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: OBJECTIVES The purpose of this study was to investigate the efficacy and safety of amiodarone and propafenone in the conversion of  chronic atrial fibrillation  in a prospect i ve , r and omized , placebo-controlled study . BACKGROUND The effectiveness of amiodarone and propafenone in the treatment of patients with chronic atrial fibrillation has not been adequately studied . METHODS One hundred one patients ( 48 men , mean age 64 + /- 9 years ) with atrial fibrillation lasting > 3 weeks participated in the study . Thirty-four patients received amiodarone ( 300 mg intravenously over 1 h , followed by 20 mg/kg over the next 24 h plus 600 mg orally , in three doses , for 1 week , then 400 mg/day orally , for three weeks ) , 32 received propafenone ( 2 mg/kg intravenously over 15 min , followed by 10 mg/kg over 24 h and then 450 mg/day orally , for one month ) and the remaining 35 served as control subjects . All patients received digoxin and anticoagulant treatment as indicated ( International Normalized Ratio 2 to 3 ) . RESULTS Conversion to sinus rhythm was achieved in 16 ( 47.05 % ) patients who received amiodarone , in 13 ( 40.62 % ) who received propafenone and in none of the control subjects ( p < 0.001 for both groups vs. control subjects ) . Those who converted had smaller atria than those who did not and atrial fibrillation of shorter duration in both the amiodarone and propafenone groups . Treatment was discontinued in one patient of the propafenone group because of significant QRS widening . CONCLUSIONS Amiodarone and propafenone appear to be safe and equally effective in the termination of chronic atrial fibrillation . Left atrial diameter and arrhythmia duration are independent predictors of conversion Background Delivery of shocks within the right atrium has been reported to be more effective than conventional external shocks in converting atrial fibrillation ( AF ) , but these two cardioversion techniques have never been compared prospect ively . The purpose of this study was to compare the efficacies of external and internal cardioversion in patients with chronic AF unresponsive to prior attempts at electrical and /or pharmacological cardioversion . Low-dose amiodarone was used in all patients after cardioversion to suppress recurrences of AF . Methods and Results One hundred twelve patients with AF of at least 1 month in duration were r and omly assigned to undergo external cardioversion with 300–360-J shocks or internal cardioversion with 200–300-J shocks delivered through a st and ard electrode catheter within the right atrium . The patients were treated with amiodarone ( 200 mg/day 5–7 days/week ) for 1 month before electrical cardioversion and afterward if the cardioversion was successful . The patients were-evaluated at regular intervals during 1 year of follow-up . The efficacy of internal cardioversion was significantly greater than that of external cardioversion ( 91 % versus 67 % , p = 0.002 ) . The only variable that was associated with the outcome of cardioversion was body weight . Among patients in whom sinus rhythm was restored , AF recurred as often after internal and external cardioversion ; at 1 year of follow-up , 37 % of patients in whom external or internal cardioversion had been effective were still in sinus rhythm .  Patients who had undergone an attempt at electrical cardioversion before entry into this study were less likely to remain in sinus rhythm after cardioversion . The only complications of cardioversion were one instance of cerebral thromboembolism after external cardioversion and one instance of transient pulmonary edema after internal cardioversion . Therapy with amiodarone was discontinued because of an adverse drug effect in only three patients . Conclusions Internal cardioversion is more effective than external cardioversion in restoring sinus rhythm and is as safe as external cardioversion in patients with chronic AF . The recurrence rate of AF is the same after both types of cardioversion . If conventional electrical cardioversion is ineffective , internal cardioversion should be attempted . The combination of low-dose amiodarone and external or internal cardioversion may result in maintaining sinus rhythm long-term in patients with refractory AF BACKGROUND Atrial fibrillation can not always be converted to sinus rhythm by transthoracic electrical cardioversion . We examined the effect of ibutilide , a class III antiarrhythmic agent , on the energy requirement for atrial defibrillation and assessed the value of this agent in facilitating cardioversion in patients with atrial fibrillation that is resistant to conventional transthoracic cardioversion . METHODS One hundred patients who had had atrial fibrillation for a mean ( + /-SD ) of 117+/-201 days were r and omly assigned to undergo transthoracic cardioversion with or without pretreatment with 1 mg of ibutilide . We design ed a step-up protocol in which shocks at 50 , 100 , 200 , 300 , and 360 J were used for transthoracic cardioversion . If transthoracic cardioversion was unsuccessful in a patient who had not received ibutilide pretreatment , ibutilide was administered and transthoracic cardioversion attempted again . RESULTS Conversion to sinus rhythm occurred in 36 of 50 patients who had not received ibutilide ( 72 percent ) and in all 50 patients who had received ibutilide ( 100 percent , P<0.001 ) . In all 14 patients in whom transthoracic cardioversion alone failed , sinus rhythm was restored when cardioversion was attempted again after the administration of ibutilide . Pretreatment with ibutilide was associated with a reduction in the mean energy required for defibrillation ( 166+/-80 J , as compared with 228+/-93 J without pretreatment ; P<0.001 ) . Sustained polymorphic ventricular tachycardia occurred in 2 of the 64 patients who received ibutilide ( 3 percent ) , both of whom had an ejection fraction of 0.20 or less . The rates of freedom from atrial fibrillation after six months of follow-up were similar in the two r and omized groups . CONCLUSIONS The efficacy of transthoracic cardioversion for converting atrial fibrillation to sinus rhythm was enhanced by pretreatment with ibutilide . However , use of this drug should be avoided in patients with very low ejection fractions OBJECTIVE To determine whether clonidine can slow ventricular rate in patients with rapid atrial fibrillation . DESIGN R and omized , controlled trial , with a 4-hour follow-up period . SETTING Emergency room of a university hospital . PATIENTS A consecutive sample of 18 hemodynamically stable patients who were evaluated or treated for rapid atrial fibrillation . Exclusion criteria included acute or terminal illness ; current use of antiarrhythmic agents , calcium-channel blockers , or beta-blockers ; excessive hypertension ; pulmonary , valvular , or pericardial disease ; and electrolyte imbalance . INTERVENTIONS Patients were r and omly assigned to receive either " no treatment " ( control group ) or clonidine , 0.075 mg orally , at baseline and after 2 hours if heart rate did not decrease by at least 20 % . MEASUREMENTS Blood pressure was measured by the same nurse in the same arm for 4 consecutive hours , and a full 12-lead electrocardiographic evaluation was done . MAIN RESULTS Heart rate decreased to below 100 beats/min in eight of nine patients receiving clonidine compared with two of nine patients in the control group . The difference in the mean decreases in heart rate was 38 beats/min ( 95 % CI , 20 to 56 beats/min ) . Six patients who were treated with clonidine and one patient in the control group reverted to normal sinus rhythm . Systolic blood pressure decreased slightly in both groups , without significant differences . Clinical follow-up was uneventful . CONCLUSION Low-dose clonidine was an easy , efficient , and effective treatment for patients with rapid atrial fibrillation who were hemodynamically stable This study evaluates the effectiveness and safety of intravenous diltiazem for the treatment of atrial fibrillation and atrial flutter . A double-blind , parallel , r and omized , placebo-controlled protocol was used , and 6 large , urban hospitals , both university-affiliated and private , participated . The study involved 113 patients with atrial fibrillation or flutter , a ventricular rate greater than or equal to 120 beats/min and systolic blood pressure greater than or equal to 90 mm Hg without severe heart failure . The dose of intravenous diltiazem ( or identical placebo ) was 0.25 mg/kg/2 minutes followed 15 minutes later by 0.35 mg/kg/2 minutes if the first dose was tolerated but ineffective . If a patient did not respond , the code was broken and the patient was allowed to receive open-label diltiazem if placebo had been given . Of 56 patients , 42 ( 75 % ) r and omized to receive diltiazem responded to 0.25 mg/kg and 10 of 14 responded to 0.35 mg/kg , for a total response rate of 52 of 56 patients ( 93 % ) , whereas 7 of 57 patients ( 12 % ) responded to placebo ( p less than 0.001 ) . After the double-blind protocol , 49 of the 57 patients who received placebo were then given diltiazem ; 47 of 49 responded , for an overall response rate of 99 of 105 patients ( 94 % ) with diltiazem . The median time from the start of drug infusion to the maximal decrease in heart rate was 4.3 minutes . Side effects occurred in 14 patients , 7 of whom had asymptomatic hypotension not requiring intervention . Thus , intravenous diltiazem was rapidly effective for slowing the ventricular response in most patients with atrial fibrillation or atrial flutter . Blood pressure decreased slightly . Side effects were mild Dofetilide may be advantageous in terminating  atrial fibrillation/atrial flutter ( AFl )  when there are contraindications for class I drugs ( left ventricular dysfunction and /or manifest myocardial ischemia ) and beta blockers . In particular , its successful outcome in usually drug-resistant AFl is promising and underscores the importance of selective class III action for terminating AFl OBJECTIVE This study was performed to characterize the risk of stroke in elderly patients with recurrent intermittent atrial fibrillation ( AF ) . BACKGROUND Although intermittent AF is common , relatively little is known about the attendant risk of stroke . METHODS A longitudinal cohort study was performed comparing 460 participants with intermittent AF with 1,552 with sustained AF treated with aspirin in the Stroke Prevention in Atrial Fibrillation studies and followed for a mean of two years . Independent risk factors for ischemic stroke were identified by multivariate analysis . RESULTS Patients with intermittent AF were , on average , younger ( 66 vs. 70 years , p < 0.001 ) , were more often women ( 37 % vs. 26 % p < 0.001 ) and less often had heart failure ( 11 % vs. 21 % , p < 0.001 ) than those with sustained AF . The annualized rate of ischemic stroke was similar for those with intermittent ( 3.2 % ) and sustained AF ( 3.3 % ) . In patients with intermittent AF , independent predictors of ischemic stroke were advancing age ( relative risk [ RR ] = 2.1 per decade , p < 0.001 ) , hypertension ( RR = 3.4 , p = 0.003 ) and prior stroke ( RR = 4.1 , p = 0.01 ) . Of those with intermittent AF predicted to be high risk ( 24 % ) , the observed stroke rate was 7.8 % per year ( 95 % confidence interval 4.5 to 14 ) . CONCLUSIONS In this large cohort of AF patients given aspirin , those with intermittent AF had stroke rates similar to patients with sustained AF and similar stroke risk factors . Many elderly patients with recurrent intermittent AF have substantial rates of stroke and likely benefit from anticoagulation . High-risk patients with intermittent AF can be identified using the same clinical criteria that apply to patients with sustained AF The aim of the study was to compare the effects of atenolol ( 50 mg b.i.d . ) , verapamil ( 80 mg b.i.d . ) , xamoterol ( 200 mg b.i.d . ) , and matching placebo on heart rate ( HR ) and exercise tolerance in digitalised patients with chronic atrial fibrillation . Each treatment was taken for 4 weeks , and digoxin was continued throughout the study . During treatment with placebo ( digoxin alone ) , the mean postexercise heart rate was 164 beats/min , and four subjects had rates of greater than or equal to 170 beats/min . Atenolol , verapamil , and xamoterol achieved significantly better control of exercise-induced tachycardia , mean postexercise heart rates being reduced to 120 , 131 , and 130 beats/min , respectively ( p less than 0.01 for each ) . However , minimum HRs less than or equal to 45 beats/min occurred during treatment with placebo , atenolol , and verapamil , whereas treatment with xamoterol was associated with a minimum heart rate of 5 
    Output:
    
agent
They also have an increased risk for thromboembolism .
Comparing with age-matched controls , the relative risk for stroke is increased 2- to 7-fold in patients with nonrheumatic atrial fibrillation ( 3 , 8 , 13 ) , and the absolute risk for stroke is between 1 % and 5 % per year , depending on clinical characteristics ( 3 , 12 , 14 - 16 ) .
Paroxysmal atrial fibrillation disrupts the lives of patients ( 17 ) , but this perception may not be associated with frequency or duration of symptoms .
Warfarin therapy affects quality of life because of frequent blood testing and recommendations for limiting some activities .
Data Synthesis Does Aggressive Rhythm Control Improve Mortality and Morbidity Compared with Rate Control ?
***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: OBJECTIVES The purpose of this study was to investigate the efficacy and safety of amiodarone and propafenone in the conversion of  chronic atrial fibrillation  in a prospect i ve , r and omized , placebo-controlled study . BACKGROUND The effectiveness of amiodarone and propafenone in the treatment of patients with chronic atrial fibrillation has not been adequately studied . METHODS One hundred one patients ( 48 men , mean age 64 + /- 9 years ) with atrial fibrillation lasting > 3 weeks participated in the study . Thirty-four patients received amiodarone ( 300 mg intravenously over 1 h , followed by 20 mg/kg over the next 24 h plus 600 mg orally , in three doses , for 1 week , then 400 mg/day orally , for three weeks ) , 32 received propafenone ( 2 mg/kg intravenously over 15 min , followed by 10 mg/kg over 24 h and then 450 mg/day orally , for one month ) and the remaining 35 served as control subjects . All patients received digoxin and anticoagulant treatment as indicated ( International Normalized Ratio 2 to 3 ) . RESULTS Conversion to sinus rhythm was achieved in 16 ( 47.05 % ) patients who received amiodarone , in 13 ( 40.62 % ) who received propafenone and in none of the control subjects ( p < 0.001 for both groups vs. control subjects ) . Those who converted had smaller atria than those who did not and atrial fibrillation of shorter duration in both the amiodarone and propafenone groups . Treatment was discontinued in one patient of the propafenone group because of significant QRS widening . CONCLUSIONS Amiodarone and propafenone appear to be safe and equally effective in the termination of chronic atrial fibrillation . Left atrial diameter and arrhythmia duration are independent predictors of conversion Background Delivery of shocks within the right atrium has been reported to be more effective than conventional external shocks in converting atrial fibrillation ( AF ) , but these two cardioversion techniques have never been compared prospect ively . The purpose of this study was to compare the efficacies of external and internal cardioversion in patients with chronic AF unresponsive to prior attempts at electrical and /or pharmacological cardioversion . Low-dose amiodarone was used in all patients after cardioversion to suppress recurrences of AF . Methods and Results One hundred twelve patients with AF of at least 1 month in duration were r and omly assigned to undergo external cardioversion with 300–360-J shocks or internal cardioversion with 200–300-J shocks delivered through a st and ard electrode catheter within the right atrium . The patients were treated with amiodarone ( 200 mg/day 5–7 days/week ) for 1 month before electrical cardioversion and afterward if the cardioversion was successful . The patients were-evaluated at regular intervals during 1 year of follow-up . The efficacy of internal cardioversion was significantly greater than that of external cardioversion ( 91 % versus 67 % , p = 0.002 ) . The only variable that was associated with the outcome of cardioversion was body weight . Among patients in whom sinus rhythm was restored , AF recurred as often after internal and external cardioversion ; at 1 year of follow-up , 37 % of patients in whom external or internal cardioversion had been effective were still in sinus rhythm .  Patients who had undergone an attempt at electrical cardioversion before entry into this study were less likely to remain in sinus rhythm after cardioversion . The only complications of cardioversion were one instance of cerebral thromboembolism after external cardioversion and one instance of transient pulmonary edema after internal cardioversion . Therapy with amiodarone was discontinued because of an adverse drug effect in only three patients . Conclusions Internal cardioversion is more effective than external cardioversion in restoring sinus rhythm and is as safe as external cardioversion in patients with chronic AF . The recurrence rate of AF is the same after both types of cardioversion . If conventional electrical cardioversion is ineffective , internal cardioversion should be attempted . The combination of low-dose amiodarone and external or internal cardioversion may result in maintaining sinus rhythm long-term in patients with refractory AF BACKGROUND Atrial fibrillation can not always be converted to sinus rhythm by transthoracic electrical cardioversion . We examined the effect of ibutilide , a class III antiarrhythmic agent , on the energy requirement for atrial defibrillation and assessed the value of this agent in facilitating cardioversion in patients with atrial fibrillation that is resistant to conventional transthoracic cardioversion . METHODS One hundred patients who had had atrial fibrillation for a mean ( + /-SD ) of 117+/-201 days were r and omly assigned to undergo transthoracic cardioversion with or without pretreatment with 1 mg of ibutilide . We design ed a step-up protocol in which shocks at 50 , 100 , 200 , 300 , and 360 J were used for transthoracic cardioversion . If transthoracic cardioversion was unsuccessful in a patient who had not received ibutilide pretreatment , ibutilide was administered and transthoracic cardioversion attempted again . RESULTS Conversion to sinus rhythm occurred in 36 of 50 patients who had not received ibutilide ( 72 percent ) and in all 50 patients who had received ibutilide ( 100 percent , P<0.001 ) . In all 14 patients in whom transthoracic cardioversion alone failed , sinus rhythm was restored when cardioversion was attempted again after the administration of ibutilide . Pretreatment with ibutilide was associated with a reduction in the mean energy required for defibrillation ( 166+/-80 J , as compared with 228+/-93 J without pretreatment ; P<0.001 ) . Sustained polymorphic ventricular tachycardia occurred in 2 of the 64 patients who received ibutilide ( 3 percent ) , both of whom had an ejection fraction of 0.20 or less . The rates of freedom from atrial fibrillation after six months of follow-up were similar in the two r and omized groups . CONCLUSIONS The efficacy of transthoracic cardioversion for converting atrial fibrillation to sinus rhythm was enhanced by pretreatment with ibutilide . However , use of this drug should be avoided in patients with very low ejection fractions OBJECTIVE To determine whether clonidine can slow ventricular rate in patients with rapid atrial fibrillation . DESIGN R and omized , controlled trial , with a 4-hour follow-up period . SETTING Emergency room of a university hospital . PATIENTS A consecutive sample of 18 hemodynamically stable patients who were evaluated or treated for rapid atrial fibrillation . Exclusion criteria included acute or terminal illness ; current use of antiarrhythmic agents , calcium-channel blockers , or beta-blockers ; excessive hypertension ; pulmonary , valvular , or pericardial disease ; and electrolyte imbalance . INTERVENTIONS Patients were r and omly assigned to receive either " no treatment " ( control group ) or clonidine , 0.075 mg orally , at baseline and after 2 hours if heart rate did not decrease by at least 20 % . MEASUREMENTS Blood pressure was measured by the same nurse in the same arm for 4 consecutive hours , and a full 12-lead electrocardiographic evaluation was done . MAIN RESULTS Heart rate decreased to below 100 beats/min in eight of nine patients receiving clonidine compared with two of nine patients in the control group . The difference in the mean decreases in heart rate was 38 beats/min ( 95 % CI , 20 to 56 beats/min ) . Six patients who were treated with clonidine and one patient in the control group reverted to normal sinus rhythm . Systolic blood pressure decreased slightly in both groups , without significant differences . Clinical follow-up was uneventful . CONCLUSION Low-dose clonidine was an easy , efficient , and effective treatment for patients with rapid atrial fibrillation who were hemodynamically stable This study evaluates the effectiveness and safety of intravenous diltiazem for the treatment of atrial fibrillation and atrial flutter . A double-blind , parallel , r and omized , placebo-controlled protocol was used , and 6 large , urban hospitals , both university-affiliated and private , participated . The study involved 113 patients with atrial fibrillation or flutter , a ventricular rate greater than or equal to 120 beats/min and systolic blood pressure greater than or equal to 90 mm Hg without severe heart failure . The dose of intravenous diltiazem ( or identical placebo ) was 0.25 mg/kg/2 minutes followed 15 minutes later by 0.35 mg/kg/2 minutes if the first dose was tolerated but ineffective . If a patient did not respond , the code was broken and the patient was allowed to receive open-label diltiazem if placebo had been given . Of 56 patients , 42 ( 75 % ) r and omized to receive diltiazem responded to 0.25 mg/kg and 10 of 14 responded to 0.35 mg/kg , for a total response rate of 52 of 56 patients ( 93 % ) , whereas 7 of 57 patients ( 12 % ) responded to placebo ( p less than 0.001 ) . After the double-blind protocol , 49 of the 57 patients who received placebo were then given diltiazem ; 47 of 49 responded , for an overall response rate of 99 of 105 patients ( 94 % ) with diltiazem . The median time from the start of drug infusion to the maximal decrease in heart rate was 4.3 minutes . Side effects occurred in 14 patients , 7 of whom had asymptomatic hypotension not requiring intervention . Thus , intravenous diltiazem was rapidly effective for slowing the ventricular response in most patients with atrial fibrillation or atrial flutter . Blood pressure decreased slightly . Side effects were mild Dofetilide may be advantageous in terminating  atrial fibrillation/atrial flutter ( AFl )  when there are contraindications for class I drugs ( left ventricular dysfunction and /or manifest myocardial ischemia ) and beta blockers . In particular , its successful outcome in usually drug-resistant AFl is promising and underscores the importance of selective class III action for terminating AFl OBJECTIVE This study was performed to characterize the risk of stroke in elderly patients with recurrent intermittent atrial fibrillation ( AF ) . BACKGROUND Although intermittent AF is common , relatively little is known about the attendant risk of stroke . METHODS A longitudinal cohort study was performed comparing 460 participants with intermittent AF with 1,552 with sustained AF treated with aspirin in the Stroke Prevention in Atrial Fibrillation studies and followed for a mean of two years . Independent risk factors for ischemic stroke were identified by multivariate analysis . RESULTS Patients with intermittent AF were , on average , younger ( 66 vs. 70 years , p < 0.001 ) , were more often women ( 37 % vs. 26 % p < 0.001 ) and less often had heart failure ( 11 % vs. 21 % , p < 0.001 ) than those with sustained AF . The annualized rate of ischemic stroke was similar for those with intermittent ( 3.2 % ) and sustained AF ( 3.3 % ) . In patients with intermittent AF , independent predictors of ischemic stroke were advancing age ( relative risk [ RR ] = 2.1 per decade , p < 0.001 ) , hypertension ( RR = 3.4 , p = 0.003 ) and prior stroke ( RR = 4.1 , p = 0.01 ) . Of those with intermittent AF predicted to be high risk ( 24 % ) , the observed stroke rate was 7.8 % per year ( 95 % confidence interval 4.5 to 14 ) . CONCLUSIONS In this large cohort of AF patients given aspirin , those with intermittent AF had stroke rates similar to patients with sustained AF and similar stroke risk factors . Many elderly patients with recurrent intermittent AF have substantial rates of stroke and likely benefit from anticoagulation . High-risk patients with intermittent AF can be identified using the same clinical criteria that apply to patients with sustained AF The aim of the study was to compare the effects of atenolol ( 50 mg b.i.d . ) , verapamil ( 80 mg b.i.d . ) , xamoterol ( 200 mg b.i.d . ) , and matching placebo on heart rate ( HR ) and exercise tolerance in digitalised patients with chronic atrial fibrillation . Each treatment was taken for 4 weeks , and digoxin was continued throughout the study . During treatment with placebo ( digoxin alone ) , the mean postexercise heart rate was 164 beats/min , and four subjects had rates of greater than or equal to 170 beats/min . Atenolol , verapamil , and xamoterol achieved significantly better control of exercise-induced tachycardia , mean postexercise heart rates being reduced to 120 , 131 , and 130 beats/min , respectively ( p less than 0.01 for each ) . However , minimum HRs less than or equal to 45 beats/min occurred during treatment with placebo , atenolol , and verapamil , whereas treatment with xamoterol was associated with a minimum heart rate of 5 
    Output:
    