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PubMedDate not supplied

Evolution of the optimum bidirectional (+/- biphasic) wave for defibrillation.

Introduction of the asymmetric bidirectional (+/- biphasic) current waveform has made it possible to achieve ventricular defibrillation with less energy and current than are needed with a unidirectional (monophasic) waveform. The symmetrical bidirectional (sinusoidal) waveform was used for the first human-heart defibrillation. Subsequent studies employed the underdamped and overdamped sine waves, then the trapezoidal (monophasic) wave. Studies were then undertaken to investigate the benefit of adding a second identical and inverted wave; little success rewarded these efforts until it was discovered that the second inverted wave needed to be much less in amplitude to lower the threshold for defibrillation. However, there is no physiologic theory that explains the mechanism of action of the bidirectional wave, nor does any theory predict the optimum amplitude and time dimensions for the second inverted wave. The authors analyze the research that shows that the threshold defibrillation energy is lowest when the charge in the second, inverted phase is slightly more than a third of that in the first phase. An ion-flux, spatial-K+ summation hypothesis is presented that shows the effect on myocardial cells of adding the second inverted current pulse.

Animals↗
PubMed2001

Comparison of internal cardioverter defibrillator implantation techniques: subpectoral position.

BACKGROUND: To compare surgical techniques for subpectoral implantation of internal cardioverter defibrillator (ICD). METHODS: Sequential comparison with review of the literature. SETTING: University Hospital. PARTICIPANTS: the patients requiring ICD. INTERVENTIONS: ICD insertions and device testing. MEASUREMENTS: defibrillation and pacing thresholds, defibrillator lead impedance, operative time, and proximity of generator site to midline, clinical outcomes. RESULTS: Comparable efficacy in defibrillation, surgical time and medial placement. No wound infections, seromas or lead dislodgments. Preservation of pectoral muscle integrity. CONCLUSIONS: Lateral single incision subpectoral ICD generator placement can be applied consistently with good RESULTS.

Arrhythmias, Cardiac↗
PubMed1999

Transvenous pectoral implantation of single lead implantable cardioverter defibrillator.

OBJECTIVE: To report our initial experience of transvenous pectoral implantation of single lead implantable cardioverter defibrillator (ICD) in fifteen patients. METHODS: Fifteen patients (male 13, female 2, mean age of 51.7 years), including dilated cardiomyopathy in 4, hypertrophic cardiomyopathy in 2, coronary artery disease in 5 and syncope of unknown etiology in 2, underwent ICD implantation. Indications for ICD implantation were ventricular fibrillation (8 patients) and refractory ventricular tachycardia (7 patients). All patients had syncope out of hospital. The ICD system were Medtronic Jewel active can in 5 patients (Model 7219C in 2, 7220C in 3) and CPI Ventak PRxIII in 9 patients. For active can, shocks were delivered through distal coil to ICD shell and for PRxIII through the endotak lead of proximal to distal coil. Successful implantation criteria was 2 consecutive defibrillation at less than 24 J. RESULTS: All 15 patients had successful implantation using single lead ICD system in catheter laboratory. The mean defibrillation threshold was 12.8 J (5-15 J) and R wave was 9.9 mV (3.7-14.6 mV). All devices were of pectoral implantation. No operative and perioperative complications occurred. In 7.6 months (1-18 months) of follow-up, 3 patients had VT terminated by antitachycardia pacing (ATP) and 1 patient VF terminated by shock. CONCLUSION: Transvenous pectoral implantation of single lead ICD is easy to perform and has high defibrillation efficacy and should be a preferred approach.

Defibrillators, Implantable↗
PubMed2001

Implantation of dual chamber pacemaker defibrillator and placement of endocardial leads via the axillary vein.

OBJECTIVES: To assess the preliminary clinical results of implantation of dual chamber pacemaker defibrillator and to evaluate the safety and effectiveness of placement of endocardial leads in the axillary vein. METHODS: Seven patients with ventricular tachycardia and/or ventricular fibrillation (VT/VF), associated with bradyanhythmia received implantation of a dual chamber pacemaker defibrillator, including 5 patients with coronary artery disease and 2 patients with dilated cardiomyopathy. The atrial and ventricular leads were introduced via the axillary vein under venographic guidance. RESULTS: Dual chamber pacemaker defibrillators were successfully implanted in the left chest subcutaneous pocket in 5 patients and the left pectoral muscular pocket in 2 patients. All the VT/VF occurring either inducibly during the procedure or spontaneuously during follow-up were detected promptly and treated successfully. Both the pacing and sensing functions were satisfactory. The endocardial leads required were successfully introduced via the axillary vein without major complications. CONCLUSIONS: Dual chamber pacemaker defibrillators can provide reliable therapy for VT/VF and the dual chamber pacing function. Placement of endocardial leads via the axillary vein under venographic guidance is safe and effective.

Aged↗
PubMed2001

Implantable cardioverter-defibrillator: beyond efficacy.

OBJECTIVES: The introduction of the implantable cardioverter-defibrillator was a very important advance in the treatment of malignant ventricular arrhythmias. However, its use is associated with some possible adverse events, which should be taken into consideration when a patient is proposed for implantation. These complications may occur early after implantation and be associated with the procedure itself, or they may be late complications, usually associated with the device or the arrhythmia. It was our objective to assess the incidence of these complications in our population of patients. POPULATION AND METHODS: We describe the complications found in 98 patients (55.9 +/- 13.9 years, 89% male) with an implantable cardioverter-defibrillator and compare our results with the incidence of complications described by other authors. RESULTS: We found complications associated with the presence of the implantable cardioverter-defibrillator in 32% of patients. The most frequent complication was inappropriate shocks in 13%. The presence of infection was detected in 4%, lead insulation faults in 5%, need for lead extraction in 2%, repositioning in 1% and re-establishment of the connection with the generator in 2%. In 5% of patients, there was inefficacy of the device, 3% due to non-detected ventricular tachycardias (slow tachycardias) and 2% due to electrical storms. There was syncope in 2% of patients. The total mortality in a 2.9 +/- 1.9 year follow-up was 13% (sudden death in 3%). CONCLUSIONS: Major complications associated with implantable cardioverter-defibrillators were in our experience relatively rare, our results agreeing with those of other centers.

Defibrillators, Implantable↗
PubMed2005

Prevention of sudden cardiac death: the role of the implantable cardioverter-defibrillator.

Sudden cardiac death, usually due to fatal ventricular tachyarrhythmias, results in the loss of 300,000-400,000 lives each year in the United States. Implantable cardioverter-defibrillator therapy has revolutionized both the secondary and, increasingly, the primary prevention of sudden cardiac death. In the last decade, subcutaneous pectoral implantation with transvenous lead placement has lessened perioperative risk considerably, raising the benefit/risk ratio for many candidates. As a consequence, the list of approved indications for implantable cardioverter-defibrillator therapy has expanded rapidly in recent years. Current devices offer tiered therapy utilizing bradycardia pacing, anti-tachycardia pacing, low-energy cardioversion, and high-energy defibrillation. Hybrid therapy, combining device, drugs and radiofrequency catheter ablation as required, has become the standard of care for reducing both appropriate and inappropriate shocks. As implantation rates continue to rise, so will the number of patients presenting with electrical storm. The dilemma of how our society will cope with the enormous projected costs of implantable cardioverter-defibrillator therapy has yet to be resolved.

Death, Sudden, Cardiac↗
PubMed2005

Keeping current with biphasic defibrillation waveforms.

In recent years, defibrillators that use a biphasic waveform instead of the traditional monophasic waveform have become increasingly common. In fact, since we last published on this topic in 2001, most defibrillator suppliers have begun concentrating solely on developing and marketing biphasic defibrillators while phasing out their monophasic models. Healthcare facilities are wondering if they should do the same. ECRI believes that the time has come for healthcare facilities to begin making the switch to biphasic models. That's not to say, however, that immediate replacement is required. Continuing to use a monophasic device that is in proper working condition is certainly acceptable, and replacing all models at once would be a large--and we believe unnecessary--financial burden. Rather, ECRI recommends that healthcare facilities implement a plan to phase out their monophasic defibrillators over the next few years. We discuss why, and offer recommendations to facilitate a safe and smooth transition, on the pages that follow.

Defibrillators↗
PubMed1994

[Atrial defibrillator: dream or reality?].

The experience acquired with the use of automatic ventricular cardiovertor-defibrillator led to the idea of developing an atrial device capable of automatically detecting and reducing atrial fibrillation. The large group of patients with paroxysmal atrial fibrillation not responding to pharmacological therapy makes this a particularly relevant question. The first problem is to define the need of this type of device. There is only one group of patients with resistant and/or poorly tolerated paroxysmal atrial fibrillation in whom non-pharmacological therapy is considered, for example ablation of the AV node with implantation of a pacemaker or surgery. The second problem concerns the technical feasibility of an atrial defibrillator with the difficulty related to the detection of the arrhythmia and atrial defibrillation. The recognition of atrial fibrillation may be envisaged from endocavitary signals with satisfactory specificity and sensitivity. The problems related to atrial defibrillation with low energy shocks have not yet been solved clinically, although experimental studies have given promising results. The possible dangers are dominated by a pro-arrhythmic effect and the risk of ventricular fibrillation, but they could be avoided by synchronizing the atrial shock with ventricular activation based on results also obtained in the animal. Before the dream becomes reality, trials are necessary to develop a safe and effective automatic device. Intermediary stages of evaluation of such a device could include a device activated by the physician.

Animals↗
PubMed1995

Perceived quality of life before and after implantation of an internal cardioverter defibrillator.

BACKGROUND: Although use of the internal cardioverter defibrillator in selected high-risk patient groups has significantly improved survival, questions have arisen regarding its impact on psychological adjustment and quality of life. OBJECTIVES: To determine whether there was a difference in perceived quality of life of internal cardioverter defibrillator recipients before implantation, reported retrospectively, and after implantation. METHODS: Survey packets containing a demographic data form, a modified version of the Ferrans and Powers Quality of Life Index: Cardiac Version, and a consent form were mailed to internal cardioverter defibrillator recipients accrued from two hospitals; 70 patients comprised the convenience sample. RESULTS: No significant difference in perceived overall quality of life was revealed by before and after implantation scores of t tests or analyses of variance. Young, unemployed patients with multiple health problems were most at risk for quality of life deficits. Overall, recipients in this study appeared to adapt effectively to the stresses associated with the device. CONCLUSIONS: Our results suggest that the internal cardioverter defibrillator did not prolong life at a sacrifice to quality of life. These findings can help identify patients at increased risk for quality of life deficits.

Adaptation, Psychological↗
PubMed1994

Transvenous endocardial cardioverter defibrillator systems. Is the future here?

The development of nonthoracotomy lead systems for the implantable cardioverter defibrillator has ushered in a new era in the field of device therapy for malignant ventricular tachyarrhythmias. Surgical mortality and morbidity are thus significantly reduced, the hospital stay is shortened, and the cost of such therapy is lowered. Although several problems (mainly lead related) were initially encountered with earlier-generation systems, improvements have made this less invasive method of defibrillator therapy an attractive alternative to conventional epicardial implants. It is rapidly becoming a first-choice approach in the treatment of malignant ventricular tachyarrhythmias. Transvenous leads were used in combination with a subcutaneous patch for effective defibrillation in the majority of patients, according to most published reports, while the number of "transvenous only" systems being implanted has been steadily increasing. A description of currently available nonthoracotomy lead defibrillator systems and a discussion of the clinical results, advantages, and limitations of their use are presented herein.

Defibrillators, Implantable↗
PubMed1993

[The automatic implantable cardioverter-defibrillator for prevention of sudden heart death in children and adolescents].

Little experience exists with the automatic implantable cardioverter-defibrillator in the pediatric population. Since 1990, an automatic implantable cardioverter defibrillator was implanted in four young patients (mean age 15.8 years, mean body weight 53.3 kg) with life-threatening ventricular tachyarrhythmias at our institution. In three patients, a cardiac anomaly was evident (dilated cardiomyopathy, status post Rastelli operation for complex transposition of the great arteries, status post atrial switch for transposition of the great arteries), the last patient had a normal cardiac anatomy. Indications for implantation were resuscitation from documented hypotensive ventricular tachycardia in one patient and recurrent syncope of suspected cardiac origin in the remaining three patients. At preimplantation electrophysiological study, all four patients had inducible ventricular tachycardia and/or ventricular fibrillation. At implantation of the cardioverter defibrillator in the operating theatre, the ventricular tachyarrhythmias were again induced and terminated reliably by the device. After a mean follow-up of 13 months, three of the four patients had appropriate discharges without syncope or resuscitation. The automatic implantable cardioverter-defibrillator appears to be a feasible and effective therapy also in pediatric patients for prevention of sudden cardiac death due to ventricular tachyarrhythmias.

Adolescent↗
PubMed1993

Nonthoracotomy lead system for implantable defibrillator.

Over a 2-year period, 110 patients underwent attempted implantation of an automatic cardioverter-defibrillator using the nonthoracotomy lead system. Indications included sustained monomorphic ventricular (n = 62), nonsustained with poor ventricular function (n = 7), ventricular fibrillation (n = 21), ventricular tachycardia/fibrillation (n = 18), and familial long QT syndrome (n = 2). There were 90 male and 20 female patients. Mean age was 57 +/- 15 years. Sixty percent had previous coronary bypass or valve operations, or both. Mean left ventricular ejection fraction was 30% +/- 14%, cardiac index was 2.4 +/- 0.9 L/m2, and systolic pulmonary artery pressure was 41 +/- 14 mm Hg. Under general anesthesia, the nonthoracotomy lead was introduced through the left subclavian vein. The subcutaneous patch and generator were placed posteriorly on the serratus muscle and left upper quadrant, respectively. The length of the procedure was 116 +/- 44 minutes and the mean number of defibrillation shocks for a successful implant was 8 +/- 4. Eighty-five patients (77%) had successful implantations. Failures were due to high defibrillation threshold (n = 23) and inability to place a right ventricular lead (n = 2). Predictors of failure included preoperative antiarrhythmic drugs and cardiac index of 1.8 +/- 4 L/m2 or less (p = 0.004). Three patients (2.7%) died after the operation of heart failure (n = 2) and chronic heart transplant rejection (n = 1). Complications included lead migration or dislodgment (n = 8), infection (n = 1), and hematoma (n = 3). In summary, the nonthoracotomy lead system may provide an alternative in patients undergoing cardioverter-defibrillator implantation.

Aged↗
PubMed1996

[Implantable cardioverter-defibrillators in patients resuscitated from sudden death and in patients with sustained refractory ventricular tachycardia].

OBJECTIVE: The aim of this study was to evaluate the results of our experience with implantable cardioverter-defibrillator therapy. PATIENT SELECTION: We treated with implantable cardioverter-defibrillator (ICD) 18 patients, 15 male and 3 female, mean age 51 years, ranging from 12 to 76 years, with life threatening ventricular arrhythmias. Eleven patients were resuscitated from cardiac arrest and seven had refractory ventricular tachycardia. The underlying condition was coronary artery disease in 12 patients, dilated cardiomyopathy in two, congenital long QT syndrome in one, mitral regurgitation in one and idiopathic in two patients. METHODS: All patients underwent cardiac catheterization and electrophysiological study before ICD implantation. In the first patient epicardial leads were used, but a transvenous approach was used in the remaining 17 patients. The device was implanted in an abdominal position in all patients. Defibrillation and pacing threshold tests were performed during the implantation procedure and whenever necessary. After implantation, patients were followed up in an outpatient basis, with evaluation of therapy efficacy and reprogramming of the device if required. The mean follow-up time was 16 months, ranging from 1 to 40 months. RESULTS: The implantation was successful and without complications in all patients. Defibrillation threshold was considered within normal range, with an electrode impedance ranging from 40 to 65 Ohms. During the follow-up period no deaths occurred, 8 patients (44%) had episodes of VT or VF that were successfully treated, with shock in six patients, with antitachycardia pacing in one and with both modalities in another patient. Inappropriate shocks were observed in three patients (16%). The device was reprogrammed in five patients. CONCLUSIONS: Our experience with implantable ICD in patients who survived cardiac arrest or with refractory VT has shown a low surgical risk with no mortality. The incidence of ICD discharges was high, with a satisfactory efficacy rate and the number of inappropriate shocks was acceptable. The careful patient selection made possible a good cost/benefit relation.

Adolescent↗
PubMed1996

[Clinical experiences with pectoral defibrillator implantation].

UNLABELLED: The pectoral approach to implantation of cardioverter/defibrillators has the aim to further simplify the implantation of transvenous defibrillation systems. The PCD 7219 D/C is a device of the fourth generation which makes the pectoral implantation feasible due to a weight of 132 g, a size of 89 x 64 x 18 mm, a volume of 83 cm3 and a surface of 108 cm2. The use of the "active-can"-system (PCD 7219 C) requires the implantation of only one right ventricular lead. The PCD 7219 D/C was implanted in 75 patients with ventricular tachyarrhythmias, the follow-up period was 12 +/- 4 (1-24) months. Subpectoral implantation was feasible in 59 patients (79%), in 55 with a left pectoral, in 4 with a right pectoral approach due to previous left-sided operation or thrombosis of the left subclavian vein. Male sex (p < 0.005), body weight (p < 0.005) and body surface (p < 0.05) were predictors of pectoral implantation. In the 45 patients (60%) with a unipolar defibrillation system ("active can") the defibrillation threshold was significantly lower compared to those with a dual lead system (9.9 +/- 6.5, 2.5-24 Joule vs. 19 +/- 4.5, 6-24 Joule p < 0.0001). In one patient with pectoral and in one patient with abdominal implantation a dislodgement of the right ventricular lead was diagnosed and an operative revision was indicated. CONCLUSION: The down-sized implantable cardioverter/defibrillator PCD 7219 D/C makes the pectoral implantation feasible in the majority of patients. The use of the "active-can"-system requires the implantation of only one right ventricular lead with significantly lower defibrillation thresholds.

Adolescent↗
PubMed1996

Thoracoscopic versus laparoscopic placement of defibrillator patches.

Nonthoracotomy lead systems have been developed to reduce the morbidity associated with cardioverter/defibrillator implantation. Total endocardial lead systems are effective in only about 50% of patients with standard monophasic waveforms; so patch placement is frequently required. We developed a new patch design and surgical techniques for thoracoscopic patch placement over the left ventricle and laparoscopic placement under the diaphragm. To compare the efficacy of these approaches, patches were placed in both locations in pigs acutely with a right ventricular coil serving as the anode for defibrillation. Defibrillation testing was performed, alternating between patches. The energies associated with 50% (DF50) and 90% (DF90) probability of successful defibrillation with biphasic shocks with determined. Defibrillator thresholds were significantly lower with intrathoracic than with subdiaphragmatic patches. Animal autopsy following more than 30 shocks from each patch revealed no gross damage to the lung or diaphragm in any animal.

Animals↗
PubMed1996

[Shock-induced, but not terminated ventricular tachycardia in a patient with implantable defibrillator].

A 62-year-old male patient with coronary artery disease and drug refractory sustained ventricular tachycardia received an implantable cardioverter defibrillator (PRX III, model 1720, CPI) with a transvenous lead system (Endotak, model 0115, CPI) in combination with a subcutaneous array electrode (SQ array, model 049, CPI). The intraoperative defibrillation threshold was 15 J and was confirmed 1 week later at the hospital discharge test. Three months after discharge from hospital the patient reported 5 shocks during moderate physical exertion followed by a tachycardia associated with dizziness which terminated spontaneously. The print out of the stored electrogram showed a supraventricular tachycardia (probably sinus tachycardia) with a heart rate of 154/min which activated the device. Antitachycardia pacing did not terminate the supraventricular tachycardia, and hence shock therapy was delivered. The first shock (34 J) converted the supraventricular tachycardia to a ventricular tachycardia with a heart rate of 178/min, which was not terminated by four consecutive 34 J DC shocks. There was no hint of a device or lead failure. Determination of the defibrillation threshold reconfirmed the 15 J value for termination of ventricular fibrillation. However, neither a 1 J shock nor a 34 J shock terminated a monomorphic sustained ventricular tachycardia (cycle length 340 ms) induced by noninvasive programmed electrical stimulation. The ventricular tachycardia was, however, reproducibly terminate by antitachycardia pacing. It is concluded that an inappropriate high-energy DC shock might induce a sustained ventricular tachycardia. However, a sufficient defibrillation threshold for the termination of ventricular fibrillation does not necessarily mean that a sustained ventricular tachycardia will be terminated by a high-energy DC shock.

Coronary Disease↗
PubMed1998

Advances in the treatment of arrhythmias: implantable cardioverter-defibrillators.

Implantable cardioverter-defibrillators are commonly used in patients who have life-threatening ventricular arrhythmias. With these implanted electronic devices, bradyarrhythmias and tachyarrhythmias can be recognized promptly and treated with electrical pacing, cardioversion or defibrillation. Implantable cardioverter-defibrillators have been shown to substantially reduce the incidence of sudden cardiac death in patients with known life-threatening ventricular arrhythmias. Their role in the primary prevention of sudden cardiac death in patients at high risk for ventricular arrhythmias is being evaluated. Technologic advances have allowed transvenous implantation of cardiac leads, obviating the need for open heart surgery and thereby lowering the risk of perioperative morbidity and mortality. Most electrical therapies are triggered appropriately to treat ventricular tachycardia/fibrillation. Inappropriate discharges may occur secondary to supraventricular causes of tachycardia, environmental interference from electromagnetic devices or malfunction of the cardioverter-defibrillator. All episodes of discharge merit investigation. With recurrent or frequent discharges, prompt evaluation and hospitalization are often necessary.

Arrhythmias, Cardiac↗
PubMed1998

The effects of endocardial defibrillation on left ventricular function: a transoesophageal echocardiographic study.

This study evaluates the immediate effects of the endocardial electrical shocks delivered by a transvenous defibrillation system on left ventricular (LV) function in a pig model. A triple-lead system consisting of two endocardial electrodes, in the right ventricular apex and the junction of superior cava-right atrium, and a custom-made defibrillation can implanted subcutaneously in the thorax was set up in 10 close-chest pigs. Transesophageal echocardiography with two dimensional image, m-Mode, and pulse Doppler was performed at baseline and after several episodes of fibrillation/defibrillation (F/DF). Each animal underwent an average of 8 (range 6 to 11) episodes of ventricle F/DF for a total of 210 (range 165 to 290) joules of biphasic-waveform defibrillation shocks. Heart rate, blood pressure, LV end-systolic area, end-diastolic area and fractional area contraction, isovolumic relaxation time, and both ratios of velocities and time-velocity integrals in transmitral Doppler flow E and A waves were unchanged after the shocks. This animal study suggests that multiple countershocks up to 210 joules delivered by a transvenous defibrillation system do not cause LV global systolic and/or diastolic dysfunction.

Animals↗