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PubMedDate not supplied

Optimal spacing of right ventricular bipolar catheter electrodes for detecting cardiac pumping by an automatic implantable defibrillator.

Our defibrillation-detecting system uses both ECG and right ventricular impedance change (delta Z). We studied the effect of catheter electrode spacing on delta Z in 10 dogs with body weights of 10 to ,5 kg and heart weights of 67 to 220 g. Impedance to 20-kHz 100--muA square waves was measured between two 1-cm-long electrodes mounted on a No. 12F catheter and wedged into the right ventricular apex. Catheters with spacings of 5 to 25 mm between the electrodes were tested during sinus rhyhm and ventricular fibrillation. During sinus rhythm the mean beat-to-beat delta Z was 23 +/- 4 omega using the 5-mm spacing. Wider spacing gave smaller, and hence less desirable, delta Z. Some delta Z signals were recorded during ventricular fibrillation, and 5-mm spacing was more sensitive to these than wider spacing. This resulted in some prolongation of the time between onset of fibrillation and application of the defibrillation shock, but should decrease false positive diagnosis of fibrillation. No clear relationship was observed between delta Z and body weight or heart weight. We conclude that the 5-mm spacing is best for detection of pumping by the catheter-impedance method in hearts of this weight range.

Animals↗
PubMed1999

[Anesthetic management for implantation of implantable cardioverter-defibrillators].

Implantable cardioverter-defibrillators (ICDs) were implanted in 44 patients at the authors' institution. The anesthetic management was reviewed retrospectively. Ten of the 44 patients received the third generation ICD devices, while the rest received the fourth generation devices. For thirteen patients receiving the fourth generation devices, implantation was performed under local anesthesia with monitored care of anesthesiologists. Propofol was infused to achieve deep sedation during induced ventricular fibrillation and later cardioversion for testing the devices. Implantation was performed under general anesthesia with combination of fentanyl and volatile anesthetics for the remaining 31 patients. Patients who received ICDs under local anesthesia had significantly greater values of ejection fraction in preoperative examination than values in patients who received ICDs under general anesthesia. Operation time of the implantation under local anesthesia was significantly shorter than that under general anesthesia. Though infusion of propofol produced a moderate decrease of blood pressure in patients who received ICDs under local anesthesia, no patient showed major complication. Local anesthesia with sedation with propofol can be an option in anesthetic management for implantation of an ICD if an anesthesiologist cares the patient whose cardiac function is not compromised.

Adult↗
PubMed1999

Potential proarrhythmic effects of implantable cardioverter-defibrillators.

Implantable cardioverter-defibrillator (ICD) interventions have the potential to be proarrhythmogenic. New arrhythmias can occur in the setting of clinically appropriate therapies, as well as during a cardiac rhythm for which therapy is not intended. Cardioversion/defibrillation therapies, antitachycardia pacing, and antibradycardia pacing are potential triggers for the development of new arrhythmias. Newer ICDs allow better recognition and interpretation of the arrhythmias that are induced by delivered therapies. Two cases of ICD-induced proarrhythmias are described. Based on the course of these patients and review of previous reports, proarrhythmic effects of ICD interventions along with prevention and management strategies are discussed.

Adult↗
PubMed2001

Effect of clinical risk stratification on cost-effectiveness of the implantable cardioverter-defibrillator: the Canadian implantable defibrillator study.

BACKGROUND: Three randomized clinical trials showed that implantable cardioverter-defibrillators (ICDs) reduce the risk of death in survivors of ventricular tachyarrhythmias, but the cost per year of life gained is high. A substudy of the Canadian Implantable Defibrillator Study (CIDS) showed that 3 clinical factors, age >/=70 years, left ventricular ejection fraction </=35%, and New York Heart Association class III, predicted the risk of death and benefit from the ICD. We estimated the extent to which selecting patients for ICD therapy based on these risk factors makes ICD therapy more economically attractive. METHODS AND RESULTS: Patients in CIDS were grouped according to whether they had >/=2 of 3 risk factors. Incremental cost-effectiveness of ICD therapy was computed as the ratio of the difference in mean cost to the difference in life expectancy between the 2 groups. Over 6.3 years, the mean cost per patient in the ICD group was Canadian (C) $87 715 versus $38 600 in the amiodarone group (C$1 approximately US$0.67). Life expectancy for the ICD group was 4.58 years versus 4.35 years for amiodarone, for an incremental cost-effectiveness of ICD therapy of C$213 543 per life-year gained. The cost per life-year gained in patients with >/=2 factors was C$65 195, compared with C$916 659 with <2 risk factors. CONCLUSIONS: The cost-effectiveness of ICD therapy varies by patient risk factor status. The use of ICD therapy in patients who have >/=2 risk factors of age >/=70 years, left ventricular ejection fraction </=35%, and NYHA class III is C$65 195 to gain a year of life.

Aged↗
PubMed1993

Automatic implantable cardioverter defibrillator: cost effectiveness.

Unexpected out-of-hospital cardiac arrest is in most cases due to ventricular fibrillation or rapid ventricular tachycardia. The usual therapeutic strategy in survivors starts with drug treatment, in case of failure followed by nonpharmacological therapy, which may include catheter ablation, ablative surgery, and finally defibrillator implantation. In most cases, this strategy is long lasting and very expensive. Implantation of a defibrillator as a first choice therapy may be cost effective, especially if the probability of successful drug treatment is low. However, cost-effective aspects have been studied only retrospectively and in models. In 1989 we started a prospective cost-effectiveness analysis of implantation of the automatic implantable cardioverter defibrillator (AICD) as first choice therapy ("early" AICD implantation) in successfully resuscitated postinfarct patients. Evaluation is being done in a randomized way with one group having early AICD implantation and the other group following the usual conventional therapeutic strategy. We compare medical, economic, and quality-of-life aspects. As of June 1992, 46 patients have entered the study. Totally 60 patients will be included. Results are expected in 1993 and will be expressed as cost effectiveness ratios in both study arms.

Cost-Benefit Analysis↗
PubMed2000

Emergencies related to implantable cardioverter-defibrillators.

Implantable cardioverter-defibrillators (ICDs) have become the dominant therapeutic modality for patients with life-threatening ventricular arrhythmias. ICDs are implanted using techniques similar to standard pacemaker implantation. They not only provide high-energy shocks for ventricular fibrillation and rapid ventricular tachycardia, but also provide antitachycardia pacing for monomorphic ventricular tachycardia and antibradycardia pacing. Devices incorporating an atrial lead allow dual-chamber pacing and better discrimination between ventricular and supraventricular tachyarrhythmias. Intensivists are increasingly likely to encounter patients with ICDs. Electrosurgery can be safely performed in ICD patients as long as the device is deactivated before the procedure and reactivated and reassessed immediately afterward. Prompt and skilled intervention can prove to be life-saving in patients presenting with ICD-related emergencies, including lack of response to ventricular tachyarrhythmias, pacing failure, and multiple shocks. Recognition and treatment of tachyarrhythmia can be temporarily disabled by placing a magnet on top of an ICD. The presence of an ICD should not deter standard resuscitation techniques. Multiple ICD discharges in a short period of time constitute a serious situation. Causes include ventricular electrical storm, inefficient defibrillation, nonsustained ventricular tachycardia, and inappropriate shocks caused by supraventricular tachyarrhythmias or oversensing of signals. ICD system infection requires hardware removal and intravenous antibiotic therapy. Deactivation of an ICD with the consent of the patient or relatives is reasonable and ethical in terminally ill patients.

Contraindications↗