***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 We conducted a prospect i ve , multicenter , r and omized comparison of implantable cardioverter-defibrillator ( ICD ) versus antiarrhythmic drug therapy in survivors of cardiac arrest secondary to documented ventricular arrhythmias . METHODS AND RESULTS From 1987 , eligible patients were r and omized to an ICD , amiodarone , propafenone , or metoprolol ( ICD versus antiarrhythmic agents r and omization ratio 1:3 ) . Assignment to propafenone was discontinued in March 1992 , after an interim analysis conducted in 58 patients showed a 61 % higher all-cause mortality rate than in 61 ICD patients during a follow-up of 11.3 months . The study continued to recruit 288 patients in the remaining 3 study groups ; of these , 99 were assigned to ICDs , 92 to amiodarone , and 97 to metoprolol . The primary end point was all-cause mortality . The study was terminated in March 1998 , when all patients had concluded a minimum 2-year follow-up . Over a mean follow-up of 57+/-34 months , the crude death rates were 36.4 % ( 95 % CI 26.9 % to 46.6 % ) in the ICD and 44.4 % ( 95 % CI 37.2 % to 51.8 % ) in the amiodarone/metoprolol arm . Overall survival was higher , though not significantly , in patients assigned to ICD than in those assigned to drug therapy ( 1-sided P=0.081 , hazard ratio 0.766 , [ 97.5 % CI upper bound 1.112 ] ) . In ICD patients , the percent reductions in all-cause mortality were 41.9 % , 39.3 % , 28 . 4 % , 27.7 % , 22.8 % , 11.4 % , 9.1 % , 10.6 % , and 24.7 % at years 1 to 9 of follow-up . CONCLUSIONS During long-term follow-up of cardiac arrest survivors , therapy with an ICD is associated with a 23 % ( nonsignificant ) reduction of all-cause mortality rates when compared with treatment with amiodarone/metoprolol . The benefit of ICD therapy is more evident during the first 5 years after the index event Background Carvedilol therapy has been reported to be more effective than other beta-blockers in patients with chronic heart failure ( CHF ) .  Amiodarone is an anti-arrhythmic medicine that has also been reported to be effective in patients with CHF . But the usefulness of combined therapy with carvedilol and amiodarone has not been reported . Methods We compared 15 patients ( M/F=3/12 , age=57±8 y ) with dilated cardiomyopathy ( DCM ) receiving carvedilol and amiodarone with 15 patients ( M/F=3/12 , age=61±9 y ) receiving carvedilol alone . Patients were studied before and after 1 year of treatment ( 1Y ) . NYHA class and exercise capacity based on the specific-activity-scale ( SAS ) , were assessed . Cardiac sympathetic nerve activity was estimated using total defect score ( TDS ) , H/M ratio and washout rate ( WR ) of 123I-MIBG imaging . Cardiac function was evaluated using 99mTc-MIBI QGS . Results Combined , therapy improved several parameters much more than carvedilol alone ( p<0.05 ) including delta-TDS ( 15.0±8.6 vs. 7.6±7.2 ) and delta- WR ( 15.9±11.0 % vs. 7.3±10.0 % ) for 123I-MIBG imaging , delta-LVEF ( 26.1±11.4 % vs. 15.5±13.8 % ) , delta-endsystolic volume ( 100±63.8 ml vs. 58.9±47.3 ml ) , 1Y NYHA class ( 1.5±0.5 vs. 1.9±0.5 ) , 1Y SAS ( 7.3±0.7 Mets vs. 6.2±1.0 Mets ) , and delta-SAS ( 3.4±0.8 Mets vs. 2.6±1.1 Mets ) . Conclusion Combined therapy with carvedilol and amiodarone is more effective in improving cardiac symptoms , exercise capacity , cardiac function and cardiac sympathetic nerve activity in patients with DCM Background In the Basel Antiarrhythmic Study of Infa rct Survival trial , low-dose amiodarone improved 1-year survival in patients with asymptomatic complex ventricular arrhythmias persisting 2 weeks after myocardial infa rct ion . To assess whether this beneficial effect persisted despite discontinuation of amiodarone after 1 year , the long-term outcomes of all patients of the amiodarone-treated group ( initially n=98 ) and those of the control group ( n=114 ) were assessed . Methods and Results After a mean follow-up of 72 ( 55–125 ) months , information on 96 % of patients ( 203 of 212 ) was obtained regarding survival or cause of death . The probability of death after 84 months according to actuarial life-table analysis ( Kaplan-Meier ) was 30%1 for the amiodarone-treated patients and 45 % for control patients . For the total follow-up , mortality remained significantly lower in the amiodarone group versus the control group regarding all deaths ( p=0.03 ) as well as cardiac death ( p=0.047 ) . This mortality reduction was entirely due to the first-year amiodarone effect , since there was no significant mortality difference between groups when considering survival after discontinuation of amiodarone only . Conclusion These data suggest that the beneficial effect of amiodarone on survival in this high-risk group of patients persists for several years . In addition , the results stress the importance of early treatment after myocardial infa rct ion , whereas the rate of sudden death and all cardiac death is low ( 1.6 % and 4.1 % per year , respectively ) during late follow-up and therefore may not warrant further therapy Background — Corresponding with a continuing decline in the prevalence of sudden cardiac arrest cases presenting with ventricular fibrillation ( VF ) , there has been a significant rise in the prevalence of  pulseless electrical activity ( PEA ) . Given significantly lower survival from PEA versus VF , we comprehensively investigated PEA correlates by incorporating first-responder data with lifetime clinical history information . Methods and Results — In the Portl and , Ore , metropolitan area ( population ≈1 million ) , cases of out-of-hospital sudden cardiac arrest who underwent attempted resuscitation were identified prospect ively ( 2002–2007 ) . Those presenting with PEA versus VF and asystole were compared with & khgr;2 tests , ANOVA , and logistic regression . A total of 1277 cases aged ≥18 years underwent resuscitation by first responders ( mean age , 65±16 years ; 67 % male ) . Presenting arrhythmia was VF in 48 % , PEA in 25 % , and asystole/other in the remainder . Compared with VF cases , PEA cases were older ( mean age , 68 versus 63 years ; P=0.0002 ) , more likely to be female ( 37 % versus 26 % ; P=0.0008 ) , and less likely to survive to hospital discharge ( 6 % versus 25 % ; P<0.0001 ) . A history of syncope was strongly associated with PEA ( odds ratio , 2.6 ; confidence interval , 1.3 to 5.3 ) after adjustment for age , gender , response time , and arrest circumstances . Black race was also independently associated with PEA ( odds ratio , 2.6 ; confidence interval , 1.3 to 5.4 ) . Pulmonary disease and female gender were significant factors associated with PEA ( P for interaction=0.04 ) . In a subgroup analysis of resting ECGs ( n=391 ) , there were no differences in cardiac clinical history or prevalence of cardiac conduction system disease ( PEA , 31.6 % versus VF , 32.2 % ; P=0.48 ) . Conclusions — PEA cases had a significantly higher prevalence of syncope in their lifetime , with other correlates , including black race , that were distinct from VF cases . Potential mechanistic links between syncope and future manifestation with PEA warrant further exploration Objective : To study the therapeutic effects of low-dose amiodarone and Betaloc on hypertrophic cardiomyopathy complicated by malignant ventricular arrhythmias . Methods : Eighty-two such patients were selected and divided into a treatment group and a control group by the r and om number method ( n=41 ) , which were administered with low-dose amiodarone plus Betaloc and individual Betaloc respectively . Results : The treatment group had a significantly higher overall effective rate ( 85.4 % ) than the control group ( 65.9 % ) did . Based on the New York Heart Association 's classification of cardiovascular disease , the treatment group mainly comprised Class III and IV patients before treatment , which were significantly relieved after treatment ( P<0.05 ) . The heart rate was evidently decreased from ( 119.99±18.91 ) bpm to ( 80.98±12.34 ) bpm , and the incidences of premature ventricular contraction and tachycardia were significantly reduced ( P<0.05 ) . The longest QT intervals after and before treatment were ( 421±32 ) ms and ( 411±35 ) ms respectively . The shortest QT interval after treatment [ ( 350±36 ) ms ] was significantly longer than that before [ ( 307±31 ) ms ] . The QT dispersion before treatment [ ( 96±29 ) ms ] was significantly higher that after [ ( 64±17 ) ms ] ( P<0.05 ) . Six out of eighty two patients in the treatment group succumbed to adverse reactions ( 14.63 % ) . Conclusion : Hypertrophic cardiomyopathy complicated with malignant ventricular arrhythmias can be well treated with low-dose amiodarone and Betaloc , with mitigated symptoms , improved prognosis and few adverse reactions OBJECTIVES The purpose of this multicenter r and omized trial was to compare total mortality during therapy with amiodarone or an implantable cardioverter-defibrillator ( ICD ) in patients with nonischemic dilated cardiomyopathy ( NIDCM ) and nonsustained ventricular tachycardia ( NSVT ) . BACKGROUND Whether an ICD reduces mortality more than amiodarone in patients with NIDCM and NSVT is unknown . METHODS One hundred three patients with NIDCM , left ventricular ejection fraction < or = 0.35 , and asymptomatic NSVT were r and omized to receive either amiodarone or an ICD . The primary end point was total mortality . Secondary end points included arrhythmia-free survival , quality of life , and costs . RESULTS The study was stopped when the prospect i ve stopping rule for futility was reached . The percent of patients surviving at one year ( 90 % vs. 96 % ) and three years ( 88 % vs. 87 % ) in the amiodarone and ICD groups , respectively , were not statistically different ( p = 0.8 ) . Quality of life was also similar with each therapy ( p = NS ) . There was a trend with amiodarone , as compared to the ICD , towards improved arrhythmia-free survival ( p = 0.1 ) and lower costs during the first year of therapy ( $ 8,879 US dollars vs. $ 22,039 US dollars , p = 0.1 ) . CONCLUSIONS Mortality and quality of life in patients with NIDCM and NSVT treated with amiodarone or an ICD are not statistically different . There is a trend towards a more beneficial cost profile and improved arrhythmia-free survival with amiodarone therapy Background —Sudden cardiac death ( SCD ) is a leading cause of death in the United States , but the relative public health burden is unknown . We estimated the burden of premature death from SCD and compared it with other diseases . Methods and Results —Analyses were based on the following data sources ( using most recent sources that provided appropriately stratified data ): ( 1 ) leading causes of death among men and women from 2009 US death certificate reporting ; ( 2 ) individual cancer mortality rates from 2008 death certificate reporting from the Centers for Disease Control and Prevention ’s National Program of Cancer Registries ; ( 3 ) county , state , and national population data for 2009 from the US Census Bureau ; and ( 4 ) SCD rates from the Oregon Sudden Unexpected Death Study ( SUDS ) population -based surveillance study of SCD between 2002 and 2004 . Cases were identified from multiple sources in a prospect ively design ed surveillance program . Incidence , counts , and years of potential life lost for SCD and other major diseases were compared . The age-adjusted national incidence of SCD was 60 per 100 000 population ( 95 % confidence interval , 54–66 per 100 000 ) . The burden of premature death for men ( 2.04 million years of potential life lost ; 95 % uncertainty interval , 1.86–2.23 million ) and women ( 1.29 million years of potential life 
    Output:
    
Compared to other antiarrhythmics ( four studies , 839 participants ) amiodarone appeared to increase the risk of SCD ( RR 1.40 ; 95 % CI 0.56 to 3.52 ; very low quality of evidence ) , but there was no effect in all-cause mortality ( RR 1.03 ; 95 % CI 0.75 to 1.42 ; low quality evidence ) .Amiodarone was associated with an increase in pulmonary and thyroid adverse events .
AUTHORS ' CONCLUSIONS There is low to moderate quality evidence that amiodarone reduces SCD , cardiac and all-cause mortality when compared to placebo or no intervention for primary prevention , and its effects are superior to other antiarrhythmics .