Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Defibrillators”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed2001

Initial experience with an active-fixation defibrillation electrode and the presence of nonphysiological sensing.

Nonphysiological sensing by a pacing and defibrillation electrode may result in inappropriate defibrillator discharges and/or inhibition of pacing. Active-fixation electrodes may be more likely to sense diaphragmatic myopotentials because of the protrusion of the screw for fixation. In addition, the movement of the fixation screw in an integrated bipolar lead system could also result in inappropriate sensing. This may be increasingly important in patients who are pacemaker dependent because the dynamic range of the autogain feature of these devices is much more narrow. Five of 15 consecutive patients who received a CPI model 0154 or 0155 active-fixation defibrillation electrode with an ICD system (CPI Ventak A V3DR model 1831 or CPI Ventak VR model 1774 defibrillator) are described. In 2 of the 15 patients, nonphysiological sensing appearing to be diaphragmatic myopotentials resulted in inappropriate defibrillator discharges. Both patients were pacemaker dependent. Changes in the sensitivity from nominal to less sensitive prevented inappropriate discharges. In one patient, discreet nonphysiological sensed events with the electrogram suggestive of ventricular activation was noted at the time of implantation. This was completely eliminated by redeployment of the active-fixation lead in the interventricular septum. In two other patients, discreet nonphysiological sensed events resulted in intermittent inhibition of ventricular pacing after implantation. These were still seen in the least sensitive autogain mode for ventricular amplitude. These were not seen on subsequent interrogation 1 month after implantation. Increased awareness of nonphysiological sensing is recommended. The CPI 0154 and 0155 leads seem to be particularly prone to this abnormality. Particular attention should be made when deploying an active-fixation screw for an integrated bipolar lead. This increased awareness is more important when a given individual is pacemaker dependent, which may warrant DFT testing in a least or less sensitive mode in these patients.

Adult↗
PubMed2002

Human experience with transvenous biventricular defibrillation using an electrode in a left ventricular vein.

This study investigated the safety and feasibility of transvenous biventricular defibrillation in ICD patients. Some patients may have high DFTs due to weak shock field intensity on the LV. Animal studies showed a LV shocking electrode dramatically lowered DFTs. This approach might benefit heart failure patients already receiving a LV lead or conventional ICD patients with high DFTs. A modified guidewire was used as a temporary left venous access defibrillation electrode (LVA lead). In 24 patients receiving an ICD, the LVA lead was advanced through a guide catheter in the coronary sinus (CS) and into a randomized LV vein (anterior or posterior) using a venogram for guidance. Paired DFT testing compared a standard right ventricular defibrillation system to a biventricular defibrillation system. There were no complications or adverse events. As randomized, LVA lead insertion success was 87% and 71% for anterior and posterior veins, respectively, and 100% after crossover. Total insertion process time included venogram time (32.5 +/- 26.9 minutes, range 5-115, mode 15 minutes) and LVA lead insertion time (15 +/- 14 minutes, range 1-51, mode 7 minutes). An apical LVA lead position was achieved in 11 (45%) of 24 patients and 7 (64 %) of these 11 displayed a DFT reduction; however, mean DFTs were not statistically different. Transvenous biventricular defibrillation is feasible and was safe under the conditions tested. Additional clinical studies are justified to determine if optimized LV lead designs, lead placement, and shock configurations can yield the same large DFT reductions as observed in animals.

Aged↗
PubMed2002

1-year performance of a defibrillation lead with a small electrode surface for high impedance pacing: a randomized, controlled study.

A small electrode surface reduces pacing current drain and can extend generator longevity. The study evaluated the performance of a tined, quadripolar defibrillation lead (model 6944) that has a small-surfaced, steroid-eluting electrode tip for high impedance pacing. In a prospective, controlled study, 34 patients with conventional ICD indications were randomized one to one to receive the high impedance model 6944 or a tined defibrillation lead with a conventional sized, steroid-eluting electrode tip model 6942. Lead performance was evaluated at implant, prior to hospital discharge, and 1, 3, 6, and 12 months thereafter. Baseline characteristics did not differ significantly between patients implanted with lead model 6942 (n = 16) or model 6944 (n = 17). One patient randomized to receive the model 6942 was excluded from the study and was implanted with an active-fixation lead after stable lead positioning was neither possible with the 6942 nor with the 6944 electrode. No other lead related adverse events were observed. At implant, there were no significant differences between pacing thresholds, sensing performance, defibrillation impedances, and defibrillation thresholds in both groups, but pacing impedance of the model 6944 (988.6 +/- 217.7 omega) was approximately twice as high as high as in the model 6942 (431.7 +/- 83.7 omega; P < 0.0001). This difference remained highly significant throughout the observation period of 12 months, while R wave amplitudes and pacing thresholds remained equal in both lead models. The use of a tined defibrillation lead with a small, steroid-eluting electrode tip appears safe and results in a high pacing impedance without compromising system performance.

Defibrillators, Implantable↗
PubMed2003

Safety of a single successful conversion of ventricular fibrillation before the implantation of cardioverter defibrillators.

UNLABELLED: Multiple successful conversions of ventricular fibrillation (VF) at 10 J below the maximum output of implantable cardioverter defibrillator (ICD) have been recommended as a minimum device implantation criterion. This recommendation is based on the probabilistic properties of defibrillation that necessitates multiple shocks to establish an adequate safety margin for the conversion of subsequent spontaneous arrhythmias. We hypothesized that a single successful shock at a 14 J may suffice. METHODS AND RESULTS: The Low Energy Safety Study (LESS) enrolled 720 patients undergoing initial ICD implantation with a dual-coil transvenous lead and active pulse generator. At implant, an enhanced defibrillation threshold (DFT++) was determined by a rigorous protocol beginning at 14 J, and requiring at least 4 shocks. Fifty percent of all patients were then randomized to full output shock energy and the conversion rates for spontaneous ventricular tachyarrhythmias at rates > 200 beats/min were measured. There were 318 patients randomized to 31 J, of whom 254 were successfully defibrillated by an initial 14 J shock. During a mean follow-up of 24 +/- 12 months, 112 spontaneous VF episodes occurred in 31 patients. The combined conversion success of the first and second shock (when needed) did not differ between the subgroup of patients who were successfully defibrillated by an initial 14 J shock, regardless of the results of additional testing, and the whole cohort who underwent more systematic testing (97% vs 97%). All spontaneous episodes of VF were successfully treated during long-term follow-up. CONCLUSIONS: A first successful shock of 14 J may be a sufficient endpoint to allow the implantation of ICDs with the Triad lead configuration, when programming all shocks to 31 J.

Aged↗
PubMed2003

Psychosocial aspects of patient-activated atrial defibrillation.

UNLABELLED: Atrial Defibrillator. INTRODUCTION: The atrial defibrillator empowers patients to cardiovert themselves from atrial arrhythmias at a time that is socially and physically acceptable, thereby preventing hospitalization. The long-term psychosocial effects of repeated use of the patient-activated atrial defibrillator at home are unknown. METHODS AND RESULTS: Eighteen patients underwent placement of the Jewel AF atrial defibrillator for persistent atrial fibrillation only. All patients performed manually activated cardioversions at home under self-administered sedation. Automatic shock therapies were disabled. Hospital Anxiety and Depression Scale and Multidimensional Health Locus of Control questionnaires were obtained before implant. All patients completed questionnaires 1 year after device implant and at long-term follow-up. The spouse or partner of each patient was interviewed to identify positive and negative aspects of manual cardioversion at home. The baseline patient scores for both anxiety (5.7 +/- 2.7) and depression (3.4 +/- 2.3) fell within the predefined range of normality. At 1 year, there was no significant change in anxiety (4.9 +/- 3.7, P = 0.39) or depression (2.4 +/- 1.8, P = 0.06). At long-term follow-up (mean 28 months), a total of 377 patient-activated cardioversions were performed out of hospital (median 15 per patient). Scores for anxiety (6.0 +/- 4.0, P = 0.70) and depression (3.2 +/- 2.5, P = 0.68) remained unchanged. CONCLUSION: During long-term follow-up, patient-activated cardioversion using the atrial defibrillator was not associated with increased anxiety or depression. The procedure was well tolerated by patients and their partners, offering an acceptable treatment option for patients with recurrent persistent atrial fibrillation.

Adult↗
PubMed2004

Effect of rapid biphasic shock subpulse switching on ventricular defibrillation thresholds.

INTRODUCTION: The aim of this study was to demonstrate that significant reductions in defibrillation threshold (DFT) can be achieved by rapidly switching defibrillation pulses within an overall biphasic envelope between multiple endovascular electrode sets. METHODS AND RESULTS: Defibrillation electrodes were implanted in four locations in nine anesthetized swine (41.7 +/- 8.7 kg). Electrodes were implanted into the right ventricular apex (RV), the superior vena cava (SVC), over the left pectoral region as a "hot can" (Can), and within the middle cardiac vein on the posterior left ventricular (LV) surface. The 50% DFT (level for which 50% of delivered shocks successfully defibrillated) for control shocks (7-ms first phase, 0.5-ms interpulse period, 4-ms second phase, RV- --> SVC+ + Can+) were determined to have energy of 20.5 +/- 5.5 J (mean +/- SD). Mean 50% DFTs were also determined for waveforms that split each phase of the same overall biphasic waveform between various electrode sets. Each phase was divided into 2, 3, 4, or 6 subpulses, the defibrillation shock was sequentially delivered to multiple electrode sets, and DFTs were determined (11.9 +/- 4.8 J, 11.7 +/- 2.9 J, 17.9 +/- 8.7 J, 16.7 +/- 6.1 J, respectively). DFT energy was statistically lower than the control (Wilcoxon sign rank test; P < 0.05) when each phase was divided into 2 or 3 subpulses. CONCLUSION: Rapid shock switching within an overall biphasic waveform between electrode sets including an electrode in the middle cardiac vein potentially can lower DFT energy by 40% or more.

Animals↗
PubMed1998

Experience with pectoral versus abdominal implantation of a small defibrillator. A multicenter comparison in 778 patients. European Jewel Investigators.

AIMS: The aim of the study was to examine the results of implanting small sized cardioverter defibrillators in the pectoral as opposed to the abdominal area. Hitherto. owing to the large size of the early defibrillators, the site of implantation had been confined to the abdomen. METHODS: Between 30 March 1993 and 1 November 1994, 778 patients from 63 centres in 14 countries underwent their first device implantation. The study was set up to evaluate the safety and the efficacy of Medtronic models 7219 D, a multi-lead abdominal/pectoral implantable cardioverter defibrillator, and 7219 C, a pectoral single-lead Active Can implantable cardioverter defibrillator. There were 155 abdominal and 623 pectoral implants. Survival data were comparable during a mean follow-up period of 4.0 +/- 4.6 months, with no difference regarding the pectoral placement of single (n = 392) or multi-lead (n = 231) devices. The only significant difference was related to severe lead-related events: 5.3% in the pectoral vs 11.6% the abdominal group (P < 0.05). These events were mainly related to lead dislodgement. Kaplan-Meier estimates showed that both single and multi-lead systems, in either the pectoral or abdominal position, demonstrated a similar severe adverse event-free survival. CONCLUSION: These findings suggest that an implantable cardioverter defibrillator (18 mm thick, 80 cc volume, 129 g weight) can be implanted in the pectoral position without an increase in clinically relevant adverse events compared to abdominal implantation. Pectoral implantation was associated with significantly reduced lead-related severe adverse event rate.

Abdominal Muscles↗
PubMed2001

In-vivo testing of digital cellular telephones in patients with implantable cardioverter-defibrillators.

AIMS: To investigate the susceptibility of implantable cardioverter defibrillators to electromagnetic interference generated by digital cellular telephones, functioning in both international transmission technologies: the Global System for Mobile Communication (GSM) and the Digital Cellular System (DCS 1800). METHODS AND RESULTS: In 36 patients with transvenous implantable cardioverter defibrillators from two manufacturers (Medtronic and Guidant/CPI), cellular telephones with different levels of minimal and maximal power output were tested in the transmitting and receiving mode. Evaluation was performed in activated implantable defibrillators during spontaneous cardiac activity and continuous VVI or DDD pacing to assess possible electromagnetic interference. In two patients, appropriateness of ventricular fibrillation detection and therapy was judged during telephone testing. There was no damage, reprogramming, inappropriate shock therapy or pacing inhibition during the tests. In seven pre-pectoral Medtronic implantable defibrillators, transient electromagnetic interference caused 19 erroneous sensing events, when the operating phone was held in close vicinity to the programmer head. These 'pseudo-oversensing' events, which did not result in logging of arrhythmia episodes in the device counter, were interpreted as an adverse interaction between the telephone and the programming device. CONCLUSION: Digital cellular telephones do not represent a risk to Medtronic and Guidant/CPI recipients of the specific implantable defibrillator models herein tested.

Defibrillators, Implantable↗
PubMed2002

Efficacy of a dual chamber defibrillator with atrial antitachycardia functions in treating spontaneous atrial tachyarrhythmias in patients with life-threatening ventricular tachyarrhythmias.

BACKGROUND: Atrial fibrillation has a high incidence in patients wearing an implantable cardioverter defibrillator for ventricular tachyarrhythmias and may lead to palpitations, heart failure, angina, stroke and inappropriate defibrillator discharge. The aim of the study was to evaluate the efficacy of a dual chamber defibrillator with atrial antitachycardia functions in treating spontaneous atrial tachyarrhythmias. METHODS: One hundred and twelve patients, 88 male, mean age 64+/-11 years, were enrolled. Seventy-six had ischaemic heart disease, 21 idiopathic dilated cardiomyopathy, nine other heart diseases, six no structural heart disease. The mean left ventricular ejection fraction was 40+/-11%. Sixty-two had prior atrial tachyarrhythmias. RESULTS: Follow-up lasted 11+/-9 months (range 1-42). Among 933 ventricular tachyarrhythmia episodes, 100% of ventricular fibrillation and 92% of ventricular tachycardia were successfully cardioverted. Among 414 detected sustained atrial tachyarrhythmias, 195 were classified as atrial tachycardia (47.1%), 192 as atrial fibrillation (46.4%) and 27 (6.5%) as sinus rhythm. The detection-positive predictive value was 93.5%. Therapy success rates: antitachy pacing on atrial tachycardia = 71.3% (crude estimate); 66.1% (adjusted estimate); 50 Hertz on atrial fibrillation=36.2% (crude estimate); 13.5% (adjusted estimate); atrial shock on atrial fibrillation = 62.5% (mean energy 7.8+/-14.1J). Shock efficacy was 32% when delivered energy was < or = 2 atrial defibrillation threshold at implant and 92% when >2. Duration of successfully treated atrial episodes was significantly lower than that of unsuccessfully treated (6+/-26 min vs 42+/-60). CONCLUSIONS: Atrial antitachy pacing and shock therapies demonstrated very high efficacy in treating atrial tachyarrhythmias in defibrillator patients.

Atrial Fibrillation↗
PubMed2004

[Clinical significance of stress reactivity for frequency of electric shock discharges in patients with implanted cardioverter-defibrillators].

BACKGROUND AND OBJECTIVE: Recent research indicates that discharges of implanted cardioverter-defibrillators (ICD) are triggered by psychosocial stress. This study examined the presence of patterns of psychophysiological stress reactivity in ICD-patients. Further more potential relationship between factors of stress reactivity and the frequency of implantable cardioverter-defibrillators discharges was investigated. PATIENTS AND METHODS: In 46 consecutive patients (38 male, 8 female; age: 26-80 years) with implantable cardioverter-defibrillators the following parameters of physiological reactivity were measured in a standardised experimental stress test: Heart rate, skin conductance, muscle tension and respiratory activity. In a standardised interview anxiety sensitivity, depression, desire for control, stress load, and attitude towards the defibrillator were evaluated and quantified. The relationship between the mentioned parameters were examined with factor analysis to reveal patterns of psychophysiological reactivity. Potential relationship between psychophysiological factors and frequency of shock delivery was verified with linear regression analysis. RESULTS: Factor analysis revealed four independent psychophysiological traits. The factors were named "Play Dead Reflex", "Heart Phobia", "Negativism" and "Irritability". Linear regression model showed significant correlation between "Play Dead Reflex" and discharge frequency. CONCLUSIONS: Results confirm the presence of specific psychophysiological stress reaction patterns in ICD-patients. The stress reaction pattern "Play Dead Reflex" could be discussed as a potential risk factor in developing life-threatening tachyarrhythmias leading to an increase in defibrillator discharges in patients with ICD. This hypothesis should be considered in prospective studies and psychosomatic treatment of concerned patients.

Adult↗
PubMed2006

[In-hospital resuscitation. Concept of first-responder resuscitation using semi-automated external defibrillators (AED)].

BACKGROUND AND OBJECTIVE: The prognosis after in-hospital resuscitation has not significantly improved in the last 40 years. This account presents the results over a three-year period of a hospital-wide emergency plan which implements the use of an automated external defibrillator (AED) by the first responder to the emergency call. BACKGROUND AND OBJECTIVE: 15 "defibrillator points" were installed, which could be reached within 30 s from all wards, out-patient departments and other areas, thus making them accessible for immediate defibrillator application. The hospital personnel is trained periodically in the alarm sequence, cardiopulmonary resuscitation and use of the defibrillator. Data on 57 patients who had sustained a cardiac arrest were prospectively recorded and analysed. RESULTS: In 46 patients (81%) the "on-the-spot" personnel (first-responder) was able to apply AED before arrival of the hospital's resuscitation team. Mean period between arrest alarm and activation of the AED was 2.2 (0.7-4.7) min. Ventricular fibrillation or ventricular tachyarrhythmia was recorded in 40 patients, making immediate shock delivery by AED possible. Restoration of the circulation was achieved in 23 (80%) of the patients and 20 (50%) were discharged home, 17 (43%) without neurological deficit. The high proportion of first-responder AED applications and evaluation of the personnel training indicate a wide acceptance of the emergency plan among the personnel. CONCLUSION: An immediate resuscitation plan consisting of an integrated programme of early defibrillation is feasible and seems to achieve an improved prognosis for patients who have sustained an in-hospital cardiac arrest.

Adult↗
PubMed1999

Effects of defibrillator implantation testing on myocardial metabolism.

BACKGROUND: The effects of fibrillation/defibrillation episodes (FDEs) during defibrillator implantation on myocardial metabolism were investigated at various defibrillation energies in patients with different cardiac pathologies. METHODS: Myocardial lactate extraction (MLE) was examined during defibrillation threshold (DFT) testing in patients with either coronary artery disease (CAD, n = 20) or non-ischemic cardiomyopathy (CM, n = 10). Defibrillation pulses were released 15 seconds after induced fibrillation. A test cycle of four FDEs separated by 2-minute intervals was applied in each case. RESULTS: Mean MLE decreased significantly from 28 +/- 4% before FDEs to 8 +/- 5% immediately after all episodes in CAD patients, but recovered to 27 +/- 7% within 2 minutes even in patients with reduced left-ventricular function. In patients with CM mean MLE decreased markedly from 29 +/- 3% to -11 +/- 3% immediately after each FDE but increased to baseline (33 +/- 8%) within the recovery period. MLE changes were independent of defibrillation energy in all cases. CONCLUSIONS: Myocardial lactate production, suggesting cardiac ischemia, was observed in patients with CM, but not in patients with CAD. But recovery of myocardial lactate extraction was not faster in CAD patients, indicating that the fixed FDE cycle used was well tolerated by all patients.

Adult↗
PubMed1996

[Driving of a motor vehicle after implantation of a cardioverter-defibrillator in malignant heart rhythm disorders. Criteria for the medical assessment of driving fitness in Europe].

AIM OF STUDY: To investigate how medical permission to drive in patients with a cardioverter defibrillator is handled in various European countries. METHODS: A specially developed questionnaire was sent to all 46 delegates of the pacemaker groups of the European Society of Cardiology. They were asked to provide information on the procedures and criteria used in the various countries regarding a driving ban after cardioverter defibrillator implantation (ICD). RESULTS: 39 answers (83%) were received from representatives of 24 countries. 22 (56%) of those replying advised their patients not to drive. A permanent driving ban was recommended by 13 (33%), a temporary one of 3-18 (mean 9 +/- 4) months by 26 (67%). Presyncope was named as a criterion for a ban by 15 (38%), syncope by 13 (33%) and multiple defibrillator shocks by two (5%). Contrary to medical advice not to drive about one third of patients resumed driving, half of them after 6 months. 12 months after implantation most of the patients were again driving. Defibrillator discharges occurred in 2 patients, without consequence. One patient had a fatal car accident, unrelated to loss of consciousness or defibrillator shock. CONCLUSIONS: 1. ICD discharges are an extremely rare cause of driving accidents. 2. About half of the cardiologists recommended a driving ban for a mean of 9 months after ICD. 3. Despite medical ban about half of the patients resumed driving after 6 months. 4. There are as yet no uniform criteria in Europe for judging fitness to drive.

Accidents, Traffic↗
PubMed1997

Prophylactic use of implanted cardiac defibrillators in patients at high risk for ventricular arrhythmias after coronary-artery bypass graft surgery. Coronary Artery Bypass Graft (CABG) Patch Trial Investigators.

BACKGROUND: Patients with coronary heart disease, left ventricular dysfunction, and abnormalities on signal-averaged electrocardiograms have an increased risk sudden death. We evaluated the effect on survival of the prophylactic implantation of cardioverter-defibrillators in such patients at the time of coronary-artery bypass surgery. METHODS: Over the course of five years, 37 clinical centers screened all patients who were scheduled for elective coronary bypass surgery. Patients were eligible for the trial if they were less than 80 years old, had a left ventricular ejection fraction of less than 0.36, and had abnormalities on signal-averaged electrocardiograms. We identified 1422 eligible patients, enrolled 1055, and randomly assigned 900 to therapy with an implantable cardioverter-defibrillator (446 patients) or to the control group (454 patients). The primary end point of the study was overall mortality, and the two groups were compared in an intention-to-treat analysis. RESULTS: The base-line characteristics of the two groups were similar. During an average follow-up of 32+/-16 months, there were 101 deaths in the defibrillator group (71 from cardiac causes) and 95 in the control group (72 from cardiac causes). The hazard ratio for death from any cause was 1.07 (95 percent confidence interval, 0.81 to 1.42; P=0.64). There was no statistically significant interaction between defibrillator therapy and any of 10 preselected base-line covariates. CONCLUSIONS: We found no evidence of improved survival among patients with coronary heart disease, a depressed left ventricular ejection fraction, and an abnormal signal-averaged electrocardiogram in whom a defibrillator was implanted prophylactically at the time of elective coronary bypass surgery.

Aged↗
PubMed2005

Cost-effectiveness of implantable cardioverter-defibrillators.

BACKGROUND: Eight randomized trials have evaluated whether the prophylactic use of an implantable cardioverter-defibrillator (ICD) improves survival among patients who are at risk for sudden death due to left ventricular systolic dysfunction but who have not had a life-threatening ventricular arrhythmia. We assessed the cost-effectiveness of the ICD in the populations represented in these primary-prevention trials. METHODS: We developed a Markov model of the cost, quality of life, survival, and incremental cost-effectiveness of the prophylactic implantation of an ICD, as compared with control therapy, among patients with survival and mortality rates similar to those in each of the clinical trials. We modeled the efficacy of the ICD as a reduction in the relative risk of death on the basis of the hazard ratios reported in the individual clinical trials. RESULTS: Use of the ICD increased lifetime costs in every trial. Two trials--the Coronary Artery Bypass Graft (CABG) Patch Trial and the Defibrillator in Acute Myocardial Infarction Trial (DINAMIT)--found that the prophylactic implantation of an ICD did not reduce the risk of death and thus was both more expensive and less effective than control therapy. For the other six trials--the Multicenter Automatic Defibrillator Implantation Trial (MADIT) I, MADIT II, the Multicenter Unsustained Tachycardia Trial (MUSTT), the Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial, the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) trial, and the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT)--the use of an ICD was projected to add between 1.01 and 2.99 quality-adjusted life-years (QALY) and between 68,300 dollars and 101,500 dollars in cost. Using base-case assumptions, we found that the cost-effectiveness of the ICD as compared with control therapy in these six populations ranged from 34,000 dollars to 70,200 dollars per QALY gained. Sensitivity analyses showed that this cost-effectiveness ratio would remain below 100,000 dollars per QALY as long as the ICD reduced mortality for seven or more years. CONCLUSIONS: Prophylactic implantation of an ICD has a cost-effectiveness ratio below 100,000 dollars per QALY gained in populations in which a significant device-related reduction in mortality has been demonstrated.

Cost-Benefit Analysis↗
PubMed2001

Multicenter study of principles-based waveforms for external defibrillation.

STUDY OBJECTIVE: The efficacy of a shock waveform for external defibrillation depends on the waveform characteristics. Recently, design principles based on cardiac electrophysiology have been developed to determine optimal waveform characteristics. The objective of this clinical trial was to evaluate the efficacy of principles-based monophasic and biphasic waveforms for external defibrillation. METHODS: A prospective, randomized, blinded, multicenter study of 118 patients undergoing electrophysiologic testing or receiving an implantable defibrillator was conducted. Ventricular fibrillation was induced, and defibrillation was attempted in each patient with a biphasic and a monophasic waveform. Patients were randomly placed into 2 groups: group 1 received shocks of escalating energy, and group 2 received only high-energy shocks. RESULTS: The biphasic waveform achieved a first-shock success rate of 100% in group 1 (95% confidence interval [CI] 95.1% to 100%) and group 2 (95% CI 94.6% to 100%), with average delivered energies of 201+/-17 J and 295+/-28 J, respectively. The monophasic waveform demonstrated a 96.7% (95% CI 89.1% to 100%) first-shock success rate and average delivered energy of 215+/-12 J for group 1 and a 98.2% (95% CI 91.7% to 100%) first-shock success rate and average delivered energy of 352+/-13 J for group 2. CONCLUSION: Using principles of electrophysiology, it is possible to design both biphasic and monophasic waveforms for external defibrillation that achieve a high first-shock efficacy.

Aged↗
PubMedDate not supplied

A comparison of biphasic and monophasic shocks for external defibrillation. Physio-Control Biphasic Investigators.

BACKGROUND AND OBJECTIVE: The ability of a shock to defibrillate the heart depends on its waveform and energy. Past studies of biphasic truncated exponential (BTE) shocks for external defibrillation focused on low energy levels. This prospective, randomized, double-blind clinical trial compared the first-shock efficacies of 200-joule (J) BTE, 130-J BTE, and 200-J monophasic damped sine wave shocks. METHODS: Ventricular fibrillation (VF) was induced in 115 patients during evaluation of implantable cardioverter-defibrillator function and 39 patients during electrophysiologic evaluation of ventricular arrhythmias. After 19 +/- 10 seconds of VF, a randomized transthoracic shock was administered. Mean first-shock success rates of the three groups were compared using a "Tukey-like" statistical test, adjusting for multiple comparisons. Blood pressures and arterial oxygen saturations were measured before VF induction and 30, 90, and 150 seconds after successful defibrillation. RESULTS: First-shock success rates were 61/68 (90%) for 200-J monophasic, 39/39 (100%) for 200-J biphasic, and 39/47 (83%) for 130-J biphasic shocks. The 200-J biphasic shocks were simultaneously superior in first-shock efficacy to both 200-J monophasic and 130-J biphasic shocks (experimentwise error rate, alpha < 0.01). There was no significant difference between the efficacies of 200-J monophasic and 130-J biphasic shocks, nor was there any significant difference between the three groups in hemodynamic parameters after successful shocks. CONCLUSIONS: Biphasic shocks of 200 J provide better first-shock defibrillation efficacy for short-duration VF than 200-J monophasic and 130-J biphasic shocks and thus may allow earlier termination of VF in cardiac arrest patients.

Adult↗
PubMed1997

Experience with implantable cardioverter defibrillator therapy in elderly patients.

AIM: Concern exists about the benefit of implantable defibrillator therapy in elderly patients. We assessed the utility of implantable defibrillator therapy and its effect on mortality in patients 70 years and older and compared results in this group to those in younger patients. METHODS AND RESULTS: Thirty-two out of 200 consecutive patients (16%) were 70 years or older at the time of implantation of a defibrillator. When comparing elderly to younger patients no significant differences were noted with respect to presenting arrhythmia, left ventricular ejection fraction or presence of an old myocardial infarction. Elderly patients had a higher prevalence of ischaemic heart disease, while in the younger group more patients had idiopathic ventricular tachycardia. Cumulative survival curves (Kaplan-Meier method) for all-cause mortality, sudden cardiac death and non-sudden cardiac death were constructed for elderly and younger patients. No significant differences for cumulative survival from all-cause mortality (75 vs 74%), sudden cardiac death (0 vs 4%) and non-sudden cardiac death (97 vs 93%) were found. The incidence of appropriate shocks during follow-up was comparable (65 vs 72%). CONCLUSION: Implantable defibrillator therapy was effective in preventing sudden cardiac death in the elderly. Total mortality was similar to younger patients at a follow-up of 19 +/- 14 and 25 +/- 19 months, respectively. Age itself should be no contraindication to implantable cardioverter defibrillator therapy.

Aged↗