Implantable Cardioverter Defibrillator Electrode Research Articles

Is a Mechanic Prosthetic Valve in Tricuspid Position an Absolute Impediment to Implant a Definitive Electrode in the Right Ventricle?

This is the case of a middle-aged woman with Ebstein anomaly, who had a tricuspid valve replacement with a mechanic Starr-Edwards caged-ball valve many years ago, and needed an implantable cardioverter defibrillator (ICD) and ventricular pacing due to ventricular tachycardia and atrioventricular block with syncope. Furthermore, she has a chronic respiratory disease that make open chest surgery inadvisable. Prosthetic valves are a real obstacle to cross them and place catheters in the distal chamber. This report shows a technique to get access to the right ventricle endocardium through the annulus and placing the ICD electrode with correct sensing and pacing.

Treatment of Ventricular Tachycardia Induced by Coil of Ventricular Lead of Implantable Cardioverter Defibrillator

Implantable cardioverter defibrillator (ICD) -DDD for arrhythmogenic heart disease of unknown etiology, with the induction of ventricular tachycardia by the right ventricle (RV) of the shock electrode. The arrhythmia generated by the ICD electrode itself was the cause of multiple episodes with appropriate anti-tachycardia pacing (ATP) and shock therapy. The etiology of the arrhythmia was confirmed by electrophysiological study and successful treatment was performed with ablation, without the need for surgical repositioning of the electrode.

Tratamento de Taquicardia Ventricular Induzida por Mola de Choque de Eletrodo de Cardioversor Desfi brilador Implantável

Paciente portador de cardioversor desfi brilador implantável (CDI)-DDD por cardiopatia arritmogênica de etiologia desconhecida, com induçãode taquicardia ventricular pela mola de ventrículo direito (VD) do eletrodo dechoque. A arritmia gerada pelo próprio eletrodo do CDI foi causa de múltiplos episódios com terapia apropriada por anti-tachycardia pacing (ATP) e choque. Confi rmada a etiologia da arritmia por estudo eletrofi siológico erealizado tratamento bem-sucedido com ablação, sem necessidadede reposicionamento cirúrgico do eletrodo

New generation cardioverter-defibrillator lead with a floating atrial sensing dipole: Long-term performance.

The study aim is to present the long-term performance of a new generation implantable cardioverter defibrillator (ICD) electrode with floating atrial dipole (Linox S DX, Biotronik, Berlin, Germany). The single ICD electrode with a floating dipole in the atrial chamber was introduced about 15 years ago to overcome risk of inappropriate shock. After implantation, internal electrocardiogram data were prospectively collected via telemonitoring (Home Monitoring, Biotronik). A total of 93 patients (81.5% male, 18.5% female; 58.9 ± 12.3 years) were implanted with a single-chamber ICD using the Linox S DX. Patients were followed up for a median of 693 days (33-2,460 days). At time of implantation average p-wave value was 3.5 ± 1.7mV and remained stable throughout follow-up with an average value of 3.7 ± 1mV (P=0.2). A total of 460 arrhythmic episodes were recorded and 185 (40.2%) were incorrectly stratified by the device software. Seven patients (7.5%) experienced inappropriate ICD therapy. In three patients, VT episodes were not detected and remained untreated. Although the Linox S DX lead presents a satisfactory long-term stability of the atrial sensing, many of the messages sent to the device during follow-up were incorrectly classified by the ICD software. As a result, inappropriate therapy occurred with a rate similar to that observed with dual-chamber ICDs, but some malignant arrhythmias remained undiagnosed and untreated while occurring. Results in larger prospective cohorts should be analyzed and software improvements of the device should be suggested to overcome these potential drawbacks.

Removal of the broken part of implantable cardioverter-defibrillator's electrode causing pulmonary embolism via femoral vein

A 66-year-old patient with idiopathic dilated cardiomyopathy underwent transvenous extraction of an implantable cardioverter-defibrillator. The distal part of the electrode was broken during manual traction through the left subclavian vein. In the present case, we showed a rare complication of transvenous lead extraction and its management.

Evaluating the Efficacy and Safety of Internal Cardioversion with Implantable Cardioverter Defibrillator Device for Atrial Fibrillation in Systolic Heart Failure Patients

Atrial fibrillation (AF) commonly observed in patients with heart failure and cardioversion was often needed to restore the sinus rhythm. Previously, there is no study evaluating usefulness of internal cardioversion with implantable cardioverter defibrillator (ICD) device. In this study, we aimed to compare the efficacy and long-term effects of internal cardioversion with ICD devices compared to conventional external cardioversion in patients with AF and heart failure. Seventy patients with AF and heart failure who underwent electrical cardioversion were enrolled in the study. Forty patients (mean age 65.36 ± 10.37, 35 male) were assigned to undergo internal cardioversion with approximately 35 J shocks delivered through the ICD electrode. Standard external cardioversion was performed for the remaining patients (30 patients; mean age 66.20 ± 11.89; 24 male) that were similar with regard to baseline, and electrocardiographic characteristics. Sinus rhythm was restored in 32 of 40 patients (80.0%) assigned to internal cardioversion compared with 25 of 30 patients (83.3%) assigned to external cardioversion (P = 0.725). We did not witness any serious complication during the procedure and hospitalization. On the follow-up, there was no statistically significant difference in recurrence of AF and incidence of major cardiovascular events between the internal and external cardioversion groups. Internal cardioversion with ICD device is an effective and safe method to restore sinus rhythm in heart failure patients with AF.

Safety of mid-septal electrode placement in implantable cardioverter defibrillator recipients — Results of the SPICE (Septal Positioning of ventricular ICD Electrodes) study

BackgroundDetrimental effects of right ventricular (RV) apical pacing have directed the interest toward alternative pacing sites such as the RV mid-septum. As safety data are scarce for implantable cardioverter defibrillator (ICD) recipients the study aims to evaluate ICD lead performance in the mid-septal position. Methods and resultsA total of 299 ICD recipients (79% male, aged 65.2±12.1years, 83% primary prevention of sudden cardiac death) were randomized to receive the RV ICD electrode either in a mid-septal (n=145) or apical (n=154) location. Event-free survival was evaluated at 3 (primary endpoint) and 12months (secondary endpoint). Events included a composite of lead revision, suboptimal right ventricular electrode performance (including defibrillation thresholds (DFT)>25J) or lead position not in accordance with randomized location. Event-free survival at 3 (12) months was observed in 80.6% (72.3%) of patients randomized to a mid-septal and in 82.2% (72.1%) of patients randomized to an apical lead position, p=0.726 (p=0.969). Pre-defined margins for non-inferiority were not reached at 3 or 12months. High DFT was found in 7 patients (5.0%) of the mid-septal and in 3 (2.2%) patients of the apical group (p=0.209). ConclusionIn ICD recipients electrode positioning to the RV mid-septum or the RV apex results in slightly different rates concerning the survival free of lead revision, suboptimal right ventricular electrode performance or non-randomized lead position. Non-inferiority of the mid-septal lead location cannot be concluded. This should be taken into consideration when a mid-septal lead position is pursued. Clinical trial registrationClinicalTrials.gov identifier NCT00745745.

Implantable Cardioverter Defibrillators in Electric and Magnetic Fields of 400 kV Power Lines

Implantable cardioverter defibrillator (ICD) therapy has increased in Western countries. The aim of the study was to investigate the function of ICDs using a human-shaped phantom in electric and magnetic fields of 400 kV power lines. The phantom was used in the following manner: isolated from the ground, earthed from a foot, or earthed from a hand. We performed 37 ICD tests using 10 different ICD devices. When the electric fields varied from 6.8 kV/m to 7.5 kV/m (humidity 70.5%) and the magnetic field was 2.0 μT, one of the ICDs tested recorded 258 ventricular beats/min when a simulated heart signal was applied to ICD electrodes. When the exposure was 5.1 kV/m, the same ICD had a similar disturbance; however, in a 0.9 kV/m field, it worked correctly. Consequently, no effect on ICDs functioning was observed up to 0.9 kV/m, while anomalous behavior in some conditions was observed when levels exceeded 5.1 kV/m; ICD malfunctioning seems possible within 11.5 m from 400 kV power lines or in conditions inducing exposures exceeding 5 kV/m. Further development of this research field is needed.

Implantable Defibrillator Electrograms and Origin of Left Ventricular Impulses: An Analysis of Regionalization Ability and Visual Spatial Resolution

The implantable cardioverter-defibrillator (ICD) electrogram (EG) is a documentation of ventricular tachycardia. We prospectively analyzed EGs from ICD electrodes located at the right ventricle apex to establish (1) ability to regionalize origin of left ventricle (LV) impulses, and (2) spatial resolution to distinguish between paced sites. LV electro-anatomic maps were generated in 15 patients. ICD-EGs were recorded during pacing from 22 ± 10 LV sites. Voltage of far-field EG deflections (initial, peak, final) and time intervals between far-field and bipolar EGs were measured. Blinded visual analysis was used for spatial resolution. Initial deflections were more negative and initial/peak ratios were larger for lateral versus septal and superior versus inferior sites. Time intervals were shorter for apical versus basal and septal versus lateral sites. Best predictive cutoff values were voltage of initial deflection <-1.24 mV, and initial/peak ratio >0.45 for a lateral site, voltage of final deflection <-0.30 for an inferior site, and time interval <80 milliseconds for an apical site. In a subsequent group of 9 patients, these values predicted correctly paced site location in 54-75% and tachycardia exit site in 60-100%. Recognition of paced sites as different by EG inspection was 91% accurate. Sensitivity increased with distance (0.96 if ≥ 2 cm vs 0.84 if < 2 cm, P < 0.001) and with presence of low-voltage tissue between sites (0.94 vs 0.88, P < 0.001). Standard ICD-EG analysis can help regionalize LV sites of impulse formation. It can accurately distinguish between 2 sites of impulse formation if they are ≥2 cm apart.

Rationale and design of the SPICE study—septal positioning of ventricular ICD electrodes

Detrimental effects of right ventricular apical pacing have prompted the search for alternative pacing sites. Data from pacemaker studies suggest that the mid-septum may be a hemodynamically favorable pacing site within the right ventricle. However, data on the safety of implantable cardioverter defibrillator (ICD) lead placement in this location are limited. The aim of the SPICE study is to ascertain that implantation of a ventricular ICD lead at the mid-septum is not inferior to the traditional apical site in terms of feasibility and safety. In total, 286 patients with the indication for ICD implantation will be included in the study and stratified in a 1:1 ratio to have the lead placed in the right ventricular apex or the mid-septum. Primary outcome measure of this randomized, prospective study is the event-free survival of lead-related complications at 3months. The combined end point includes the feasibility to reach the randomized pacing site in combination with the achievement of adequate pacing, sensing, and defibrillation thresholds. Data analysis and sample size calculation are based on a non-inferiority design. This trial will primarily assess the feasibility, safety, and efficacy of right ventricular ICD lead positioning in the mid-septum compared to the traditional apical position. Documentation of non-inferiority of the novel lead position in terms of applicability and safety will be the prerequisite for potential further trials that may evaluate long-term clinical effects associated with mid-septal lead positions.

Reinitiation of Ventricular Macroreentry within the His‐Purkinje System by Back‐Up Ventricular Pacing—A Mechanism of Ventricular Tachycardia Storm

We describe immediate reinitiation of macroreentry ventricular tachycardia (VT) involving the His-Purkinje system by ventricular pacing from the electrode of an implantable cardioverter defibrillator (ICD) as a mechanism of VT storm refractory to ICD therapy. Repetitive reinitiation of bundle branch reentry tachycardia (BBRT), interfascicular tachycardia, or both VTs by ventricular pacing was identified in four ICD patients presenting with VT storm or incessant VT. All patients had a pre-existing prolonged HV interval (75 +/- 9 ms) and left bundle branch block (LBBB) or bifascicular block during sinus rhythm. The VTs included BBRT with LBBB in three patients and interfascicular tachycardia with right bundle branch block (RBBB) and left anterior or left posterior fascicular block in two patients. The paced beats from the ICD electrode exhibited a LBBB pattern of depolarization in two patients and a RBBB contour in V1 and V2 with left axis deviation in two patients. The QRS complex during pacing from the ICD electrode closely resembled that of the recurrent VT in all four patients suggesting that the pacing site of the ICD electrode was in proximity to the myocardial exit site of the bundle fascicle used for antegrade conduction during the reinitiated VT. Ventricular pacing from the ICD electrode after termination of the VT apparently encountered the retrograde refractoriness of this bundle fascicle and allowed immediate re-propagation of the wavefront orthodromically along the VT circuit. BBRT was eliminated by ablation of the right bundle branch. Successful ablation of the interfascicular tachycardias was achieved by targeting (1) an abnormal potential of the distal left posterior Purkinje network or (2) a diastolic potential during VT in the midinferior left ventricular (LV) septum. Repetitive reinitiation of BBRT and interfascicular tachycardia by ventricular pacing from the ICD electrode should be considered as a mechanism of VT storm refractory to ICD therapy in patients with a pre-existing conduction delay within the His-Purkinje system.

Pacemaker and ICD Generator Reliability

Despite there being millions of pacemaker and implantable cardioverter-defibrillator (ICD) generator implants worldwide, little is known about device reliability. To perform a meta-analysis of prospective pacemaker and ICD registries to determine annual rates of pacemaker and ICD malfunction and to identify trends in these rates. MEDLINE (January 1966 to April 2005), the Cochrane Central Register of Controlled Trials (through second quarter 2005), the Cochrane Database of Systematic Reviews (through second quarter 2005), and a bibliographic review of secondary sources. Search terms included pacemaker, artificial; defibrillators, implantable; registries; performance; and malfunction. Eligible registries were prospective; reported the number of patients with pacemaker, ICD, or both; and allowed determination of the annual number of device malfunctions. Of 1007 references screened, 3 registries meeting the selection criteria were identified and included 2.1 million pacemaker person-years and 14,821 ICD person-years of observation. Included the annual number of patients with pacemakers and ICDs at risk of device failure and the annual number of generator malfunctions (1983-2004 for pacemakers, 1988-2004 for ICDs). A device malfunction was defined as an integral component failure that required device explantation prior to reaching elective replacement. Failures of pacemaker and ICD electrodes were not included in the study. There were 2981 pacemaker and 384 ICD generator malfunctions. Pacemaker reliability improved markedly during the 1980s (P for trend <.001) and the pacemaker malfunction rate remained low during the remainder of the study. Implantable cardioverter-defibrillator reliability improved during the first 10 study years (P for trend <.001). From 1998-2002, however, the ICD malfunction rate increased more than 4-fold (P for trend <.001), before decreasing substantially in the latter 2 years of the study. Overall, the mean (SE) annual ICD malfunction rate was about 20-fold higher than the pacemaker malfunction rate (26.5 [3.8] vs 1.3 [0.1] malfunctions per 1000 person-years, P<.001). Battery malfunctions were the most common cause of device failure. Pacemaker reliability has improved markedly. In contrast, after more than a decade of improving device reliability, the ICD malfunction rate transiently increased before experiencing substantial reductions in the latter 2 study years. Whether increasing device sophistication accounts for the observed decrease in reliability is not known. Continued monitoring of pacemaker and ICD performance is required.

“Natural death” of a patient with a deactivated implantable-cardioverter-defibrillator (ICD)?

A 66-year-old patient with terminal heart insufficiency (NYHA IV) received maximum medical therapy, but was also in need of an implantable-cardioverter-defibrillator (ICD). The ICD functioned flawlessly for the whole duration of implantation. It reverted several ventricular tachycardias with anti-tachycardial pacing alone, whereas some needed cardioversion as well. The patient died on the fourth day of hospitalization for a routine check of his ICD. The post-mortem examination revealed, that the ICD was deactivated and that the data had been erased after the patient’s death. By reading off the raw data still stored within the ICD, the erased information could be restored. The stored EGMs showed traces of old ICD interventions as well as a permanent deactivation provoked by exposition to a magnetic field just hours before the patient’s death. The problem of archiving and documenting the volatile electronic data inside the ICD is discussed. The need of a full autopsy after telemetric reading of the ICD data, including the explantation of the ICD aggregate and electrodes, as a means of quality assurance and under forensic aspects is emphasized.

Simulated internal defibrillation in humans using an anatomically realistic three-dimensional finite element model of the thorax.

Determination of the optimal electrode configuration during implantable cardioverter defibrillator (ICD) implantation remains largely an empirical process. This study investigated the feasibility of using a finite element model of the thorax to predict clinical defibrillation metrics for internal defibrillation in humans. Computed defibrillation metrics from simulations of three common electrode configurations with a monophasic waveform were compared to pooled metrics for similar electrode and waveform configurations reported in humans. A three-dimensional finite element model was constructed from CT cross-sections of a human thorax. Myocardial current density distributions for three electrode configurations (epicardial patches, right ventricular [RV] coil/superior vena cava [SVC] coil, RV coil/SVC coil/subcutaneous patch) and a truncated monophasic pulse with a 65% tilt were simulated. Assuming an inexcitability threshold of 25 mA/cm2 (10 V/cm) and a 75% critical mass criterion for successful defibrillation, defibrillation metrics (interelectrode impedance, defibrillation threshold current, voltage, and energy) were calculated for each electrode simulation. Values of these metrics were within 1 SD of sample-size weighted means for the corresponding metrics determined for similar electrode configurations and waveforms reported in human clinical studies. Simulated myocardial current density distributions suggest that variations in current distribution and uniformity partially explain differences in defibrillation energy requirements between electrode configurations. Anatomically realistic three-dimensional finite element modeling can closely simulate internal defibrillation in humans. This may prove useful for characterizing patient-specific factors that influence clinically relevant properties of current density distributions and defibrillation energy requirements of various ICD electrode configurations.

Subxiphoid approach for implantable cardioverter defibrillator in patients with previous coronary bypass surgery.

From February 1988 until August 1991, 28 patients with prior coronary artery bypass grafting (CABG) received implantable cardioverter defibrillator (ICD) therapy via a subxiphoid approach. Only one patient required conversion to a median sternotomy incision. The mean defibrillation threshold was 11.9 +/- 4.4 J. The mean R wave was 8.2 +/- 3.7 mV. One perioperative death occurred due to heart failure (mortality rate 1/28 [3.50%]). No patient required reexploration for bleeding. The subxiphoid method for ICD electrode implantation is safe and reliable in patients with prior CABG surgery.