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Aims Fragmented QRS complex with visible notching on standard 12-lead electrocardiogram (ECG) is understood to represent depolarization abnormalities and to signify risk of cardiac events. Depolarization abnormalities with similar prognostic implications likely exist beyond visual recognition but no technology is presently suitable for quantification of such invisible ECG abnormalities. We present such a technology. Methods and results A signal processing method projects all ECG leads of the QRS complex into optimized three perpendicular dimensions, reconstructs the ECG back from this three-dimensional projection, and quantifies the difference (QRS 'micro'-fragmentation, QRS- μf) between the original and reconstructed signals. QRS 'micro'-fragmentation was assessed in three different populations: cardiac patients with automatic implantable cardioverter-defibrillators, cardiac patients with severe abnormalities, and general public. The predictive value of QRS- μf for mortality was investigated both univariably and in multivariable comparisons with other risk factors including visible QRS 'macro'-fragmentation, QRS- Mf. The analysis was made in a total of 7779 subjects of whom 504 have not survived the first 5 years of follow-up. In all three populations, QRS- μf was strongly predictive of survival (P < 0.001 univariably, and P < 0.001 to P = 0.024 in multivariable regression analyses). A similar strong association with outcome was found when dichotomizing QRS- μf prospectively at 3.5%. When QRS- μf was used in multivariable analyses, QRS- Mf and QRS duration lost their predictive value. Conclusion In three populations with different clinical characteristics, QRS- μf was a powerful mortality risk factor independent of several previously established risk indices. Electrophysiologic abnormalities that contribute to increased QRS- μf values are likely responsible for the predictive power of visible QRS- Mf. [ABSTRACT FROM AUTHOR]

Introduction: Cardiac resynchronization defibrillator (CRT‐D) as primary prevention is known to reduce mortality. At the time of replacement, higher age and comorbidities may attenuate the benefit of implantable cardioverter‐defibrillator (ICD) therapy. The purpose of this study was to evaluate the progression of comorbidities after implantation and their association with mortality following CRT‐D generator replacement. In addition, a risk score was developed to identify patients at high risk for mortality after replacement. Methods and Results: We identified patients implanted with a primary prevention CRT‐D (n = 648) who subsequently underwent elective generator replacement (n = 218) from two prospective ICD registries. The cohort consisted of 218 patients (median age: 70 years, male gender: 73%, mean left ventricular ejection fraction [LVEF]: 36 ± 11% at replacement). Median follow‐up after the replacement was 4.2 years during which 64 patients (29%) died and 11 patients (5%) received appropriate ICD shocks. An increase in comorbidities was observed in 77 patients (35%). The 5‐year mortality rate was 41% in patients with ≥2 comorbidities at the time of replacement. A risk score incorporating age, gender, LVEF, atrial fibrillation, anemia, chronic kidney disease, and history of appropriate ICD shocks at time of replacement accurately predicted 5‐year mortality (C‐statistic 0.829). Patients with a risk score of greater than 2.5 had excess mortality at 5‐year postreplacement compared with patients with a risk score less than 1.5 (57% vs. 6%; p <.001). Conclusion: A simple risk score accurately predicts 5‐year mortality after replacement in CRT‐D patients, as patients with a risk score of greater than 2.5 are at high risk of dying despite ICD protection. [ABSTRACT FROM AUTHOR]

Objective: Diabetes increases the risk of all-cause mortality and sudden cardiac death (SCD). The exact mechanisms leading to sudden death in diabetes are not well known. We compared the incidence of appropriate shocks and mortality in patients with versus without diabetes with a prophylactic implantable cardioverter defibrillator (ICD) included in the retrospective EU-CERT-ICD registry.Research Design and Methods and Results: A total of 3,535 patients from 12 European EU-CERT-ICD centers with a mean age of 63.7 ± 11.2 years (82% males) at the time of ICD implantation were included in the analysis. A total of 995 patients (28%) had a history of diabetes. All patients had an ICD implanted for primary SCD prevention. End points were appropriate shock and all-cause mortality. Mean follow-up time was 3.2 ± 2.3 years. Diabetes was associated with a lower risk of appropriate shocks (adjusted hazard ratio [HR] 0.77 [95% CI 0.62-0.96], P = 0.02). However, patients with diabetes had significantly higher mortality (adjusted HR 1.30 [95% CI 1.11-1.53], P = 0.001).Conclusions: All-cause mortality is higher in patients with diabetes than in patients without diabetes with primary prophylactic ICDs. Subsequently, patients with diabetes have a lower incidence of appropriate ICD shocks, indicating that the excess mortality might not be caused primarily by ventricular tachyarrhythmias. These findings suggest a limitation of the potential of prophylactic ICD therapy to improve survival in patients with diabetes with impaired left ventricular function. [ABSTRACT FROM AUTHOR]

Background: Due to high failure rates, Medtronic withdrew the Sprint Fidelis lead (SFL) from the market. Passive fixation lead models exhibited better survival than active models, but most studies have limited follow‐up. Aim of this study was to give insights into passive lead survival with a follow‐up of 10 years. Methods: In two large Swiss centers, patients with passive SFLs were identified and data from routine implantable cardioverter defibrillator (ICD) follow‐ups were collected. Patients were censored at time of death, last device interrogation (if lost to follow‐up), time of lead revision (in non‐SFL‐related problems), or at database closure (31th December 2017). We defined lead failure as any of the following: lead fracture with inappropriate discharge; sudden increase in low‐voltage impedance to >1500 or high‐voltage impedance to >100 Ω; >300 nonphysiological short VV‐intervals. Results: We identified 145 patients. Age at implant was 60 ± 12 years with a median follow‐up of 10.2 (interquartile range [IQR]: 5.0‐11.2) years. Thirty‐five percent of patients died after 5.4 ± 2.7 years. A total of 19 leads (13%) failed after 6.7 ± 3.2 years (range: 1.2‐12.0). Overt malfunction with shocks existed in four patients (3%). Cumulative lead survival was 93.1% at 6, 88.2% at 8, 83.8% at 10, and 77.6% at 11 years, respectively, with 35% of implanted leads under monitoring at 10 years. Lead survival fits best a Weibull distribution with accelerating failure rates (k = 1.95, 95% CI 1.32‐2.87, P < 0.001). Conclusions: During very long‐term follow‐up, failure rate of the passive SFL shows an increase resulting in an impaired lead survival of 84% at 10 years. [ABSTRACT FROM AUTHOR]

Aims: The clinical effectiveness of primary prevention implantable cardioverter defibrillator (ICD) therapy is under debate. The EUropean Comparative Effectiveness Research to Assess the Use of Primary ProphylacTic Implantable Cardioverter Defibrillators (EU‐CERT‐ICD) aims to assess its current clinical value. Methods and results: The EU‐CERT‐ICD is a prospective investigator‐initiated non‐randomized, controlled, multicentre observational cohort study performed in 44 centres across 15 European Union countries. We will recruit 2250 patients with ischaemic or dilated cardiomyopathy and a guideline indication for primary prophylactic ICD implantation. This sample will include 1500 patients at their first ICD implantation and 750 patients who did not receive a primary prevention ICD despite having an indication for it (non‐randomized control group). The primary endpoint is all‐cause mortality; the co‐primary endpoint in ICD patients is time to first appropriate shock. Secondary endpoints include sudden cardiac death, first inappropriate shock, any ICD shock, arrhythmogenic syncope, revision procedures, quality of life, and cost‐effectiveness. At baseline (and prior to ICD implantation if applicable), all patients undergo 12‐lead electrocardiogram (ECG) and Holter ECG analysis using multiple advanced methods for risk stratification as well as detailed documentation of clinical characteristics and laboratory values. Genetic biobanking is also organized. As of August 2018, baseline data of 2265 patients are complete. All subjects will be followed for up to 4.5 years. Conclusions: The EU‐CERT‐ICD study will provide a necessary update about clinical effectiveness of primary prophylactic ICD implantation. This study also aims for improved risk stratification and patient selection using clinical and ECG risk markers. [ABSTRACT FROM AUTHOR]

Background: Some but not all prior studies have shown that women receiving a primary prophylactic implantable cardioverter defibrillator (ICD) have a lower risk of death and appropriate shocks than men. Purpose: To evaluate the effect of gender on the risk of appropriate shock, all-cause mortality and inappropriate shock in contemporary studies of patients receiving a primary prophylactic ICD. Data Source: PubMed, LIVIVO, Cochrane CENTRAL between 2010 and 2016. Study Selection: Studies providing at least 1 gender-specific risk estimate for the outcomes of interest. Data Extraction: Abstracts were screened independently for potentially eligible studies for inclusion. Thereby each abstract was reviewed by at least two authors. Data Synthesis: Out of 680 abstracts retained by our search strategy, 20 studies including 46’657 patients had gender-specific information on at least one of the relevant endpoints. Mean age across the individual studies varied between 58 and 69 years. The proportion of women enrolled ranged from 10% to 30%. Across 6 available studies, women had a significantly lower risk of first appropriate shock compared with men (pooled multivariable adjusted hazard ratio 0.62 (95% CI [0.44; 0.88]). Across 14 studies reporting multivariable adjusted gender-specific hazard ratio estimates for all-cause mortality, women had a lower risk of death than men (pooled hazard ratio 0.75 (95% CI [0.66; 0.86]). There was no statistically significant difference for the incidence of first inappropriate shocks (3 studies, pooled hazard ratio 0.99 (95% CI [0.56; 1.73]). Limitations: Individual patient data were not available for most studies. Conclusion: In this large contemporary meta-analysis, women had a significantly lower risk of appropriate shocks and death than men, but a similar risk of inappropriate shocks. These data may help to select patients who benefit from primary prophylactic ICD implantation. [ABSTRACT FROM AUTHOR]

Background Clinical guidelines on implantable cardioverter defibrillator (ICD) therapy changed significantly in the last decades with potential inherent effects on therapy efficacy. We aimed to study therapy rates in time and the association between therapies and mortality. Methods All patients receiving an ICD, primary and secondary prevention, were included in a single-center retrospective registry. Information on first appropriate and inappropriate therapies was documented. Dates of implant were divided in P1: 1996-2001, P2: 2002-2008, and P3: 2009-2014. Results A total of 727 patients, 84.9% male-66.4% ischemic cardiomyopathy (ICM)-56% primary prevention-mean follow-up 5.2 ± 4.1 years, were included. There was a shift from secondary to primary prevention indications, from ischemic to non-ICM, and from single chamber to cardiac resynchronization therapy defibrillator devices. The annual 1- and 3-year appropriate shock (AS) rate declined from 29.4% and 15.1% in P1, over 13.3% and 9.2% in P2 to 7.8% and 5.7% in P3 (log-rank P < 0.001), while inappropriate shock (IAS) rates remained unchanged (log-rank P = 0.635). After multivariate regression analysis a higher age at implant, lower left ventricular ejection fraction, history of stroke, diabetes mellitus, intake of loop diuretics or digitalis, higher creatinine, and longer QTc were independent predictors of mortality. Conclusion These changes in clinical practice with a shift to primary prevention and rise in non-ICM implants caused a significant decrease in AS incidence, while IAS remained stable. Receiving AS or IAS was not an independent predictor of mortality in our real-life cohort. [ABSTRACT FROM AUTHOR]

Aims: Longevity of implantable cardioverter defibrillators (ICDs) is crucial for patients and healthcare systems as replacements impact on infection rates and cost-effectiveness. Aim was to determine longevity using very large databases of two teaching hospitals with a high number of replacements and a rather homogeneous distribution among manufacturers.Methods and Results: The study population consists of all patients in whom an ICD was inserted in. All ICD manufacturers operating in Switzerland and the Netherlands and all implanted ICDs were included. Implantable cardioverter defibrillator replacements due to normal battery depletion were considered events, and other replacements were censored. Longevity was assessed depending on manufacturers, pacing mode, implant before/after 2006, and all parameters combined. We analysed data from 3436 patients in whom 4881 ICDs [44.2% VVI-ICDs, 27.4% DDD-ICDs, 26.3% cardiac resynchronization therapy (CRT)-ICDs, 2.0% subcutaneous ICDs] were implanted. The four major manufacturers had implant shares between 18.4 and 31.5%. Replacement due to battery depletion (27.4%) was performed for 1339 ICDs. Patient survival at 5 years was 80.1%. Longevity at 5 years improved in contemporary compared with elderly ICDs [63.9-80.6% across all ICDs, of 73.7-92.1% in VVIs, 58.2-76.1% in DDDs, and of 47.1-66.3% in CRT defibrillators, all P value < 0.05]. Remarkable differences were seen among manufacturers, and those with better performance in elderly ICDs were not those with better performance in contemporary ones.Conclusion: Implantable cardioverter defibrillator longevity increased in contemporary models independent of manufacturer and pacing mode. Still, significant differences exist among manufacturers. These results might impact on device selection. [ABSTRACT FROM AUTHOR]

Background Many patients receiving an implantable cardioverter-defibrillator (ICD) also have atrial fibrillation (AF). Shock testing during ICD implantation carries a potential risk of cardioversion to sinus rhythm (SR) and thrombembolic events. We aimed to analyze the recurrence of AF after cardioversion to SR during ICD shock testing. Methods A total of 555 consecutive patients referred to a tertiary hospital in Switzerland for ICD implantation or generator exchange between 02/2002 and 03/2010 were screened for AF. Fifty-seven patients who were in AF at the time of ICD shock testing were included. Results Forty-four patients (77%) were successfully cardioverted from AF to SR. Type of AF (persistent, not permanent 64 vs 31% of cardioverted patients) was the only predictor. Thirty-nine patients (89%) experienced a recurrence of AF/atrial flutter after a median of 54 days (interquartile range 35-251 days). The only predictor for recurrence of AF was previous AF declared as permanent. No ischemic stroke occurred during hospitalization for the procedure. Conclusions For patients in AF undergoing shock testing at the time of ICD implant, there is a high chance of cardioversion from AF to SR, but there is also a high risk of early recurrence. Decisions regarding long-term anticoagulation should not be based on the heart rhythm immediately following shock testing. [ABSTRACT FROM AUTHOR]

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 prospective 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 implantation and 30±24 months after device replacement. Following replacement, 3-year cumulative incidence of appropriate ICD therapy was 13.7% (95% CI 8.6 to 18.8%). No predictive factors associated with appropriate ICD therapy after replacement could be identified in spite of including seven clinically relevant factors. Conclusions: A considerable number of primary prevention patients without previous appropriate ICD therapy before first ICD replacement received appropriate ICD therapy after replacement. As there were no predictors of appropriate ICD therapy after replacement, replacing an ICD is still recommended in all primary prevention patients despite the lack of appropriate ICD therapy during first battery service life. [ABSTRACT FROM AUTHOR]

Objective: The implantable cardioverter defibrillator (ICD) is very effective in the prevention of sudden cardiac death, but its benefit is impaired by competing risks. A simple risk model to predict mortality was designed for patients with primary prevention and ischaemic cardiomyopathy. We aimed to apply this score to a general ICD population. Methods: This retrospective registry study included all patients in whom an ICD was implanted at a tertiary referral hospital. Risk factors were age >70 years, QRS width >120 ms, atrial fibrillation, New York Heart Association Functional Classification class >2 and glomerular filtration rate <60 mL/min/1.73 m². Kaplan- Meier curves were constructed according to the presence of 0, 1, 2 and >2 risk factors. Results: The cohort consists of 1032 patients, 881 (86%) were men, mean age was 61±14 years and mean follow-up 66±46 months. 256 patients (25%) died 58 ±41 months after implant. The setting was secondary prevention in 498 patients (48%). No risk factors was present in 32% of patients, 1 in 27%, 2 in 20% and >2 in 21%, respectively. There was a significant and comprehensible relation between risk score and mortality. Cumulative survival was 82% in patients with 0 risk factors, 63% in those with 1, 41% in those with 2 and 23% in those with >2 risk factors (p < 0.0001). ICD therapies were documented in 421 patients (41%) without correlation to risk factors. Conclusions: In a mixed population of primary and secondary preventive ICD carriers, application of a simple risk score predicts long-term mortality but not appropriate use of the ICD. [ABSTRACT FROM AUTHOR]

Role of Defibrillation Threshold Testing. Introduction: Defibrillation threshold (DFT) testing has been performed to prove functionality of the implantable cardioverter defibrillator (ICD). Over the past years it has become increasingly controversial because of possible morbidity and mortality. The goal of this study was to determine unsuccessful shock testing and report strategies used to overcome these problems. Methods and Results: A total of 314 patients with a de novo implantation of an ICD and 127 patients receiving a generator exchange were identified retrospectively. All patients underwent defibrillation threshold testing after induction of VF using a low-energy T-wave shock during the intervention, 2 shock tests after de novo implantations, 1 after generator change. A safety margin of 10 J or more was requested. Seven (2.3%) patients in the de novo group and 2 patients (1.4%) in the generator exchange group could not be defibrillated using the standard approach. All of those patients had either chronic amiodarone therapy, secondary prevention or a cardiac resynchronization therapy device (CRT). In univariate analysis, amiodarone therapy, dilated cardiomyopathy, and lower ejection fraction were predictors of failure. Conclusion: Our study's results as well as a review of the current literature favor shock testing, especially in patients with specific risk factors as mentioned above. (J Cardiovasc Electrophysiol, Vol. 24, pp. 437-441, April 2013) [ABSTRACT FROM AUTHOR]

Remote monitoring is useful for management of implantable cardioverter defibrillator (ICD) patients regarding detection of arrhythmias and probable device or lead failure. We report the case of a patient who died suddenly while being on remote monitoring. The ICD was not retrieved postmortem. Even though clinical circumstances were suspicious of an arrhythmic death, this was excluded due to a distinctive manufacturer feature of the system. (PACE 2012; 35:e280-e283) [ABSTRACT FROM AUTHOR]

The article presents the results of a study on the effectiveness of single-lead atrial sensing system and dual-chamber (DR) implantable cardioverter-defibrillator (ICD) system in indicating the presence of supraventricular tachyarrhythmias in patients without antibradycardia pacing. According to the authors, an atrial electrogram is necessary to obtain better rhythm discrimination. They add that an atrial ICD system is equivalent to a standard DR-ICD system with regard to the detection of ventricular and superventricular tachyarrhythmias.

Aims The aim of this study was to determine the relationship between improved ejection fraction (EF) and occurrence of arrhythmias in patients with cardiac resynchronization therapy devices with defibrillator function (CRT-D). The hypothesis was that patients who experienced a marked improvement in EF also had fewer appropriate defibrillator interventions. Methods and results We analysed data of 270 patients from2 prospective registries with follow-up of ≥12 months and echocardiography performed ≥8 months after CRT-D implantation. The discriminator was whether left ventricular ejection fraction (LVEF) improved to >35% [cut-off for primary prevention implantable cardioverter-defibrillator (ICD) implantation]. Mean age was 61 ± 11 years, LVEF 22 ± 5%, and follow-up 40 ± 22 months. Ischaemic cardiomyopathy was present in 48%, and secondary prevention indication was present in 25%. Implantable cardioverter-defibrillator interventions were delivered to 35% of patients. Echocardiography (20 ± 15 months after implantation) showed an improvement in LVEF from 22% (SD 5.4%) to 30% (SD 9.8%). Improvement to >35% was seen in 21% of patients. Those who improved to >35% had fewer ICD interventions than those who did not (23 vs.38%; P-value 0.03). Analysing only patients with a primary prevention indication and stratifying again in patients with and without improvement of LVEF to >35%, the latter had highly significant more ICD-therapies (6 vs. 31%; P-value 0.0008). Conclusion Patients with CRT-D for primary prevention, whose LVEF improved to >35% during mid-term follow-up, are at low risk of first ICD therapies beyond year 1. If similar findings are reported in other patient cohorts, this might impact on decision-making at the time of battery depletion. [ABSTRACT FROM AUTHOR]

Introduction: The effect of oral amiodarone therapy on defibrillation energy requirements in patients with an implantable defibrillator has not been established. Methods and Results: Twenty-one consecutive patients with implantable biphasic waveform defibrillators underwent a step-down determination of the defibrillation energy requirement 211 ± 12 days before and 73 ± 22 days after initiation of amiodarone therapy (mean total dose 26.7 ± 11.1 g). Serum amiodarone and desethylamiodarone concentrations were measured at the time of defibrillation energy requirement determination. The mean defibrillation energy requirement before amiodarone therapy was 9.9 ± 4.6 J. After initiation of amiodarone therapy, the mean defibrillation energy requirement increased to 137 ± 5.6 J (P = 0.004). A linear relationship between the amiodarone (P = 0.02, r = 0.6), desethylamiodarone (P = 0.02, r = 0.6), and combined amiodarone- desethylamiodarone concentrations (P = 0.01, r = 0.6) and the defibrillation energy requirement was noted. Stepwise regression analysis demonstrated that the combined amiodaronedesethylamiodarone concentration was the only independent predictor of increase in the defibrillation energy requirement. Conclusion: Chronic oral amiodarone therapy Increases the defibrillation energy requirement by approximately 62% in patients with an Implantable defibrillator. The combined amiodarone. desethylamiodarone concentration is directly related to the increase in the defibrillation energy requirement. [ABSTRACT FROM AUTHOR]

Background: The wearable cardioverter defibrillator (WCD) uses surface electrodes to detect arrhythmia before initiating a treatment sequence. However, it is also prone to inappropriate detection due to artefacts. Objective: The aim of this study is to assess the alarm burden in patients and its impact on clinical outcomes. Methods: Patients from the nationwide Swiss WCD Registry were included. Clinical characteristics and data were obtained from the WCDs. Arrhythmia recordings ≥30 s in length were analysed and categorized as VT/VF, atrial fibrillation (AF), supraventricular tachycardia (SVT) or artefact. Results: A total of 10653 device alarms were documented in 324 of 456 patients (71.1%) over a mean WCD wear-time of 2.0 ± 1.6 months. Episode duration was 30 s or more in 2996 alarms (28.2%). One hundred and eleven (3.7%) were VT/VF episodes. The remaining recordings were inappropriate detections (2736 (91%) due to artefacts; 117 (3.7%) AF; 48 (1.6%) SVT). Two-hundred and seven patients (45%) had three or more alarms per month. Obesity was significantly associated with three or more alarms per month (p = 0.01, 27.7% vs. 15.9%). High alarm burden was not associated with a lower average daily wear time (20.8 h vs. 20.7 h, p = 0.785) or a decreased implantable cardioverter defibrillator implantation rate after stopping WCD use (48% vs. 47.3%, p = 0.156). Conclusions: In patients using WCDs, alarms emitted by the device and impending inappropriate shocks were frequent and most commonly caused by artefacts. A high alarm burden was associated with obesity but did not lead to a decreased adherence. [ABSTRACT FROM AUTHOR]

Treatment with an ICD is the first-line treatment for survivors of sudden cardiac death. More recently, evidence accumulates that prophylactic ICD therapy may be beneficial for selected subgroups of patients after myocardial infarction. Particularly for future studies on the value of prophylactic ICD therapy, downsized devices are needed to allow easy pectoral implantation with a single lead configuration and featuring extended memory capabilities. Accordingly, this study assesses the clinical performance of a downsized fourth-generation ICD in 162 consecutive patients. All devices could be successfully implanted pectorally, in 96% with a single lead configuration with a low defibrillation threshold of 10.6 ± 5.2 J. During a 3-month follow-up, 26% of the patients received ICD therapy. Twenty percent had appropriate therapy for ventricular fibrillation (n = 9) and VT (n = 23), which was effective in all cases. Of the 450 episodes of VT, 426 were terminated by antitachycardia pacing. Fourteen patients (9%) had inappropriate ICD therapy mainly due to atrial fibrillation or sinus tachycardia, which could be reliably diagnosed by the ICD stored intracardiac electrograms. [ABSTRACT FROM AUTHOR]

Delivery of inappropriate therapy of implantable cardioverter defibrillators (ICD) due to inaccurate arrhythmia detection represents a major clinical problem. Different arrhythmia detection criteria such as the ‘stability’ of the cycle length or the suddenness of ‘onset’ of tachycardia have been implemented in ICD software to prevent inappropriate therapy. The new Medtronic model 7223Cx ICD offers an additional detection parameter (QHS width), which reflects changes in the duration of ventricular depolarization as a tool to distinguish supraventricular from ventricular tachycardias. Although this criterion can be programmed based on ECG parameters derived from resting ECGs, this may not be sufficient since QRS width is subject to considerable changes due to transient myocardial ischemia, changes in autonomic tone, or frequency dependent effects of antiarrhythmic drugs. The present study aimed to determine frequency dependent changes in QRS width in individual patients at rest and during symptom-limited exercise testing in 16 patients with documented ventricular tachycardia (N = 13) or ventricular fibrillation (N = 3). The optimal EGM slew threshold and the individual variation of QRS width were determined. Measurements obtained at the end of the implantation procedure were compared to those performed at hospital discharge. The majority of patients showed a wider variation in QRS duration as measured from 30 consecutive cycles during exercise as compared to rest. For example, the QRS range (i.e., the difference between the maximal and the minimal QRS width measured) averaged 7 ± 3 ms at rest and increased to 11 ± 3 ms during exercise (P = 0.004) with an increase of ≥ 4 ms observed in 11 (69%) of 16 patients. In 13 (81%) of 16 patients a reprogramming of at least one QRS width parameter from its value at the time of implantation was necessary. Thus, the QRS width measured from the intracardiac EGM shows significant intra-individual variations in different physiological conditions. For optimal programming of the QRS width parameter, measurements obtained during exercise are important. [ABSTRACT FROM AUTHOR]

Stored atrial and ventricular electrograms retrieved from dual chamber implantable defibrillators facilitate the diagnosis of arrhythmias. This case also illustrates the usefulness of programmed atrial and ventricular stimulation for noninvasive rhythm diagnosis in patients with a wide QBS tachycardia and an implantable defibrillator. [ABSTRACT FROM AUTHOR]

Discusses the case of a 56-year-old man who experienced inappropriate shock therapy from his implantable cardioverter defibrillator (ICD). Patient with hypertrophic obstructive cardiomyopathy; Numerous episodes of syncope due to tachycardia; History of paroxysmal atrial flutter and fibrillation; Atrial oversensing; Increase of his sotalol dosage to prevent further episodes of atrial flutter.

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Current guidelines have indicated an implantable cardioverter-defibrillator (ICD) for patients with severe idiopathic dilated cardiomyopathy, for both primary and secondary prevention. Compared to coronary artery disease, the overall benefit has been smaller. A more refined risk assessment, using the left ventricular ejection fraction (LVEF) and prevention mode (primary/secondary), is still needed to guide ICD implantation. Patients included in 2 large ICD registers were analyzed regarding the appropriate therapies and improvement of LVEF, overall and in subgroups of prevention mode and LVEF <20% versus >20%. Overall, 349 patients were included; 70% were men, the mean age was 54 years, and the mean follow-up was 33 months. Cardiac resynchronization therapy (CRT) was used in 57%, and secondary prevention was present in 30%. ICD therapies were delivered to 33% of the patients, in most for ventricular tachycardia. Patients receiving an ICD for secondary prevention and non-CRT were more likely to have arrhythmic events (both p <0.05). The cumulative event rates at 5 years were 53% for secondary and 33% for primary prevention (p <0.001). Depending on the prevention mode and LVEF status (<20% vs >20%), the event rates ranged from 30% to 76%. The mean LVEF improved by 10%, independently of the stimulation mode (CRT 22% to 31%, non-CRT 26% to 35%; p <0.0001). A persistent improvement to >35% was seen in only 25% of CRT patients but in 45% of non-CRT patients (p = 0.004). In conclusion, the results from the present study have demonstrated that in patients with idiopathic dilated cardiomyopathy, the potential for LVEF improvement is considerable and that the rate of ICD interventions strongly depends on the prevention mode and LVEF. These findings could be the basis for additional risk stratification tools. [ABSTRACT FROM AUTHOR]

Abnormal 12-lead electrocardiogram (ECG) can predict cardiovascular events, including sudden cardiac death. We tested the hypothesis that ECG provides useful information on guiding implantable cardioverter defibrillator (ICD) therapy into individuals with impaired left ventricular ejection fraction (LVEF). Retrospective data of primary prevention ICD implantations from 14 European centers were gathered. The registry included 5111 subjects of whom 1687 patients had an interpretable pre-implantation ECG available (80.0% male, 63.3 ± 11.4 years). Primary outcome was survival without appropriate ICD shocks or heart transplantation. A low-risk ECG was defined as a combination of ECG variables that were associated with the primary outcome. A total of 1224 (72.6%) patients survived the follow-up (2.9 ± 1.7 years) without an ICD shock, 224 (13.3%) received an appropriate shock and 260 (15.4%) died. Low-risk ECG defined as QRS duration <120 ms, QTc interval <450 ms for men and <470 ms for women, and sinus rhythm, were met by 515 patients (30.5%). Multivariable Cox regression showed that the hazard (HR) for death, heart transplantation or appropriate shock were reduced by 42.5% in the low-risk group (HR 0.575; 95% CI 0.45–0.74; p < 0.001), compared to the high-risk group. The HR for the first appropriate shock was 42.1% lower (HR 0.58; 95% CI 0.41–0.82; p = 0.002) and the HR for death was 48.0% lower (HR 0.52; 95% CI 0.386–0.72; p < 0.001) in the low-risk group. Sinus rhythm, QRS <120 ms and normal QTc in standard 12-lead ECG provides information about survival without appropriate ICD shocks and might improve patient selection for primary prevention ICD therapy. • 12-lead ECG identifies the patients who may not benefit from primary prophylactic ICD patients. • Low risk ECG is defined as QRS duration <120 ms, sinus rhythm, and normal QTc duration. • 12-lead ECG can be used together with other risk variables in identifying the candidate for prophylactic ICD therapy. [ABSTRACT FROM AUTHOR]

Background: A small proportion of patients undergoing primary prophylactic implantation of implantable cardioverter defibrillators (ICDs) experiences malignant arrhythmias. We postulated that periodic repolarisation dynamics, a novel marker of sympathetic-activity-associated repolarisation instability, could be used to identify electrically vulnerable patients who would benefit from prophylactic implantation of ICDs by way of a reduction in mortality.Methods: We did a prespecified substudy of EUropean Comparative Effectiveness Research to Assess the Use of Primary ProphylacTic Implantable Cardioverter Defibrillators (EU-CERT-ICD), a prospective, investigator-initiated, non-randomised, controlled cohort study done at 44 centres in 15 EU countries. Patients aged 18 years or older with ischaemic or non-ischaemic cardiomyopathy and reduced left ventricular ejection fraction (≤35%) were eligible for inclusion if they met guideline-based criteria for primary prophylactic implantation of ICDs. Periodic repolarisation dynamics from 24-h Holter recordings were assessed blindly in patients the day before ICD implantation or on the day of study enrolment in patients who were conservatively managed. The primary endpoint was all-cause mortality. Propensity scoring and multivariable models were used to assess the interaction between periodic repolarisation dynamics and the treatment effect of ICDs on mortality.Findings: Between May 12, 2014, and Sept 7, 2018, 1371 patients were enrolled in our study. 968 of these patients underwent ICD implantation, and 403 were treated conservatively. During follow-up (median 2·7 years [IQR 2·0-3·3] in the ICD group and 1·2 years [0·8-2·7] in the control group), 138 (14%) patients died in the ICD group and 64 (16%) patients died in the control group. We noted a 43% reduction in mortality in the ICD group compared with the control group (adjusted hazard ratio [HR] 0·57 [95% CI 0·41-0·79]; p=0·0008). Periodic repolarisation dynamics significantly predicted the treatment effect of ICDs on mortality (adjusted p=0·0307). The mortality benefits associated with ICD implantation were greater in patients with periodic repolarisation dynamics of 7·5 deg or higher (n=199; adjusted HR 0·25 [95% CI 0·13-0·47] for the ICD group vs the control group; p<0·0001) than in those with periodic repolarisation dynamics less than 7·5 deg (n=1166; adjusted HR 0·69 [95% CI 0·47-1·00]; p=0·0492; pinteraction=0·0056). The number needed to treat was 18·3 (95% CI 10·6-4895·3) in patients with periodic repolarisation dynamics less than 7·5 deg and 3·1 (2·6-4·8) in those with periodic repolarisation dynamics of 7·5 deg or higher.Interpretation: Periodic repolarisation dynamics predict mortality reductions associated with prophylactic implantation of ICDs in contemporarily treated patients with ischaemic or non-ischaemic cardiomyopathy. Periodic repolarisation dynamics could help to guide treatment decisions about prophylactic ICD implantation.Funding: The European Community's 7th Framework Programme. [ABSTRACT FROM AUTHOR]

The Seattle Heart Failure Model (SHFM) is a validated multivariate risk prediction model for mortality in patients with heart failure, using widely available clinical variables. The aim of this study was to assess the performance of the SHFM when applied to patients with heart failure who received cardiac resynchronization therapy devices with defibrillation. A total of 413 patients were identified from 2 prospective implantable cardioverter-defibrillator registries who received cardiac resynchronization therapy devices with defibrillation for the primary prevention of sudden death. Baseline laboratory and clinical data were entered in the SHFM to calculate predicted survival. The end point was all-cause mortality. During a median follow-up period of 2.8 years, 78 patients died and 9 underwent heart transplantation. Observed versus predicted 5-year mortality rates were 11.6% versus 11.4%, 21.5% versus 22.1%, and 41.4% versus 46.1% by ascending tertile of Seattle Heart Failure Score, respectively. No systematic or substantial errors of risk estimation were observed. Discrimination was excellent; the C-statistic ranged from 0.78 at 1-year follow-up to 0.70 at 5-year follow-up, and the Hosmer-Lemeshow chi-square statistic was 0.87 (p = 0.65). In conclusion, in patients with heart failure who received cardiac resynchronization therapy devices with defibrillation, the SHFM offers adequate discrimination of risk for all-cause mortality and estimation of mortality risk without substantial or systematic errors. [Copyright &y& Elsevier]