Defibrillation Capability Research Articles

A Novel Combination Therapy for Post-Operative Arrhythmias

Atrial fibrillation (AF) is a common heart rhythm disorder, effecting about 20% of cardiac surgical patients. While often benign, it leads to a prolonged hospital stay, and potentially to malignant arrhythimas. Many anti-arrhythmic drugs have been used to both prevent and treat post-operative AF and other post-operative arrhythmias; however, they have potentially harmful side-effects (e.g., hypotension, pulmonary fibrosis). Cardioversion is often the therapy of last resort to restore a perfusable rhythm. We propose a novel, innovative concept that allows for local pharmacological and electrical therapy of the heart. We have shown in animal models that such delivery increases the efficacy of the therapy and reduces side effects. Several variations of the device have been conceived and prototypes are currently being developed. The simplest version is a multi-port infusion catheter incorporated into a temporary pacing lead. Placement of the device would be trivial for surgeons, who routinely place temporary pacing leads prior to closing the chest. Removal of the device post-operatively would be equally simple. More complex iterations include an expandable wick to maintain the infused drug in a desired location. Designs may also include epicardial defibrillation capabilities, which would lower the energy required for defibrillation. To demonstrate proof of principle, cadaver and animal investigations were performed. In a fresh cadaver, a sternotomy and pericardiotomy was performed. A catheter was placed in the pericardium, and an infusion of radio-opaque contrast was administered under fluoroscopy. The majority of the contrast collected near the pulmonary veins, which are often the origin of atrial arrhythmias. To evaluate the efficacy of drugs administered into the pericardium as compared with drugs administered through the conventional route (intravenously), animal studies in swine were performed. Results demonstrated that pericardially administered metoprolol had a greater and more lasting effect on heart rate than when given intravenously. Additionally, during pericardial delivery myocardial contractility was better preserved. Only trace amounts of metoprolol were found in the circulation. Thus pericardial delivery may enhance certain therapeutic effects of drugs while limiting side effects. Currently, studies are underway to evaluate the efficacy other pharmacologic agents delivered into the pericardium. Should our animal studies continue to show promising results, we anticipate moving into clinical trials. Development and refinement of prototype delivery devices will also continue as we pursue this promising new therapy for post-operative arrhythmias.

Defibrillation Threshold Testing: Tradition or Necessity?

Implantable cardioverter defibrillators (ICDs) have become an essential tool for primary and secondary prevention of sudden cardiac death. Traditionally, defibrillation threshold (DFT) testing is part of the "lege artis" ICD implantation. Taking into consideration that the absolute mortality reduction in primary prevention trials is estimated around 8% and in secondary prevention trials around 7%, it is only in these patients that an acceptable DFT is expected to affect survival. Using a high-energy ICD, the likelihood of obtaining an inadequate DFT is about 2.5%. Thus, the number of patients needed to be subjected to DFT testing in order to avert one potential death is about 500. Application of antitachycardia pacing for rapid ventricular tachycardias further reduces the percentage of patients dependent on reliable ICD defibrillation capability. Thus, the mortality rate that can be prevented by DFT testing is below 0.2%. This contrasts a 0.4% risk of life-threatening complications and a low but not negligible mortality risk owed to the procedure. Although in light of these data the balance between DFT-related risk and benefit seems to tilt toward the former, insights gained from prospective randomized trials will clarify whether the abandonment of routine DFT testing can be claimed on a rightful basis.

Programmed inappropriate ICD ventricular defibrillation for cardioversion of persistent atrial fibrillation

In this report we briefly describe a patient with a dual chamber implantable cardioverter defibrillator in the context of severe ischemic cardiomyopathy who developed persistent atrial fibrillation. After appropriate anticoagulation and under mild sedation the patient was successfully cardioverted to sinus rhythm after a programmed ventricular synchronized defibrillation using his defibrillator. Programmed internal cardioversion of persistent atrial fibrillation in patients who have an implantable cardioverter defibillator without atrial defibrillation capabilities could be an effective and safe therapeutic option. Unlike external electrical cardioversion, this strategy does not interfere with the implantable cardioverter defibrillator, is more effective, and obviates the need of general anesthesia. This strategy should be further evaluated in clinical trials.

Innovations in the Development of Cardiac Resynchronization Therapy Devices with Defibrillation Capability—the Boston Scientific Experience

Cardiac resynchronization therapy (CRT) has been clinically proven to improve symptoms, exercise capacity, and quality of life and promote reduction in ventricular dimensions. When combined with a defibrillator (CRT-D), significant reductions in all-cause mortality alone and in combination with cause-specific hospitalization have also been demonstrated. We trace Boston Scientific Corporation's experience in the development of CRT-D devices from the first human implant worldwide 10 years ago using transthoracic lead technology, through the clinical studies that led to regulatory approval using transvenous leads and pulse generators with features specifically designed for heart failure patients. We conclude with innovations for CRT-D that are currently under study.

Evaluation of a Novel Ventricular Support Device with Defibrillation Capabilities in Canine and Porcine Animal Models

Sudden death is prevalent in heart failure patients. We tested an implantable ventricular support device consisting of a wireform harness with one or two pairs of integrated defibrillation electrode coils. The device was implanted into six pigs (36-44 kg) through a subxiphoid incision. Peak voltage (V) defibrillation thresholds (DFT) were determined for five test configurations compared with a control transvenous lead (RV to CanPect). Defibrillator can location (abdominal or pectoral) and common coil separation on the implant (0 degrees or 60 degrees ) were studied.(.) The DFT for RV60 to LV60 + CanPect was significantly less than control (348 +/- 57 vs 473 +/- 27 V, P < 0.05). The DFTs for other vectors were similar to control except for RV0 to LV0 + CanAbd (608 +/- 159 V). The device was implanted into 12 adult dogs for 42, 90, or 180 days with DFT and pathological examination performed at the terminal study. Cardiac pressures were determined at baseline, after implantation, and at the terminal study. The DFT was also determined in a separate group of four dogs at 42 days following implantation of the support device with one pair of defibrillation electrodes. The DFTs at implant and explant in dogs with one pair (8 +/- 1.5 Joules [J] and 6 +/- 1.9 J) or two pairs (8 +/- 3.4 J and 7 +/- 1.9 J) of defibrillation electrodes were not significantly different from each other but significantly less than control measured at the terminal study (18 +/- 3.4 J). Left-sided pressures were significantly decreased at explant but within expected normal ranges. Right-sided pressures were not different except for RV systolic. Histopathology indicated mild to moderate epicardial inflammation and fibrosis, consistent with a foreign body healing response. This defibrillation-enabled ventricular support system maintained mechanical functionality for up to 6 months while inducing typical chronic healing responses. The DFT was equal to or lower than a standard transvenous vector.

Passive Ventricular Restraint Device with Defibrillation Capabilities: Is There a Panacea for Heart Failure on the Horizon?

Passive Ventricular Restraint Device with Defibrillation Capabilities: Is There a Panacea for Heart Failure on the Horizon?

Mortality in Cardiac Resynchronization Therapy with defibrillator capability

Mortality in Cardiac Resynchronization Therapy with defibrillator capability

Preventing pacemaker problems with nerve stimulators

Preventing pacemaker problems with nerve stimulators

Electrotherapy of cardiac failure

Intracardiac conduction disturbances, mostly manifested as a left bundle branch block (LBBB), are common findings in cardiac failure and associated with a poor prognosis. LBBB is a marker of disease progression and also leads to worsened cardiac hemodynamics by dyssynchronous contraction that can accelerate progression of the underlying disease. Cardiac resynchronization therapy (CRT) can reduce the negative effects of these disturbances leading to improvement in hemodynamics and long-term improvement in cardiopulmonary exercise tolerance, reduction of left ventricular volumes and functional mitral regurgitation. Prospective multicenter studies, such as the CARE-HF and COMPANION trials have demonstrated reduced mortality with CRT or combined treatment with defibrillator capability (CRT-D). Thus, CRT has been adopted in the current guidelines of cardiology societies. Nevertheless, there are a number of open issues with CRT, such as the high number of non-responders or the value of CRT in patients with atrial fibrillation, narrow QRS complex and mild cardiac failure or asymptomatic left ventricular dysfunction. In addition, the question whether every CRT patient needs a device with defibrillating capabilities is not fully resolved, at least for patients with dilative cardiomyopathy.

A Novel Procedure for Left Side Implantation of CRT-D Generator in a Patient with Left Subclavian Vein Stenosis

Cardiac resynchronization therapy with defibrillation capability (CRT-D) has been expected as an effective therapy for patients with dyssynchronous LV dysfunction and VT. Here we report a 52-year-old woman with heart failure due to d-HCM and VT in whom CRT-D was dramatically effective. A single chamber ICD had been implanted, and a RV sensing lead had been added due to sensing failure. As heart failure deteriorated after implantation, we planed to up-grade the ICD to CRT-D. At the first procedure, we could not introduce the lead through the left subclavian vein because of the stenosis at the venous angle.

Lack of Early Defibrillation Capability and Automated External Defibrillators in Nursing Homes

To determine the availability of early defibrillation and automated external defibrillators in nursing homes in selected cities. A standardized telephone survey was conducted of all skilled nursing facilities to characterize early defibrillation capabilities. The study involved nursing homes in Philadelphia, Omaha, Seattle, and Boston. All skilled nursing facilities not physically attached to hospitals in the selected cities based on listings from the Centers for Medicare and Medicaid Services as of January 2004. Each site was queried as to whether or not they had an automated external defibrillator (AED), if they were physically freestanding facilities, if a manual defibrillator was present, and if staff were present 24 hours a day to use the defibrillator. Early defibrillation was defined as the presence of either a manual defibrillator or AED in addition to 24-hour trained staff availability. There were 126 nursing homes identified from the Medicare listing and 81% (102) responded to our phone survey. After exclusion of non-freestanding facilities, 90 nursing homes (71.4%) were available for analysis. Overall, 16.7% (95% CI 8.8-24.5) of nursing homes reported early defibrillation capabilities via manual defibrillator or AEDs; 6.7% (95% CI 1.4-11.9) of nursing homes reported AEDs; 10.0% (95% CI 3.7-16.3) of nursing homes reported manual defibrillators. Nursing homes in Seattle had a higher rate of early defibrillation capability than the other 3 cities. Despite the fact that nursing homes have been identified as locations with multiple cardiac arrests, the early defibrillation capabilities and prevalence of AEDs in this setting remains low. AEDs may play a role in improving survival from cardiac arrest in nursing homes. The placement of AEDs in nursing homes needs further consideration and study.

How, Why, and When May Atrial Defibrillation Find a Specific Role in Implantable Devices? A Clinical Viewpoint

This viewpoint article discusses the potential for incorporation of atrial defibrillation capabilities in modern multi-chamber devices. In the late 1990s, the possibility of using shock-only therapy to treat selected patients with recurrent atrial fibrillation (AF) was explored in the context of the stand-alone atrial defibrillator. The failure of this strategy can be attributed to the technical limitations of the stand-alone device, low tolerance of atrial shocks, difficulties in patient selection, a lack of predictive knowledge about the evolution of AF, and, last but not least, commercial considerations. An open question is how atrial defibrillation capability may now assume a specific new role in devices implanted for sudden death prevention or cardiac resynchronization. For patients who already have indications for implantable devices, device-based atrial defibrillation appears attractive as a "backup" option for managing AF when preventive pharmacological/electrical measures fail. This and several other personalized hybrid therapeutic approaches await exploration, though assessment of their efficacy is methodologically challenging. Achievement of acceptance by patients is an essential premise for any updated atrial defibrillation strategy. Strategies that are being investigated to improve patient tolerance include waveform shaping, pharmacologic modulation of pain, and patient-activated defibrillation (patients might also perceive the problem of discomfort somewhat differently in the context of a backup therapy). The economic impact of implementing atrial defibrillation features in available devices is progressively decreasing, and financial feasibility need not be a major issue. Future studies should examine clinically relevant outcomes and not be limited (as occurred with stand-alone defibrillators) to technical or other soft endpoints.

Cardiac resynchronization pacing without defibrillator capability: is this a viable option?

Improved cardiac resynchronization by pacemakers (CRT-P) and implantable defibrillators (CRT-D) benefits cardiac function, reduces heart failure (HF) admissions, and diminishes mortality in patients with severe left ventricular (LV) dysfunction. In terms of mortality benefit, current evidence suggests that CRT-D may be better than CRT-P alone when a broad range of HF patients is considered. However, the differential benefit may be small in certain patients. In individuals with severe and worsening HF due to systolic LV dysfunction, HF complications other than ventricular tachyarrhythmias contribute importantly to both quality-of-life (QoL) and duration of survival; these patients may be served cost-effectively by CRT-P enhancing QoL. A clinical trial evaluating CRT-D vs. CRT-P in terms of QoL and survival in such patients would assist physicians and payers to understand better the relative roles of CRT-P and CRT-D in the care of the sickest HF patients.

AB13-1: Evaluation of a novel ventricular support device with defibrillation capabilities

Surgical interventions, including passive restraining devices, can decrease ventricular dilation and improve heart failure. We tested an implantable ventricular support device consisting of a self-anchoring self-tensioning nitinol wireform harness containing 2 pair of integrated defibrillation electrodes (Paracor Medical) that connected to an ICD. The implant was placed on the epicardium of the left (LV) and right (RV) ventricles through a subxiphoid approach using an introducer and delivery system. We assessed the lead integrity, defibrillation threshold (DFT), hemodynamic responses, and histopathology following 42-180 days of implantation.

Experience with coronary sinus lead implantations for cardiac resynchronization therapy in 244 patients

Cardiac resynchronization therapy (CRT) using coronary sinus (CS) leads is a new method for the therapy of congestive heart failure (CHF). Because the intervention is more complex than regular pacemaker implantations, information on the feasibility and side effects of this method are of interest. From 1999 to June 2005, CRT implantations were attempted in 244 patients (pts; mean age 64+/-12 years, range 14-90 years), 82% were male, 44% had coronary artery disease, 29% were in atrial fibrillation, 71 had preexisting pacemakers. In 97% of the pts the intervention was successful (27% of the systems with defibrillation capabilities). In 285 interventions, 255 CS leads were positioned according to CS vein anatomy in 130 posterolateral, 97 anterolateral and 28 anterior side branches (16 patients received 2 CS leads). Over-the-wire leads were used in 88%, 71% were additionally preshaped. We observed no mortality but 37 complications (12.5%): CS dissection in 9, CS perforation in 1, ventricular fibrillation in 4, asystole in 5, pulmonary edema in 1, pneumothorax in 2, need for early CS lead revision in 19 (dislodgement n=7, phrenic nerve stimulation n=12) and infection with explantation in 2 cases. An improvement in NYHA functional class was found in 88% of pts (only 55% if anterior lead position). Perioperative complications during CS lead implantation occur in 10-15% of cases. Most patients responded well to CRT. Patients should be informed about the possible need for a reoperation. During implantation, immediate defibrillation and stimulation capabilities must be available. Anterior lead positions should be avoided.

Defibrillation Energy Requirements in an ICD Population Receiving Cardiac Resynchronization Therapy

While defibrillation energy requirements (DERs) have been extensively studied in patients receiving conventional defibrillators, the DERs of patients receiving cardiac resynchronization therapy with defibrillation capability (CRT-D) devices have not been well described. The purpose of this analysis was to characterize DERs (defined as true threshold or the presence of appropriate safety margins) in patients undergoing implant of a CRT-D and to determine whether DERs in this population were similar to those reported for patients undergoing implantation of conventional defibrillators. Data were analyzed retrospectively from the VENTAK CHF/CONTAK CD biventricular pacing study. An appropriate safety margin of at least 10 J was verified with at least two successful conversions with 21 J or less. Multivariate logistic regression was performed to determine baseline predictors of failed DER testing. Of 501 patients enrolled, 444 (89%) had successful DER test outcomes. Of the remaining 57 patients, 34 converted with energies > or = 21J, and 23 had their testing terminated prematurely or were not tested, primarily due to patient condition. Larger left ventricular internal dimension in diastole (P = 0.003) and prolonged procedure time (P = 0.01) were significant predictors of higher energy requirements. Few significant complications arose from DER testing. DER testing can be accomplished safely and successfully in the majority of CRT-D patients. However, safety margins cannot be ascertained in a significant number of these patients. Left ventricular inner diameter in diastole (LVIDd) and prolonged procedure time may predict higher DERs, and could be used to anticipate the need for a high-energy device or inclusion of a subcutaneous array.

Prospective assessment of integrating the existing emergency medical system with automated external defibrillators fully operated by volunteers and laypersons for out-of-hospital cardiac arrest: the Brescia Early Defibrillation Study (BEDS)

There are few data on the outcomes of cardiac arrest (CA) victims when the defibrillation capability of broad rural and urban territories is fully operated by volunteers and laypersons. In this study, we investigated whether a programme based on diffuse deployment of automated external defibrillators (AEDs) operated by 2186 trained volunteers and laypersons across the County of Brescia, Italy (area: 4826 km(2); population: 1 112 628), would safely and effectively impact the current survival among victims of out-of-hospital CA. Forty-nine AEDs were added to the former emergency medical system that uses manual EDs in the emergency department of 10 county hospitals and in five medically equipped ambulances. The primary endpoint was survival free of neurological impairment at 1-year follow-up. Data were analysed in 692 victims before and in 702 victims after the deployment of the AEDs. Survival increased from 0.9% (95% CI 0.4-1.8%) in the historical cohort to 3.0% (95% CI 1.7-4.3%) (P=0.0015), despite similar intervals from dispatch to arrival at the site of collapse [median (quartile range): 7 (4) min vs. 6 (6) min]. Increase of survival was noted both in the urban [from 1.4% (95% CI 0.4-3.4 %) to 4.0% (95% CI 2.0-6.9 %), P=0.024] and in the rural territory [from 0.5% (95% CI 0.1-1.6%) to 2.5% (95% CI 1.3-4.2%), P=0.013]. The additional costs per quality-adjusted life year saved amounted to euro39 388 (95% CI euro16 731-49 329) during the start-up phase of the study and to euro23 661 (95% CI euro10 327-35 528) at steady state. Diffuse implementation of AEDs fully operated by trained volunteers and laypersons within a broad and unselected environment proved safe and was associated with a significantly higher long-term survival of CA victims.

自動型体外式除細動器を使用して看護師が除細動を成功させた心室細動患者の１例

The American Heart Association has included the use of automated external defibrillators (AEDs) for early defibrillation by first responders as a standard of care for in-hospital ventricular fibrillation (VF). However, there are as yet no reports on the in-hospital early defibrillation program in Japan. To make the program successful, an early defibrillation capability by all nurses is essential. Recent studies have indicated that hospital nurses can easily use AEDs, because AEDs preclude the need for extensive training on ECG recognition, and there is also no fear of delivering shocks to a patient. Therefore, the use of AEDs can facilitate the introduction of the in-hospital early defibrillation program. Here, we report the case of a 70-year-old hospitalized man who developed an episode of VF outside our critical care area. Using AED, a nurse delivered shock to revert the VF, and succeeded in restoring the patient's circulation before the arrival of a physician. The delay between recognition of the VF and the delivery of the first shock was under 2 minutes. The physician arrived in the ward 74 seconds after the delivery of the shock. This case highlights the importance of the ability of nurses to successfully use defibrillation to strengthen the in-hospital chain-of-survival. The use of AEDs may thus promote the in-hospital chain-of-survival.

Late-Breaking Clinical Trial Abstracts

Late-Breaking Clinical Trial Abstracts

108th ENMC International Workshop, 3rd Workshop of the MYO-CLUSTER project: EUROMEN, 7th International Emery-Dreifuss Muscular Dystrophy (EDMD) Workshop, 13–15 September 2002, Naarden, The Netherlands

Inserm UR582 (ex 523), Institut de Myologie, Bâtiment Babinski, G.H. Pitie-Salpetriere, 47, boulevard de l’Hopital, 75 651 Paris Cedex 13, France Laboratoire de Genetique Moleculaire et Chromosomique, IURC, Montpellier, France Institute of Cardiology, University of Bologna, Bologna, Italy Department of Paediatrics and Neonatal Medicine, Imperial College School of Medicine, Hammersmith Campus, London, UK Department of Neurology, Academic Medical Centre, Amsterdam, The Netherlands Service de Cardiologie, GH Cochin, Paris, France Randall Center, Kings College, London, UK Neuromuscular Unit, M.R.C. Polish Academy of Sciences, Warsaw, Poland ITOI, Unit of Bologna, c/o IOR, Bologna, Italy Istituto Ortopedico Rizzoli, Neuromuscular Unit, Bologna, Italy MRIC, North East Wales Institute, Wrexham, UK Department of Internal Medicine and Cardiology Medical University of Warsaw, Warsaw, Poland Department of Cardiology, University Hospital Maastricht, Maastricht, The Netherlands Dipartimento di Biopatologia e Diagnostica per Immagini, Rome, Italy Istituto di Genetica Biochimica ed Evoluzionistica, CNR (IGBE-CNR), Pavia, Italy Division of Medical Genetics, University of Leicester, Leicester, UK Institute of Human Genetics, Greifswald, Germany