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PubMed1997

Pacing threshold increase in nonthoracotomy implantable defibrillator leads: implications for battery longevity and margin of safety.

Just as a stable defibrillation threshold is required for implantable defibrillators to maintain efficacy and a margin of safety for the conversion of life-threatening ventricular arrhythmias, a stable pacing threshold is also required to provide bradycardia support and pacing to terminate ventricular tachycardias. This article reports the temporal course of pacing thresholds in patients treated with a tripolar, tined endocardial defibrillator lead capable of bipolar sensing and pacing, and defibrillation. Seventeen patients who underwent implantation of an implantable defibrillator system using an integrated bipolar pacing/sensing system were prospectively studied over 18 months. There were 16 males and one female, with a mean age of 69 +/- 5 years (range 61-75 years). At implantation, predischarge, and every 2 months thereafter, the pacing pulse-width threshold was tested at both 2.5 and 5.0 V stimulus amplitudes. After a mean follow-up of 363 +/- 173 days (range 34-597 days), the pacing threshold increased from 0.08 +/- 0.08 ms to 0.5 +/- 0.3 ms at the 2.5 V amplitude (p < or = 0.01, CI-0.57 to -0.27) and from 0.04 +/- 0.02 ms to 0.25 +/- 0.14 ms at the 5.0 V amplitude (p < or = 0.01, CI -0.28 to -0.14). Eight of the 17 patients (47%) received spontaneous implantable defibrillator shocks for clinically detected arrhythmias, and the total number of joules delivered via the leads did not correlate with the pacing threshold changes. We conclude that the pacing threshold for the nonthoracotomy implantable defibrillator lead system studied is not stable and increases with time. This finding has implications for defibrillator battery life in patients who use implantable defibrillators for bradycardia pacing.

Aged↗
PubMed1984

Surgical techniques for implanting the automatic implantable defibrillator.

Since February 1980, the automatic defibrillator was implanted in 77 survivors of multiple cardiac arrest. The subxiphoid technique was used in 28 patients and the thoracotomy technique was used in 20 patients with previous cardiac surgery. Median sternotomy was used in 29 patients undergoing open heart procedures as well as defibrillator implantation. While the subxiphoid is the most benign procedure employed, all are safe and well tolerated. The method used is determined by the clinical picture. Survival studies indicate improved survival in this high risk population.

Adolescent↗
PubMed1998

[Patients with structural heart disease, syncope of unknown etiology and inducible ventricular arrhythmias treated with implantable defibrillators].

OBJECTIVES: This study evaluates the hypothesis that in patients with syncope of unknown origin and heart anomalies, inducible ventricular arrhythmias are specific arrhythmias and therefore should be treated as such. BACKGROUND: Although syncope is a frequent clinical entity, the evaluation and treatment of patients with syncope without a clear etiology still remains undefined. Many patients with syncope of undetermined origin undergo invasive electrophysiologic evaluation. Abnormalities of the sinus node, prolongation of conduction times or inducible arrhythmias found during these evaluations are usually assumed to be the cause of syncope, and are consequently treated. However, whether tachyarrhythmias are truly the cause of syncope, and whether treatment of these tachyarrhythmias can prevent recurrent syncope and arrhythmic death, is unknown. PATIENTS AND METHODS: An electrophysiological study was performed on 160 patients with structural heart disease and syncope of unknown origin. In 23 out of the 160 patients (16%), programmed electrical stimulation induced sustained ventricular arrhythmias. In 18 out of the 23 patients an automatic defibrillator was implanted and they form the study group. RESULTS: In these 18 patients, programmed ventricular stimulation induced sustained monomorphic ventricular tachycardia in 12, sustained polymorphic ventricular tachycardia in 2 and ventricular fibrillation in 4. During a mean follow-up of 14 months, 9 patients received 81 appropriate therapies from the device (53 because of ventricular tachycardia and 23 because of ventricular fibrillation). The probability of appropriate therapy was 100% at 1 year follow-up. There were no episodes of sudden death and 1 patient died of congestive heart failure. CONCLUSIONS: In patients with syncope of undetermined origin, heart disease and inducible ventricular tachyarrhythmias treated with a implantable cardioverter defibrillator, there is a high incidence of appropriate therapies. Our results support the practice of using implantable cardioverter defibrillators in patients with syncope of unknown origin, heart disease and inducible ventricular arrhythmias.

Adolescent↗
PubMed1994

[Pectoral cardioverter-defibrillator implantation combined with transvenous bipolar defibrillation electrodes].

Ultimately, implantable cardioverter-defibrillators (ICD) will one day be implantable like present pacemakers. However, due to the size of the pulse generator and the low defibrillation efficacy of monophasic shocks, only a few selected patients have been implanted transvenously-pectorally. Therefore, we have prospectively investigated whether a transvenous-pectoral approach is in general feasible with a new downsized ICD capable of delivering biphasic shocks. Out of 33 patients, 76% received a bipolar transvenous defibrillation lead system. In the first 13 consecutive patients, a randomized crossover study showed that this high efficacy was above all achieved by a superior defibrillation efficacy of the biphasic waveform in comparison to the monophasic waveform (69% vs. 23%; p = 0.03). Not a single patient could be defibrillated exclusively with the monophasic waveform. In a further 15 consecutive patients, a crossover study showed that a position of the transvenous anode within the Vena anonyma instead of the Vena cava superior is, in general, not superior (87% vs. 80%; p = 0.67). Only one patient could be exclusively defibrillated with the V. anonyma position. Intraoperatively, no complications occurred and all but one patient received a pectoral implantation of the pulse generator. Postoperatively, in five patients local complications related to the ICD system were seen; two needed a surgical revision. In two patients movements of the left shoulder joint were temporarily restricted. Thus, in the majority of patients a new downsized ICD capable of biphasic shocks can be implanted transvenously-pectorally like a pacemaker.

Adult↗
PubMed2001

Lead- and device-related complications in the antiarrhythmics versus implantable defibrillators trial.

BACKGROUND: Implantation of transvenous implantable cardioverter defibrillators (ICDs) by use of a nonthoracotomy approach has become routine therapy for survivors of life-threatening tachyarrhythmias. The purpose of this study was to identify and prospectively characterize the frequency of lead- and ICD-related complications from the Antiarrhythmics versus Implantable Defibrillators (AVID) Trial. METHODS AND RESULTS: Between June 1, 1993, and April 7, 1997, 539 patients received nonthoracotomy ICDs either as initial treatment assignment (477) or as crossover from medical management (62). A total of 62 first complications occurred. The subclavian route of insertion resulted in more complications than the cephalic vein route, 46 of 339 (14%) versus 6 of 135 (4%), P = .005, as did the abdominal versus pectoral generator site, 31 of 238 (13%) versus 17 of 291 (6%), P<.02. Most dislodgements and system infections tended to occur in the 3 months after implantation, whereas lead fractures continued to occur throughout follow-up. Failure to use perioperative antibiotics was a predictor of system infection (P = .001). CONCLUSIONS: These data suggest that cephalic vein access and pectoral generator site may result in fewer complications. The continued occurrence of lead fractures and the need for premature system revision supports the practice of close routine ICD system surveillance.

Anti-Arrhythmia Agents↗
PubMedDate not supplied

Implantable defibrillator recipients' responses to device implantation and design.

The implantable cardioverter defibrillator (ICD) is a surgically inserted device that follows a well-established pattern of technology innovation and rapid adoption without extensive clinical trials. Few devices are as obviously life-saving in potentially fatal situations and deliver such sudden and sometimes painful therapy. Although patients' quality of life and adjustment to the device both physically and psychologically are relatively well-documented, few studies have explored recipients' responses to the device itself or elicited their thoughts on the technological design. The findings presented here are from a prospective Australian study that surveyed 110 ICD recipients pre-insertion and at 3, 12, and 18 months post-insertion. Recipients' responses to the device and their thoughts on design were sought. Respondents were overwhelmingly willing to: 1) accept the ICD, 2) recommend it to others, and 3) welcome such innovations as warning tones, device-controlled drug delivery, and telephone interrogation of the device.

Adolescent↗
PubMed1997

Upper limit of vulnerability predicts chronic defibrillation threshold for transvenous implantable defibrillators.

INTRODUCTION: The upper limit of vulnerability (ULV) is the shock strength at or above which ventricular fibrillation cannot be induced when delivered in the vulnerable period. It correlates acutely with the acute defibrillation threshold (DFT) and can be determined with a single episode of fibrillation. The goal of this prospective study was to determine the relationship between the ULV and the chronic DFT. METHODS AND RESULTS: We studied 40 patients at, and 3 months after, implantation of transvenous cardioverter defibrillators. The ULV was defined as the weakest biphasic shock that failed to induce fibrillation when delivered 0, 20, and 40 msec before the peak of the T wave. patients were classified as clinically stable or unstable based on prospectively defined criteria. There were no significant differences between the group means for the acute and chronic determinations of ULV (13.5 +/- 5.3 J vs 12.4 +/- 6.8 J, P = 0.25) and DFT (10.1 +/- 5.0 J vs 9.9 +/- 5.7 J, P = 0.74). Five patients (15%) were classified as unstable. The strength of the correlation between acute ULV and acute DFT (r = 0.74, P < 0.001) was similar to that between the chronic ULV and chronic DFT (r = 0.82, P < 0.001). There was a correlation between the change in ULV from acute to chronic and the corresponding change in DFT (r = 0.67, P < 0.001). The chronic DFT was less than the acute ULV +3 J in all 35 stable patients, but it was greater in 2 of 5 unstable patients (P = 0.04). CONCLUSIONS: The strength of the correlation between the chronic ULV and the chronic DFT is comparable to that between the acute ULV and the acute DFT. Temporal changes in the ULV predict temporal changes in the DFT. In clinically stable patients, a defibrillation safety margin of 3 J above the acute ULV proved an adequate chronic safety margin.

Aged↗
PubMed1993

Predictors of defibrillation efficacy in patients undergoing epicardial defibrillator implantation. The Multicenter Pacemaker-Cardioverter-Defibrillator (PCD) Investigators Group.

OBJECTIVES: The objective of this study was to identify predictors of defibrillation threshold in patients undergoing epicardial defibrillator implantation. BACKGROUND: Factors that predict epicardial defibrillation efficacy are poorly defined. METHODS: The data from 375 consecutive adult patients were reviewed. After exclusion of 137 patients in whom defibrillation threshold was not obtained, 238 patients (32 women and 206 men) with a mean age of 58.9 +/- 13.3 years formed the study group. Coronary heart disease was present in 175 patients and the mean left ventricular ejection fraction was 35.8 +/- 15.4%. At device implantation, three epicardial patch sizes were available and shocks could be delivered over one current pathway (two patches) or over two current pathways (three patches with simultaneous or sequential shocks). Defibrillation threshold was defined as the lowest programmed energy that successfully defibrillated the heart, provided there had been an unsuccessful shock at a lower energy level or successful defibrillation at < or = 5 J. RESULTS: The mean defibrillation threshold was 8.6 +/- 5.3 J. With univariate analysis, female gender, sequential shocks with three patches, higher left ventricular ejection fraction and lower New York Heart Association functional class predicted a lower defibrillation threshold. In the multivariate analysis, female gender (coefficient -3.9; 95% confidence interval [CI] -1.9 to -5.0 J), ejection fraction (coefficient -0.6; CI -0.1 to -1.0 J/decile) and sequential shocks (coefficient -2.5; CI -1.0 to -4.0 J) were independently associated with a lower defibrillation threshold. Total epicardial patch conductive surface area normalized to body surface area reached borderline significance (coefficient 0.004; CI 0 to 0.01; p = 0.10). Antiarrhythmic drug use, including amiodarone, did not predict defibrillation threshold. CONCLUSIONS: Female gender, high left ventricular ejection fraction and the use of sequential pulse shocks were important determinants of improved defibrillation efficacy.

Aged↗
PubMed1996

[Limiting costs of implanted defibrillators].

The use of implanted defibrillators is increasing recently. In view of the costs of a gadget, which amount to DM 40,000 to 45,000, arises the questions which juridical requirement have to exist, that after the death of a patient it is possible to reuse a still functional defibrillator. The solution should be that the health insurance keeps the property, whereas the patient receives merely the defibrillator as loan.

Cost Savings↗
PubMed1980

The automatic implantable defibrillator.

The automatic implantable defibrillator is an electronic device programmed to monitor the cardiac rhythm continuously, to recognize ventricular fibrillation and ventricular tachyarrhythmias characterized by sinusoidal waveform, and to deliver corrective difibrillatory discharges when indicated. Three patients suffering from recurrent malignant ventricular arrhythmias refractory to medical therapy underwent permanent implantation of this device. Seven episodes of ventricular tachycardia and flutter-fibrillation were documented during the weeks following the implantations; two were induced at electrophysiologic studies and five occurred spontaneously. All were correctly identified and six were automatically reverted to normal sinus rhythm by the implanted device; one induced episode was cardioverted externally before the unit could recycle. Although many problems remain to be solved and the ultimate value of this therapeutic modality has to be determined, a new approach to prevention of sudden death in patients at high risk of developing lethal ventricular arrhythmias has become available.

Adolescent↗
PubMed1997

Rise in chronic defibrillation energy requirements necessitating implantable defibrillator lead system revision.

The chronic defibrillation energy requirement (DER) is believed to remain clinically stable in patients with defibrillators. Six patients (two with an epicardial and four with a nonthoracotomy system) were identified with a rise in their chronic DER, which eliminated a 10-J safety margin, thus necessitating a defibrillator lead system revision. The mean increase in DER was 14.7 +/- 4 J and was discovered at a mean of 16.0 +/- 18 months (range 2-41) following implantation. Management included placement of a defibrillator with a biphasic waveform, placement of an additional defibrillation electrode, or both. At 2 months following revision of the defibrillation system, a 10-J DER safety margin was present in each patient. In some patients, there is a progressive increase in the chronic DER with elimination of a 10-J safety margin necessitating revision of the defibrillation system. Routine reevaluation of the chronic DER, therefore, is necessary to identify these patients.

Aged↗
PubMed1988

Automatic implantable defibrillators.

The automatic implantable defibrillator was developed in the USA by Mirowski. This device automatically detects ventricular fibrillation or ventricular tachycardia and delivers a low energy (30 J) shock directly to the myocardium via patch electrodes on the epicardial surface or through a combination of a pericardial patch and an endocardial wire. These devices are being implanted in large numbers in the USA and represent a major contribution to the management and refractory ventricular arrhythmias. Unfortunately their high cost has limited their use in this country despite impressive clinical results.

Electric Countershock↗
PubMed1989

Nursing care for patients with implantable defibrillators.

Patients with implantable defibrillators are a new patient population that presents challenging issues and concerns. The size of this population will increase as the device's availability increases and design improvements are made that widen its applicability. These protocols have evolved during our first year with these patients and will doubtless change as we accrue experience in assisting patients to assume the role of being their own most important healthcare manager.

Arrhythmias, Cardiac↗
PubMed1990

An analysis of the cost effectiveness of the implantable defibrillator.

The automatic implantable defibrillator has been shown to decrease the mortality of patients who have survived cardiac arrest due to ventricular tachycardia or fibrillation and are at high risk for recurrence. We performed a cost-effectiveness analysis of this seemingly expensive new technology with data obtained from the 1984 Medicare data base, the medical literature, Medicare carriers, individual pharmacies and hospitals, and expert opinion. Analyzing combinations of principal and secondary discharge diagnoses across 18 diagnosis-related groups, we estimated the cost of hospitalization for a comparison group of patients. Hospitalization costs for the defibrillator group were obtained from reported empirical data. Rehospitalization rates and other health-care use estimates were solicited from an expert panel of physicians, and mortality rates for both groups were obtained from the literature. Using a decision-analytic model, we estimated that the net cost effectiveness of the defibrillator, when used in the high-risk patient, is approximately $17,100 per life-year saved, with sensitivity analyses suggesting that the true value lies between $15,000 and $25,000. This estimate is well within the range that is currently accepted by the US medical care system for other life-saving interventions. We also estimated the cost effectiveness of the defibrillator in a 1991 scenario to be $7,400 per life-year saved, when the device would have greater longevity, would be programmable, and would not require a thoracotomy. Sensitivity analyses suggest that the true value lies between a value that is cost saving (less expensive than pharmacologic therapy) and $19,600 per life-year saved.

Arrhythmias, Cardiac↗
PubMedDate not supplied

The automatic implantable defibrillator.

The automatic implantable defibrillator is undergoing clinical trials in the United States. The device is a self-contained unit designed to detect malignant ventricular arrhythmias as they occur and to terminate them with a defibrillating current. Early clinical trials demonstrate its safety and effectiveness in terminating ventricular tachyarrythmias as well as its ability to reduce markedly the incidence of sudden cardiac death in high-risk patients. Continued refinements should further improve reliability and safety of the device.

Clinical Trials as Topic↗
PubMed2000

Canadian implantable defibrillator study (CIDS) : a randomized trial of the implantable cardioverter defibrillator against amiodarone.

BACKGROUND: Patients surviving ventricular fibrillation (VF) or sustained ventricular tachycardia (VT) are at a high risk of death due to a recurrence of arrhythmia. The implantable cardioverter defibrillator (ICD) terminates VT or VF, but it is not known whether this device prolongs life in these patients compared with medical therapy with amiodarone. METHODS AND RESULTS: A total of 659 patients with resuscitated VF or VT or with unmonitored syncope were randomly assigned to treatment with the ICD or with amiodarone. The primary outcome measure was all-cause mortality, and the secondary outcome was arrhythmic death. A total of 328 patients were randomized to receive an ICD. A thoracotomy was done in 33, no ICD was implanted in 18, and the rest had a nonthoracotomy ICD. All 331 patients randomized to amiodarone received it initially. At 5 years, 85.4% of patients assigned to amiodarone were still receiving it at a mean dose of 255 mg/day, 28.1% of ICD patients were also receiving amiodarone, and 21.4% of amiodarone patients had received an ICD. A nonsignificant reduction in the risk of death was observed with the ICD, from 10.2% per year to 8.3% per year (19.7% relative risk reduction; 95% confidence interval, -7.7% to 40%; P=0.142). A nonsignificant reduction in the risk of arrhythmic death was observed, from 4.5% per year to 3.0% per year (32.8% relative risk reduction; 95% confidence interval, -7.2% to 57.8%; P=0.094). CONCLUSIONS: A 20% relative risk reduction occurred in all-cause mortality and a 33% reduction occurred in arrhythmic mortality with ICD therapy compared with amiodarone; this reduction did not reach statistical significance.

Aged↗
PubMed2006

Predictors of appropriate defibrillator therapy among patients with an implantable defibrillator that delivers cardiac resynchronization therapy.

INTRODUCTION: The purpose of this study was to determine predictors of appropriate implantable defibrillator (ICD) therapy among patients with heart failure who are treated with a cardiac resynchronization therapy-defibrillator (CRT-D). METHODS AND RESULTS: Patients enrolled in the Ventak CHF/Contak CD study were treated with a CRT-D device and were required to have NYHA class II-IV CHF, QRS duration > or = 120 msec, and a class I or II indication for an ICD. The study database was retrospectively analyzed during the 6-month postimplant period to identify predictors of appropriate ICD therapy. Five hundred and one of the 581 patients enrolled in the trial had successful device implantation and were included in this analysis. Patients were mostly male (83%), 66 +/- 11 years old, and had coronary artery disease (69%), a mean left ventricular ejection fraction (EF) = 0.22 +/- 0.07, and NYHA class II (33%), III (58%), or IV (9%) CHF symptoms. During 6 months of follow-up, 73 of 501 (14%) patients received an appropriate ICD therapy. Two independent predictors of appropriate therapy were identified: a history of a spontaneous, sustained ventricular arrhythmia (HR = 2.05; 95% CI = 1.31-3.20; P = 0.002) and NYHA class IV CHF (HR = 1.81; 95% CI = 1.10-2.96; P = 0.019). When patients with NYHA class II were excluded from analysis, a history of a sustained ventricular arrhythmia and the presence of NYHA class IV CHF symptoms remained as independent predictors of appropriate ICD therapy. CONCLUSIONS: In a select population of advanced heart failure patients receiving a CRT-D, NYHA class IV CHF was a powerful independent predictor of appropriate ICD therapy. Approximately one-quarter of the patients with NYHA class IV CHF who received a CRT-D device received an appropriate ICD therapy within 3 months after implant. Additional studies are needed to confirm an association between class IV CHF symptoms and an increased frequency of ICD shocks.

Aged↗