r and omized to receive either PVI using radiofrequency ablation ( n=33 ) or antiarrhythmic drug treatment ( n=37 ) , with a 1-year follow-up . MAIN OUTCOME MEASURES Recurrence of AF , hospitalization , and quality of life assessment . RESULTS Two patients in the antiarrhythmic drug treatment group and 1 patient in the PVI group were lost to follow-up . At the end of 1-year follow-up , 22 ( 63 % ) of 35 patients who received antiarrhythmic drugs had at least 1 recurrence of symptomatic AF compared with 4 ( 13 % ) of 32 patients who received PVI ( P<.001 ) . Hospitalization during 1-year follow-up occurred in 19 ( 54 % ) of 35 patients in the antiarrhythmic drug group compared with 3 ( 9 % ) of 32 in the PVI group ( P<.001 ) . In the antiarrhythmic drug group , the mean ( SD ) number of AF episodes decreased from 12 ( 7 ) to 6 ( 4 ) , after initiating therapy ( P = .01 ) . At 6-month follow-up , the improvement in quality of life of patients in the PVI group was significantly better than the improvement in the antiarrhythmic drug group in 5 subclasses of the Short-Form 36 health survey . There were no thromboembolic events in either group . Asymptomatic mild or moderate pulmonary vein stenosis was documented in 2 ( 6 % ) of 32 patients in the PVI group . CONCLUSION Pulmonary vein isolation appears to be a feasible first-line approach for treating patients with symptomatic AF . Larger studies are needed to confirm its safety and efficacy Background —Circumferential pulmonary vein ablation ( CPVA ) is effective in curing  atrial fibrillation ( AF ) , but new-onset left atrial tachycardia ( AT ) is a potential complication . We evaluated whether a modified CPVA approach including additional ablation lines on posterior wall and the mitral isthmus would reduce the incidence of AT after PV ablation . Methods and Results —A total of 560 patients ( 291 men , 52 % ; age , 56.5±7.3 years ) entered the study ; 280 were r and omized to CPVA alone ( group 1 ) and 280 to modified CPVA ( group 2 ) . The primary end point was freedom from AT after the procedure . In group 1 , 28 patients ( 10 % ) experienced new-onset AT , and 41 ( 14.3 % ) experienced recurrent AF . In group 2 , 11 patients ( 3.9 % ) experienced AT , and 36 ( 12.9 % ) had recurrent AF . Group 1 was more likely to experience AT than group 2 ( P=0.005 ) . Freedom from AF after ablation was similar in both groups ( P=0.57 ) . Among those in group 1 , gap-related macroreentrant AT was documented in 23 of the 28 patients ( 82 % ) , and focal AT was found in 5 ( 18 % ) . In group 2 , gap-related macroreentrant AT was found in 8 of the 11 patients ( 73 % ) , and focal AT was seen in 3 ( 27 % ) . Two patients in group 1 and 1 patient in group 2 had both AT and AF . The strongest predictor of AT was the presence of gaps ( P<0.001 ) . Conclusions —Modified CPVA is as effective as CPVA in preventing AF but is associated with a lower risk of developing incessant AT 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 —The AFFIRM Study showed that treatment of patients with atrial fibrillation and a high risk for stroke or death with a rhythm-control strategy offered no survival advantage over a rate-control strategy in an intention-to-treat analysis . This article reports an “ on-treatment ” analysis of the relationship of survival to cardiac rhythm and treatment as they changed over time . Methods and Results —Modeling techniques were used to determine the relationships among survival , baseline clinical variables , and time-dependent variables . The following baseline variables were significantly associated with an increased risk of death : increasing age , coronary artery disease , congestive heart failure , diabetes , stroke or transient ischemic attack , smoking , left ventricular dysfunction , and mitral regurgitation . Among the time-dependent variables , the presence of sinus rhythm ( SR ) was associated with a lower risk of death , as was warfarin use . Antiarrhythmic drugs ( AADs ) were associated with increased mortality only after adjustment for the presence of SR . Consistent with the original intention-to-treat analysis , AADs were no longer associated with mortality when SR was removed from the model . Conclusions —Warfarin use improves survival . SR is either an important determinant of survival or a marker for other factors associated with survival that were not recorded , determined , or included in the survival model . Currently available AADs are not associated with improved survival , which suggests that any beneficial antiarrhythmic effects of AADs are offset by their adverse effects . If an effective method for maintaining SR with fewer adverse effects were available , it might be beneficial BACKGROUND We conducted a r and omized , controlled trial of circumferential pulmonary-vein ablation for the treatment of chronic atrial fibrillation . METHODS A total of 146 patients with a mean ( + /-SD ) age of 57+/-9 years who had chronic atrial fibrillation were r and omly assigned to receive amiodarone and undergo two cardioversions during the first three months alone ( the control group ) or in combination with circumferential pulmonary-vein ablation . Cardiac rhythm was assessed with daily telephonic transmissions for one year . The left atrial diameter and the severity of symptoms were assessed at 12 months . RESULTS Among the 77 patients assigned to undergo circumferential pulmonary-vein ablation , ablation was repeated because of recurrent atrial fibrillation in 26 percent of patients and atypical atrial flutter in 6 percent . An intention-to-treat analysis showed that 74 percent of patients in the ablation group and 58 percent of those in the control group were free of recurrent atrial fibrillation or flutter without antiarrhythmic-drug therapy at one year ( P=0.05 ) . Among the 69 patients in the control group , 53 ( 77 percent ) crossed over to undergo circumferential pulmonary-vein ablation for recurrent atrial fibrillation by one year and only 3 ( 4 percent ) were in sinus rhythm without antiarrhythmic-drug therapy or ablation . There were significant decreases in the left atrial diameter ( 12+/-11 percent , P<0.001 ) and the symptom severity score ( 59+/-21 percent , P<0.001 ) among patients who remained in sinus rhythm after circumferential pulmonary-vein ablation . Except for atypical atrial flutter , there were no complications attributable to circumferential pulmonary-vein ablation . CONCLUSIONS Sinus rhythm can be maintained long term in the majority of patients with chronic atrial fibrillation by means of circumferential pulmonary-vein ablation independently of the effects of antiarrhythmic-drug therapy , cardioversion , or both . The maintenance of sinus rhythm is associated with a significant decrease in both the severity of symptoms and the left atrial diameter Background —The objective of this study was to assess the incidence and impact of asymptomatic arrhythmia in patients with highly symptomatic atrial fibrillation ( AF ) who qualified for radiofrequency ( RF ) catheter ablation .  Methods and Results —In this prospect i ve study , 114 patients with at least 3 documented AF episodes together with corresponding symptoms and an ineffective trial of at least 1 antiarrhythmic drug were selected for  RF ablation .  With the use of CARTO , circumferential lesions around the pulmonary veins and linear lesions at the roof of the left atrium and along the left atrial isthmus were placed . A continuous , 7-day , Holter session was recorded before ablation , right after ablation , and after 3 , 6 , and 12 months of follow-up . During each 7-day Holter monitoring , the patients recorded quality and duration of any complaints by using a detailed symptom log . More than 70 000 hours of ECG recording were analyzed . In the 7-day Holter records before ablation , 92 of 114 patients ( 81 % ) had documented AF episodes . All episodes were symptomatic in 35 patients ( 38 % ) . In 52 patients ( 57 % ) , both symptomatic and asymptomatic episodes were recorded , whereas in 5 patients ( 5 % ) , all documented AF episodes were asymptomatic . After ablation , the percentage of patients with only asymptomatic AF recurrences increased to 37 % ( P<0.05 ) at the 6-month follow-up . An analysis of patient characteristics and arrhythmia patterns failed to identify a specific subset who were at high risk for the development of asymptomatic AF . Conclusions —Even in patients presenting with highly symptomatic AF , asymptomatic episodes may occur and significantly increase after catheter ablation . A symptom-only – based follow-up would substantially overestimate the success rate . Objective measures such as long-term Holter monitoring are needed to identify asymptomatic AF recurrences after ablation OBJECTIVES We tested the hypothesis that the response to flecainide infusion can identify patients with atrial fibrillation ( AF ) in whom the hybrid pharmacologic and ablation therapy reduces the recurrences of AF . BACKGROUND Infusion of class IC anti-arrhythmic drugs may promote transformation of AF into atrial flutter . Catheter ablation of atrial flutter has been demonstrated to be highly effective in preventing recurrences of atrial flutter . METHODS Seventy-one consecutive patients with paroxysmal or chronic AF , in whom flecainide infusion ( 2 mg/kg body weight , intravenously ) determined the transformation of AF into common atrial flutter ( positive response ) , were r and omized to receive one of the following treatments : oral pharmacologic treatment with flecainide ( group A , n = 23 ) ; the hybrid treatment ( catheter ablation of the inferior vena cava-tricuspid annulus isthmus , plus oral flecainide ) ( group B , n = 24 ) ; or catheter ablation of the isthmus only ( group C , n = 24 ) . Thirty-seven patients with a negative response to flecainide , who chose to be su bmi tted to the hybrid treatment , were selected as the control group ( group D ) . RESULTS During a mean follow-up period of 24 + /- 7.2 months , the recurrences of AF and atrial flutter in group B ( 42 % ) were significantly lower than those in group A ( 78 % , p < 0.001 ) , group C ( 92 % , p < 0.001 ) and group D ( 92 % , p < 0.001 ) . CONCLUSIONS The creation of a complete bi-directional conduction block at the inferior vena cava-tricuspid annulus isthmus , plus flecainide administration , reduces the recurrences of both AF and atrial flutter in patients with class IC atrial flutter . Moreover , the early response to fle 
    Output:
    
agent
We observed statistically significantly better AT recurrence-free survival with CPVA than with ADT .
***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: CONTEXT Treatment with antiarrhythmic drugs and anticoagulation is considered first-line therapy in patients with symptomatic atrial fibrillation ( AF ) .  Pulmonary vein isolation ( PVI ) with radiofrequency ablation may cure AF , obviating the need for antiarrhythmic drugs and anticoagulation . OBJECTIVE To determine whether PVI is feasible as first-line therapy for treating patients with symptomatic AF . DESIGN , SETTING , AND PARTICIPANTS A multicenter prospect i ve r and omized study conducted from December 31 , 2001 , to July 1 , 2002 , of 70 patients aged 18 to 75 years who experienced monthly symptomatic AF episodes for at least 3 months and had not been treated with antiarrhythmic drugs . INTERVENTION Patients were r and omized to receive either PVI using radiofrequency ablation ( n=33 ) or antiarrhythmic drug treatment ( n=37 ) , with a 1-year follow-up . MAIN OUTCOME MEASURES Recurrence of AF , hospitalization , and quality of life assessment . RESULTS Two patients in the antiarrhythmic drug treatment group and 1 patient in the PVI group were lost to follow-up . At the end of 1-year follow-up , 22 ( 63 % ) of 35 patients who received antiarrhythmic drugs had at least 1 recurrence of symptomatic AF compared with 4 ( 13 % ) of 32 patients who received PVI ( P<.001 ) . Hospitalization during 1-year follow-up occurred in 19 ( 54 % ) of 35 patients in the antiarrhythmic drug group compared with 3 ( 9 % ) of 32 in the PVI group ( P<.001 ) . In the antiarrhythmic drug group , the mean ( SD ) number of AF episodes decreased from 12 ( 7 ) to 6 ( 4 ) , after initiating therapy ( P = .01 ) . At 6-month follow-up , the improvement in quality of life of patients in the PVI group was significantly better than the improvement in the antiarrhythmic drug group in 5 subclasses of the Short-Form 36 health survey . There were no thromboembolic events in either group . Asymptomatic mild or moderate pulmonary vein stenosis was documented in 2 ( 6 % ) of 32 patients in the PVI group . CONCLUSION Pulmonary vein isolation appears to be a feasible first-line approach for treating patients with symptomatic AF . Larger studies are needed to confirm its safety and efficacy Background —Circumferential pulmonary vein ablation ( CPVA ) is effective in curing  atrial fibrillation ( AF ) , but new-onset left atrial tachycardia ( AT ) is a potential complication . We evaluated whether a modified CPVA approach including additional ablation lines on posterior wall and the mitral isthmus would reduce the incidence of AT after PV ablation . Methods and Results —A total of 560 patients ( 291 men , 52 % ; age , 56.5±7.3 years ) entered the study ; 280 were r and omized to CPVA alone ( group 1 ) and 280 to modified CPVA ( group 2 ) . The primary end point was freedom from AT after the procedure . In group 1 , 28 patients ( 10 % ) experienced new-onset AT , and 41 ( 14.3 % ) experienced recurrent AF . In group 2 , 11 patients ( 3.9 % ) experienced AT , and 36 ( 12.9 % ) had recurrent AF . Group 1 was more likely to experience AT than group 2 ( P=0.005 ) . Freedom from AF after ablation was similar in both groups ( P=0.57 ) . Among those in group 1 , gap-related macroreentrant AT was documented in 23 of the 28 patients ( 82 % ) , and focal AT was found in 5 ( 18 % ) . In group 2 , gap-related macroreentrant AT was found in 8 of the 11 patients ( 73 % ) , and focal AT was seen in 3 ( 27 % ) . Two patients in group 1 and 1 patient in group 2 had both AT and AF . The strongest predictor of AT was the presence of gaps ( P<0.001 ) . Conclusions —Modified CPVA is as effective as CPVA in preventing AF but is associated with a lower risk of developing incessant AT 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 —The AFFIRM Study showed that treatment of patients with atrial fibrillation and a high risk for stroke or death with a rhythm-control strategy offered no survival advantage over a rate-control strategy in an intention-to-treat analysis . This article reports an “ on-treatment ” analysis of the relationship of survival to cardiac rhythm and treatment as they changed over time . Methods and Results —Modeling techniques were used to determine the relationships among survival , baseline clinical variables , and time-dependent variables . The following baseline variables were significantly associated with an increased risk of death : increasing age , coronary artery disease , congestive heart failure , diabetes , stroke or transient ischemic attack , smoking , left ventricular dysfunction , and mitral regurgitation . Among the time-dependent variables , the presence of sinus rhythm ( SR ) was associated with a lower risk of death , as was warfarin use . Antiarrhythmic drugs ( AADs ) were associated with increased mortality only after adjustment for the presence of SR . Consistent with the original intention-to-treat analysis , AADs were no longer associated with mortality when SR was removed from the model . Conclusions —Warfarin use improves survival . SR is either an important determinant of survival or a marker for other factors associated with survival that were not recorded , determined , or included in the survival model . Currently available AADs are not associated with improved survival , which suggests that any beneficial antiarrhythmic effects of AADs are offset by their adverse effects . If an effective method for maintaining SR with fewer adverse effects were available , it might be beneficial BACKGROUND We conducted a r and omized , controlled trial of circumferential pulmonary-vein ablation for the treatment of chronic atrial fibrillation . METHODS A total of 146 patients with a mean ( + /-SD ) age of 57+/-9 years who had chronic atrial fibrillation were r and omly assigned to receive amiodarone and undergo two cardioversions during the first three months alone ( the control group ) or in combination with circumferential pulmonary-vein ablation . Cardiac rhythm was assessed with daily telephonic transmissions for one year . The left atrial diameter and the severity of symptoms were assessed at 12 months . RESULTS Among the 77 patients assigned to undergo circumferential pulmonary-vein ablation , ablation was repeated because of recurrent atrial fibrillation in 26 percent of patients and atypical atrial flutter in 6 percent . An intention-to-treat analysis showed that 74 percent of patients in the ablation group and 58 percent of those in the control group were free of recurrent atrial fibrillation or flutter without antiarrhythmic-drug therapy at one year ( P=0.05 ) . Among the 69 patients in the control group , 53 ( 77 percent ) crossed over to undergo circumferential pulmonary-vein ablation for recurrent atrial fibrillation by one year and only 3 ( 4 percent ) were in sinus rhythm without antiarrhythmic-drug therapy or ablation . There were significant decreases in the left atrial diameter ( 12+/-11 percent , P<0.001 ) and the symptom severity score ( 59+/-21 percent , P<0.001 ) among patients who remained in sinus rhythm after circumferential pulmonary-vein ablation . Except for atypical atrial flutter , there were no complications attributable to circumferential pulmonary-vein ablation . CONCLUSIONS Sinus rhythm can be maintained long term in the majority of patients with chronic atrial fibrillation by means of circumferential pulmonary-vein ablation independently of the effects of antiarrhythmic-drug therapy , cardioversion , or both . The maintenance of sinus rhythm is associated with a significant decrease in both the severity of symptoms and the left atrial diameter Background —The objective of this study was to assess the incidence and impact of asymptomatic arrhythmia in patients with highly symptomatic atrial fibrillation ( AF ) who qualified for radiofrequency ( RF ) catheter ablation .  Methods and Results —In this prospect i ve study , 114 patients with at least 3 documented AF episodes together with corresponding symptoms and an ineffective trial of at least 1 antiarrhythmic drug were selected for  RF ablation .  With the use of CARTO , circumferential lesions around the pulmonary veins and linear lesions at the roof of the left atrium and along the left atrial isthmus were placed . A continuous , 7-day , Holter session was recorded before ablation , right after ablation , and after 3 , 6 , and 12 months of follow-up . During each 7-day Holter monitoring , the patients recorded quality and duration of any complaints by using a detailed symptom log . More than 70 000 hours of ECG recording were analyzed . In the 7-day Holter records before ablation , 92 of 114 patients ( 81 % ) had documented AF episodes . All episodes were symptomatic in 35 patients ( 38 % ) . In 52 patients ( 57 % ) , both symptomatic and asymptomatic episodes were recorded , whereas in 5 patients ( 5 % ) , all documented AF episodes were asymptomatic . After ablation , the percentage of patients with only asymptomatic AF recurrences increased to 37 % ( P<0.05 ) at the 6-month follow-up . An analysis of patient characteristics and arrhythmia patterns failed to identify a specific subset who were at high risk for the development of asymptomatic AF . Conclusions —Even in patients presenting with highly symptomatic AF , asymptomatic episodes may occur and significantly increase after catheter ablation . A symptom-only – based follow-up would substantially overestimate the success rate . Objective measures such as long-term Holter monitoring are needed to identify asymptomatic AF recurrences after ablation OBJECTIVES We tested the hypothesis that the response to flecainide infusion can identify patients with atrial fibrillation ( AF ) in whom the hybrid pharmacologic and ablation therapy reduces the recurrences of AF . BACKGROUND Infusion of class IC anti-arrhythmic drugs may promote transformation of AF into atrial flutter . Catheter ablation of atrial flutter has been demonstrated to be highly effective in preventing recurrences of atrial flutter . METHODS Seventy-one consecutive patients with paroxysmal or chronic AF , in whom flecainide infusion ( 2 mg/kg body weight , intravenously ) determined the transformation of AF into common atrial flutter ( positive response ) , were r and omized to receive one of the following treatments : oral pharmacologic treatment with flecainide ( group A , n = 23 ) ; the hybrid treatment ( catheter ablation of the inferior vena cava-tricuspid annulus isthmus , plus oral flecainide ) ( group B , n = 24 ) ; or catheter ablation of the isthmus only ( group C , n = 24 ) . Thirty-seven patients with a negative response to flecainide , who chose to be su bmi tted to the hybrid treatment , were selected as the control group ( group D ) . RESULTS During a mean follow-up period of 24 + /- 7.2 months , the recurrences of AF and atrial flutter in group B ( 42 % ) were significantly lower than those in group A ( 78 % , p < 0.001 ) , group C ( 92 % , p < 0.001 ) and group D ( 92 % , p < 0.001 ) . CONCLUSIONS The creation of a complete bi-directional conduction block at the inferior vena cava-tricuspid annulus isthmus , plus flecainide administration , reduces the recurrences of both AF and atrial flutter in patients with class IC atrial flutter . Moreover , the early response to fle 
    Output:
    