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PubMed2004

Comparing the efficacy and safety of a novel monophasic waveform delivered by the passive implantable atrial defibrillator with biphasic waveforms in cardioversion of atrial fibrillation.

BACKGROUND: The passive implantable atrial defibrillator (PIAD) (with no battery or discharging capacitor and powered transcutaneously by radio-frequency energy) delivering a novel monophasic low-tilt waveform is more efficacious than the standard monophasic waveform at atrial defibrillation. Standard biphasic (STB) waveforms, however, are more efficacious and safer than monophasic waveforms. This study compared the efficacy and safety of the PIAD waveform with biphasic waveforms. METHODS AND RESULTS: Sustained atrial fibrillation (AF) was induced by rapid atrial pacing. Cardioversion was attempted via 2 atrial defibrillation leads. The efficacy of the PIAD was compared with 3 biphasic waveforms (standard, single rounded, and double rounded) at varying voltage settings in 10 pigs. After a synchronized shock, hemodynamic changes between the PIAD, standard biphasic, and monophasic waveforms were compared at 1.5 and 3.0 J in 12 pigs. Myocardial injury (biochemical and histological) after ten 5-J PIAD shocks was compared with a no-shock group in 14 pigs. The PIAD 100-V setting was significantly more efficacious than the STB (100/-50 V: 100% [1.88+/-0.02 J] versus 90% [0.89+/-0.0 J]; P=0.025). No arrhythmic, hemodynamic, or myocardial injury was observed with the PIAD waveform. CONCLUSIONS: Defibrillation with the PIAD is more efficacious than with the STB waveform and appears safe. This device could provide a more effective option for cardioversion.

Animals↗
PubMed1999

Use of sedation during cardioversion with the implantable atrial defibrillator.

BACKGROUND: The low shock energy used during internal atrial defibrillation may decrease the need for sedation during defibrillation with an implantable atrial defibrillator. METHODS AND RESULTS: The atrial defibrillator (Metrix Atrioverter) was implanted in 12 patients. During the in-hospital treatment of atrial fibrillation (AF) episodes, intravenous sedation was given only on patient request. The Atrioverter was programmed for ambulatory therapy in 4 patients. Efficacy, number of shocks delivered, and sedation requirements were recorded. A total of 393 shocks (1.8+/-1. 6 shocks/AF episode) were delivered to treat 213 AF episodes; 85 of 213 AF episodes (40%) were treated away from the hospital. Sinus rhythm was restored in 195 AF episodes (92%). Five patients never requested sedation. No sedation was needed for ambulatory-treated AF episodes. During the treatment of 26 of 213 AF episodes (12%), 75 shocks were delivered after patients received sedation. The number of shocks required to treat an AF episode determined the need for sedation (4.3+/-2.1 shocks for AF episodes requiring sedation versus 2+/-1 shocks for AF episodes requiring no sedation; P<0.001). These additional shocks were needed to treat immediate reinitiation of AF (14 episodes) or initial failure to cardiovert (4 episodes). For 8 AF episodes, sedation was requested before the first shock. CONCLUSIONS: This study suggests that, in a selected group of patients, AF can be treated with Atrioverter therapy without sedation. Successful ambulatory treatment of AF episodes with the Atrioverter, programmed to deliver </=2 shocks, did not require sedation. When multiple shocks were required to treat an AF episode, the need for sedation increased and included patients initially not requesting sedation.

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PubMed2000

Initial clinical experience with ambulatory use of an implantable atrial defibrillator for conversion of atrial fibrillation. Metrix Investigators.

BACKGROUND: A recent study has shown that the implantable atrial defibrillator can restore sinus rhythm in patients with recurrent atrial fibrillation when therapy was delivered under physician observation. The objective of this study was to evaluate the safety and efficacy of ambulatory use of the implantable atrial defibrillator. METHODS AND RESULTS: An atrial defibrillator was implanted in 105 patients (75 men; mean age, 59+/-12 years) with recurrent, symptomatic, drug-refractory atrial fibrillation. After successful 3-month testing, patients could transition to ambulatory delivery of shock therapy. Patients completed questionnaires regarding shock therapy discomfort and therapy satisfaction using a 10-point visual-analog scale (1 represented "not at all," 10 represented "extremely") after each treated episode of atrial fibrillation. During a mean follow-up of 11.7 months, 48 of 105 patients satisfied criteria for transition and received therapy for 275 episodes of atrial fibrillation. Overall shock therapy efficacy was 90% with 1.6+/-1.2 shocks delivered per episode (median, 1). Patients rated shock discomfort as 5.2+/-2.4 for successful therapy and 4.2+/-2.2 for unsuccessful therapy (P:>0.05). The satisfaction score was higher for successful versus unsuccessful therapy (3.4+/-3. 3 versus 8.7+/-1.3, P:<0.05). There was no ventricular proarrhythmia observed throughout the course of this study. CONCLUSIONS: Ambulatory use of an implantable atrial defibrillator can safely and successfully convert most episodes of atrial fibrillation, often requiring only a single shock. Successful therapy is associated with high satisfaction and only moderate discomfort.

Adult↗
PubMed1996

Hospital readmission in patients treated with tiered-therapy implantable defibrillators.

BACKGROUND: We wished to determine the incidence, reasons, costs, and predictors of cardiac-related hospital readmission in patients with tiered-therapy implantable defibrillators. Hospital readmission in patients with defibrillators reduces their quality of life and increases the cost associated with such therapy. METHODS AND RESULTS: We retrospectively studied 65 consecutive local patients (median age, 67 years; median ejection fraction, 0.34) who underwent tiered-therapy defibrillator implantation at this institution. Patients were followed for a median of 19 months (interquartile range, 10 to 27 months). The cause, duration, costs, and predictors of cardiac-related rehospitalizations were analyzed. There were 76 cardiac admissions for 34 patients. The rate of cardiac-related hospital readmission was 0.72 per patient-year of follow-up. Arrhythmia-related admissions accounted for 43 of such admissions in 24 patients. Actuarial freedom from cardiac-related admissions was 0.57 and 0.40 at 1 and 2 years, respectively. The median length of stay for hospital readmissions was 5 days (interquartile range, 3 to 8 days). The median cost per admission was $5842 (interquartile range, $3549 to $12 170). The time to first readmission and the total rehospitalization time per year of follow-up were associated with a poor preimplant New York Heart Association functional class. Readmission for cardiac arrhythmias was not predicted by clinical parameters. CONCLUSIONS: Rehospitalization for cardiac reasons is common in patients receiving implantable defibrillators and is responsible for substantial resource consumption. The need for readmission for arrhythmia-related reasons cannot be predicted by clinical parameters at the time of device implantation.

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PubMed1997

Automatic arrhythmia identification using analysis of the atrioventricular association. Application to a new generation of implantable defibrillators. Participating Centers of the Automatic Recognition of Arrhythmia Study Group.

BACKGROUND: Atrioventricular association is a key criterion for arrhythmia diagnosis. Its use in a defibrillator should significantly reduce the incidence of inappropriate shocks. Therefore, we evaluated the diagnostic accuracy of an algorithm that uses dual-chamber sensing and analysis of atrioventricular association to discriminate ventricular from supraventricular arrhythmias in a prototype of an implantable defibrillator. METHODS AND RESULTS: The algorithm performed a stepwise analysis of arrhythmias. The rhythm was first classified on the basis of cycle lengths. Each episode was then classified as supraventricular or ventricular in origin on the basis of the stability of cycle lengths and atrioventricular association. This algorithm was evaluated in 156 episodes of induced sustained tachycardias. Eighty-nine tachycardias were taken from the Ann Arbor electrogram library; the others were recorded in 50 patients during electrophysiological studies. The atrial and ventricular signals were stored on an external recorder and then injected into an external prototype of a defibrillator system. The algorithm correctly diagnosed 96% of ventricular tachycardia episodes, 100% of ventricular fibrillation episodes, and 92% of double-tachycardia episodes. The mean detection time for ventricular tachycardia was 2.6 +/- 0.8 seconds, and for ventricular fibrillation, it was 2.1 +/- 0.4 seconds. The positive predictive values for the diagnoses of atrial fibrillation and atrial flutter were 92% and 86%, respectively. For ventricular tachycardia and ventricular fibrillation, the values were 95% and 100%, respectively. CONCLUSIONS: Analysis of atrioventricular association promotes reliable differentiation between ventricular and supraventricular tachycardias and should enhance the diagnostic capabilities of implantable defibrillators.

Algorithms↗
PubMed1997

Programming of implantable cardioverter-defibrillators on the basis of the upper limit of vulnerability.

BACKGROUND: A patient-specific measure of defibrillation efficacy that requires a minimum number of ventricular fibrillation (VF) episodes would be valuable for programming implantable cardioverter-defibrillators (ICDs). The upper limit of vulnerability (ULV) is the weakest shock strength at or above which VF is not induced when a stimulus is delivered during the vulnerable phase of the cardiac cycle. It correlates with the defibrillation threshold (DFT) and can be determined with a single episode of VF. The objective of this study was to test the hypothesis that ICDs programmed on the basis of the ULV convert spontaneous ICD-detected VF reliably. METHODS AND RESULTS: We studied 100 consecutive patients at ICD implantation and during follow-up of 20 +/- 7 months. At implantation, the ULV and DFT were determined, and the ICD system was tested at a shock strength equal to the ULV + 3 J. During follow-up, the strength of the first shock was programmed to the ULV + 5 J for arrhythmias detected in the VF zone (cycle length < 292 +/- 17 ms). We reviewed stored detection intervals and electrograms from spontaneous episodes of ICD-detected VF to determine the success rate for appropriate first shocks. The programmed first-shock strength was 17.5 +/- 5.2 J. During follow-up, there were 120 appropriate first shocks in 37 patients. The arrhythmia was rapid monomorphic ventricular tachycardia (VT) in 70% of episodes (31 patients), VF in 11% (13 patients), polymorphic VT in 1%, and unclassified in 17% (15 patients). The first shock was successful in 119 of 120 episodes (99%; 95% CI, 93% to 100%). One unclassified episode required two shocks. No patient had syncope associated with an ICD shock or arrhythmic death. CONCLUSIONS: ICD shocks can be programmed on the basis of the ULV, a measurement made in regular rhythm, without a direct measure of defibrillation efficacy.

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PubMed2006

Multiple failed external defibrillation attempts during robot-assisted internal mammary harvest for myocardial revascularization.

We describe multiple failed external defibrillation attempts via rescue defibrillation pads for ventricular fibrillation that occurred secondary to direct electrical current transmission through the pericardial sac from electrocautery during robot-assisted internal mammary harvest. Only after resumption of two-lung ventilation and decompression of the iatrogenic pneumothorax was the patient successfully defibrillated. Conditions necessary for robotic intrathoracic surgery may make defibrillation and resuscitation difficult if they become necessary.

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PubMed2005

Reduced ejection fraction after myocardial infarction: is it sufficient to justify implantation of a defibrillator?

BACKGROUND: Improved survival after prophylactic implantation of a defibrillator in patients with reduced left ventricular ejection fraction (EF) after myocardial infarction (MI) has been demonstrated in patients who experienced remote MIs in the 1990s. The absolute survival benefit conferred by this recommended strategy must be related to the current risk of arrhythmic death, which is evolving. This study evaluates the mortality rate in survivors of MI with impaired left ventricular function and its relation to pre-hospital discharge baseline characteristics. METHODS: The clinical records of patients who had sustained an acute MI between 1999 and 2000 and had been discharged from the hospital with an EF of < or = 40% were included. Baseline characteristics, drug prescriptions, and invasive procedures were recorded. Bivariate and multivariate analyses were performed using a primary end point of total mortality. RESULTS: One hundred sixty-five patients were included. During a median follow-up period of 30 months (interquartile range, 22 to 36 months) 18 patients died. The 1-year and 2-year mortality rates were 6.7% and 8.6%, respectively. Variables reflecting coronary artery disease and its management (ie, prior MI, acute reperfusion, and complete revascularization) had a greater impact on mortality than variables reflecting mechanical dysfunction (ie, EF and Killip class). CONCLUSIONS: The mortality rate among survivors of MIs with reduced EF was substantially lower than that reported in the 1990s. The strong decrease in the arrhythmic risk implies a proportional increase in the number of patients needed to treat with a prophylactic defibrillator to prevent one adverse event. The risk of an event may even be sufficiently low to limit the detectable benefit of defibrillators in patients with the prognostic features identified in our study. This argues for additional risk stratification prior to the prophylactic implantation of a defibrillator.

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PubMed2004

Elevated defibrillation threshold with venlafaxine therapy.

Depression is a common comorbidity in patients with heart failure or implantable cardioverter-defibrillators (ICDs). A 35-year-old woman with depression, nonischemic cardiomyopathy, and a history of cardiac arrest had an ICD implanted. During initial testing, the device failed to internally defibrillate the patient. Venlafaxine, an antidepressant with cardiac sodium channel blocking activity, was identified as a potential contributor to her elevated defibrillation threshold. After the venlafaxine was discontinued, the ICD was able to successfully internally defibrillate the patient. Clinicians should be aware of this potential adverse drug-device interaction. Further studies are needed to determine the clinical significance of venlafaxine therapy in patients with ICDs.

Adult↗
PubMed2005

Antiarrhythmic drugs in patients with implantable cardioverter-defibrillators.

Antiarrhythmic drugs need to be initiated in up to 70% of patients with implantable cardioverter-defibrillators (ICDs) in order to treat atrial tachyarrhythmias, decrease the frequency of defibrillator shocks, and terminate ventricular arrhythmias along with antitachycardia pacing. trial fibrillation (AF) occurs in about 20% of patients with ICDs (the majority with congestive heart failure [CHF]). Antiarrhythmic drugs are initiated for this indication in 2-20% of the ICD population. Data from CHF-STAT (Congestive Heart Failure: Survival Trial of Antiarrhythmic Therapy; amiodarone vs placebo) and DIAMOND-AF (Danish Investigations of Arrhythmia and Mortality ON Dofetilide--rial Fibrillation; dofetilide vs placebo) support the approach that restoration and maintenance of sinus rhythm might be beneficial in CHF, even though no study has specifically addressed the CHF population with ICDs. Further clarification on potential benefits of rhythm control in CHF-associated AF will come from the AF-CHF (Atrial Fibrillation and Congestive Heart Failure) trial that is currently underway. The vast majority of patients with ICDs will have discharges of their devices during follow-up. Although class III antiarrhythmic drugs are widely considered to be effective for prophylaxis against frequent shocks, there are surprisingly few controlled studies that demonstrate this. In contrast to conflicting amiodarone data, sotalol has been found to be effective in preventing shocks from ICDs in prospective, randomized, placebo-controlled studies. A large study (SHIELD; SHock Inhibition Evaluation with azimiLiDe) has shown that azimilide significantly reduces ventricular tachyarrhythmia recurrence, thereby reducing the burden of symptomatic ventricular tachyarrhythmia. Other novel antiarrhythmic drugs, such as dofetilide or dronedarone, as well as different strategies (e.g. in the OPTIC [Optimal Pharmacological Therapy in Implantable Cardioverter] trial; beta-adrenoceptor antagonist therapy alone, amiodarone plus beta-adrenoceptor antagonist therapy, or sotalol alone) for the prevention of ICD shocks are under evaluation. The majority of antiarrhythmic drugs, including sotalol, dofetilide, and azimilide, have no effect on, or are even associated with a decrease in, defibrillation thresholds in humans. Amiodarone, in contrast, has been shown to be related to higher defibrillation thresholds at implant and during follow-up of monophasic devices. Potential cardiac (e.g. ventricular proarrhythmia, negative inotropic effect) and drug-specific non-cardiac adverse effects are a frequent cause for drug discontinuation and need to be considered when initiating and maintaining antiarrhythmic drug therapy. In conclusion, antiarrhythmic drugs are frequently used in ICD patients, the main indications being treatment of atrial tachyarrhythmias and prevention of ICD shocks. Despite potential adverse effects, antiarrhythmics can be administered safely, as long as ICD/drug interactions are appreciated. Controlled studies that will further define the role of concomitant antiarrhythmic drug utilization in patients with ICDs are underway.

Adrenergic beta-Antagonists↗
PubMed1993

Nonthoracotomy lead implantable cardioverter defibrillators: normal radiographic appearance.

Recently, cardioverter defibrillators with leads and patches that can be implanted via a combination of transvenous and subcutaneous routes rather than via thoracotomy have been developed. Early experience in patients subject to serious ventricular arrhythmias suggests that, as with surgically implanted defibrillators, these nonthoracotomy defibrillators can reduce the risk of sudden death due to cardiac arrest [1]. Moreover, high perioperative complication rates associated with thoracotomy-inserted cardioverter defibrillators are avoided [2]. Four models are currently undergoing clinical trials in the United States. We have used three of these models: PCD (Medtronic, Minneapolis, MN), ENDOTAK (Cardiac Pacemakers Inc., St. Paul, MN), and RES-Q (Intermedics, Freeport, TX). This essay illustrates the normal radiographic appearance of these devices.

Defibrillators, Implantable↗
PubMed1997

Value of radiography in diagnosing complications of cardioverter defibrillators implanted without thoracotomy in 437 patients.

OBJECTIVE: This study evaluated the usefulness of radiography in assessing the frequency and cause of complications of nonthoracotomy-implanted cardioverter defibrillators. MATERIALS AND METHODS: Between May 1992 and December 1995, 437 consecutive patients at our institution underwent cardioverter defibrillator placement. Routine follow-up included external device testing at 6 weeks after placement and every 3 months thereafter. Chest radiographs were obtained immediately after placement, annually, and at the time of any suspected complication. Retrospective review of radiographs and medical charts was done for all patients with clinical complications. RESULTS: Forty-five complications (10%) were clinically diagnosed: lead or patch fracture in fifteen (33%) patients, electric lead dysfunction in eight (18%), infection in eight (18%), lead retraction in six (13%), patch fold in two (5%), hematoma in two (5%), and other complications in four (9%) patients. Eighteen complications (40%) were radiographically evident. Lead retraction, hematoma, patch fold, patch migration, and the twiddler syndrome were radiographically confirmed in 100% of cases. The average time for these complications to be detected was 68 days; 92% were detected within 23 days. Conversely, only four (27%) lead fractures, one (13%) electric lead dysfunction, and one (13%) infection were radiographically confirmed. These latter complications were discovered an average of 579 days after cardioverter defibrillator placement. CONCLUSION: Radiography plays a secondary role in the diagnosis of cardioverter defibrillator complications and is particularly limited beyond 1 month after placement. Radiographs may be helpful in the first month after placement because early complications are the most radiographically apparent.

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PubMed1999

Bronchopericardial fistula after placement of an automatic implantable cardioverter defibrillator: radiographic and CT findings.

OBJECTIVE: We describe our experience with bronchopericardial fistula as a complication of infection in patients who have undergone placement of automatic implantable cardioverter defibrillator systems. CONCLUSION: Bronchopericardial fistula should be suspected in patients who present with hemoptysis and who have undergone placement of an automatic implantable cardioverter defibrillator using pericardial or epicardial defibrillator patches. Air between a defibrillator patch and the heart on chest radiographs or CT is diagnostic.

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PubMed2003

Simultaneous use of bilateral subthalamic nucleus stimulators and an implantable cardiac defibrillator. Case report.

Bilateral electrical stimulation of the subthalamic nucleus is being used with increasing frequency as a treatment for severe Parkinson disease (PD). Implantable cardiac defibrillators improve survival in certain high-risk patients with coronary artery disease and ventricular arrhythmias. Because of concern about possible interaction between these devices, deep brain stimulation (DBS) systems are routinely disconnected before defibrillators are implanted in patients with PD and arrhythmia. The authors report on a patient with bilateral subthalamic stimulators who underwent successful placement of an implantable defibrillator. Testing of the devices over a wide range of settings revealed no interaction. The patient subsequently underwent multiple episodes of cardioversion when the ventricular lead became dislodged. There was no evidence of adverse neurological effects, and interrogation of the DBS devices after cardioversion revealed no changes in stimulus parameters. The outcome in this case indicates that DBS systems may be safely retained in selected patients who require implantable cardiac defibrillators.

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PubMed1994

A new approach: a single triple electrode lead system interfaced with a third generation defibrillator.

The efficacy of implantable third generation cardioverter defibrillators has been well established for the treatment of patients with malignant ventricular arrhythmias and survivors of cardiac arrest. However, many patients have been reluctant or unwilling to endure the discomfort of an open chest procedure, despite their need for the device. Furthermore, morbidity (pneumothorax, pneumonia, sepsis, pleural effusion, hemorrhage, pericarditis, etc.) and mortality associated with the application of epicardial lead systems is of concern. Finally, the mean overall expense of $80,433 for the epicardial method of defibrillator implantation is a consideration in an era of increasing cost-awareness in health care. Fortunately, the recent market-release of a single lead transvenous defibrillation system [Endotak, Cardiac Pacemakers, Inc. (CPI), St. Paul, Minnesota] may address these pressing issues. The specific purpose of this report is to demonstrate the patient benefit derived from interfacing a single endocardial lead system with a biphasic third generation defibrillator.

Defibrillators, Implantable↗
PubMedDate not supplied

Patent foramen ovale and implantable cardioverter defibrillator.

A case of patent foramen ovale opening was observed concomitantly to a defibrillation threshold determination in the setting of an internal cardioverter defibrillator implantation. The subsequent transient right-to-left shunt was confirmed by a peroperative transoesophageal echocontrast study. The underlying mechanism of this incident may be related to a transient reversal of the interatrial gradient, due to the pre-existence of pulmonary hypertension and tricuspid regurgitation, associated with ongoing mechanical ventilation and modifications of intracardiac pressures regimen secondary to the succeeding ventricular tachyarrhythmia and defibrillation. Paradoxical embolism can be an aetiology for neurologic injury during internal cardioverter defibrillator implantation.

Defibrillators, Implantable↗
PubMed1999

The Food and Drug Administration and atrial defibrillation devices.

CONTEXT: Atrial fibrillation is a common arrhythmia. It leads to significant morbidity and mortality, primarily from the increased incidence of stroke. The implantable atrial defibrillator, a new therapeutic option for the management of atrial fibrillation, is currently undergoing Food and Drug Administration (FDA) scrutiny for approval to market in the United States. DATA SOURCES: A review of the basic epidemiology of atrial fibrillation, as well as the current status of accepted treatment options in light of the development of the implantable atrial defibrillator, was conducted. A literature search using the terms atrial fibrillation, implantable defibrillator, Food and Drug Administration, medical devices, and medical device regulatory law was conducted using the MEDLINE and Current Contents databases. RESULTS: Currently, there is no consensus on the optimal treatment of atrial fibrillation. Despite the lack of definitive studies showing overall benefit associated with maintaining sinus rhythm in patients in atrial fibrillation, the implantable atrial defibrillator may soon reach the general market. We examine the FDA process for the evaluation of this new medical device and discuss implications for the patient, physician, industry, and health insurers. CONCLUSIONS: Current FDA approval processes for new devices are a compromise between (a) the needs for expediency and encouraging innovation by the medical device industry and (b) the need to ensure that new devices will contribute to improved patient outcomes. We suggest alternative FDA-approval processes that address these issues.

Atrial Fibrillation↗
PubMed1999

[Implantable ventricular defibrillator. Systematic induction of ventricular arrhythmia is not useful except for implantation].

Checking the efficacy of a defibrillator after its implantation is current practice. This control usually entails induction of ventricular fibrillation (VF). The aim of this study was to assess the utility of this practice in patients with an endovascular system of electrodes. Implantation was acquired when a margin of security of 10 days or more had been obtained. During the postoperative test, the choice of energy was that which reduced VF at implantation. Of the 84 patients included in this study, 59 were implanted with an endovascular electrode system alone and the other 25 patients had endovascular electrodes associated with a subcutaneous patch electrode. The average time from implantation to the postoperative test was 31 +/- 12 days. Arrhythmia sensing was normal and reduction by the defibrillator was observed in all patients. The average energy of the electric shocks was not significantly different to that observed at implantation (18.6 +/- 3.6 J and 19.3 +/- 4.7 J). Fifty patients had antiarrhythmic drugs (amiodarone = 43) at implantation, and 32 at the time of the postoperative test (amiodarone = 17). This study showed that the postoperative test with induction of VF was normal in all patients. Therefore, the authors propose that follow-up should consist of consultation including interrogation of the defibrillator and a chest X-ray to check the position of the electrodes. If one of these tests is abnormal or if the perioperative threshold of defibrillation does not provide an adequate margin of safety, induction of a ventricular arrhythmia is necessary to check the function of the system.

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