***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: Background Many patients who survive a myocardial infa rct ion ( MI ) remain at risk of sudden cardiac death despite revascularization and optimal medical treatment . We used the modified moving average ( MMA ) method to assess the utility of  T-wave alternans ( TWA ) and heart rate turbulence ( HRT ) as risk markers in MI patients with or without diabetes mellitus ( DM ) . Methods We prospect ively enrolled 248 consecutive patients : 96 with MI ( post-MI patients ) ; 77 MI with DM ( post-MI + DM patients ) ; 75 controls without cardiovascular disease ( group control ) .  Both TWA and HRT were measured on ambulatory electrocardiograms ( AECGs ) . HRT  was assessed by two parameters ─ turbulence onset ( TO ) and turbulence slope ( TS ) . HRT was considered positive when both TO ≥0 % and TS ≤2.5 ms/R-R interval were met . The endpoint was cardiac mortality . Results TWA values differed significantly between MI and controls . Post-MI + DM patients had higher TWA values than post-MI patients ( 58 ± 21 μV VS 52 ± 18 μV , P = 0.029 ) . Impaired HRT -- increased TO and decreased TS were observed in MI patients with or without DM . During follow-up of 578 ± 146 days , cardiac death occurred in ten patients and three of them suffered sudden cardiac death ( SCD ) . Multivariate analysis determined that a HRT-positive outcome [ HR ( 95 % CI ) : 5.01 , 1.33–18.85 ; P = 0.017 ] , as well as the combination of abnormal TWA ( ≥47 μV ) and positive HRT had significant association with the endpoint [ HR ( 95 % CI ) : 9.08 , 2.21–37.2 ; P = 0.002 ) ] . Conclusion This study indicates that AECGs-based TWA and HRT can predict cardiac mortality in MI patients with or without DM . Combined analysis TWA and HRT may be a convenient and useful method of identifying patients at high risk for cardiovascular death Aims To investigate the combination of heart rate turbulence ( HRT ) and deceleration capacity ( DC ) as risk predictors in post-infa rct ion patients with left ventricular ejection fraction ( LVEF ) > 30 % . Methods and results We enrolled 2343 consecutive survivors of acute myocardial infa rct ion ( MI ) ( < 76 years ) in sinus rhythm .  HRT and DC were obtained from 24 h Holter recordings . Patients with both abnormal HRT ( slope ≤ 2.5 ms/RR and onset ≥ 0 % ) and abnormal DC ( ≤4.5 ms ) were considered suffering from severe autonomic failure ( SAF ) and prospect ively classified as high risk . Primary and secondary endpoints were all-cause , cardiac , and sudden cardiac mortality within the first 5 years of follow-up . During follow-up , 181 patients died ; 39 deaths occurred in 120 patients with LVEF ≤ 30 % , and 142 in 2223 patients with LVEF>30 % ( cumulative 5-year mortality rates of 37.9 % and 7.8 % , respectively ) . Among patients with LVEF > 30 % , SAF identified another high-risk group of 117 patients with 37 deaths ( cumulative 5-year mortality rates of 38.6 % and 6.1 % , respectively ) . Merging both high-risk groups ( i.e. LVEF ≤ 30 % and /or SAF ) doubled the sensitivity of mortality prediction compared with LVEF ≤ 30 % alone ( 21.1 % vs. 42.1 % , P < 0.001 ) while preserving 5-year mortality rate ( 38.2 % ) . Conclusion In post-MI patients with LVEF>30 % , SAF identifies a high-risk group equivalent in size and mortality risk to patients with LVEF ≤ 30 % 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 : Previous studies have described the clinical usefulness of the presence of nonsustained ventricular tachycardia ( NSVT ) and defined heart rate turbulence ( HRT ) in stratifying patients at risk . We prospect ively assessed whether HRT can facilitate the predictive accuracy of NSVT for identifying patients at risk for serious arrhythmic events in patients with left ventricular ( LV ) dysfunction BACKGROUND Ventricular arrhythmias are a major cause of death after myocardial infa rct ion , especially in patients with poor left-ventricular function . Previous attempts to identify and suppress arrhythmias with various antiarrhythmic drugs failed to reduce or actually increase mortality .  Amiodarone is a powerful antiarrhythmic drug with several potentially beneficial actions , and has shown benefit in several small-scale studies . We postulated that this drug might reduce mortality in patients at high risk of death after myocardial infa rct ion because of impaired ventricular function , irrespective of whether they had ventricular arrhythmias . METHODS The European Myocardial Infa rct Amiodarone Trial ( EMIAT ) was a r and omised double-blind placebo-controlled trial to assess whether amiodarone reduced all-cause mortality ( primary endpoint ) and cardiac mortality and arrhythmic death ( secondary endpoints ) in survivors of myocardial infa rct ion with a left-ventricular ejection fraction ( LVEF ) of 40 % or less . Intention-to-treat and on-treatment analyses were done . FINDINGS EMIAT enrolled 1486 patients ( 743 in the amiodarone group , 743 in the placebo group ) . Median follow-up was 21 months . All-cause mortality ( 103 deaths in the amiodarone group , 102 in the placebo group ) and cardiac mortality did not differ between the two groups . However , in the amiodarone group , there was a 35 % risk reduction ( 95 % CI 0 - 58 , p = 0.05 ) in arrhythmic deaths . INTERPRETATION Our findings do not support the systematic prophylactic use of amiodarone in all patients with depressed left-ventricular function after myocardial infa rct ion . However , the lack of proarrhythmia and the reduction in arrhythmic death support the use of amiodarone in patients for whom antiarrhythmic therapy is indicated Heart rate turbulence ( HRT ) is a promising marker for risk of mortality after acute myocardial infa rct ion ( AMI ) . We investigated HRT for risk stratification in high-risk patients after MI .  HRT from 24-hour Holter monitoring in 481 hospitalized patients after AMI with heart failure and /or diabetes with left ventricular dysfunction before r and omization in the Eplerenone Post-Acute Myocardial Infa rct ion Heart Failure Efficacy and Survival Study ( EPHESUS ) . Over a 1-year follow-up , 55 died , 49 of cardiovascular causes .  HRT onset ( TO ) and slope ( TS ) were calculated using previous and cohort-optimized cutpoints and their independent contribution to risk of cardiovascular death determined . Models were tested with < 5 ventricular premature complexes ( PVCs ) categorized as normal ( n = 452 ) and with < 5 VPCs excluded ( n = 342 ) . In EPHESUS , optimal cutpoints were TS < or = 3.0 and TO > or = 0.0 . The strongest model for predicting cardiovascular mortality used EPHESUS cutpoints excluding subjects with < 5 VPCs . On 3-category HRT model multivariate analysis ( TS and TO normal , TS or TO abnormal , TS and TO abnormal ) , both TS and TO abnormal ( relative risk 3.64 , 95 % confidence interval 1.55 to 8.55 , p = 0.003 ) and left ventricular ejection fraction < or = 30 % ( relative risk 1.97 , 95 % confidence interval 1.04 to 3.73 , p = 0.037 ) independently predicted cardiovascular death . In conclusion , HRT is an independent predictor of cardiovascular death in a high-risk population after AMI , with a possibly higher optimal cutpoint for HRT slope than previously reported BACKGROUND As treatment strategies for patients with chronic heart failure ( HF ) become more sophisticated , identifying patients at high risk of death and predicting mode of death is important . The aim of this study was to explore the potential utility of heart rate turbulence ( HRT ) to identify patients with HF at high risk of death . METHODS AND RESULTS In a prospect i ve study , 553 ambulant out patients age 63+/-10 with symptoms of HF and evidence of cardiac dysfunction were recruited . All patients underwent 24-h Holter ECG recordings , which were analysed for arrhythmias , heart rate variability and HRT a measurement that is thought to quantify cardiac autonomic regulatory mechanisms . Baseline chest radiograph , biochemistry and 12-lead electrocardiograms were also obtained . In patients with HRT measurements at 5 years follow up , 146 patients had died , 59 due to decompensated HF . Independent predictors of death from decompensated HF at 5-year follow up ( Cox proportional hazard model ) were HRT slope ( HR for 10 % increment 0.84 , 95 % CI 0.77 - 0.91 ) , serum sodium ( HR for 10 % increment 0.75 , 95 % CI 0.62 - 0.91 ) and serum creatinine ( for 10 % increment HR 1.14 , 95 % CI 1.08 - 1.19 ) all P<0.01 . These 3 variables combined had excellent discrimination between patients dying of decompensated HF and other patients , C-statistic=0.82 . CONCLUSIONS In patients with mild-to-moderate HF , HRT slope is an independent predictor of death due to decompensated HF . HRT may have the potential to help tailor therapy in this patient group BACKGROUND In the Sudden Cardiac Death in Heart Failure Trial ( SCD-HeFT ) , a significant fraction of the patients with congestive heart failure ultimately did not die suddenly of arrhythmic causes . Patients with CHF will benefit from better tools to identify if implantable cardioverter-defibrillator ( ICD ) therapy is needed . OBJECTIVES We aim ed to identify predictor variables from baseline SCD-HeFT patients ' R-R intervals that correlate to arrhythmic sudden cardiac death ( SCD ) and mortality and to design an ICD therapy screening test . METHODS Ten predictor variables were extracted from  prer and omization Holter data from 475 patients enrolled in the ICD arm of the SCD-HeFT by using novel and traditional heart rate variability methods . All variables were correlated to SCD using the Mann-Whitney-Wilcoxon test and receiver operating characteristic analysis . ICD therapy screening tests were design ed by minimizing the cost of false classifications . Survival analysis , including log-rank test and Cox models , was also performed . RESULTS A short-term fractal exponent , α1 , and a long-term fractal exponent , α2 , from detrended fluctuation 
    Output:
    
CONCLUSIONS HRT is a powerful predictor of both CD and arrhythmic events , particularly in postacute myocardial infa rct ion patients with ejection fraction > 30 % .
HRT power increases in combination with T-wave alternans analysis