Detection Of Ventricular Arrhythmias Research Articles

Subcutaneous Implantable Cardioverter Defibrillator

Implantable cardioverter-defibrillators (ICDs) represent a very effective therapy for primary and secondary prevention of sudden cardiac death (SCD). However, implantation of endocardial leads using a transvenous approach is associated with significant procedural and long term complications. An entirely subcutaneous ICD (S-ICD) has been developed, potentially eliminating many of the complications associated with traditional transvenous ICDs. This novel approach has been demonstrated to be a reliable and effective system for detection and termination of ventricular arrhythmias. The available therapeutic interventions are a result of the unique characteristics of a high energy subcutaneous delivery system, and therefore require appropriate patient selection to optimize therapeutic benefit and minimize the limitations of the first generation S-ICD. By maintaining the effectiveness of conventional ICDs while limiting the associated complications, the S-ICD provides an alternative therapy for clinicians treating many patients at risk for SCD. This review will examine the development of the subcutaneous ICD, its advantages, limitations, and potential clinical role in the treatment of ventricular tachyarrhythmias and prevention of SCD. Despite advances in cardiovascular care, SCD remains a significant public health issue.1 A variety of nonpharmacologic therapies for primary and secondary prevention of SCD exist, including ICDs by endovascular lead implantation or placement of epicardial defibrillation patches. Nonimplantable strategies for SCD protection in high risk patients have also been attempted, including a wearable defibrillator vest,2,3 as well as automated external defibrillator use at home in selected cohorts.4 The subcutaneous ICD provides an alternative device for treatment of SCD.5 The development of an entirely subcutaneous ICD was motivated initially by special circumstances where a traditional endovascular system was not practical. It was first applied in the pediatric population, where congenital anatomic variation often precludes safe endocardial lead placement; the technique was extended to other patient populations in whom venous …

Detection of premature ventricular contraction arrhythmias in electrocardiogram signals with kernel methods

In this paper, we propose to investigate the capabilities of two kernel methods for the detection and classification of premature ventricular contractions (PVC) arrhythmias in Electrocardiogram (ECG signals). These kernel methods are the support vector machine and Gaussian process (GP). We propose to study these two classifiers with various feature representations of ECG signals, such as morphology, discrete wavelet transform, higher-order statistics, and S transform. The experimental results obtained on 48 records (i.e., 109,887 beats) of the MIT-BIH Arrhythmia database showed that for all feature representation adopted in this work, the GP detector trained only with 600 beats from PVC and Non-PVC classes can provide an overall accuracy and a sensitivity above 90 % on 20 records (i.e., 49,774 beats) and 28 records (i.e., 60,113 beats) seen and unseen, respectively, during the training phase.

Prenatal diagnosis of long QT syndrome: implications for delivery room and neonatal management

This case describes the prenatal diagnosis and integrated peripartum management of a foetus with 2:1 atrioventricular block and torsade de pointes due to congenital long QT syndrome. The unique issues related to the detection of intrauterine conduction abnormalities and ventricular arrhythmias, along with the immediate postnatal care, have been described as an interesting teaching case with successful outcome.

Head‐To‐Head Comparison of Arrhythmia Discrimination Performance of Subcutaneous and Transvenous ICD Arrhythmia Detection Algorithms: The START Study

The development of a totally subcutaneous implantable defibrillator (S-ICD) system requires a new approach for arrhythmia detection. To evaluate arrhythmia discrimination of one such system, the Subcutaneous versus Transvenous Arrhythmia Recognition Testing (START) study was designed as a prospective, multicenter trial comparing simulated sensing performances of the S-ICD system with single- (SC-TV) and dual-chamber transvenous (DC-TV) implantable cardioverter-defibrillator (ICD) systems. At ICD implantation, induced ventricular and atrial arrhythmias were recorded simultaneously in transvenous (right ventricular [RV] → superior vena cava [SVC]+ Coil) and cutaneous electrode configurations. Recorded signals of ventricular (n = 46) and atrial arrhythmias (n = 50) with ventricular rates >170 bpm from 64 patients were used to compare detection performance of the S-ICD system with TV-ICD systems from 3 manufacturers. Appropriate detection of ventricular tachyarrhythmias was assessed with devices programmed in single-zone (rate ≥ 170 bpm) and dual-zone configurations (ventricular fibrillation ≥ 240 bpm; ventricular tachycardia ≥ 170 bpm). S-ICD specificity performance for supraventricular arrhythmias was compared to single- and dual-chamber devices in a dual-zone configuration. Appropriate detection of ventricular tachyarrhythmias for subcutaneous and TV devices in single- and dual-zone configurations was 100% and >99%, respectively. Specificity for supraventricular arrhythmias was significantly better for the S-ICD system compared to 2 of 3 TV systems, as well as the composite of TV devices (98.0%[S-ICD] vs 76.7%[SC-TV range: 64.0-92.0%] vs 68.0%[DC-TV range: 32.7-89.8%; P < 0.001]). Appropriate ventricular arrhythmia detection is excellent for all ICD systems evaluated; however, specificity of supraventricular arrhythmia discrimination by the S-ICD system is better than discrimination by 2 of 3 TV systems.

Inappropriate external defibrillation

In critically ill patients, alterations of the electrocardiogram (ECG) signal in monitors should be promptly evaluated as rapid interventions could be lifesaving. This requires taking into account the clinical condition of the patient and a series of other indicators about the patient's status. ECG artifacts could potentially precipitate an inappropriate management course leading to unnecessary diagnostic and therapeutic interventions [1]. We report and discuss a case where incorrect interpretation of the ECG signal led to an inappropriate medical decision to deliver external defibrillation. A 68 year old woman with ischemic cardiomyopathy (ejection fraction 26%) presented to a regional hospital with decompensated congestive heart failure (CHF). She had received an implantable cardioverter-defibrillator (ICD) (Medtronic Secura VR, MN, USA) about one month prior for primary prevention of sudden cardiac death. She soon developed respiratory distress requiring intubation andwas transferred to our center via air ambulance for further management. During transport, an ECG monitor tracing (Fig. 1) prompted manual external defibrillation at 360 V (Medtronic Lifepak 12, MN, USA). Upon arrival, shewas transferred to the intensive care unit (ICU) for closemonitoring. No abnormal rhythms were detected on telemetry. ICD interrogation revealed no detection of ventricular arrhythmias or therapies. After further management in the ICU including diuresis for CHF, she was

Using Floating Atrial Electrodes to Combat the Rising Tide of Inappropriate Defibrillator Therapies

Despite various implantable defibrillator algorithms and strategies used to improve discrimination between potentially life-threatening ventricular arrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]) and more benign supraventricular tachycardias (SVTs), this remains a problem. In addition to significant discomfort and impairment of quality of life, there is some suggestion that shocks may increase mortality.1 Recording atrial intracardiac electrograms during arrhythmic episodes would be expected to improve our ability to discriminate tachycardias and thus reduce the number of inappropriate shocks. It may also lead to the diagnosis of otherwise unsuspected atrial arrhyhmias that may require specific therapy, such as anticoagulation therapy for patients with atrial flutter or atrial fibrillation (AF). Article see p 56 The evidence available so far, however, does not clearly demonstrate that atrial electrograms reduce inappropriate shocks.2–7 Although some studies performed in patients with a dual-chamber device have shown a reduction in inappropriate detection, inappropriate shocks also were avoided in the single-chamber detection arm by using anti tachycardia pacing.2 In addition, placement of an atrial lead is associated with a risk of lead dislodgement (≈4.5%) and increased procedural and fluoroscopy times compared to a single-chamber defibrillator. Thus, there currently is no strong evidence to support the addition of an atrial lead for the sole purpose of SVT discrimination and reducing implantable cardioverter-defibrillator (ICD) shocks.8 Using a single-pass VDD defibrillator lead holds the promise of offering atrial electrograms without the additional risks and procedural time related to implantation of a separate atrial lead. Similar lead designs with integrated atrial electrodes have been used in VDD pacemakers.9 In a study published by Sticherling et al in this issue of Circulation: Arrythmia and Electrophysiology , the ADRIA (Study to Verify Proper Detection of Supraventricular Tachyarrhythmia With Single-Lead Dual-Chamber Implantable Cardioverter-Defibrillators) study, the authors investigated the use …

ECG spectral and morphological parameters reviewed and updated to detect adult and paediatric life-threatening arrhythmia

Since the International Liaison Committee on Resuscitation approved the use of automated external defibrillators (AEDs) in children, efforts have been made to adapt AED algorithms designed for adult patients to detect paediatric ventricular arrhythmias accurately. In this study, we assess the performance of two spectral (A2 and VFleak) and two morphological parameters (TCI and CM) for the detection of lethal ventricular arrhythmias using an American Heart Association (AHA) compliant database that includes adult and paediatric arrhythmias. Our objective was to evaluate how those parameters can be optimally adjusted to discriminate shockable from nonshockable rhythms in adult and paediatric patients. A total of 1473 records were analysed: 751 from 387 paediatric patients (⩽16 years of age) and 722 records from 381 adult patients. The spectral parameters showed no significant differences (p > 0.01) between the adult and paediatric patients for the shockable records; the differences for nonshockable records however were significant. Still, these parameters maintained the discrimination power when paediatric rhythms were included. A single threshold could be adjusted to obtain sensitivities and specificities above the AHA goals for the complete database. The sensitivities for ventricular fibrillation (VF) and ventricular tachycardia (VT) were 91.1% and 96.6% for VFleak, and 90.3% and 99.3% for A2. The specificities for normal sinus rhythm (NSR) and other nonshockable rhythms were 99.5% and 96.3% for VFleak, and 99.0% and 97.7% for A2. On the other hand, the morphological parameters showed significant differences between the adult and paediatric patients, particularly for the nonshockable records, because of the faster heart rates of the paediatric rhythms. Their performance clearly degraded with paediatric rhythms. Using a single threshold, the sensitivities and specificities were below the AHA goals, particularly VT sensitivity (60.4% for TCI and 65.8% for CM) and the specificity for other nonshockable rhythms (51.7% for TCI and 34.5% for CM). The specificities, particularly for the adult case, improve when the thresholds are independently adjusted for each adult and paediatric database.

Treating the Long-QT Syndrome in the Era of Implantable Defibrillators

We live in an era of defensive medicine. Implantable cardioverter defibrillators (ICDs) increasingly are used to treat patients with congenital long-QT syndrome (LQTS), although not always with compelling indications.1 In different series, some patients underwent ICD implantation without ever receiving β-blockers,1–3 others never had symptoms1,4 and a few did not even have LQTS to begin with.5 A few studies probably boosted the use of ICDs in LQTS: (1) In a case-control study2 comparing ICD therapy with conservative management in high-risk patients with LQTS, ICDs were associated with decreased 3-year mortality (1.3% versus 16%, P =0.07). However, as explained elsewhere,6 the mortality reduction associated with the ICD was probably overestimated in that study, because 26% of conservatively managed patients did not receive β-blockers after the cardiac arrest, and some died shortly thereafter, probably due to sequelae of the cardiac arrest. (2) Several studies3,4,7,8 showed that high proportions (22% to 60%) of ICD-treated patients with LQTS receive appropriate ICD shocks within 2 to 5 years (Table). These impressive rates of life-saving therapy probably convinced many physicians that ICDs may be the treatment of choice for LQTS; however, these high rates of “life-saving therapy” (higher than the expected mortality in LQTS)9 could be related in part to the definition of “appropriate ICD therapy.” In these studies, appropriate ICD therapy was defined as an “ICD shock that terminated a ventricular tachyarrhythmia,” regardless of its duration and whether or not it caused symptoms. As appreciated from the Table, only 2 of the studies reported the parameters used for detection of ventricular arrhythmias. One can calculate that ICD shocks in these studies were probably delivered within 10 to 12 seconds from arrhythmia onset (Table). This is consequential, because torsade de pointes often terminates spontaneously (Figure). It is …

Wavelet based detection of ventricular arrhythmias with neural network classifier

This paper presents an algorithm based on the wavelet decomposition, for feature extraction from the Electrocardiogram (ECG) signal and recognition of three types of Ventricular Arrhythmias using neural networks. A set of Discrete Wavelet Transform (DWT) coefficients, which contain the maximum information about the arrhythmias, is selected from the wavelet decomposition. These coefficients are fed to the feed forward neural network which classifies the arrhythmias. The algorithm is applied on the ECG registrations from the MIT-BIH arrhythmia and malignant ventricular arrhythmia databases. We applied Daubechies 4 wavelet in our algorithm. The wavelet decomposition enabled us to perform the task efficiently and produced reliable results.

Failure of an implantable cardioverter-defibrillator to detect sustained ventricular tachycardia: A consequence of the latching phenomenon

The latching phenomenon is a potentially catastrophic anomaly in which an implantable cardioverter-defibrillator (ICD) becomes latched or stuck in whatever function it is performing at the time. In June 2005, the Guidant Corporation notified physicians and patients that Vitality AVT ICDs had the potential to latch. They reported that a latched device will “suspend detection and treatment of atrial and ventricular arrhythmias,” and that “telemetry, programming and magnet response mode are not available.”1 Of particular concern was the possibility of device latching during delivery of antitachycardia pacing (ATP) therapy.

Prospective screening for occult cardiomyopathy in dogs by measurement of plasma atrial natriuretic peptide, B-type natriuretic peptide, and cardiac troponin-I concentrations

To evaluate the use of measuring plasma concentrations of atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and cardiac troponin-I (cTnI) to detect dogs with occult dilated cardiomyopathy (DCM). 118 client-owned dogs. Dogs were prospectively examined by use of ECG; echocardiography; and evaluation of concentrations of ANP, BNP, and cTnI. Occult DCM was diagnosed by evaluation of echocardiographic left ventricular dimensions and detection of ventricular arrhythmias on ECG. Sensitivity and specificity of assays for measurement of plasma concentrations of ANP, BNP, and cTnI to detect dogs with occult DCM were determined. Occult DCM was diagnosed in 21 dogs. A concentration of > 6.21 pg/mL for BNP had a sensitivity of 95.2% and specificity of 61.9% for identifying dogs with occult DCM. In contrast, concentrations of ANP and cTnI had relatively low predictive values. Blood-based screening for occult DCM in dogs can be accomplished by use of a BNP assay. Additional studies should be performed to optimize this method of screening dogs to detect occult DCM.

Complexity-Measure-Based Sequential Hypothesis Testing for Real-Time Detection of Lethal Cardiac Arrhythmias

A novel approach that employs a complexity-based sequential hypothesis testing (SHT) technique for real-time detection of ventricular fibrillation (VF) and ventricular tachycardia (VT) is presented. A dataset consisting of a number of VF and VT electrocardiogram (ECG) recordings drawn from the MIT-BIH database was adopted for such an analysis. It was split into two smaller datasets for algorithm training and testing, respectively. Each ECG recording was measured in a 10-second interval. For each recording, a number of overlapping windowed ECG data segments were obtained by shifting a 5-second window by a step of 1 second. During the windowing process, the complexity measure (CM) value was calculated for each windowed segment and the task of pattern recognition was then sequentially performed by the SHT procedure. A preliminary test conducted using the database produced optimal overall predictive accuracy of. The algorithm was also implemented on a commercial embedded DSP controller, permitting a hardware realization of real-time ventricular arrhythmia detection.

Microelectrode arrays: A new tool to measure embryonic heart activity

The analysis of the sequential excitation of cardiac tissue is of high relevance, both for clinical pathophysiological purposes, eg, detection of sustained ventricular arrhythmias, as well as for experimental electrophysiology. Clinically, different technical approaches such as single electrode measurements and bipolar mapping electrode catheters have been used. In experimental setups several techniques to record cardiac activity have been proposed. Beside the well-established intracellular current-clamp recordings of action potentials, recent studies have performed extracellularly activation sequence mapping or simultaneous multichannel action potential electrode array measurements. Measurement of extracellularly recorded field potentials (FPs) hereby especially provides detailed information about the origin and spread of excitation in the heart. A similar analytical approach for cardiac FPs advanced the analysis of excitation spread and arrhythmic activity in multicellular preparations like developmental differentiation tissue of mouse embryonic stem cells, multicellular preparations of isolated native embryonic cardiomyocytes or the embryonic heart in toto. The use of substrate-integrated Microelectrode Arrays (MEAs, Multi Channel Systems, Reutlingen, Germany) with 60 electrodes of 10–30 μm diameters on a 100–200 μm grid, coated with porous titanium nitride to minimize the impedance allows recording of FPs at a high signal to noise ratio. The possibility to electrically stimulate the tissue further expands the range of applications and bioassays. It may thus facilitate the evaluation of drug research providing detailed information about the interplay of the complex cardiac network, and might improve the predictability of physiological and pathophysiological conditions or drug effects in embryonic heart tissue.

Efficacy of Atrial Antitachycardia Functions for Treating Atrial Fibrillation: Observations in Patients with a Dual-Chamber Defibrillator

In patients with conventional indication for ICD implantation, atrial fibrillation may occur in more than 50% during the life-span of the device and may lead to severe adverse events. Dual chamber defibrillators with atrial antitachycardia functions, including prevention algorithms, arrhythmia detection capability and atrial therapy options (antitachy pacing and cardioversion) have been recently introduced. The aim of this review is to examine the effectiveness of these new devices and to identify patients who may benefit. We recently studied 112 patients who received the device because of life-threatening ventricular arrhythmias. Fifty-five percent of them had atrial fibrillation prior to implantation. During the follow-up (one year on average), 27% had at least one episode of sustained atrial tachyarrhythmia. Effectiveness of atrial antitachy pacing was 71% on regular atrial tachycardia and 36% on irregular atrial tachyarrhythmias. Atrial shock efficacy was over 90% when adequately programmed. Interestingly, near half of the episodes started as regular atrial tachycardia and accelerated and became less organized in few minutes. Early delivery of antitachy pacing may increase success rate and decrease the need for atrial shock. Furthermore, it may prevent atrial remodeling and reduce atrial fibrillation burden. Based on our experience, we recommend that all patients with a class I indication for defibrillator implantation (related to risk of ventricular arrhythmias) who have a history of or are at risk of developing atrial tachyarrhythmias should receive a dual chamber defibrillator equipped with atrial antitachycardia functions. Furthermore, patients either with a history of heart failure, with poor functional capacity (functional class III or IV), depressed left ventricular ejection fraction, a need for monitoring of atrial rhythm, or in whom there is some concern about appropriate detection of ventricular arrhythmias, may benefit from a single device capable of managing ventricular and supraventricular arrhythmias.

Detection time comparison between induced episodes

Background: Implantable cardioverter defibrillators (ICD) have been shown to reduce total mortality in patients with ventricular tachyarrhythmias in randomized clinical trials. Appropriate and rapid detection of ventricular arrhythmias are essential in the prevention of sudden cardiac death in these devices. During an ICD implant, ventricular fibrillation (VF) is often induced multiple times to test appropriate detection and arrhythmia conversion. The effect of biventricular sensing on VF detection times has not been explored and it is unknown whether serial inductions result in prolonged VF detection times, particularly in a heart failure population.

Implantable Cardioverter Defibrillator Incorporated with Biventricular Pacing Among Heart Failure Patients

Implantable cardioverter defibrillator (ICD) with biventricular pacing (BiV) is available for drug- refractory heart failure patient who has class I indication for ICD and inter-ventricular conduction delay. We studied 32 patients with mean age of 61 years (M:F=9:1) with mean ejection fraction about 30% who has underwent implantation of implantable cardioverter defibrillator incorporated with left ventricular pacing. It showed its efficacy in terms of improvement in functional status and ejection fraction as confirmed by echocardiogram, episodes of cardiac related rehospitalization (p<0.05) and appropriate therapy for ventricular tachycardia among our patients in the mean follow up period of 22 months. Permanent left ventricular pacing is achieved by pacing of the distal branches of coronary sinus with a specially designed left ventricular (LV) lead. The optimal placement of LV lead is identified by a satisfactory pacing threshold, ventricular sensing and late sensing of LV electrical activity in order to optimize the resynchronization process. At the end of follow-up, all LV leads were fully functional with stable thresholds and appropriate sensing. Eight episodes of ventricular fibrillation and 18 episodes of ventricular tachycardia were successfully detected. The detection of ventricular arrhythmia detection was 100%. Four patients received 28 inappropriate shocks secondary to supraventricular tachycardia. Conclusion: Implantable cardioverter defibrillator incorporated with biventricular pacing is an efficient and safe mean of providing patient with cardiac resynchronization therapy in patient with drug refractory heart failure with interventricular conduction delay.

Implantable dual-chamber cardioverter-defibrillator-pacemaker

The fifth generation of implantable cardioverter-defibrillators offer enhanced modes of detection of atrial and ventricular arrhythmias, antitachycardia pacing and shocks, multiprogrammability, intracardiac electrogram storage, and all functions of antibradycardia dual-chamber pacing including rate responsiveness and mode switching. There is no consensus on the indications for dual-chamber pacemaker defibrillator systems. This review focuses on the four major options of newer devices that might benefit patients: 1) permanent dual-chamber pacing in ischemic coronary disease patients, 2) detection and management of atrial fibrillation or other atrial tachyarrhythmias, 3) some newer indications for pacing, and 4) the suppression of inappropriate interventions. On the basis of published data, newer indications for the dual-chamber systems, advantages and limitations, and future perspectives are discussed.

Efficacy of biventricular detection and treatment of ventricular arrhythmias: Preliminary observations in heart failure patients

Efficacy of biventricular detection and treatment of ventricular arrhythmias: Preliminary observations in heart failure patients

Incidence of ventricular arrhythmias during silent myocardial ischaemia in coronary artery disease

This study investigated the relationship between silent myocardial ischaemia during daily life and ventricular ectopic activity in patients with angiographically confirmed coronary artery disease and preserved left ventricular function. We studied 45 patients (37 men, 8 women, aged 42–70 years) who satisfied the above criteria. All underwent 72-h continuous electrocardiographic monitoring for the detection of silent ischaemic episodes and ventricular arrhythmias. A total of 225 ischaemic episodes were recorded, of which 198 (88%) were silent. Fourteen of the silent episodes (7.1%) were associated with ventricular arrhythmias. There was no statistically significant relationship between the association of silent ischaemia with arrhythmias and the patients' exercise test or angiography findings. However, the ventricular arrhythmias tended to be associated with ischaemic episodes of longer duration and with greater maximum ST-segment depression. Silent myocardial ischaemia during everyday activity is accompanied by ventricular ectopic activity in only a small percentage of cases. The association between ischaemia and ventricular arrhythmias seems to have more to do with the duration of the ischaemic episode and the degree of ST segment depression than with the severity of the underlying coronary artery disease.

The pacer-cardioverter-defibrillator: function and clinical experience.

Pacer-Cardioverter-Defibrillator. This article reviews the function of the pacer-cardioverter-defibrillator (PCD). Detection of ventricular arrhythmias occurs in two programmable zones, with onset and stability modifiers available to diminish overdetection of sinus tachycardia and atrial fibrillation, respectively. The sensing circuitry utilizes an auto-adjusting sensitivity with exponential decay to allow detection of low-amplitude ventricular fibrillation electrograms without T wave oversensing. Treatment can be accomplished by tiered therapy with two types of antitachycardia pacing, cardioversion and defibrillation. Cardioversion and defibrillation shocks are programmable between single pathway when two leads are used and simultaneous or sequential shock delivery when a three-lead system is used. A telemetered marker channel and electrogram aid in assessing device function during implantation and follow-up. Previously published literature is cited to expand on various aspects of PCD function and programming.