***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 
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    Input: AIMS Increase in life expectancy has led to increased rate of implantable cardioverter-defibrillator ( ICD ) implantation in patients in their 80s , but there are no current formal recommendations to guide physicians when elderly patients with ICDs require elective unit replacement ( EUR ) . This study aims at assessing survival and rates of ICD therapies  in patients who have had ICD implantation or EUR above the age of 80 , focusing on the latter . METHODS AND RESULTS Retrospective analysis of a prospect ively kept data base of all ICD-related procedures carried out in a single tertiary centre . Patients 80 years of age or older su bmi tted to ICD implantation ( n = 42 ) or EUR ( n = 34 ) between November 1991 and May 2012 were included . Using collected baseline and outcome data from this cohort , we assessed survival of these patients and the rates of ICD therapies . Median additional years of life after ICD implantation and ICD EUR in patients who died before data retrieval was 2.5 and 1.2 , respectively , and while 65 % of deceased patients after ICD implantation died in the first 3 years after the procedure , 50 % of deceased post-ICD EUR patients died within the first year . Mortality rates at 1 and 2 years post-EUR were 23.1 and 38.1 % , respectively . Furthermore , ventricular tachycardia occurred in a small minority of patients after EUR ( 16.7 % ) and no ventricular fibrillation-triggered ICD therapies were reported in both groups . CONCLUSION In octogenarians who are due for an ICD EUR , careful thought should be given to the current clinical status , comorbidities , and general frailty prior to considering them for the procedure . A survival benefit from ICD EUR in this age stratum is not likely The multicenter unsustained tachycardia trial ( MUSTT ) tested the value of electrophysiologically guided antiarrhythmic drug therapy against no therapy in high risk coronary artery disease with poor left ventricular function ( LV-EF ≤ 40 % ) and nonsustained ventricular tachycardia . Risk assessment was performed by testing inducibility of a sustained ventricular tachycardia . The primary endpoint of the study was sudden arrhythmic death or cardiac arrest . Significant information on risk stratification was gathered by the follow-up of patients that were noninducible . Although MUSTT was not a specific ICD trial for primary prevention of SCD the results of the trial revealed that only with ICD back-up — a significant reduction of arrhythmic death or cardiac arrest can be achieved . EP-guided antiarrhythmic drug treatment had a lower incidence of SCD/CA compared to no treatment ( 12 % versus 25 % , p = 0.043 , hazard ratio 0.73 after 24 months and 18 % versus 32 % after 60 months ) . A subgroup analysis showed that the benefit of antiarrhythmic treatment was only due to ICD implantation . No difference was found between those inducible pts treated exclusively with antiarrhythmic drugs  and those who were r and omized to no drug treatment . Patients who were not inducible did significantly better than pts who were inducible wether or not treated with antiarrhythmic drugs . MUSTT results strengthen the data of the MADIT study . They confirm the inducibility testing as the most accurate risk stratifier . MUSST demonstrated the poor value of serial EP drug testing as well as the risk of “ st and alone ” antiarrhythmic drug  treatment AIMS Prevention of sudden cardiac death by means of the implantable cardioverter/defibrillator ( ICD ) is considered to be a lifelong therapy . However , it is still unresolved if patients who never experienced an appropriate ICD intervention during generator longevity really need to undergo device replacement . METHODS AND RESULTS The INSURE trial was a multicentre prospect i ve observational cohort study that enrolled patients at the time of their first ICD replacement . Patients with and without previous appropriate ICD therapy were enrolled prospect ively and were evaluated every 3 - 6 months after ICD replacement . Primary endpoint of the study was the first occurrence of appropriate ICD therapy after device replacement . Five hundred and ten patients ( 83 % males , mean age 65 ± 10 years , mean ejection fraction 39 ± 16 % ) were enrolled between 2002 and 2007 in the study after an average lifespan of their first ICD generator of 62 ± 18 months . Three years after elective ICD replacement , the rates of appropriate ICD therapies in patients with ( n = 245 ) and without ( n = 265 ) former appropriate ICD intervention were 48.1 and 21.4 % ( adjusted hazard ratio 3.08 , CI : 2.15 - 4.39 , P < 0.001 ) . Notably , no predictive factors for lower need of ICD therapy could be identified in patients without prior appropriate ICD intervention . CONCLUSIONS In this study , a significant number of ICD-indicated patients without the need for therapy by their first device received appropriate ICD intervention after generator replacement . There were no predictors for lower need of ICD therapy . Hence , ICD replacement appears still necessary in patients without prior ICD interventions The objective of this study was to develop a prospect ively applicable method for classifying comorbid conditions which might alter the risk of mortality for use in longitudinal studies . A weighted index that takes into account the number and the seriousness of comorbid disease was developed in a cohort of 559 medical patients . The 1-yr mortality rates for the different scores were : " 0 " , 12 % ( 181 ) ; " 1 - 2 " , 26 % ( 225 ) ; " 3 - 4 " , 52 % ( 71 ) ; and " greater than or equal to 5 " , 85 % ( 82 ) . The index was tested for its ability to predict risk of death from comorbid disease in the second cohort of 685 patients during a 10-yr follow-up . The percent of patients who died of comorbid disease for the different scores were : " 0 " , 8 % ( 588 ) ; " 1 " , 25 % ( 54 ) ; " 2 " , 48 % ( 25 ) ; " greater than or equal to 3 " , 59 % ( 18 ) . With each increased level of the comorbidity index , there were stepwise increases in the cumulative mortality attributable to comorbid disease ( log rank chi 2 = 165 ; p less than 0.0001 ) . In this longer follow-up , age was also a predictor of mortality ( p less than 0.001 ) . The new index performed similarly to a previous system devised by Kaplan and Feinstein . The method of classifying comorbidity provides a simple , readily applicable and valid method of estimating risk of death from comorbid disease for use in longitudinal studies . Further work in larger population s is still required to refine the approach because the number of patients with any given condition in this study was relatively small BACKGROUND Sudden death from cardiac causes remains a leading cause of death among patients with congestive heart failure ( CHF ) . Treatment with amiodarone or an implantable cardioverter-defibrillator ( ICD ) has been proposed to improve the prognosis in such patients . METHODS We r and omly assigned 2521 patients with New York Heart Association ( NYHA ) class II or III CHF and a left ventricular ejection fraction ( LVEF ) of 35 percent or less to conventional therapy for CHF plus placebo ( 847 patients ) , conventional therapy plus amiodarone ( 845 patients ) , or conventional therapy plus a conservatively programmed , shock-only , single-lead ICD ( 829 patients ) . Placebo and amiodarone were administered in a double-blind fashion . The primary end point was death from any cause . RESULTS The median LVEF in patients was 25 percent ; 70 percent were in NYHA class II , and 30 percent were in class III CHF . The cause of CHF was ischemic in 52 percent and nonischemic in 48 percent . The median follow-up was 45.5 months . There were 244 deaths ( 29 percent ) in the placebo group , 240 ( 28 percent ) in the amiodarone group , and 182 ( 22 percent ) in the ICD group . As compared with placebo , amiodarone was associated with a similar risk of death ( hazard ratio , 1.06 ; 97.5 percent confidence interval , 0.86 to 1.30 ; P=0.53 ) and ICD therapy was associated with a decreased risk of death of 23 percent ( 0.77 ; 97.5 percent confidence interval , 0.62 to 0.96 ; P=0.007 ) and an absolute decrease in mortality of 7.2 percentage points after five years in the overall population . Results did not vary according to either ischemic or nonischemic causes of CHF , but they did vary according to the NYHA class . CONCLUSIONS In patients with NYHA class II or III CHF and LVEF of 35 percent or less , amiodarone has no favorable effect on survival , whereas single-lead , shock-only ICD therapy reduces overall mortality by 23 percent BACKGROUND Patients with reduced left ventricular function after myocardial infa rct ion are at risk for life-threatening ventricular arrhythmias . This r and omized trial was design ed to evaluate the effect of an implantable defibrillator on survival in such patients . METHODS Over the course of four years , we enrolled 1232 patients with a prior myocardial infa rct ion and a left ventricular ejection fraction of 0.30 or less . Patients were r and omly assigned in a 3:2 ratio to receive an implantable defibrillator ( 742 patients ) or conventional medical therapy ( 490 patients ) . Invasive electrophysiological testing for risk stratification was not required . Death from any cause was the end point . RESULTS The clinical characteristics at base line and the prevalence of medication use at the time of the last follow-up visit were similar in the two treatment groups . During an average follow-up of 20 months , the mortality rates were 19.8 percent in the conventional-therapy group and 14.2 percent in the defibrillator group . The hazard ratio for the risk of death from any cause in the defibrillator group as compared with the conventional-therapy group was 0.69 ( 95 percent confidence interval , 0.51 to 0.93 ; P=0.016 ) . The effect of defibrillator therapy on survival was similar in subgroup analyses stratified according to age , sex , ejection fraction , New York Heart Association class , and the QRS interval . CONCLUSIONS In patients with a prior myocardial infa rct ion and advanced left ventricular dysfunction , prophylactic implantation of a defibrillator improves survival and should be considered as a recommended therapy BACKGROUND It would be useful to identify patients at high risk of implantable cardioverter defibrillator ( ICD ) therapy  via additional antiarrhythmic measures to minimize the morbidity of ICD therapies . OBJECTIVE We assessed baseline characteristics for predictors of device therapy in a general ICD population . We also compared the likelihood of therapy delivery by replacement ICDs implanted for battery depletion with the original implants . METHODS Clinical and ICD interrogation data from patients followed up at a UK center were analyzed looking for predictors of appropriate ICD therapy . Univariate and multivariate analysis was performed using Cox regression . We compared time to first appropriate therapy between first and second ICDs in patients who had undergone ICD replacement for battery depletion by log-rank testing . RESULTS One hundred and sixty-one patients were studied ( 129 men , age 65.7 + /- 12.9 years , follow-up 908 + /- 676 days ) . Appropriate therapy was delivered in 68 patients ( 42 % ) . Univariate risk factors for appropriate ICD therapy were presentation with stable ventricular tachycardia ( VT ) ( P = 0.0002 ) , ischemic etiology ( P = 0.03 ) , tiered therapy programmed ICDs ( P = 0.01 ) , and beta-blocker use ( P = 0.001 ) . Stable VT and beta blocker use were independent predictors of ICD therapy on multivariate analysis . Thirty-three patients ( 20 % ) had at least one ICD replacement . Time to first appropriate therapy was no different between first and second ICD implants ( P = 0.8 ) . CONCLUSION Patients who present with cardiovascularly stable VT have a higher probability of receiving appropriate ICD therapy than those who do not . Following battery depletion of an original ICD , the replacement device is no less likely to administer therapy than the first Objective It is not clear whether patients who received an implantable cardioverter-defibrillator ( ICD ) for primary prevention  should undergo device replacement if they never experienced an appropriate ICD therapy during the first generator longevity . This study evaluated the incidence and predictors of appropriate ICD therapy after device replacement in this specific population . Methods From two large prospect i ve ICD registries , we identified all primary prevention patients who had a first ICD replacement without previous appropriate ICD therapy . Cox regression analysis was used to identify predictors of appropriate ICD therapy . Results Of 403 primary prevention patients needing first ICD replacement , 275 patients ( 68 % ) had not received previous appropriate ICD therapy . Patients without previous appropriate ICD therapy before first ICD replacement ( mean age at replacement 62±12 years , 75 % male ) had a mean follow-up of 86±24 months after the initial implant 
    Output:
    
Without non-ICD control groups , the true risk reduction provided by the ICD following replacement is unknown .
Rates of complications associated with ICD replacement are substantial .
Our analysis did not identify a subgroup at low risk of therapies following replacement .