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 Atrial fibrillation ( AF ) and left ventricular systolic dysfunction ( LVSD ) frequently co-exist despite adequate rate control . Existing r and omized studies of AF and LVSD of varying etiologies have reported modest benefits with a rhythm control strategy . OBJECTIVES The goal of this study was to determine whether catheter ablation ( CA ) for AF could improve LVSD compared with medical rate control ( MRC ) where the etiology of the LVSD was unexplained , apart from the presence of AF . METHODS This multicenter , r and omized clinical trial enrolled patients with persistent AF and idiopathic cardiomyopathy ( left ventricular ejection fraction [ LVEF ] ≤45 % ) . After optimization of rate control , patients underwent cardiac magnetic resonance ( CMR ) to assess LVEF and late gadolinium enhancement , indicative of ventricular fibrosis , before r and omization to either CA or ongoing MRC . CA included pulmonary vein isolation and posterior wall isolation . AF burden post-CA was assessed by using an implanted loop recorder , and adequacy of MRC was assessed by using serial Holter monitoring . The primary endpoint was change in LVEF on repeat CMR at 6 months . RESULTS A total of 301 patients were screened ; 68 patients were enrolled between November 2013 and October 2016 and r and omized with 33 in each arm ( accounting for 2 dropouts ) .  The average AF burden post-CA was 1.6 ± 5.0 % at 6 months . In the intention-to-treat analysis , absolute LVEF improved by 18 ± 13 % in the CA group compared with 4.4 ± 13 % in the MRC group ( p < 0.0001 ) and normalized ( LVEF ≥50 % ) in 58 % versus 9 % ( p = 0.0002 ) . In those undergoing CA , the absence of late gadolinium enhancement predicted greater improvements in absolute LVEF ( 10.7 % ; p = 0.0069 ) and normalization at 6 months ( 73 % vs. 29 % ; p = 0.0093 ) . CONCLUSIONS AF is an underappreciated reversible cause of LVSD in this population despite adequate rate control . The restoration of sinus rhythm with CA results in significant improvements in ventricular function , particularly in the absence of ventricular fibrosis on CMR . This outcome challenges the current treatment paradigm that rate control is the appropriate strategy in patients with AF and LVSD . ( Catheter Ablation Versus Medical Rate Control in Atrial Fibrillation and Systolic Dysfunction [ CAMERA-MRI ] ; ACTRN12613000880741 ) 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 Objective To determine whether or not radiofrequency ablation ( RFA ) for persistent atrial fibrillation in patients with advanced heart failure leads to improvements in cardiac function . Setting Patients were recruited from heart failure outpatient clinics in Scotl and . Design and intervention Patients with advanced heart failure and severe left ventricular dysfunction were r and omised to RFA ( rhythm control ) or  continued medical treatment  ( rate control ) . Patients were followed up for a minimum of 6 months . Main outcome measure Change in left ventricular ejection fraction ( LVEF ) measured by cardiovascular MRI . Results 22 patients were r and omised to RFA and 19 to medical treatment . In the RFA group , 50 % of patients were in sinus rhythm at the end of the study ( compared with none in the medical treatment group ) . The increase in cardiovascular magnetic resonance ( CMR ) LVEF in the RFA group was 4.5±11.1 % compared with 2.8±6.7 % in the medical treatment group ( p=0.6 ) . The RFA group had a greater increase in radionuclide LVEF ( a prespecified secondary end point ) than patients in the medical treatment group ( + 8.2±12.0 % vs + 1.4±5.9 % ; p=0.032 ) . RFA did not improve N-terminal pro-B-type natriuretic peptide , 6 min walk distance or quality of life . The rate of serious complications related to RFA was 15 % . Conclusions RFA result ed in long-term restoration of sinus rhythm in only 50 % of patients . RFA did not improve CMR LVEF compared with a strategy of rate control . RFA did improve radionuclide LVEF but did not improve other secondary outcomes and was associated with a significant rate of serious complications . Clinical trials registration number NCT00292162 Background —Restoring sinus rhythm in patients with heart failure ( HF ) and atrial fibrillation ( AF ) may improve left ventricular ( LV ) function and HF symptoms . We sought to compare the effect of a catheter ablation strategy with that of a medical rate control strategy in patients with persistent AF and HF . Methods and Results — Patients with persistent AF , symptomatic HF , and LV ejection fraction < 50 % were r and omized to catheter ablation or medical rate control . The primary end-point was the difference between groups in LV ejection fraction at 6 months . Baseline LV ejection fraction was 32±8 % in the ablation group and 34±12 % in the medical group . Twenty-six patients underwent catheter ablation  , and 24 patients were rate controlled .  Freedom from AF was achieved in 21/26 ( 81 % ) at 6 months off antiarrhythmic drugs . LV ejection fraction at 6 months in the ablation group was 40±12 % compared with 31±13 % in the rate control group ( P=0.015 ) . Ablation was associated with better peak oxygen consumption ( 22±6 versus 18±6 mL/kg per minute ; P=0.014 ) and Minnesota living with HF question naire score ( 24±22 versus 47±22 ; P=0.001 ) compared with rate control . Conclusions —Catheter ablation is effective in restoring sinus rhythm in selected patients with persistent AF and HF , and can improve LV function , functional capacity , and HF symptoms compared with rate control . Clinical Trial Registration —URL : http://www . clinical trials.gov . Unique identifier : OBJECTIVES The aim of this study was to determine the independent hemodynamic effects of an irregular sequence of ventricular cycle lengths in patients with atrial fibrillation ( AF ) . BACKGROUND Atrial fibrillation may reduce cardiac output by several possible mechanisms , including loss of the atrial contribution to left ventricular filling , valvular regurgitation , increased ventricular rate or irregular RR intervals . This study was design ed to evaluate the effects of an irregular RR interval , independent of the average ventricular rate , on cardiac hemodynamic data during AF . METHODS Sixteen patients with AF were studied invasively . During intrinsically conducted AF ( mean rate 102 + /- 22 beats/ min ) , the right ventricular apex electrogram was recorded onto frequency-modulated ( FM ) tape . After atrioventricular node ablation , the right ventricular apex was stimulated in three pacing modes in r and omized sequence : 1 ) VVI at 60 beats/min ; 2 ) VVI at the same average rate as during intrinsically conducted AF ( 102 + /- 22 beats/min ) ; and 3 ) during VVT pacing in which the pacemaker was triggered by playback of the FM tape recording of the right ventricular apex electrogram previously recorded during intrinsically conducted AF ( VVT 102 + /- 22 beats/min ) . RESULTS Compared with VVI pacing at the same average rate , an irregular sequence of RR intervals decreased cardiac output ( 4.4 + /- 1.6 vs. 5.2 + /- 2.4 liters/min , p < 0.01 ) , increased pulmonary capillary wedge pressure ( 17 + /- 7 vs. 14 + /- 6 mm Hg , p < 0.002 ) and increased right atrial pressure ( 10 + /- 6 vs. 8 + /- 4 mm Hg , p < 0.05 ) . CONCLUSIONS An irregular sequence of RR intervals produces adverse hemodynamic consequences that are independent of heart rate BACKGROUND Pulmonary-vein isolation is increasingly being used to treat atrial fibrillation in patients with heart failure . METHODS In this prospect i ve , multicenter clinical trial , we r and omly assigned patients with symptomatic , drug-resistant atrial fibrillation , an ejection fraction of 40 % or less , and New York Heart Association class II or III heart failure to undergo either pulmonary-vein isolation or atrioventricular-node ablation with biventricular pacing .  All patients completed the Minnesota Living with Heart Failure question naire ( scores range from 0 to 105 , with a higher score indicating a worse quality of life ) and underwent echocardiography and a 6-minute walk test ( the composite primary end point ) . Over a 6-month period , patients were monitored for both symptomatic and asymptomatic episodes of atrial fibrillation . RESULTS In all , 41 patients underwent pulmonary-vein isolation  , and 40 underwent atrioventricular-node ablation with biventricular pacing ; none were lost to follow-up at 6 months . The composite primary end point favored the group that underwent pulmonary-vein isolation , with an improved question naire score at 6 months ( 60 , vs. 82 in the group that underwent atrioventricular-node ablation with biventricular pacing ; P<0.001 ) , a longer 6-minute-walk distance ( 340 m vs. 297 m , P<0.001 ) , and a higher ejection fraction ( 35 % vs. 28 % , P<0.001 ) . In the group that underwent pulmonary-vein isolation , 88 % of patients receiving antiarrhythmic drugs and 71 % of those not receiving such drugs were free of atrial fibrillation at 6 months . In the group that underwent pulmonary-vein isolation , pulmonary-vein stenosis developed in two patients , pericardial effusion in one , and pulmonary edema in another ; in the group that underwent atrioventricular-node ablation with biventricular pacing , lead dislodgment was found in one patient and pneumothorax in another . CONCLUSIONS Pulmonary-vein isolation was superior to atrioventricular-node ablation with biventricular pacing in patients with heart failure who had drug-refractory atrial fibrillation . ( Clinical Trials.gov number , NCT00599976 . IMPORTANCE Atrial fibrillation ( AF ) is the most common rhythm disorder seen in clinical practice . Antiarrhythmic drugs are effective for reduction of recurrence in patients with symptomatic paroxysmal AF .  Radiofrequency ablation is an accepted therapy in patients for whom antiarrhythmic drugs have failed ; however , its role as a first-line therapy needs further investigation . OBJECTIVE To compare radiofrequency ablation with antiarrhythmic drugs ( st and 
    Output:
    
agent
Surrogate outcomes showed a similar benefit favoring CA .
Conclusion and Relevance Catheter ablation for AF in HFrEF is associated with improvement in patient-centered outcomes and surrogate outcomes when compared to st and ard medical therapy with or without device therapy
***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 Atrial fibrillation ( AF ) and left ventricular systolic dysfunction ( LVSD ) frequently co-exist despite adequate rate control . Existing r and omized studies of AF and LVSD of varying etiologies have reported modest benefits with a rhythm control strategy . OBJECTIVES The goal of this study was to determine whether catheter ablation ( CA ) for AF could improve LVSD compared with medical rate control ( MRC ) where the etiology of the LVSD was unexplained , apart from the presence of AF . METHODS This multicenter , r and omized clinical trial enrolled patients with persistent AF and idiopathic cardiomyopathy ( left ventricular ejection fraction [ LVEF ] ≤45 % ) . After optimization of rate control , patients underwent cardiac magnetic resonance ( CMR ) to assess LVEF and late gadolinium enhancement , indicative of ventricular fibrosis , before r and omization to either CA or ongoing MRC . CA included pulmonary vein isolation and posterior wall isolation . AF burden post-CA was assessed by using an implanted loop recorder , and adequacy of MRC was assessed by using serial Holter monitoring . The primary endpoint was change in LVEF on repeat CMR at 6 months . RESULTS A total of 301 patients were screened ; 68 patients were enrolled between November 2013 and October 2016 and r and omized with 33 in each arm ( accounting for 2 dropouts ) .  The average AF burden post-CA was 1.6 ± 5.0 % at 6 months . In the intention-to-treat analysis , absolute LVEF improved by 18 ± 13 % in the CA group compared with 4.4 ± 13 % in the MRC group ( p < 0.0001 ) and normalized ( LVEF ≥50 % ) in 58 % versus 9 % ( p = 0.0002 ) . In those undergoing CA , the absence of late gadolinium enhancement predicted greater improvements in absolute LVEF ( 10.7 % ; p = 0.0069 ) and normalization at 6 months ( 73 % vs. 29 % ; p = 0.0093 ) . CONCLUSIONS AF is an underappreciated reversible cause of LVSD in this population despite adequate rate control . The restoration of sinus rhythm with CA results in significant improvements in ventricular function , particularly in the absence of ventricular fibrosis on CMR . This outcome challenges the current treatment paradigm that rate control is the appropriate strategy in patients with AF and LVSD . ( Catheter Ablation Versus Medical Rate Control in Atrial Fibrillation and Systolic Dysfunction [ CAMERA-MRI ] ; ACTRN12613000880741 ) 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 Objective To determine whether or not radiofrequency ablation ( RFA ) for persistent atrial fibrillation in patients with advanced heart failure leads to improvements in cardiac function . Setting Patients were recruited from heart failure outpatient clinics in Scotl and . Design and intervention Patients with advanced heart failure and severe left ventricular dysfunction were r and omised to RFA ( rhythm control ) or  continued medical treatment  ( rate control ) . Patients were followed up for a minimum of 6 months . Main outcome measure Change in left ventricular ejection fraction ( LVEF ) measured by cardiovascular MRI . Results 22 patients were r and omised to RFA and 19 to medical treatment . In the RFA group , 50 % of patients were in sinus rhythm at the end of the study ( compared with none in the medical treatment group ) . The increase in cardiovascular magnetic resonance ( CMR ) LVEF in the RFA group was 4.5±11.1 % compared with 2.8±6.7 % in the medical treatment group ( p=0.6 ) . The RFA group had a greater increase in radionuclide LVEF ( a prespecified secondary end point ) than patients in the medical treatment group ( + 8.2±12.0 % vs + 1.4±5.9 % ; p=0.032 ) . RFA did not improve N-terminal pro-B-type natriuretic peptide , 6 min walk distance or quality of life . The rate of serious complications related to RFA was 15 % . Conclusions RFA result ed in long-term restoration of sinus rhythm in only 50 % of patients . RFA did not improve CMR LVEF compared with a strategy of rate control . RFA did improve radionuclide LVEF but did not improve other secondary outcomes and was associated with a significant rate of serious complications . Clinical trials registration number NCT00292162 Background —Restoring sinus rhythm in patients with heart failure ( HF ) and atrial fibrillation ( AF ) may improve left ventricular ( LV ) function and HF symptoms . We sought to compare the effect of a catheter ablation strategy with that of a medical rate control strategy in patients with persistent AF and HF . Methods and Results — Patients with persistent AF , symptomatic HF , and LV ejection fraction < 50 % were r and omized to catheter ablation or medical rate control . The primary end-point was the difference between groups in LV ejection fraction at 6 months . Baseline LV ejection fraction was 32±8 % in the ablation group and 34±12 % in the medical group . Twenty-six patients underwent catheter ablation  , and 24 patients were rate controlled .  Freedom from AF was achieved in 21/26 ( 81 % ) at 6 months off antiarrhythmic drugs . LV ejection fraction at 6 months in the ablation group was 40±12 % compared with 31±13 % in the rate control group ( P=0.015 ) . Ablation was associated with better peak oxygen consumption ( 22±6 versus 18±6 mL/kg per minute ; P=0.014 ) and Minnesota living with HF question naire score ( 24±22 versus 47±22 ; P=0.001 ) compared with rate control . Conclusions —Catheter ablation is effective in restoring sinus rhythm in selected patients with persistent AF and HF , and can improve LV function , functional capacity , and HF symptoms compared with rate control . Clinical Trial Registration —URL : http://www . clinical trials.gov . Unique identifier : OBJECTIVES The aim of this study was to determine the independent hemodynamic effects of an irregular sequence of ventricular cycle lengths in patients with atrial fibrillation ( AF ) . BACKGROUND Atrial fibrillation may reduce cardiac output by several possible mechanisms , including loss of the atrial contribution to left ventricular filling , valvular regurgitation , increased ventricular rate or irregular RR intervals . This study was design ed to evaluate the effects of an irregular RR interval , independent of the average ventricular rate , on cardiac hemodynamic data during AF . METHODS Sixteen patients with AF were studied invasively . During intrinsically conducted AF ( mean rate 102 + /- 22 beats/ min ) , the right ventricular apex electrogram was recorded onto frequency-modulated ( FM ) tape . After atrioventricular node ablation , the right ventricular apex was stimulated in three pacing modes in r and omized sequence : 1 ) VVI at 60 beats/min ; 2 ) VVI at the same average rate as during intrinsically conducted AF ( 102 + /- 22 beats/min ) ; and 3 ) during VVT pacing in which the pacemaker was triggered by playback of the FM tape recording of the right ventricular apex electrogram previously recorded during intrinsically conducted AF ( VVT 102 + /- 22 beats/min ) . RESULTS Compared with VVI pacing at the same average rate , an irregular sequence of RR intervals decreased cardiac output ( 4.4 + /- 1.6 vs. 5.2 + /- 2.4 liters/min , p < 0.01 ) , increased pulmonary capillary wedge pressure ( 17 + /- 7 vs. 14 + /- 6 mm Hg , p < 0.002 ) and increased right atrial pressure ( 10 + /- 6 vs. 8 + /- 4 mm Hg , p < 0.05 ) . CONCLUSIONS An irregular sequence of RR intervals produces adverse hemodynamic consequences that are independent of heart rate BACKGROUND Pulmonary-vein isolation is increasingly being used to treat atrial fibrillation in patients with heart failure . METHODS In this prospect i ve , multicenter clinical trial , we r and omly assigned patients with symptomatic , drug-resistant atrial fibrillation , an ejection fraction of 40 % or less , and New York Heart Association class II or III heart failure to undergo either pulmonary-vein isolation or atrioventricular-node ablation with biventricular pacing .  All patients completed the Minnesota Living with Heart Failure question naire ( scores range from 0 to 105 , with a higher score indicating a worse quality of life ) and underwent echocardiography and a 6-minute walk test ( the composite primary end point ) . Over a 6-month period , patients were monitored for both symptomatic and asymptomatic episodes of atrial fibrillation . RESULTS In all , 41 patients underwent pulmonary-vein isolation  , and 40 underwent atrioventricular-node ablation with biventricular pacing ; none were lost to follow-up at 6 months . The composite primary end point favored the group that underwent pulmonary-vein isolation , with an improved question naire score at 6 months ( 60 , vs. 82 in the group that underwent atrioventricular-node ablation with biventricular pacing ; P<0.001 ) , a longer 6-minute-walk distance ( 340 m vs. 297 m , P<0.001 ) , and a higher ejection fraction ( 35 % vs. 28 % , P<0.001 ) . In the group that underwent pulmonary-vein isolation , 88 % of patients receiving antiarrhythmic drugs and 71 % of those not receiving such drugs were free of atrial fibrillation at 6 months . In the group that underwent pulmonary-vein isolation , pulmonary-vein stenosis developed in two patients , pericardial effusion in one , and pulmonary edema in another ; in the group that underwent atrioventricular-node ablation with biventricular pacing , lead dislodgment was found in one patient and pneumothorax in another . CONCLUSIONS Pulmonary-vein isolation was superior to atrioventricular-node ablation with biventricular pacing in patients with heart failure who had drug-refractory atrial fibrillation . ( Clinical Trials.gov number , NCT00599976 . IMPORTANCE Atrial fibrillation ( AF ) is the most common rhythm disorder seen in clinical practice . Antiarrhythmic drugs are effective for reduction of recurrence in patients with symptomatic paroxysmal AF .  Radiofrequency ablation is an accepted therapy in patients for whom antiarrhythmic drugs have failed ; however , its role as a first-line therapy needs further investigation . OBJECTIVE To compare radiofrequency ablation with antiarrhythmic drugs ( st and 
    Output:
    