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PubMed1996

Serial defibrillation lead impedance in patients with epicardial and nonthoracotomy lead systems.

INTRODUCTION: The stability of implantable cardiac defibrillation lead impedance subsequent to implantation has not been reported and may have important clinical implications. The objective was to characterize the incidence and degree of impedance changes occurring after implantation of defibrillation lead systems. METHODS AND RESULTS: The study cohort consisted of patients who received epicardial or nonthoracotomy lead systems. Defibrillation impedance was recorded at implantation, prior to hospital discharge (predischarge), and during follow-up. For each individual the magnitude of the impedance change relative to implantation was characterized. Among patients with an epicardial system, a significant decrease in impedance was observed at predischarge (mean 9.3 omega). The magnitude of the decrease was large in 39% and moderate in 31% of individuals. Subsequently, a gradual rise in mean impedance was apparent. At 18-21 months postimplantation, impedance was significantly increased relative to implantation (mean 6.8 omega). At this time, the magnitude of the increase was large in 46% and moderate in 23% of patients. Among patients with a nonthoracotomy lead system including a subcutaneous patch, a significant decrease in mean impedance was observed at predischarge (mean 3.5 omega). The magnitude of the decrease was large in 8% and moderate in 50% of individuals. Subsequently, a gradual rise in impedance was apparent. At 5-6 months, it was significantly increased relative to implantation (mean 2.3 omega). The magnitude of the increase was large in 10% and moderate in 33% of patients. Among the group of patients whose nonthoracotomy lead system did not include a subcutaneous patch, there was no significant change in mean impedance at predischarge relative to implantation. In subsequent intervals, a gradual rise was apparent. At 5-6 months, impedance was significantly increased relative to implantation (mean 4.3 omega). The magnitude of the increase was large in 16% and moderate in 47% of individuals. CONCLUSION: Significant changes in defibrillation lead impedance occur after implantation of epicardial and nonthoracotomy defibrillation lead systems. These data may serve as a standard for identifying the anticipated maximum change in lead impedance and thus may be useful as a tool for recognizing problems with defibrillation lead integrity.

Defibrillators, Implantable↗
PubMed1997

Delivery of noncommitted shocks for nonsustained ventricular arrhythmias by a new implantable cardioverter defibrillator with abortive shock capability.

INTRODUCTION: To describe the delivery of noncommitted implantable cardioverter defibrillator (ICD) shocks despite self-termination of ventricular arrhythmias. Abortive shock capability should eliminate the delivery of shocks for self-terminating ventricular arrhythmias. The delivery of noncommitted shocks despite abortive shock capability is, therefore, unexpected and previously unreported. METHODS AND RESULTS: Among 118 patients who received the Transvene nonthoracotomy lead system and the Jewel ICD (model 7219D), three patients (1.7%) experienced supurious, noncommitted shocks for self-terminating arrhythmias. Only one detection zone (i.e., ventricular fibrillation) had been programmed in the defibrillator in each patient. In all three patients, the ventricular arrhythmias self-terminated during the charging period. One patient received seven shocks during periods of asystole, and the other two patients received one shock each. Two different mechanisms for shock delivery in this setting were identified: one occurring in the absence of electrical activity at the end of the bradycardia escape interval (i.e., associated with bradyarrhythmias), and the other when two sensed electrical events (i.e., escape beats) occurred during the so-called "synchronization" window of the defibrillator. CONCLUSIONS: In rare patients with the Jewel defibrillator, shocks may be delivered for self-terminating arrhythmias despite abortive shock capability. Patients who are dependent upon pacing from their implanted defibrillator are at particular risk for shock in the aftermath of self-terminating ventricular arrhythmias. Defibrillator programming strategies aimed at eliminating or diminishing the incidence of this problem are discussed.

Aged↗
PubMed1992

Automatic implantable cardioverter defibrillator: surgical approaches for implantation.

Surgical approaches for implantation of the automatic cardioverter defibrillator are sternotomy, left thoracotomy, subxiphoid, and subcostal. Although any one of these may be combined with insertion of one or more of the electrodes transvenously, surgical entry into the chest is required for every noninvestigational defibrillator implantation operation. The approaches differ in exposure provided for selecting electrode sites and for handling untoward events, in amount and location of tissue that must be divided or dissected, and in average time required. The operation is an electrical one. Its purpose is to obtain reliable rhythm sensing so that defibrillation or cardioversion shocks will occur only when necessary, and to obtain low enough defibrillation thresholds for shocks of 30 joules or less to have a 10-joule defibrillation safety margin. Many of the patients have had previous cardiac operations. They usually have low or very low ejection fractions. Intraoperative electrophysiological testing with often multiple defibrillation episodes is required. The choice of approach varies with the state of the patient, the institutional experience, and the surgeon. This article describes technique, and the advantages and disadvantages of the four approaches as used by four surgeons in four different institutions.

Defibrillators, Implantable↗
PubMed2001

Effects of biphasic vs monophasic defibrillation on the scaling exponent in a swine model of prolonged ventricular fibrillation.

OBJECTIVE: Mathematical analyses of ventricular fibrillation (VF) have resulted in the derivation of a measure termed the scaling exponent (ScE) that characterizes the duration of VF and probability of defibrillation success. The purpose of this study was to compare the effects of biphasic defibrillation waveform (BDW) and monophasic defibrillation waveform (MDW) rescue shocks on ScE in a swine model of prolonged VF. METHODS: Utstein guidelines for the laboratory study of cardiopulmonary resuscitation were followed. Twenty mixed-breed domestic swine (mass range 20.5-26.8 kg) were instrumented and randomized to receive either MDW or BDW rescue shocks. Ventricular fibrillation was induced and untreated for a nonintervention interval of 8 minutes. Rescue shocks were delivered at 8, 10, and 12 minutes of elapsed VF time. The energy sequence for the three MDW shocks was 70, 100, and 150 J (approximately 3, 4, and 6 J/kg). All BDW shocks were delivered at 50 J (approximately 2.5 J/kg). Only VF was shocked. Chest compressions and drugs were not provided. Rhythm analysis and ScE calculation were performed offline. Continuous and discontinuous linear regression models were fit to plots of ScE vs time. Defibrillation success and progression of ScE slope were analyzed using Fisher's exact test, paired t-tests, and repeated-measures analysis of variance (ANOVA). RESULTS: Baseline characteristics were similar for both groups. Successful termination of VF occurred on the first rescue shock in 1 of 10 (10%) in the MDW group and 3 of 10 (30%) in the BDW group; this difference was not statistically significant (p = 0.58). No other defibrillation successes were observed. No animals achieved return of spontaneous circulation. The ScE values during the protocol progressed from 1.330 (95% CI = 1.287 to 1.373) to 1.724 (95% CI = 1.603 to 1.845) for MDW and 1.338 (95% CI = 1.261 to 1.415) to 1.639 (95% CI = 1.530 to 1.745) for BDW. Both groups showed a trend toward increasing ScE values with successive rescue shocks. Repeated-measures ANOVA using both continuous and discontinuous models demonstrated no difference in overall ScE slope progression between study groups. CONCLUSIONS: Mode of defibrillation waveform (BDW vs MDW) does not appear to impact ScE trends. Additional studies must be performed to better evaluate the clinical implications of this finding.

Animals↗
PubMed1997

Does reducing capacitance have potential for further miniaturisation of implantable defibrillators?

OBJECTIVE: To determine whether considerably smaller capacitors could replace 125 microF capacitors as the standard for use in implantable defibrillators. METHODS: Measured energy, impedance, voltage, and current delivered were compared at defibrillation threshold in 10 mongrel dogs for defibrillation using 75 microF and 125 microF capacitors alternated randomly. Defibrillation was attempted with biphasic shocks of comparable tilt between an endocardial lead in the right ventricular apex and a "dummy" active can of an experimental implantable device placed in the subpectoral position. RESULTS: A reduction of capacitor size of 40% was associated with an increase in voltage of 21% and in current of 22%. With a 65% tilt, no significant differences were found between the two capacitances with respect to the impedance or energy required for defibrillation. CONCLUSIONS: Multiple advances in electrode material, electrode configuration, shock morphology, and shock polarity have reduced defibrillation energy requirements. Smaller capacitors could be used in implantable cardioverter/defibrillators without a major decrease in effectiveness.

Animals↗
PubMed2003

Novel passive implantable atrial defibrillator using transcutaneous radiofrequency energy transmission successfully cardioverts atrial fibrillation.

BACKGROUND: Conventional methods for cardioversion of atrial fibrillation (AF) to sinus rhythm have numerous difficulties. A novel method for cardioversion using the passive implantable atrial defibrillator (PIAD) was tested in acute animal models. This device does not have a battery or a capacitor to store energy and is activated by transferring RF energy across the skin from an external transmitter to the subcutaneously implanted defibrillator. On activation, a novel monophasic shock waveform with 5% tilt is delivered to the heart via 2 intracardiac defibrillation leads. METHODS AND RESULTS: Cardioversion attempts with the device were assessed in 2 phases: a feasibility and efficacy study and randomized comparison against standard waveforms. Defibrillation leads were placed transvenously into the distal coronary sinus and the right atrial appendage. These were connected to the subcutaneously implanted PIAD. Sustained AF was induced by rapid atrial pacing. The transmitter coil was placed on the skin overlying the defibrillator, and defibrillation synchronized to the R wave was attempted. The method was found to be efficacious at very low voltage and energy, with 100% cardioversion success observed for 10-ms 100-V shocks (mean energy, 1.54+/-0.02 J). The PIAD waveform had a higher cardioversion success rate than a truncated, 70% tilt monophasic exponential pulse (100 V, 100% versus 78.0+/-7.57%; P=0.001). There were no postshock complications. CONCLUSIONS: Considering these animal results, this method is promising for cardioverting AF in symptomatic patients.

Animals↗
PubMed1997

Additional lead improves defibrillation efficacy with an abdominal 'hot can' electrode system.

BACKGROUND: Although the left prepectoral site is preferred for "hot can" placement, this site is unavailable in some patients. We evaluated the influence of electrode location on defibrillation thresholds with alternative hot can and transvenous lead configurations. METHODS AND RESULTS: Three interrelated studies were performed. In group 1, the importance of hot can location was investigated by pairing a right ventricular lead to five different hot can placement sites in seven pigs. The defibrillation energies for right pectoral, left pectoral, left subaxillary, and right and left abdominal hot can sites were 20.3+/-2.7,* 15.9+/-3.8, 14.9+/-2.5, 32.0+/-3.4,* and 30.0+/-3.4 J,* respectively (*P<.005 versus left pectoral and left subaxillary sites). In group 2, the value of a three-electrode configuration with an abdominal hot can placement was investigated by adding a subclavian vein lead to the pectoral or abdominal hot can configurations in seven pigs. The defibrillation energies for left pectoral and abdominal sites were 18.6+/-4.2 and 29.0+/-5.8 J (P=.0001), respectively. The addition of a right or left subclavian vein lead with an abdominal hot can reduced the threshold to 19.3+/-4.2* or 18.8+/-3.2,* respectively (*P=.0001 versus abdominal site). In group 3, the contribution of the abdominal hot can electrode to the three-electrode configuration was tested by a comparison with two purely transvenous two-electrode configurations in six pigs. The defibrillation energy (19.9+/-3.2 J) for the abdominal hot can with a subclavian vein lead was lower than the transvenous lead configurations with a subclavian vein (29.0+/-2.5 J, P=.0001) or a superior vena cava lead (30.7+/-3.7 J, P=.0001). The right ventricular lead was the sole cathode during the first phase of the biphasic shock in all experiments. CONCLUSIONS: Defibrillation energy depends on the hot can placement site. The addition of a subclavian vein lead with an abdominal hot can improves defibrillation efficacy to the level of the pectoral placement and is better than a purely transvenous lead configuration.

Abdomen↗
PubMed1996

Twiddler's syndrome complicating a transvenous defibrillator lead system.

Twiddler's syndrome is a rare complication seen in patients with implanted pacemakers or defibrillators. The condition typically presents with device malfunction and occurs when the patient either consciously or unconsciously twists and rotates the implanted device in its pocket, resulting in torsion and dislodgement of the implanted lead. A case of twiddler's syndrome involving a transvenous defibrillation lead and an abdominally implanted defibrillator is described. This is the first report of this complication with this particular lead. The patient in this report was a middle-aged obese diabetic woman who presented 7 months after defibrillator implantation with device noncapture and intermittent nonsensing. Review of the literature reveals that the majority of patients with this complication are middle-aged obese women with a defibrillator pocket that exceeds the size of the defibrillator. Treatment measures are discussed both for the patient with this complication and for the patient at increased risk for its occurrence.

Defibrillators, Implantable↗
PubMed2005

The ethics of deactivating implanted cardioverter defibrillators.

Implantable cardioverter defibrillators are life-saving devices for many patients with cardiac disease. Recipients of these devices, nevertheless, often suffer from progressive comorbid and cardiac conditions. Therefore, physicians should anticipate situations in which the defibrillator is no longer desired by the patient or no longer medically appropriate. Near the end of life, many of these patients may decline cardiopulmonary resuscitation. The comanagement of do-not-resuscitate orders and implanted defibrillators can be confusing to patients and physicians alike since the former proscribe the use of electrical cardioversion while the latter provide this precise treatment. Although the use of implanted defibrillators has important ethical implications, few studies have examined these issues, and guidelines have not yet been developed to assist physicians in caring for patients who have received defibrillators. This paper discusses bioethical considerations in disabling implantable cardioverter defibrillators.

Aged↗
PubMed1995

Clinical experience with transvenous implantable cardioverter-defibrillators for treatment of malignant ventricular arrhythmias.

The need for thoracotomy has previously limited the use of the implantable cardioverter-defibrillator. Prior investigators have shown the efficacy and reduced risk of the transvenous implantable cardioverter-defibrillator. In this study, we report our experience with the transvenous implantable cardioverter-defibrillator as a first-line system. Thirty-four patients with mean age 63.2 +/- 10.3 years and mean ejection fraction 32.6 +/- 11.4% underwent implantation of a transvenous cardioverter-defibrillator using an Endotak lead with or without a subcutaneous patch. Twenty-one patients received a biphasic device and the remainder a monophasic device. Thirty-three of 34 patients (97%) were successfully implanted. The mean defibrillation threshold was than < or = 15.3 +/- 3.6J. Overall, 25 of 34 (74%) patients were implanted with a single endocardial lead alone. In the group receiving a biphasic device 19 of 21 (90%) were successfully implanted with a single endocardial lead alone whereas in the group receiving a monophasic device only 6 of 12 (50%) were successfully implanted with single endocardial lead alone (p < 0.05). There were no serious complications. One postoperative death was a result of end-staged congestive heart failure. We conclude that the transvenous implantable cardioverter-defibrillator is safe and efficacious and that incorporation of biphasic waveform may lead to higher rates of implantation of single transvenous lead alone without the need for subcutaneous patch.

Adult↗
PubMed2002

[Implantable defibrillators and prevention of sudden death: clinical and economic implications in the light of the MADIT II study].

The cardioverter-defibrillator is the most effective strategy to prevent sudden death in patients with previous episodes of ventricular tachyarrhythmia (secondary prevention of sudden death). In recent years the possibility of primary prevention of sudden death in selected groups of high risk patients has raised great interest. The MADIT II study highlighted the possibility of preventing sudden death in patients with coronary artery disease. According to this trial, identification of such patients can be performed by means of few clinical data and without expensive screenings (i.e. electrophysiological study). Indeed, patients with a previous myocardial infarction and low left ventricular ejection fraction (< 30%) may benefit from the implant of a cardioverter-defibrillator, with a reduction of the mortality risk by about 31% in the following two years. In the light of these data, implant of a cardioverter-defibrillator should be proposed in such patients, even if the problem of limited economic resources to meet the cost of the devices has to be considered even in the richest country of the world. Despite the positive scientific result, MADIT II has raised the problem of the effective possibility of adopting this therapeutic strategy in clinical practice and this question is still open. Strategies to reduce the theoretically high costs implicated by the MADIT II study include a reduction in the cost of defibrillators through dynamic market forces, the identification of subgroups at higher risk of sudden death, and the use of cheap defibrillators with limited diagnostic and therapeutic options. A long-term evaluation of the cost-effectiveness for western countries of these strategies is necessary to identify in which patient subgroups implant of a cardioverter-defibrillator is acceptable, i.e. cost-effective, in terms of primary prevention.

Clinical Trials as Topic↗
PubMed2003

Inappropriate shock delivery and biventricular pacing cardiac defibrillators.

In the United States, physicians adapt currently available defibrillators to accommodate leads for biventricular pacing in those congestive heart failure patients who might benefit from cardiac resynchronization and who are additionally at risk for sudden cardiac death. The adaptation of the lead system of available defibrillators to also allow them to function as biventricular pacemakers presents occasions in which inappropriate shocks are delivered due to double counting of the right and left ventricular depolarizations by the implantable cardiac defibrillator. We reviewed a series of inappropriate shock deliveries that occurred after the implantation of biventricular pacing cardiac defibrillators at our institution; all of these shocks were related to ventricular double counting. Each had different underlying causes and management strategies. Complications such as these emphasize the importance of attentiveness to ventricular channel electrograms and to device sensing with the use of biventricular pacing cardiac defibrillators. In addition, a thorough working knowledge of pacemaker and defibrillator operation is essential for the prediction and correction of inappropriate therapies.

Aged↗
PubMed2004

[Prevalence and clinical course of patients in Spain with acute myocardial infarction and severely depressed ejection fraction who meet the criteria for automatic defibrillator implantation].

The Multicenter Automatic Defibrillator Implantation Trial (MADIT)-II has broadened the indications for cardioverter defibrillator implantation. We present a retrospective study designed to estimate the number of patients in Spain eligible for an implantable defibrillator according to the MADIT-II criteria. From January 1999 to October 2002, 758 consecutive patients were admitted to our center with the diagnosis of acute myocardial infarction. Sixty-seven had a left ventricular ejection fraction < or = 30% (mean, 23[5]) and were not eligible for revascularization. Excluding patients older than 80 years and patients with marked co-morbidity, 47 patients met the MADIT-II criteria for an implantable defibrillator. After a mean follow-up of 18 months, there were 20 deaths, 6 of which were considered sudden. In conclusion, application of the MADIT-II criteria for defibrillator implantation may benefit 6% of the patients with myocardial infarction in Spain. This proportion translates as 4110 defibrillator implantations.

Adult↗
PubMed2005

[Role of antiarrhythmic drugs in reducing the number of defibrillation shocks].

There is a logical basis for the prescription of antiarrhythmic therapy (AAT) in patients with an implanted automatic defibrillator (IAD): the prevention of supraventricular and ventricular arrhythmias, slowing the rate of a ventricular arrhythmia to improve the haemodynamic tolerance and better efficacy of anti-tachycardia stimulation. Adjuvant therapy of this kind is used in 49 to 69% of cases. Forty six per cent of patients in the MADIT I trial had AAT at the last follow-up. In the AVID trial, despite recommendations to avoid the association of AAT and [AD, 18% of patients had this combination because of the large number of shocks in 64% of cases; AAT was associated with both a reduction in the number of shocks (p < 0.05) and in the delay to a recurrence of the arrhythmia (p < 0.0001). In the CASCADE trial, carried out in survivors of cardiac arrest, the prescription of amiodarone in patients with IAD significantly reduced the number of defibrillation shocks. Finally, almost 40% of patients with IAD have an "arrhythmia storm", sometimes during follow-up, usually requiring the association of AAT. Despite the frequent association of AAT and IAD, the results of this combination have rarely been studied systematically. Only one randomised trial has been published comparing D,L-sotalol and placebo in patients with IAD. The treatment reduced the probability of a first defibrillation shock, whether appropriate or not. Amiodarone has often been proposed in association with IAD in isolated cases. The OPTIC trial (Optimal Pharmacological Therapy in Implantable Cardioverter), currently under way, has three sub-groups of IAD (betablocker, amiodarone and betablocker, sotalol), with the aim of determining the preventive value of each AAT with respect to the IAD performance. In addition to the results of combined treatment, the interaction with the threshold of defibrillation is an important factor which is not clearly understood at present. Class I AAT increases the threshold of defibrillation whereas Sotalol reduced it. Amiodarone has a variable effect, neutral or deleterious. The OPTIC trial should provide valuable information via the sub-analysis of the effects of drugs on the threshold of defibrillation in each of the three arms of the trial.

Anti-Arrhythmia Agents↗
PubMed2005

The prevention of sudden cardiac death: the role of the automated external defibrillator.

Sudden death is usually the result of hemodynamically destabilizing ventricular tachycardia or ventricular fibrillation. Because the only definitive treatment for ventricular tachycardia/ventricular fibrillation is a direct current shock, and because that defibrillating shock must be given very quickly to be effective, the American Heart Association's "chain of survival" approach to persons with a cardiac arrest emphasizes early access to care, early cardiopulmonary resuscitation, early cardiac defibrillation and early advanced life support. The link in this chain of survival that has been changing most dramatically over the past decade is that of early defibrillation. The automated external defibrillator enables life-saving defibrillation therapy to be provided to the cardiac arrest victim by nontraditional responders, such as the general public. The present review evaluates the current role of the automated external defibrillator in the ongoing struggle to prevent sudden cardiac death.

Death, Sudden, Cardiac↗
PubMed2006

Improved electrodes for electrical defibrillation of rats.

Experimental induction of ventricular fibrillation in animals yields valuable information about this deadly arrhythmia. Human adult or pediatric defibrillators and their paddles can be used easily in larger animals such as dogs and pigs, but these animals are more difficult to house and handle, and available biochemical assays may be limited. In contrast, rats are easy and relatively inexpensive to house and handle, and numerous biochemical tests are available. However, in most cases, even pediatric electrodes are impractical for use in rats. Proper placement of defibrillation electrodes on the thorax requires that the electrical axis of the heart be situated between the defibrillator paddles. The most common approach to defibrillation in rats uses 2 electrodes: one is built into a board that underlies and touches the rat's back, and another is positioned manually on the anterior thorax. The aim of this study was to produce electrodes that are 1) easy to handle, 2) specifically designed for rats, 3) efficiently deliver defibrillation shocks along the electric axis of the heart, and 4) can be used for both in vivo defibrillation and on isolated heart preparations.

Animals↗
PubMed1995

[Experience with a transvenous pacemaker-cardioconverter-defibrillator without subcutaneous patch].

Sudden cardiac death caused by malignant ventricular arrhythmias is one of the main causes of cardiovascular mortality. Implantation of cardioverter-defibrillators has resulted in the reduction of the incidence of sudden cardiac death caused by malignant ventricular arrhythmias from the yearly 10-30% to 1%. For the very first time in Hungary, the authors applied only transvenous lead configuration for automatic cardioverter defibrillators in three patients. The indications of the implantation were ventricular fibrillation in one case, ventricular tachycardias refractory to drug treatment in two cases. Ventricular arrhythmias were secondary to coronary heart disease in two patients, dilatative cardiomyopathy in one patient. Preoperative, intraoperative and postoperative electrophysiological studies were regularly taken. Using Biotronik Phylax 03 device with a right ventricular electrode and a superior vena cava electrode and without subcutaneous patch the intraoperative defibrillation thresholds were 6, 11 and 12 J respectively. The fractally iridium coating increases the surface of the electrodes that has a very good effect on defibrillation threshold. During a mean follow-up of six months the occurring spontaneous ventricular arrhythmias (1 ventricular fibrillation and 5 ventricular tachycardias) were terminated by Phylax 03 with cardioversion-defibrillation or overdrive stimulation. The authors' results of intraoperative testing and clinical experiences show that the Phylax 03 biphasic system due to low defibrillation thresholds without subcutaneous patch can safely be applied with only transvenous implant technique in patients with major ventricular arrhythmias to prevent sudden cardiac death and to terminate ventricular tachycardia.

Arrhythmias, Cardiac↗
PubMed1993

[Implantable defibrillator using epicardial and endocardial leads. Results of 36 implantations].

The authors report their experience of implantable defibrillators over a 5 year period. Between February 1988 and July 1992, 36 patients (25 men, 11 women, average age 51 +/- 11 years, range 18 +/- 71 years) underwent implantation of an automatic defibrillator with epicardial (n = 13, Group I) or endocardial leads (n = 23, Group II) without patch electrodes (n = 7), with subcutaneous patch electrodes (n = 12) or epicardial patch electrodes (n = 4). Three serious early complications were observed: 2 cardiogenic shocks in Group I, one of which died on Day 1 and one case of infection which required explanation of the defibrillator on Day 23 in Group II. Late complications in Group I included one case of disactivation of the defibrillator, 2 losses of output, one of which required replacement of the defibrillator and 2 increases of threshold treated by implantation of an endocardial lead. In Group II, 2 patients had inappropriate shocks due to overdetection (n = 1) and double counting (n = 1). During an average follow-up period of 28.5 +/- 9 months in group I and 13 +/- 6 months in Group II, 4 patients died, 2 from sudden death. Ninety seven shocks were delivered in 19 patients (56%), 5.1 shocks per patient. In the 17 patients with an antitachycardia function, 14 (82%) developed 947 episodes of VT treated successfully by antitachycardia pacing in 917 cases. This retrospective study confirms the efficacy of implantable defibrillators in the treatment of malignant ventricular arrhythmias. The efficacy of endocardial and epicardial leads seems to be the same but there seems to be a lower immediate mortality and morbidity with the endocardial system.

Adult↗