Ventricular Fibrillation Shock Research Articles

Low Risk of Inappropriate Shock Among Pediatric Patients With an Implantable Cardioverter Defibrillator: A Single Center Experience.

Implantable cardioverter-defibrillators (ICD) are increasingly being used among the pediatric population for indications of both primary and secondary prevention. There is limited long-term data on the outcomes of pediatric patients following ICD implantation. The aim of this study was to investigate the characteristics of this population, burden of appropriate and inappropriate shock and complication rate in a large tertiary pediatric medical center. Included were children under the age of 18years who underwent ICD implantation and had clinical follow up at our center. Data were retrospectively collected between study period 2005-2020. Primary outcome was the incidence of ICD shock appropriate and inappropriate. Secondary outcome was defining our patient population characteristics. Our cohort included 51 patients who underwent ICD implantation. Mean age at implantation was 10.9 ± 4.7years and average follow-up time was 67months. Diagnoses of implanted patients were: 28 (55%) patients with syndromes with risk for sudden death, cardiomyopathy in 14 patients (27%) and congenital heart disease (CHD) in 9 patients (18%). Forty-two (82%) patients had an ICD implanted for secondary prevention after experiencing a life-threatening arrhythmia and 9 (18%) for primary prevention. An endocardial system was implanted in 39 (76%) patients and an epicardial systems in 12 (24%) patients. A total of 20 (39%) patients received appropriate shocks for ventricular fibrillation(VF). 5 patients received inappropriate shocks, 4 due to sinus tachycardia and 1 due to rapidly conducted atrial fibrillation. Those who received an inappropriate shock had a significantly shorter ICD-programmed VF detection cycle length compared to those who did not receive an inappropriate shock (320ms versus 270ms, p = 0.062). This single center study demonstrates a high rate of appropriate ICD shocks (39%) and a low rate of inappropriate ICD shocks. Accurate programming of ICD devices in the pediatric population is paramount to avoid inappropriate ICD shocks.

Post-Shock Asystole in Patients Dying Out of Hospital While Wearing a Cardioverter Defibrillator

BackgroundThe wearable cardioverter-defibrillator (WCD) prevents sudden cardiac death due to ventricular tachycardia (VT) or ventricular fibrillation (VF) but does not pace for post-shock asystole (PS-A) or bradycardia (PS-B;<50 beats/ min). ObjectivesThe purpose of this study was to assess PS-A and PS-B in patients dying out of hospital (OOH) while wearing a WCD. MethodsThe database of the U.S. Food and Drug Administration Manufacturers and User Facility Device Experience (MAUDE) was queried for manufacturers’ reports of OOH deaths while patients were wearing a WCD. Excluded were patients who did not receive a shock or were initially shocked for asystole or during resuscitation. ResultsFrom January 2017 to March 2022, 313 patients received an initial WCD shock for VF (n = 150), VT (n = 90), and non-VF/VT rhythms (n = 73). PS-A occurred in 204 patients (65.2%), and PS-B occurred in 111 (35.5%); 85 (41.7%) PS-A patients also had PS-B. Most PS-A patients (n = 185; 90.7%) had an initial shocked rhythm of VF or VT, but 19 patients (9.3%) were initially inappropriately shocked for atrial fibrillation/supraventricular tachycardia (n = 7) and idioventricular (n = 8) or sinus (n = 4) rhythm. PS-A occurred after the first WCD shock in 118 (63.8%) and after the first, second, or third shocks in 159 patients (85.9%). Seven patients had post-shock heart block. Eight patients had permanent pacemakers; 1 became nonfunctional after 1 shock, and 7 showed noncapture and/or asystole after 1 to 4 shocks. ConclusionsPost-shock asystole appears to be common in patients who die OOH after being shocked by a WCD for VF or VT. PS-A also occurs after inappropriate WCD shocks for non-VF/VT rhythms. Implanted pacemakers may not prevent PS-A after a WCD shock. WCD backup pacing should be explored.

Cardiopulmonary Exercise Testing in Athletes With Hypertrophic Cardiomyopathy

Patients with hypertrophic cardiomyopathy (HCM) have historically been restricted from athletic participation because of the perceived risk of sudden cardiac death. More contemporary research has highlighted the relative safety of competitive athletics with HCM. However, lack of published data on reference values for cardiopulmonary exercise testing (CPET) complicates clinical management and counseling on sports participation in the individual athlete. We conducted a single-center, retrospective cohort study to investigate CPET in athletes with HCM and clinical characteristics associated with objective measures of aerobic capacity. We identified 58 athletes with HCM (74% male, mean age 18±3years, mean left ventricular (LV) wall thickness 20±7mm). LV outflow tract obstruction was present in 22 (38%). A total of 15 (26%) athletes were taking a β blocker (BB), but only 4 (7%) reported exertional symptoms. Overall, exercise capacity was mildly reduced, with a peak myocardial oxygen consumption (peak VO2) of 37.9ml/min/kg (83% of predicted peak VO2). Both LV outflow tract obstruction and BB use were associated with reduced exercise capacity. Limited peak heart rate was more common in athletes taking BB (47% vs 9%, p=0.002). At a mean 5.6years follow-up, 5 patients underwent myectomy (9%), and 8 (14%) received an implantable cardioverter defibrillator (ICD) for primary prevention. One individual with massive LV hypertrophy experienced recurrent ICD shocks for ventricular fibrillation and underwent myectomy 7years after initial evaluation and was no longer participating in sports. There were no deaths over the follow-up period. In conclusion, the prognostic role of CPET remains unclear in athletes with HCM. Mildly reduced exercise capacity was common; however, reduced peak VO2 did not correlate with symptom status or clinical outcomes. A significant proportion went on to require myectomy and/or ICD, thus highlighting the need for close follow-up. These data provide some initial insight into the clinical evaluation of "real world" athletes with HCM; however, further study is warranted to help guide shared decision-making, return-to-play discussions, and the potential long-term safety of competitive athletic participation.

Survival After Implantable Cardioverter-Defibrillator Shocks

BackgroundThere are conflicting data on the impact of implantable cardioverter-defibrillator (ICD) shocks on subsequent mortality. ObjectivesThe aim of this study was to determine whether the arrhythmic substrate leading to ICD therapy or the therapy itself increases mortality. MethodsThe study cohort included 5,516 ICD recipients who were enrolled in 5 landmark ICD trials (MADIT-II, MADIT-RISK, MADIT-CRT, MADIT-RIT, RAID). The authors evaluated the association of device therapy with subsequent mortality in 4 separate time-dependent models: model I, type of ICD therapy; model II, type of arrhythmia for which ICD therapy was delivered; model III, combined assessment of all arrhythmia and therapy types during follow-up; and model IV, incremental risk associated with repeated ICD shocks. ResultsWhen analyzed by the type of ICD therapy (model I), a first appropriate ICD shock was associated with increased risk of subsequent mortality with or without concomitant occurrence of inappropriate shock during follow-up (hazard ratio [HR]: 2.78 and 2.31; p < 0.001 and p = 0.12), whereas inappropriate shock alone was not associated with mortality risk (HR: 1.23; p = 0.42). Similarly, ICD therapy for ventricular tachycardia (VT) ≥200 beats/min or ventricular fibrillation (VF) (model II) was associated with increased risk of death with or without concomitant therapy for VT <200 beats/min (HRs: 2.25 and 2.62; both p < 0.001), whereas appropriate therapy for VT <200 beats/min or inappropriate therapy (regardless of etiology) did not reach statistical significance (all p > 0.10). Combined assessment of all therapy and arrhythmia types during follow-up (model III) showed that appropriate ICD shocks for VF, shocks for fast VT (≥200 beats/min) without prior antitachycardia pacing (ATP), as well as shocks for fast VT delivered after failed ATP, were associated with the highest risk of subsequent death (HR: all >2.8; p < 0.001). Finally, 2 or more ICD appropriate shocks were not associated with incremental risk to the first appropriate ICD shock (model IV). ConclusionThe combined data from 5 landmark ICD trials suggest that the underlying arrhythmic substrate rather than the ICD therapy is the more important determinant of mortality in ICD recipients.

A method to predict ventricular fibrillation shock outcome during chest compressions

BackgroundOut-of-hospital ventricular fibrillation (VF) cardiac arrest is a leading cause of death. Quantitative analysis of the VF electrocardiogram (ECG) can predict patient outcomes and could potentially enable a patient-specific, guided approach to resuscitation. However, VF analysis during resuscitation is confounded by cardiopulmonary resuscitation (CPR) artifact in the ECG, challenging continuous application to guide therapy throughout resuscitation. We therefore sought to design a method to predict VF shock outcomes during CPR. MethodsStudy data included 4577 5-s VF segments collected during and without CPR prior to defibrillation attempts in N = 1151 arrest patients. Using training data (460 patients), an algorithm was designed to predict the VF shock outcomes of defibrillation success (return of organized ventricular rhythm) and functional survival (Cerebral Performance Category 1–2). The algorithm was designed with variable-frequency notch filters to reduce CPR artifact in the ECG based on real-time chest compression rate. Ten ECG features and three dichotomous patient characteristics were developed to predict outcomes. These variables were combined using support vector machines and logistic regression. Algorithm performance was evaluated by area under the receiver operating characteristic curve (AUC) to predict outcomes in validation data (691 patients). ResultsAUC (95% Confidence Interval) for predicting defibrillation success was 0.74 (0.71–0.77) during CPR and 0.77 (0.74–0.79) without CPR. AUC for predicting functional survival was 0.75 (0.72–0.78) during CPR and 0.76 (0.74–0.79) without CPR. ConclusionA novel algorithm predicted defibrillation success and functional survival during ongoing CPR following VF arrest, providing a potential proof-of-concept towards real-time guidance of resuscitation therapy.

P497Arrhythmic burden in patients with filamin C (FLNC) truncating variant associated cardiomyopathy

Abstract Background Truncating variants in FLNC gene are associated with an overlapping phenotype of arrhythmogenic and dilated cardiomyopathy. There are reports of high arrhythmia propensity with sudden cardiac death (SCD) often being the first symptom of the disease. It has been suggested that the current European guidelines primary prevention (PP) recommendation about implantable cardioverter-defibrillator (ICD) implantation might not be applicable in these patients and that earlier intervention should be considered. Purpose We sought to investigate the arrhythmic burden in FLNC truncation carriers in our centre. Methods Adult FLNC truncation carriers diagnosed in our centre between the years 2018 and 2019 were included in the study. We retrospectively analysed clinical data, and ICD follow-up reports in the cohort. Patients implanted with an ICD were divided in 3 groups: group A (secondary prevention ICD implantation), group B (PP indication according to the current guidelines – left ventricular ejection fraction (LVEF) below 35%) and group C (early PP– FLNC truncation carrier, LVEF &amp;lt; 50% and late gadolinium enhancement on cardiac magnetic resonance). We report the number of patients experiencing SCD and the number of appropriate and inappropriate ICD therapies per group. Results Twenty-four adult patients from 3 different families with three distinct FLNC truncating variants were identified. Ten (42%) were male; the average age was 45 ± 14 years. There were 3 (13%) SCDs in one family (2 male and one female, 29-42 years old) and two (8%) aborted SCDs in the remaining two families (one male and one female, 66 and 51 years old). Altogether eleven (46%) patients were implanted with an ICD. There were three patients in group A (2 aborted SCDs and 1 sustained ventricular tachycardia (VT)), two patients in group B and six patients in group C. Average ICD follow-up times were 42, 48 and 6 months for groups A, B and C, respectively. Eight appropriate ICD therapies occurred in 3 patients (27%). In group A, there were four sustained VT episodes successfully converted with an anti-tachycardia pacing (ATP) in two patients (67%); the average time to first therapy was 33 months. In group B, there was one appropriate shock for ventricular fibrillation (VF), and three sustained VT episodes in one patient (50%), time to first therapy was 60 months. After six months follow-up, there were no appropriate therapies registered in group C. Two patients (18%) experienced inappropriate shocks due to sinus tachycardia, one in group A and one in group C. Conclusion One-fifth of FLNC truncation carriers in our cohort experienced SCD. When patients received an ICD according to the current guidelines, majority experienced appropriate ICD therapy. Further clinical studies with longer follow-up will be needed to define appropriate risk stratification and optimal timing for prophylactic ICD intervention in these patients.

P1705The association between pre-shock ventricular fibrillation duration and shock success during out-of-hospital cardiac arrest

Abstract Background After the first shock, most ventricular fibrillation (VF) out-of-hospital cardiac arrest (OHCA) patients require subsequent shocks before organized rhythm is restored. Currently, all those shocks are given after a fixed 2 or 3-minute chest compression interval, resulting in many unsuccessful shocks. However, recently new defibrillators have been developed that can recognize VF during chest compressions, and enable earlier shocks immediately upon detection of VF. This prompts the question whether VF of shorter duration is associated with higher shock success. Purpose To study the association between pre-shock VF-duration and shock success in all subsequent shocks during OHCA. Methods Detailed VF-study on a subset of our prospective, real-world cardiac arrest-registry, focusing on patients with ≥2 shocks for VF and available ECG-tracings. These were scrutinized to determine VF-duration (time from VF-onset until shock) and shock success (return of organized rhythm within 1 min. after the shock). All first shocks were excluded. Results We studied 397 shocks from 101 patients. Of these, 77% were male and median age was 64 (interquartile range [IQR] 54–76) years. Overall shock success was 51% and survival to discharge was 19%. Overall median pre-shock VF-duration was 221s (IQR 125–433). The median pre-shock VF-duration was shorter before a successful (171s [IQR 75–295]) than before an unsuccessful shock (334s [IQR 174–740]), p&lt;0.001. Shock success decreased from 75% in the quartile with the shortest to 21% in the quartile with the longest pre-shock VF-duration, p for trend&lt;0.001 (Figure 1). Figure 1 Conclusion In shocks following the first defibrillation attempt, VF of shorter duration is associated with higher proportions of shock success. In an era of defibrillators that are able to recognize VF during chest compressions, our findings prompt the question whether shock upon detection of VF may improve the dismal outcomes of VF cardiac arrest. Acknowledgement/Funding None

Single incision technique for implantation of subcutaneous implantable cardioverter defibrillators.

Subcutaneous implantable cardioverter defibrillators (S-ICDs) have gained increasing popularity because of certain advantages over transvenous ICDs. However, while conventional ICDs require a single surgical incision to implant, S-ICDS need two or three incisions, making them less appealing. This study sought out to investigate the feasibility of using a single-incision technique to implant S-ICDs. Patients qualifying for S-ICDs were considered for a single incision. A single incision is performed by making a left inframammary incision and then the subcutaneous tissue is dissected medially toward the lower sternum. Two sutures are placed in the fascia in the xiphoid area to anchor the lead and a tunneling tool is used to dissect the tissue to place the lead parallel to the sternum. Then subcutaneous tissues are dissected down the lateral chest wall over the muscle fascia to create the pulse generator pocket in the vicinity of the fifth and sixth intercostal spaces and near the mid-axillary line. Eleven patients (six males and five females) successfully underwent S-ICD implantation with a single incision without acute complications (64% for primary prevention). The mean age is 47.4 ± 15.8 years. There were no lead dislodgements, inappropriate shocks, or any other issues during a median follow-up of 10 months (interquartile range 5-17). One patient had a successful appropriate shock for ventricular fibrillation about one year after device implant. A single incision for subcutaneous ICDs is feasible and safe in our early experience.

30-Year-Old Man With Outside-of-Hospital Cardiac Arrest

30-Year-Old Man With Outside-of-Hospital Cardiac Arrest

Minimally invasive, pericardial implantable cardioverter-defibrillator placement in a young child

We report the successful minimally invasive placement of a pericardial implantable cardioverter-defibrillator (ICD) in a 16-kg child. A transvenous ICD dual coil was advanced through a small subxiphoid incision and screwed into the oblique sinus pericardium under fluoroscopic guidance. An additional sense-pace lead was sutured onto the right ventricular apex, and the generator was placed in the upper abdominal wall through the same incision. Threshold testing demonstrated successful defibrillation at 15J. After implantation, the patient had two episodes of appropriate shock for ventricular fibrillation. The ICD system continues to show stable impedance at 6 months of follow-up.

Application of Entropy-Based Features to Predict Defibrillation Outcome in Cardiac Arrest

Prediction of defibrillation success is of vital importance to guide therapy and improve the survival of patients suffering out-of-hospital cardiac arrest (OHCA). Currently, the most efficient methods to predict shock success are based on the analysis of the electrocardiogram (ECG) during ventricular fibrillation (VF), and recent studies suggest the efficacy of waveform indices that characterize the underlying non-linear dynamics of VF. In this study we introduce, adapt and fully characterize six entropy indices for VF shock outcome prediction, based on the classical definitions of entropy to measure the regularity and predictability of a time series. Data from 163 OHCA patients comprising 419 shocks (107 successful) were used, and the performance of the entropy indices was characterized in terms of embedding dimension (m) and matching tolerance (r). Six classical predictors were also assessed as baseline prediction values. The best prediction results were obtained for fuzzy entropy (FuzzEn) with m = 3 and an amplitude-dependent tolerance of r = 80 μ V . This resulted in a balanced sensitivity/specificity of 80.4%/76.9%, which improved by over five points the results obtained for the best classical predictor. These results suggest that a FuzzEn approach for a joint quantification of VF amplitude and its non-linear dynamics may be a promising tool to optimize OHCA treatment.

Sites of Successful Ventricular Fibrillation Ablation in Bileaflet Mitral Valve Prolapse Syndrome.

Although the vast majority of mitral valve prolapse (MVP) is benign, a small subset of patients, predominantly women, with bileaflet prolapse, complex ventricular ectopy (VE), and abnormal T waves comprise the recently described bileaflet MVP syndrome. We compared findings on electrophysiological study in bileaflet MVP syndrome patients with and without cardiac arrest to identify factors that may predispose to malignant ventricular arrhythmia. Fourteen consecutive bileaflet MVP syndrome patients (n=13 women; median [limits], age at index ablation, 33.8 [21.0-58.7] years; ejection fraction, 60% [45%-67%]; all ≤ moderate mitral regurgitation; n=6 with previous cardiac arrest and implantable cardioverter defibrillator shocks for ventricular fibrillation; and n=8 without implantable cardioverter defibrillator although with symptomatic complex VE) were included. The 2 groups had similar baseline echocardiographic and electrocardiographic characteristics. All patients had at least 1 left ventricular papillary or fascicular VE focus. Purkinje origin VE was identified as the ventricular fibrillation trigger in 6 of 6 cardiac arrest patients (4 from papillary muscle) and Purkinje origin of dominant VE was seen in 5 of 8 (3 from papillary muscle) nonarrest patients. Acute success was seen in 17 of 19 procedures, and a ventricular fibrillation storm occurred within 24 hours of ablation in a single patient. Repeat ablation for recurrent symptomatic arrhythmia was performed in 6 patients. At 478 (39-2099) days of follow-up, 2 cardiac arrest patients received appropriate shocks. Symptoms from VE were reduced in 12 of 14. Bileaflet MVP syndrome is characterized by fascicular and papillary muscle VE that triggers ventricular fibrillation. Ablation of clinically dominant VE foci improves symptoms and reduces appropriate implantable cardioverter defibrillator shocks.

Intrapulmonary artery balloon pulsation improves circulatory function after acute myocardial infarction in pigs.

To examine whether pulmonary artery balloon pulsation (PABP) could improve circulatory function in acute myocardial infarction (AMI) in pigs. Ten downsize pigs were sedated and ventilated. AMI was induced by inserting a plug into the left anterior descending artery. A pulsation balloon was placed in the pulmonary artery in all animals. In the treatment group (TG), pulsations began when life-threatening arrhythmia or > 30% drop in mean blood pressure (MBP) or > 40% decrease in cardiac output compared to baseline occurred. Pulsation rate was 120/min, independent of the heartbeat, maintained for 10 min. The control group (CG) received no pulsation. In the TG (n = 5), mean BP after the AMI improved by 7 ± 12 mmHg after 150 min while in the CG, MBP decreased by 17 ± 25 mmHg, P < 0.05; coronary perfusion pressure improved by 8 ± 7 mmHg in the TG but decreased by 15 ± 12 in the CG (P < 0.05). In the CG, cardiac output did not change but in the TG it improved from 3.5 ± 0.9 after the AMI to 4.2 ± 1.1 l/min 150 min after AMI (P < 0.05). The TG required 1.8 ± 0.4 electric shocks for ventricular fibrillation versus 0.8 ± 0.4 in the pulsation group (P < 0.05). PABP could be useful in the management of AMI due to improved mean arterial BP, coronary perfusion pressure, cardiac output and electrical stability. The mechanism of this effect remains to be determined.

Re-entry using anatomically determined isthmuses: a curable ventricular tachycardia in repaired congenital heart disease.

Ventricular tachycardia (VT) is an important cause of late morbidity and mortality in repaired congenital heart disease. The substrate often includes anatomic isthmuses that can be transected by radiofrequency catheter ablation similar to isthmus block for atrial flutter. This study evaluates the long-term efficacy of isthmus block for treatment of re-entry VT in adults with repaired congenital heart disease. Thirty-four patients (49±13 years; 74% male) with repaired congenital heart disease who underwent radiofrequency catheter ablation of VT in 2 centers were included. Twenty-two (65%) had a preserved left and right ventricular function. Patients were inducible for 1 (interquartile range, 1-2) VT, median cycle length: 295 ms (interquartile range, 242-346). Ablation aimed to transect anatomic isthmuses containing VT re-entry circuit isthmuses. Procedural success was defined as noninducibility of any VT and transection of the anatomic isthmus and was achieved in 25 (74%) patients. During long-term follow-up (46±29 months), all patients with procedural success (18/25 with internal cardiac defibrillators) were free of VT recurrence but 7 of 18 experienced internal cardiac defibrillator-related complications. One patient with procedural success and depressed cardiac function received an internal cardiac defibrillator shock for ventricular fibrillation. None of the 18 patients (12/18 with internal cardiac defibrillators) with complete success and preserved cardiac function experienced any ventricular arrhythmia. In contrast, VT recurred in 4 of 9 patients without procedural success. Four patients died from nonarrhythmic causes. In patients with repaired congenital heart disease with preserved ventricular function and isthmus-dependent re-entry, VT isthmus ablation can be curative.

Riata lead failure presenting as a life-threatening electrical storm: A novel manifestation of electrical lead failure

The Riata and Riata ST family of implantable cardioverter-defibrillator leads are prone to a unique type of structural failure involving exteriorization of the conductor cables, which may present as electrical failure. We report a mode of lead failure that occurred in a patient with a Riata 1570 series dual coil 8F lead. In this case, the first appropriate shock for ventricular fibrillation resulted in noise, that in turn led to recurrent inappropriate shocks and proarrhythmia, that clinically mimicked a life-threatening electrical storm.

Cognitive impairment after appropriate implantable cardioverter-defibrillator therapy for ventricular fibrillation

Short periods of cerebral ischaemia during ventricular defibrillation testing may be associated with neuropsychological impairment. However, the impact of out-of-hospital ventricular fibrillation (VF) converted by implantable cardioverter-defibrillator (ICD) shock on cognitive functioning is unknown. To assess the impact of out-of-hospital VF converted by ICD shock on cognitive functioning. The study included 52 primary prevention ICD recipients. Patients with a history of stroke or other neurological impairment, previous head injury and individuals unable to see or speak to complete neuropsychological tests were not included.Initially, a Mini-Mental State Examination was performed in all patients and one patient with a result below 24 points was excluded from the study. The cognitive battery consisted of four tests (six measurements): 1) the Digit Span subtest of Wechsler Adult Intelligence Scale-Revised; 2) the Digit Symbol subtest of Wechsler Adult Intelligence Scale-Revised; 3) the Halstead-Reitan Trail-Making Test A and B; and 4) the Ruff Figural Fluency Test. The mean time from ICD implantation to cognitive assessment was 26 months. During this period, 15 appropriate shocks for VF were observed in seven (14%) patients. The patients with appropriate ICD therapy were significantly worse in two out of the six neuropsychological measurements and had a significantly lower aggregate result. In multivariate linear regression analysis, defibrillation therapy was an independent factor of poor cognitive functioning, along with age and education. Short periods of out-of-hospital VF converted by ICD are associated with cognitive impairment in the recipients of primary prevention ICD.

Rationale and design of the SERVE‐HF study: treatment of sleep‐disordered breathing with predominant central sleep apnoea with adaptive servo‐ventilation in patients with chronic heart failure

AimsCentral sleep apnoea/Cheyne–Stokes respiration (CSA/CSR) is a risk factor for increased mortality and morbidity in heart failure (HF). Adaptive servo-ventilation (ASV) is a non-invasive ventilation modality for the treatment of CSA/CSR in patients with HF.MethodsSERVE-HF is a multinational, multicentre, randomized, parallel trial designed to assess the effects of addition of ASV (PaceWave™, AutoSet CS™; ResMed) to optimal medical management compared with medical management alone (control group) in patients with symptomatic chronic HF, LVEF ≤45%, and predominant CSA. The trial is based on an event-driven group sequential design, and the final analysis will be performed when 651 events have been observed or the study is terminated at one of the two interim analyses. The aim is to randomize ∼1200 patients to be followed for a minimum of 2 years. Patients are to stay in the trial up to study termination. The first patient was randomized in February 2008 and the study is expected to end mid 2015. The primary combined endpoint is the time to first event of all-cause death, unplanned hospitalization (or unplanned prolongation of a planned hospitalization) for worsening (chronic) HF, cardiac transplantation, resuscitation of sudden cardiac arrest, or appropriate life-saving shock for ventricular fibrillation or fast ventricular tachycardia in implantable cardioverter defibrillator patients.PerspectivesThe SERVE-HF study is a randomized study that will provide important data on the effect of treatment with ASV on morbidity and mortality, as well as the cost-effectiveness of this therapy, in patients with chronic HF and predominantly CSA/CSR.Trial registrationISRCTN19572887

Predicting defibrillation success in sudden cardiac arrest patients

Although the importance of quality cardiopulmonary resuscitation (CPR) and its link to survival is still emphasized, there has been recent debate about the balance between CPR and defibrillation, particularly for long response times. Defibrillation shocks for ventricular fibrillation (VF) of recently perfused hearts have high success for the return of spontaneous circulation (ROSC), but hearts with depleted adenosine triphosphate (ATP) stores have low recovery rates. Since quality CPR has been shown to both slow the degradation process and restore cardiac viability, a measurement of patient condition to optimize the timing of defibrillation shocks may improve outcomes compared to time-based protocols. Researchers have proposed numerous predictive features of VF and shockable ventricular tachycardia (VT) which can be computed from the electrocardiogram (ECG) signal to distinguish between the rhythms which convert to spontaneous circulation and those which do not. We looked at the shock-success prediction performance of thirteen of these features on a single evaluation database including the recordings from 116 out-of-hospital cardiac arrest patients which were collected for a separate study using defibrillators in ambulances and medical centers in 4 European regions and the US between March 2002 and September 2004. A total of 469 shocks preceded by VF or shockable VT rhythm episodes were identified in the recordings. Based on the experts' annotation for the post-shock rhythm, the shocks were categorized to result in either pulsatile (ROSC) or non-pulsatile (no-ROSC) rhythm. The features were calculated on a 4-second ECG segment prior to the shock delivery. These features examined were: Mean Amplitude, Average Peak-Peak Amplitude, Amplitude Range, Amplitude Spectrum Analysis (AMSA), Peak Frequency, Centroid Frequency, Spectral Flatness Measure (SFM), Energy, Max Power, Centroid Power, Power Spectrum Analysis (PSA), Mean Slope, and Median Slope. Statistical hypothesis tests (two-tailed t-test and Wilcoxon with 5% significance level) were applied to determine if the means and medians of these features were significantly different between the ROSC and no-ROSC groups. The ROC curve was computed for each feature, and Area Under the Curve (AUC) was calculated. Specificity (Sp) with Sensitivity (Se) held at 90% as well as Se with Sp held at 90% was also computed. All features showed statistically different mean and median values between the ROSC and no-ROSC groups with all p-values less than 0.0001. The AUC was >76% for all features. For Sp = 90%, the Se range was 33–45%; for Se = 90%, the Sp range was 49–63%. The features showed good shock-success prediction performance. We believe that a defibrillator employing a clinical decision tool based on these features has the potential to improve overall survival from cardiac arrest.

Long-Term Complications of Implantable Defibrillator Therapy in Brugada Syndrome

Although the benefits of implantable cardioverter-defibrillator (ICD) therapy in patients with Brugada syndrome (BrS) at risk of sudden cardiac arrest are well established, these relatively young patients can encounter complications in the long term. The objective of the present study was to determine the incidence of device complications in patients with BrS during long-term follow-up. The prevalence of device-related complications and the clinical outcome were determined in 41 consecutive patients with BrS (age 48 ± 12 years; 38 men) who were treated with ICD implantation. During a median follow-up of 76 months (interquartile range 51 to 98), 15 patients (37%) experienced 21 adverse events, including 11device-related complications in 8 (20%) and ≥1 inappropriate shock in 10 (24%). Five patients (12%) received appropriate shocks for ventricular fibrillation. Excluding inappropriate shocks, 95.1%, 89.6%, 86.6%, and 73.3% of patients were free of device-related complications at 1, 3, 5, and 7 years, respectively. Also, 92.6%, 89.8%, 89.9%, and 86.1% were free of lethal arrhythmias at 1, 3, 5, and 7 years, respectively. Adverse effects related to ICD implantation are not uncommon, and their prevalence increases with the follow-up duration required for patients with BrS. In conclusion, because complications can be encountered even very late after device implantation, asymptomatic young patients should be carefully selected and educated about the long-term outcomes of ICD therapy.

The Implantable Cardioverter-Defibrillator Minimalist

The implantable cardioverter-defibrillator (ICD) was devised to satisfy the unmet need for an effective, instantaneous therapy to prevent sudden cardiac death (SCD) due to ventricular fibrillation (VF) in at-risk, ambulatory patients. That therapy was a high-voltage electric shock delivered directly into the heart muscle. More than 3 decades later, shocks are still the defining operating characteristic of ICDs, and no other instantaneously effective therapy for VF exists. This elite status was clinched by large randomized clinical trials1,2 which demonstrated that ICDs improved mortality in patients with reduced left ventricular ejection fraction, regardless of pathogenesis or accompanying symptoms of heart failure (HF), by primary prevention of SCD due to ventricular tachyarrhythmia (VTA). Like bradycardia pacemakers for asystole, the ICD resides as a therapy genre of one, with no peer, and no competitor on the horizon. These sibling therapies for lethal heart rhythm disturbances will stand prominently among the greatest medical achievements of the 20th century. The ICD is a mature technology, and neither the technique nor the tools have changed much for several decades. Despite a certain evolutionary elegance of the operating system, the ICD is still a blunt instrument. Although it is true that some innovation has occurred, it is still a matter of a shock delivered by insulated metal conductors residing somewhere in direct proximity to the heart. No innovation beyond the fundamental of a timed shock for VF has proven to enhance mortality benefit. The basic design persists simply because no one can think of a suitable alternative and the self-satisfying aphorism that “shocks save lives.” Yet there is a growing intellectual dissatisfaction with the unintended consequences of this powerful, irreplaceable therapy. The stimulus for this self-inspection is an awareness of the very high morbidity risk overhead borne by the primary prevention patient, in particular, …