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PubMed2001

Implantable cardiac defibrillators.

The implantable cardioverter defibrillator (ICD) represents an important development in the effort to reduce the incidence of sudden cardiac death (almost 400,000 yearly in the United States). Early generation ICDs, which required epicardial lead systems and abdominal placement of the pulse generator, have been replaced by transvenous leads and pectoral implants. Other important refinements, which include biphasic waveforms, extensive memory capability, antitachycardia pacing, and enhanced sensing algorithms, have greatly improved patient tolerance. Ongoing trials and those in the planning stages will continue to expand the indications for ICDs and will focus on cost-effectiveness.

Arrhythmias, Cardiac↗
PubMed1999

What risk should justify implantable cardioverter defibrillator therapy?

Implantable cardioverter defibrillators (ICDs) were developed to prevent sudden cardiac death in patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). Their safety and efficacy have been proved in multiple retrospective and prospective studies. Many of the published trials were directed at secondary prevention for patients who had already had a sudden cardiac death or a sustained VT. For primary prevention, the information available is limited, as only 2 trials have yet been published. Ongoing trials will probably allow us to broaden the indications for prophylactic ICD implantation. Justification of the risk will have to be evaluated against complexity of the implant, the latter including not only cost but quality of life and morbidity associated with an ICD. However, our efforts still have to be directed to improve risk stratification and to decrease the complexity of the procedure.

Death, Sudden, Cardiac↗
PubMed1995

Comparison of biphasic and monophasic pulses: does the advantage of biphasic shocks depend on the waveshape?

With present implantable defibrillators, the ability to vary the defibrillation technique has been shown to increase the number of patients suitable for transvenous system. As newer waveforms become available, the need for a flexible device may change. In addition, although it has been shown that the option of biphasic waveform may increase the defibrillation efficacy, this may depend upon the shape of the biphasic waveform used. Thirty patients undergoing transvenous defibrillator implant were included in the study. In 20 patients (group I), defibrillation efficacy of simultaneous monophasic, sequential monophasic, and biphasic waveform with 50% tilt was determined randomly. Similarly, in ten patients (group II) testing of simultaneous monophasic shocks and biphasic waveforms with 65% and 80% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 30 patients. In group I, 50% tilt biphasic waveform consistently provided similar or better defibrillation efficacy compared to monophasic waveforms (biphasic 7.5 +/- 5.1 joules vs simultaneous 17 +/- 7.8 joules, P < 0.01; and vs sequential 17 +/- 8.4 joules, P < 0.01). In group II, 65% tilt biphasic pulse required less energy for defibrillation as compared with simultaneous monophasic shocks (9.6 +/- 4.5 joules vs 15.6 +/- 5.1 joules, P = 0.04). No significant difference was observed in terms of defibrillation threshold between 80% tilt biphasic shocks and simultaneous monophasic pulses (11.8 +/- 6 joules vs 15.6 +/- 5.1 joules, P = NS). Biphasic shocks with smaller tilt delivered using a triple lead system more uniformly improved defibrillation threshold over standard monophasic waveforms.

Defibrillators, Implantable↗
PubMed1996

Nonthoracotomy implantation of cardioverter defibrillators: preliminary experience with a defibrillation lead placed at the right ventricular outflow tract.

UNLABELLED: Although morbidity and mortality associated with defibrillator implantation using a nonthoracotomy approach have decreased as compared with a thoracotomy approach, defibrillation thresholds have been higher and fewer patients satisfied implant criteria. It may be possible to improve on the success of nonthoracotomy defibrillator implantation by the placement of a right ventricular (RV) outflow defibrillation lead. Implantable cardioverter defibrillator implantation data of 30 consecutive patients with clinical VT or VF were reviewed. Three defibrillation leads were routinely used. When either pacing threshold at the RV apex was inadequate (n = 2) or 18-J shocks were not successful in terminating VF in 3 of 4 trials (n = 8), the RV apex lead was positioned to the RV outflow tract attaching to the septum. Defibrillation testing was first performed with the RV apex lead in combination with CS, SVC, and/or subcutaneous leads. Twenty patients satisfied implant criteria with a defibrillation threshold of 13.5 +/- 3.6 J. In 7 of the 10 patients, whose RV lead was repositioned to the RV outflow tract, this lead in combination with SVC, CS, or subcutaneous leads produced successful defibrillation at < or = 18 J or in 3 of 4 trials. This approach improved the overall success of nonthoracotomy implantation of defibrillators from 69% to 90%. After a follow-up of 27 +/- 6 months, there was no dislodgment of the RV outflow tract defibrillation leads. CONCLUSIONS: This article reports the preliminary observation that placement of defibrillation leads to the RV outflow tract in humans was possible and without dislodgment. RV outflow tract offers an alternative for placement of defibrillation leads, which may improve on the success of nonthoracotomy defibrillator implantation.

Adult↗
PubMed1998

Effect of ventricular shock strength on cardiac hemodynamics.

INTRODUCTION: The effect of implantable defibrillator shocks on cardiac hemodynamics is poorly understood. The purpose of this study was to test the hypothesis that ventricular defibrillator shocks adversely effect cardiac hemodynamics. METHODS AND RESULTS: The cardiac index was determined by calculating the mitral valve inflow with transesophogeal Doppler during nonthoracotomy defibrillator implantation in 17 patients. The cardiac index was determined before, and immediately, 1 minute, 2 minutes, and 4 minutes after shocks were delivered during defibrillation energy requirement testing with 27- to 34-, 15-, 10-, 5-, 3-, or 1-J shocks. The cardiac index was also measured at the same time points after 27- to 34-, and 1-J shocks delivered during the baseline rhythm. The cardiac index decreased from 2.30 +/- 0.40 L/min per m2 before a 27- to 34-J shock during defibrillation energy requirement testing to 2.14 +/- 0.45 L/min per m2 immediately afterwards (P = 0.001). This effect persisted for > 4 minutes. An adverse hemodynamic effect of similar magnitude occurred after 15 J (P = 0.003) and 10-J shocks (P = 0.01), but dissipated after 4 minutes and within 2 minutes, respectively. There was a significant correlation between shock strength and the percent change in cardiac index (r = 0.3, P = 0.03). The cardiac index decreased 14% after a 27- to 34-J shock during the baseline rhythm (P < 0.0001). This effect persisted for < 4 minutes. A 1-J shock during the baseline rhythm did not effect the cardiac index. CONCLUSION: Defibrillator shocks > 9 J delivered during the baseline rhythm or during defibrillation energy requirement testing result in a 10% to 15% reduction in cardiac index, whereas smaller energy shocks do not affect cardiac hemodynamics. The duration and extent of the adverse effect are proportional to the shock strength. Shock strength, and not ventricular fibrillation, appears to be most responsible for this effect. Therefore, the detrimental hemodynamic effects of high-energy shocks may be avoided when low-energy defibrillation is used.

Adult↗
PubMed2002

Halothane, isoflurane, and fentanyl increase the minimally effective defibrillation threshold of an implantable cardioverter defibrillator: first report in humans.

UNLABELLED: Placing an implantable cardioverter defibrillator (ICD) involves the induction of ventricular fibrillation, whereupon the minimally effective defibrillation energy threshold (DFT) is determined. We evaluated the effects of 0.7% halothane, 1% isoflurane, or 1.5 micro g/kg of IV fentanyl during N(2)O/oxygen-based general anesthesia (GA) or those of subcutaneous 1.5% lidocaine plus IV 0.35 mg/kg of propofol on the DFT during ICD implantation in humans (n = 20 per group). Thirty minutes after the first set of DFT measurements under such conditions, the inhaled anesthetics were withdrawn, and all three GA groups received fentanyl 1 microg/kg IV (second set). A third set was taken 30 min later, before the GA patients awakened and when only N(2)O/oxygen was delivered for GA. The lidocaine plus propofol patients were given the same IV propofol bolus 1 min before each fibrillation/defibrillation trial and at the same time points as the three GA groups. The first DFTs were 16.1 +/- 2.2 J (halothane), 17.7 +/- 2.7 J (isoflurane), 16.4 +/- 2.9 J (fentanyl), and 12.9 +/- 3.8 J (lidocaine plus propofol) (P = 0.01). The second set of DFTs were significantly lower than the first sets for the halothane (P = 0.01) and isoflurane (P = 0.02), but not the fentanyl or lidocaine plus propofol, regimens. The third DFTs were significantly (P < 0.01) lower than the first ones for the three GA groups, but not for the lidocaine plus propofol patients. Thus, halothane, isoflurane, and fentanyl increased DFT values during ICD implantation in humans, whereas lidocaine plus intermittent small-dose IV propofol minimized these thresholds. IMPLICATIONS: Halothane, isoflurane, and IV fentanyl added to N(2)O/oxygen-based general anesthesia similarly increase minimal defibrillation threshold energy requirements (DFT) during cardioverter defibrillator implantation in humans. Subcutaneous lidocaine plus intermittent small-dose IV propofol minimizes DFT compared with these general anesthetics while providing equal patient satisfaction.

Aged↗
PubMed1998

[Implanted automatic defibrillator after ventricular fibrillation treated with semi-automatic defibrillation].

We report two cases of out-of-hospital ventricular fibrillation treated without delay, with basic life support practiced by the witness, followed by a successful defibrillation by paramedics with a semi-automatic defibrillator. In the subsequent month, a cardioverter-defibrillator was implanted. In one patient, a ventricular tachycardia occurring 10 months later and a ventricular fibrillation 9 months later in the other respectively, were successfully reversed by the implanted defibrillator. These two cases illustrate the value of the "survival chain" concept (undelayed alert, basic life support by witness, early defibrillation by paramedics with a semi-automatic defibrillator, advanced life support by a physician) as well as the benefit of the implanted cardioverter-defibrillator.

Adult↗
PubMed1990

Infections in implantable cardioverter defibrillator patients.

Implantable cardioverter defibrillators (ICDs) have been documented as an effective modality in reducing arrhythmic mortality. A serious complication associated with implantation of the device is infection. Few studies have addressed this issue. Two hundred seven patients with refractory ventricular arrhythmias underwent 207 ICD implantations, and 56 subcutaneous generator changes at our institution. Eight patients developed wound infections, four following ICD implantation (4 out of 207 or 1.9%), and four following a generator change (4 out of 56 or 7.1%). Wound cultures most commonly revealed Staphylococcus aureus and Staphylococcus epidermidis. Infections treated with antibiotics alone, or with only generator removal, frequently recurred (four out of five attempts). There were no recurrences following total patch/lead and generator system removal. In five patients, the same generator unit was successfully reimplanted following ethylene oxide sterilization without infection recurrence. We conclude that treatment of device-associated infection generally requires total generator and patch/lead system removal, and that generator units can be successfully reimplanted yielding substantial cost savings.

Adult↗
PubMed1991

Sudden death mortality in implantable cardioverter defibrillator patients.

Implantable cardioverter defibrillator (ICD) prevention of sudden cardiac death (SCD) is not absolute and our experience was reviewed to determine the frequency and nature of SCD in this population. The incidence and cause of mortality in 56 consecutive patients, who underwent ICD implantation beginning May 1982 with follow-up through May 19, 1990 were analyzed. Twenty-one patients died, 33% of the mortality was due to SCD, and 52% of deaths may be considered arrhythmic. The cumulative 1, 3, and 5 year SCD survivals were 93%, 89%, and 75%. All seven patients dying of SCD presented initially with SCD, all received previous shocks prior to SCD, and two of the seven patients had devices that were probably inactive at the time of death. We conclude that ICDs reduce but by no means eliminate arrhythmic death, particularly in those at highest risk for SCD. Arrhythmic death remained the most common cause of death in this population.

Arrhythmias, Cardiac↗
PubMed1988

Relation of the intraoperative defibrillation threshold to successful postoperative defibrillation with an automatic implantable cardioverter defibrillator.

To determine the relation between the intraoperative defibrillation threshold and successful postoperative termination of induced ventricular fibrillation (VF) with the automatic implantable cardioverter defibrillator (AICD), 33 patients who underwent AICD implantation were studied. The defibrillation threshold, determined after at least 10 seconds of VF, was 5 J in 2, 10 J in 6, 15 J in 10, 20 J in 10 and 25 J in 5 patients. The AICD energy rating on the first discharge was 28 +/- 1.8 J. Defibrillation of induced VF was demonstrated postoperatively in 29 of 33 (88%) patients. The AICD terminated VF postoperatively in all 18 patients with a defibrillation threshold less than or equal to 15 J. Only 11 of the 15 (73%) patients with a defibrillation threshold greater than or equal to 20 J (p less than 0.04) had VF terminated postoperatively. In all 4 patients in whom the AICD failed to terminate induced VF, the energy difference between the AICD rating and the defibrillation threshold was less than or equal to 10 J. Among the 14 patients with a difference of less than or equal to 10 J between the AICD energy rating and the defibrillation threshold, there were no significant differences between the 4 patients with and the 10 without successful VF termination with respect to the duration of VF induced postoperatively or the AICD lead system. In summary, failure to terminate VF with the AICD is not uncommon (27%) when the defibrillation threshold approaches the energy delivering capacity of the AICD.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

Implantable cardioverter defibrillator clinic casualties: inadvertent reprogramming during routine implantable cardioverter defibrillator follow-up.

On one occasion during a busy ICD follow-up clinic, the preceding patient's parameters for rate, PDF, and delay were inadvertently programmed into the subsequent patient's generator using the CPI Programmer Model 2035. This occurred after capacitor reformation, without pressing the "Program" button. The source of this reprogramming error was failure to clear the programmer memory of the previous patient's data, usually achieved by turning the programmer off between patients (or selecting "New Patient" from the menu). At our next ICD follow-up clinic, we purposely did not turn off the programmer between two sets of patients. On both occasions the above finding was repeated and confirmed. These observations indicate the potential for serious reprogramming errors that can occur simply by not clearing the programmer's memory between clinic patients.

Defibrillators, Implantable↗
PubMed1998

Hypertrophic cardiomyopathy: role of the implantable cardioverter-defibrillator.

OBJECTIVES: We report the occurrence of cardiac events during long-term follow-up in patients with hypertrophic cardiomyopathy (HCM) after cardioverter-defibrillator implantation. BACKGROUND: The identification of patients at high risk for sudden death and the prevention of recurrence of sudden death in HCM represents a difficult problem. METHODS: We retrospectively analyzed the occurrence of cardiac events during follow-up of 13 patients with HCM who received an implantable cardioverter-defibrillator (ICD) because of aborted sudden death (n = 10) or sustained ventricular tachycardia (n = 3) (group I). Findings were compared with those in 215 patients with an ICD and other structural heart disease or idiopathic ventricular fibrillation (group II). RESULTS: After a mean (+/-SD) follow-up period of 26+/-18 months, 2 of 13 patients in group I received appropriate shocks. The calculated cumulative incidence of shocks was 21% in group I and 66% in group II after 40 months (p < 0.05). We observed a low incidence of recurrence of ventricular tachycardia/fibrillation during follow-up in patients with HCM. No deaths occurred. CONCLUSIONS: Our data suggest that ventricular tachyarrhythmias may not always be the primary mechanism of syncope and sudden death in patients with HCM. The ICD seems to have a less important impact on prognosis in patients with HCM than in patients with other etiologies of aborted sudden death.

Adult↗
PubMed1993

Cerebral monitoring during implantation of automatic internal cardiac defibrillators.

Implantation of automatic internal cardiac defibrillators (AICD) for management of arrhythmias necessitates the induction of ventricular fibrillation (VF) to test the device adequately. The profound hypotension associated with induced arrhythmia and subsequent circulatory arrest may result in cerebral ischemia. To characterize cerebral ischemia, we used a five-lead Lifescan brain activity monitor to examine changes in cerebral activity in 10 patients having AICD placement. The duration of hypotension, as defined by a mean arterial pressure (MAP) < 50 mm Hg, was recorded, and the corresponding changes in brain activity were evaluated during 51 episodes of circulatory arrest. The number of episodes for each patient ranged from 2 to 14. The average duration of hypotension per episode was 26.2 seconds, with a range of 8 to 67 seconds. Brain activity changes characteristic of cerebral ischemia occurred in 46 of the 51 events (90%). Cerebral ischemia did not occur when the duration of hypotension was less than 16 seconds (5 episodes). The duration of cerebral ischemia ranged from 50 to 279 seconds (average 84.9 seconds) and did not correlate with the duration of hypotension or the order of the episodes in the testing sequence. These findings suggest that reevaluation of standard monitoring practice for AICD implantation may be warranted.

Brain Ischemia↗
PubMed2006

Quality of life in patients with implantable cardioverter defibrillators.

BACKGROUND: The implantable cardioverter defibrillator (ICD) is a life saving device for individuals with life threatening ventricular arrhythmias. There is no doubt that it is a cost effective therapy in various congenital and acquired arrhythmogenic disorders. Nevertheless, shock delivery may be painful and frightening which causes psychological distress and deterioration of perceived quality of life. METHODS: A systematic meta-analysis on studies reporting quality of life in patients implanted with ICDs was done using professional databases. Related articles and references of the relevant articles were also searched for suitable studies. RESULTS: Thirty studies with a total of 3412 patients on implantable defibrillators were identified. Five of them were large randomised studies with a total of 1680 patients, while 25 were non-randomised studies. Medical Outcome Study 36-item Short Form health survey (SF -94 36) was the most common instrument used for assessment of quality of life. Only one of the 5 major randomised trial reported worsening of quality of life after implantation of a defibrillator. In the subgroup of patients receiving shocks, three out of the five trials reported worsening of quality of life. SUMMARY: Most of the randomised studies showed either neutral or better quality of life in patients on implantable defibrillators. In the subset of patients receiving shocks, worsening of quality of life was found in most randomised studies. Therefore, activation of antitachycardia pacing should be performed in every ICD-patient in order to miminze painful shocks and consequent deterioration of quality of life.

Journal Article↗
PubMed1990

Automatic implantable cardioverter-defibrillator: is early implantation cost-effective?

The evaluation of survivors of sudden cardiac death with serial electrophysiologic studies involves a lengthy and expensive hospitalization, especially when an automatic implantable cardioverter-defibrillator is ultimately necessary. The cost efficacy of this conventional approach was therefore compared with direct implantation of a cardioverter-defibrillator after the first electrophysiologic study. Thirty-two survivors of sudden death who had inducible ventricular tachycardia during their initial electrophysiologic study underwent serial drug trials. At discharge 12 (37%) were taking an antiarrhythmic drug found to prevent induction of ventricular tachycardia and 20 underwent cardioverter-defibrillator implantation after serial drug trials proved ineffective. The average length of hospitalization for this group that had undergone serial drug testing was 20.2 +/- 9.3 days at an average cost of $48,900 +/- $31,600. Seven survivors of sudden death had no inducible ventricular tachycardia during their initial electrophysiologic study and underwent direct cardioverter-defibrillator implantation. Their average length of hospitalization was 12.6 +/- 6.2 days at an average cost of $40,400 +/- $8,300. It is concluded that automatic implantable cardioverter-defibrillator implantation as an early intervention is not more costly and indeed may be cost-effective compared with therapy guided by serial electrophysiologic testing. As antitachycardia devices become more versatile, long lived and easier to implant, earlier implantation is likely to compare even more favorably with drug therapy.

Anti-Arrhythmia Agents↗