***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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    ***EXAMPLES*** 
    Input: Background — The most frequent complications associated with implantable cardioverter-defibrillators ( ICDs ) involve the transvenous leads . A subcutaneous implantable cardioverter-defibrillator ( S-ICD ) has been developed as an alternative system . This study evaluated the safety and effectiveness of the S-ICD System ( Cameron Health/Boston Scientific ) for the treatment of life-threatening ventricular arrhythmias ( ventricular tachycardia/ventricular fibrillation ) . Methods and Results — This prospect i ve , nonr and omized , multicenter trial included adult patients with a st and ard indication for an ICD , who neither required pacing nor had documented pace-terminable ventricular tachycardia . The primary safety end point was the 180-day S-ICD System complication-free rate compared with a prespecified performance goal of 79 % . The primary effectiveness end point was the induced ventricular fibrillation conversion rate compared with a prespecified performance goal of 88 % , with success defined as 2 consecutive ventricular fibrillation conversions of 4 attempts . Detection and conversion of spontaneous episodes were also evaluated . Device implantation was attempted in 321 of 330 enrolled patients , and 314 patients underwent successful implantation . The cohort was followed for a mean duration of 11 months . The study population was 74 % male with a mean age of 52±16 years and mean left ventricular ejection fraction of 36±16 % . A previous transvenous ICD had been implanted in 13 % . Both primary end points were met : The 180-day system complication-free rate was 99 % , and sensitivity analysis of the acute ventricular fibrillation conversion rate was > 90 % in the entire cohort . There were 38 discrete spontaneous episodes of ventricular tachycardia/ventricular fibrillation recorded in 21 patients ( 6.7 % ) , all of which successfully converted . Forty-one patients ( 13.1 % ) received an inappropriate shock . Conclusions — The findings support the efficacy and safety of the S-ICD System for the treatment of life-threatening ventricular arrhythmias . Clinical Trial Registration — URL : http://www . clinical trials.gov . Unique identifier : NCT01064076 Background For prevention of sudden cardiac death , the transvenously implantable cardioverter-defibrillator therapy ( tv-ICD ) is well accepted . The subcutaneous system ( S-ICD ® ) is promising in terms of reducing ICD complications . Nevertheless , the impact of the novel generator position on patients ’ quality of life ( QoL ) is yet unknown . Objective This study aim ed at comparing QoL and posttraumatic stress with both systems . Methods 60 S-ICD ® and 60 case – controlled tv single-chamber ICD patients were asked to respond to three st and ardized question naires . PDS [ screening for posttraumatic stress disorders ( PTSD ) ] and PHQ-D ( detection of the most predominant psychological disorders ) were used to screen for potential mental comorbidities . The SF-12 question naire was used to evaluate physical and mental well-being . Groups were compared in terms of QoL and PTSD . Results n = 42 ( 70 % ) pairs were analyzed ( n = 30 male , mean age 44.6 ± 12.2 years ) .  Prior appropriate ( p = 0.06 ) or inappropriate episodes ( p = 0.24 ) , ejection fraction ( p = 0.28 ) , or underlying cardiac disease did not differ significantly between groups . PDS revealed a PTSD in n = 6 tv-ICD and n = 6 S-ICD ® patients ( 14.3 % ) equally . In the PHQ-D question naire , n = 4 tv-ICD and n = 2 S-ICD ® patients fulfilled criteria for a major depression ( p = 0.68 ) . Panic disorders ( n = 2 tv , n = 0 S-ICD ® , p = 0.5 ) , and anxiety disorders ( n = 3 S-ICD ® , n = 0 tv-ICD , p = 0.24 ) did not differ between groups . The physical well-being score was 39.9 ± 12.5 in patients with a tv-ICD compared to 46.6 ± 9.9 in S-ICD ® patients ( p = 0.01 ) . The mental well-being score was comparable in both groups ( tv-ICD 51.8 ± 10.8 vs. S-ICD ® 51.9 ± 10.4 , p = 0.95 ) . Conclusions Our case – control study revealed equal or even better physical well-being of patients  with the S-ICD ® . PTSD occurred in almost 15 % of ICD patients irrespective of the type of system Aims The totally subcutaneous implantable-defibrillator ( S-ICD ) is a new alternative to the conventional transvenous ICD system to minimize intravascular lead complications . There are limited data describing the long-term performance of the S-ICD . This paper presents the first large international patient population collected as part of the EFFORTLESS S-ICD Registry . Methods and results The EFFORTLESS S-ICD Registry is a non-r and omized , st and ard of care , multicentre Registry design ed to collect long-term , system-related , clinical , and patient reported outcome data from  S-ICD implanted patients since June 2009 . Follow-up data are systematic ally collected over 60-month post-implant including Quality of Life . The study population of 472 patients of which 241 ( 51 % ) were enrolled prospect ively has a mean follow-up duration of 558 days ( range 13–1342 days , median 498 days ) , 72 % male , mean age of 49 ± 18 years ( range 9–88 years ) , 42 % mean left ventricular ejection fraction . Complication-free rates were 97 and 94 % , at 30 and 360 days , respectively . Three hundred and seventeen spontaneous episodes were recorded in 85 patients during the follow-up period . Of these episodes , 169 ( 53 % ) received therapy , 93 being for Ventricular Tachycardia/Fibrillation ( VT/VF ) . One patient died of recurrent VF and severe bradycardia . Regarding discrete VT/VF episodes , first shock conversion efficacy was 88 % with 100 % overall successful clinical conversion after a maximum of five shocks . The 360-day inappropriate shock rate was 7 % with the vast majority occurring for oversensing ( 62/73 episodes ) , primarily of cardiac signals ( 94 % of oversensed episodes ) . Conclusion The first large cohort of real-world data from an International patient S-ICD population demonstrates appropriate system performance with clinical event rates and inappropriate shock rates comparable with those reported for conventional ICDs . Clinical trial registration URL : http://www . clinical trials.gov . Unique identifier NCT01085435 Background Despite advances in prevention and treatment of cardiovascular disease , sudden cardiac death ( SCD ) remains a clinical challenge . Risk stratification in the general population is needed . Methods and Results Beat‐to‐beat spatiotemporal variability in the T vector was measured as the mean angle between consecutive T‐wave vectors ( mean TT′ angle ) on st and ard 12‐lead ECGs in 14 024 participants in the Atherosclerosis Risk in Communities ( ARIC ) study . Subjects with left ventricular hypertrophy , atrial arrhythmias , frequent ectopy , ventricular pacing , or QRS duration ≥120 ms were excluded . The mean spatial TT′ angle was 5.21±3.55 ° . During a median of 14 years of follow‐up ,  235 SCDs  occurred ( 1.24 per 1000 person‐years ) . After adjustment for demographics , coronary heart disease risk factors , and known ECG markers for SCD , mean TT′ angle was independently associated with SCD ( hazard ratio 1.089 ; 95 % CI 1.044 to 1.137 ; P<0.0001 ) . A mean TT′ angle > 90th percentile ( > 9.57 ° ) was associated with a 2‐fold increase in the hazard for SCD ( hazard ratio 2.01 ; 95 % CI 1.28 to 3.16 ; P=0.002 ) . In a subgroup of patients with T‐vector amplitude ≥0.2 mV , the association with SCD was almost twice as strong ( hazard ratio 3.92 ; 95 % CI 1.91 to 8.05 ; P<0.0001 ) . A significant interaction between mean TT′ angle and age was found : TT′ angle was associated with SCD in participants aged < 55 years ( hazard ratio 1.096 ; 95 % CI 0.043 to 1.152 ; P<0.0001 ) but not in participants aged ≥55 years ( Pinteraction=0.009 ) . Conclusions In a large , prospect i ve , community‐based cohort of left ventricular hypertrophy – free participants , increased beat‐to‐beat spatiotemporal variability in the T vector , as assessed by increasing TT′ angle , was associated with SCD BACKGROUND The subcutaneous implantable cardioverter-defibrillator ( S-ICD ) was developed to reduce short- and long-term complications associated with transvenous ICD leads . Early multicenter studies included younger patients with less left ventricular systolic dysfunction and fewer comorbidities than cohorts with traditional ICD . OBJECTIVE The purpose of this study was to characterize patient selection and the acute performance of the S-ICD in a contemporary real-world setting . METHODS The S-ICD Post-Approval Study is a prospect i ve registry involving 86 US centers . Patients were enrolled if they met criteria for S-ICD implantation , passed an electrocardiogram screening test , and had a life expectancy of > 1 year . Analyses of descriptive statistics , Kaplan-Meier time to event , and multivariate logistic regression were performed . RESULTS The study includes 1637 patients who underwent S-ICD implantation . The cohort included 68.6 % ( 1123/1637 ) male patients , and 13.4 % ( 220/1636 ) were receiving dialysis for end-stage renal disease . The mean age was 52 ± 15 years , with a mean left ventricular ejection fraction of 32.0 % ± 14.6 % . Electrocardiogram screening was successful for at least 1 , 2 , or 3 vectors in 100 % , 93.8 % , and 51.4 % of patients , respectively . Medical imaging ( 65.1 % , 1065/1636 ) and general anesthesia ( 64.1 % , 1048/16 ) were used in a majority of patients , and 52.2 % ( 855/1637 ) were implanted with the 2-incision technique . Induced ventricular tachycardia/ventricular tachycardia was successfully converted in 98.7 % ( 1394/1412 ) of patients . The 30-day complication-free rate was 96.2 % . Predictors of complications included diabetes , younger age , and higher body mass index . CONCLUSION Contemporary US patients with S-ICD  have more comorbidities than do previous cohorts with S-ICD , but they are younger with more end-stage renal disease than do patients with transvenous ICD . Implantation success is high , and short-term complication rates are acceptable BACKGROUND The approval of an entirely subcutaneous implantable-cardioverter defibrillator ( ICD ) system ( S-ICD ) has raised attention about this promising technology . It was developed to overcome lead failure and infection problems of conventional transvenous ICD systems . Nevertheless , lead migration of the initial design and inappropriate shock rates have raised concerns regarding its reliability and safety . OBJECTIVE The purpose of this study was to report the largest multicenter series to date of patients with the new device in comparison with a matched conventional transvenous ICD collective with focus on perioperative complications , conversion of induced ventricular fibrillation ( VF ) , and short-term follow-up . METHODS / RESULTS Sixty-nine patients ( 50 male and 19 female ; mean age 45.7 ± 15.7 years ) received an S-ICD in three German centers and were r and omly assigned to 69 sex- and age-matched conventional ICD patients . The indication was primary prevention in 41 patients ( 59.4 % ) without difference between groups ( 34 control patients ; P = .268 ) . The predominant underlying heart disease was ischemic cardiomyopathy in 11 ( 15.9 % ) , dilated cardiomyopathy in 25 ( 36.2 % ) , and hypertrophic cardiomyopathy in 10 ( 14.5 % ) in the S-ICD group . Mean implantation time was 70.8 ± 27.9 minutes ( P = .398 ) . Conversion rates of induced VF were 89.5 % for 65 J ( 15-J safety margin ) and 95.5 % including reversed shock polarity ( 15-J safety margin ) in the study group . Termination of induced VF was successful in 90.8 % ( 10-J safety margin , 
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Moreover , both devices appeared to perform equally well with respect to infection rate and death .
Conclusions : Available overall data suggested that S-ICD is associated with reducing lead-related complications , ICD shocks .
In addition , S-ICD has tendency to shorten hospitalization and reduce total complications , although the difference is no significant .