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PubMed2005

The impact of catecholamines on defibrillation threshold in patients with implanted cardioverter defibrillators.

OBJECTIVES: To determine the effect of physiologic catecholamine concentrations on the defibrillation threshold (DFT) in patients with implanted cardioverter defibrillators. BACKGROUND: DFT is the minimum energy delivered by an implanted cardioverter defibrillator that successfully converts ventricular fibrillation. DFT testing is performed under conscious sedation. Since activities of daily living enhance sympathetic tone substantially over these nadir levels, it is important to explore the impact of catecholamines on DFT. METHODS: In this double-blind study, we determined DFT by the step-down method. Patients (n = 50) were stratified by beta-blocker use and then randomized to a 7-minute infusion of epinephrine, norepinephrine, or placebo. After study infusion, DFT testing was repeated. Changes in DFT with different study medications were compared. Subgroup analyses of the effects of catecholamines on DFT, based on beta-blocker use, were also performed. RESULTS: Norepinephrine reduced DFT from baseline measurements by 22.6% (P = 0.008). Neither epinephrine nor placebo impacted DFT (P = 0.999, P = 0.317, respectively). In the subgroup analyses, DFT was reduced with norepinephrine regardless of beta-blocker use, while epinephrine reduced DFT among those receiving beta-blockers. No change in DFT was observed in either of the placebo subgroups. CONCLUSIONS: Elevation of plasma norepinephrine concentrations reduces the DFT, while elevations in epinephrine had no effect. Norepinephrine seems to reduce DFT regardless of beta-blocker therapy but epinephrine's effects are beta-blocker dependent.

Adrenergic beta-Antagonists↗
PubMed1990

Correlation between the ventricular electrogram amplitude in sinus rhythm and in ventricular fibrillation.

During testing of implantable defibrillators, ability to sense ventricular fibrillation is assessed by observing electrograms and the emitted ECG interpretation channel during induced ventricular fibrillation. We hypothesized that ventricular electrogram amplitude in sinus rhythm could be used to predict the ventricular electrogram amplitude in ventricular fibrillation and serve as a first approximation of the "safety margin" for sensing ventricular fibrillation. We compared the peak-to-peak epicardial ventricular electrogram during sinus rhythm and ventricular fibrillation in 12 patients undergoing defibrillator implantation. The ventricular electrogram was recorded with an integrated bipolar lead and filtered at 10-50 Hz. Ventricular fibrillation was induced by alternating current and the ventricular electrogram measured from cessation of alternating current to the first countershock. The mean ventricular electrogram amplitude in sinus rhythm was 15.3 +/- 5.4 mV (range 7.1-25.5) and in 37 episodes of ventricular fibrillation was 8.3 +/- 3.6 mV (range 2.1-16.3). There was a significant relationship between the mean ventricular electrogram amplitude in sinus rhythm and in ventricular fibrillation (R = 0.7, P less than 0.001). There was wide variation among individuals in the decrease in the mean ventricular electrogram amplitude during ventricular fibrillation, with the ratio of mean ventricular electrogram in sinus rhythm to mean ventricular electrogram in ventricular fibrillation ranging from 0.29 to 1.05 (mean 0.55 +/- 0.20). This suggests that up to a fourfold decrease may be expected in the mean ventricular electrogram amplitude during ventricular fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1998

The effects of pneumothorax on defibrillation thresholds during pectoral implantation of an active can implantable cardioverter defibrillator.

Pneumothorax has previously been reported to increase defibrillation thresholds and lead impedance in monophasic systems. This article demonstrates a case using an active can system in which the lead impedance between the right ventricular defibrillation coil and the device improved from 70 omega with pneumothorax to 48 omega after resolution. The defibrillation threshold also improved from > 30 J to < or = 10 J after the pneumothorax had resolved. We conclude that acute pneumothorax can increase the transthoracic lead impedance and defibrillation thresholds; however, with resolution both parameters can return to acceptable levels with an active can system.

Aged↗
PubMed1995

[Cerebral ischemia during implantation of automatic defibrillators].

In order to study the influence of repetitive episodes of ventricular fibrillation (VF) during defibrillator implantation on the electrical activity of the brain, we performed an electroencephalographic (EEG) monitoring during implantation procedure in 18 patients. For defibrillation threshold testing 62 episodes of VF (1-6 episodes per patient) were induced. The mean duration of VF was 20 +/- 12 s; the mean duration of hypotension during an episode (defined as a mean arterial pressure of 50 mm Hg or less) was 33 +/- 16 s. EEG monitoring was performed using the International 10-20 System. The duration of cardiac arrest-related EEG alteration was assessed by an experienced neurologist and could be determined in 41 test-episodes; in 21 episodes analysis was not possible due to poor recordings. Ischemia-related EEG changes started 7.8 +/- 4.6 s after VF induction and lasted 64 +/- 49 s (range, 12-240). The duration of EEG alteration was significantly (p < .001) correlated with the duration of VF episodes (r = .71) and the associated hypotension (r = .82). With regard to patients the duration of ischemia related EEG changes also correlated significantly (p = .001) with the individual cumulative duration of VF (r = .85) and the associated hypotension (r = .88). In females EEG changes lasted longer than in males (p = .03); this finding, however, was only based on 2 women. Other clinical parameters, such as patient age, degree of congestive heart failure, left ventricular ejection fraction, stroke volume and cardiac index, the order of episodes within the testing sequence, and the time interval between episodes did not correlate with the duration of EEG alteration after VF induction. The duration of ischemia-related EEG alteration during VF episodes depends on the duration of cardiac arrest. In females EEG changes tended to last longer than in males, however, this finding has to be confirmed. An association with other clinical parameters has not been observed. Limitation of VF duration appears to be the most important factor to avoid prolonged cerebral ischemia.

Adult↗
PubMed1997

Ventricular tachycardia initiated by high energy cardioversion in a patient with an implantable cardioverter defibrillator.

A transvenous implantable cardioverter defibrillator (ICD) was implanted into a 58 year old woman with idiopathic dilated cardiomyopathy who had drug refractory monomorphic ventricular tachycardia (VT). Antitachycardia pacing failed to terminate the VT; termination was attempted at 24 J, which was above the defibrillation threshold. When cardioversion at 24 J was delivered, VT with a different morphology and slower rate was reproducibly initiated. At 3 J, however, the original VT was successfully terminated without initiation of the slower VT. A new VT may be induced by high energy cardioversion. This may be a manifestation of the proarrhythmic potential of ICDs.

Cardiomyopathy, Dilated↗
PubMed1999

Development of ventricular fibrillations with different characteristics in the local electrocardiogram: large and small amplitude of activation, and its implication for implantable cardioverter defibrillator treatment.

An implantable cardioverter defibrillator (ICD) was implanted in 2 patients with ventricular tachyarrhythmia related to old myocardial infarction, and defibrillation tests were attempted at the time of ICD implantation and at 2 or 4 weeks after the operation. Ventricular fibrillation (VF) was induced by T-wave shocks, but the amplitude of the ventricular electrogram was different in each VF. In most of the VFs with large ventricular electrograms, the local activity was appropriately detected. However, many undersensed beats were observed in other VFs that had fine ventricular electrograms and a longer time was needed before delivering the shock. The amplitude of the ventricular electrogram might be small in some cases of VF and this might result in undersensing and/or unsuccessful defibrillation. Close attention must be paid to the amplitude of ventricular activation in each VF to avoid possible difficulty in ICD therapy.

Aged↗
PubMed2003

Cardiac resynchronization and implantable cardioverter defibrillator therapy: preliminary results from the InSync Implantable Cardioverter Defibrillator Italian Registry.

The aim of this study was to evaluate ventricular arrhythmias occurring in recipients of the InSync ICD for the primary and secondary prevention of sudden death. The InSync ICD was implanted in 142 patients (128 men; mean age 65 +/- 10 years) with heart failure (mean NYHA functional Class 3.0 +/- 0.7) and wide QRS (mean 159 +/- 33 ms). The underlying etiology was ischemic in 55%, idiopathic in 33%, and valvular or hypertensive cardiomyopathy in 12% of patients. The numbers of arrhythmic episodes/100 patient-months was computed with their 95% CI, assuming a Poisson distribution. Implants were performed in 48 (34%) patients who did not have an ACC/AHA guidelines Class I indication for ICD therapy. A total of 104 patients were compliant for follow-up visits. During a 9-month median (range 0.1-24) follow-up of 104 compliant patients, 19 experienced a total of 94 ventricular arrhythmias, all successfully interrupted or self-terminated, with a median number of two separate episodes, corresponding to a rate of 10 episodes/100 person-month (95% CI 8-12). A rate of 12 episodes/100 person-months (95% CI 10-15) was measured in the subgroup of patients with ACC/AHA class I indications, versus two episodes/100 person-months (95% CI 1-5) in the remainder of the population. Among 12 deaths, 9 were due to heart failure, 1 to a non-cardiovascular cause, and 2 to unknown causes. The implantation of ICD in heart failure patients has been prominently extended to primary prevention. Patients without standard ICD indications experienced life-threatening arrhythmic events. The impact of ICD combined with cardiac resynchronization therapy on arrhythmic profile, mortality, and costs in this subgroup of patients need to be more precisely studied, with a particular focus on the various types of underlying heart disease.

Adult↗
PubMedDate not supplied

Value of microvolt T-wave alternans for predicting patients who would benefit from implantable cardioverter-defibrillator therapy.

Despite considerable progress in the management of coronary artery disease and dilated cardiomyopathy, a substantial proportion of patients remains at the risk of life-threatening arrhythmic events. The Multicenter Automatic Defibrillator Implantation II and Sudden Cardiac Death Heart Failure studies have conclusively demonstrated that prophylactic implantable cardioverter-defibrillator (ICD) therapy reduces mortality among subjects with ischemic and nonischemic cardiomyopathy but at the expense of potentially unnecessary ICD implantation in a large percentage of patients. Microvolt T-wave alternans (MTWA), with a negative predictive value greater than 90%, holds promise for selecting the patients who would likely and patients not likely to benefit from ICD implantation. Accurate identification of high-risk patients by noninvasive MTWA may allow for improved widespread screening for sudden death prevention in the general population.

Cardiomyopathy, Dilated↗
PubMed1996

Can implantable cardioverter-defibrillator therapy reduce healthcare costs?

This article presents a comparison of the costs and the cost effectiveness of defibrillator implantation in a hypothetical scenario for the years 1996-2000, with recently reported actual data from the Dutch prospective study over the years 1989-1993. Recently, technological advances in pulse generator and leads have revolutionized implantable cardioverter-defibrillator (ICD) therapy. Major advances include (1) transvenous single lead positioning and (2) tremendously reduced size, combined with prolonged longevity of the pulse generator. Both have simplified implantation technique and provided for superior effectiveness and lower costs. This suggests that a more favorable cost-effectiveness is to be expected. The study group reported here consisted of patients successfully resuscitated after cardiac arrest due to malignant ventricular tachyarrhythmias in the chronic stage of myocardial infarction. During a mean follow-up of 27 months, starting on the day of therapeutic decision making, total costs and the cost-effectiveness ratio were estimated. Actual data from the prospective study in 1989-1993 are compared with a hypothetical scenario for 1996-2000. Mortality and costs for hospitalization per day, per procedure, and per device are taken from the prospective study and equalized for both scenarios. Transthoracic lead positioning and abdominal implantation of a Ventak P (CPI) defibrillator with +/- 3 years longevity were characteristic of the recently completed prospective study. The hypothetical future scenario uses the Ventak Mini-2 with assumed 5 years longevity, implanted pectorally and connected to a single transvenous lead. Implantation will be carried out in the catheterization laboratory and as first-choice treatment. Due to prolonged longevity of the device and shorter hospitalization, a cost reduction of US $11,530 per patient is expected. Total costs per patient in the 1989-1993 prospective study in the (1) conventional arm (drugs first choice), (2) early ICD arm (ICD first choice), and (3) early ICD arm in the 1996-2000 study (ICD first choice) are $63,032, $56,067, and $44,537, respectively. The corresponding cost-effectiveness ratios are $87, $64, and $51 per day alive, respectively. Thus, it appears that modem ICD technology will be associated with an increasing reduction in healthcare costs, at least in selected patients. This reduction is associated with a more favorable cost-effectiveness ratio.

Cost Control↗
PubMed1999

Ventricular fibrillation with small amplitude of activation and its implications for implantable cardioverter defibrillator treatment.

An implantable cardioverter defibrillator (ICD) was implanted in a patient with ventricular fibrillation (VF) related to old myocardial infarction. During VF, amplitude of ventricular activation was small, and the ventricular sensitivity at 1.2 mV failed to detect several small ventricular activations. When the sensitivity was changed to 0.3 mV, both under- and oversensed beats occurred during VF, and at the ventricular sensitivity of 0.15 mV, the undersensed beats disappeared while oversensed beats markedly increased. Defibrillation test was repeated one and four weeks after the implantation, and these inappropriate beats were minimized at the ventricular sensitivity of 0.3 mV. We should pay attention to the amplitude of ventricular activation to avoid possible trouble in ICD therapy.

Aged↗
PubMed2001

Interactions between pacing and arrhythmia detection algorithms in the dual chamber implantable cardioverter defibrillator.

Dual chamber implantable cardioverter defibrillator (ICD) combines the possibility to detect and treat ventricular and atrial arrhythmias with the possibility of modern heart stimulation techniques. Advanced pacing algorithms together with extended arrhythmia detection capabilities can give rise to new types of device-device interactions. Some of the possible interactions are illustrated by four cases documented in four models of dual chamber ICDs. Functioning of new features in dual chamber devices is influenced by the fact that the pacemaker is not a separate device but a part of the ICD system and that both are being used in a patient with arrhythmia. Programming measures are suggested to optimize use of new pacing algorithms while maintaining correct arrhythmia detection.

Adult↗
PubMed2003

Role of transesophageal echocardiography in detecting implantable cardioverter defibrillator lead infection.

Implantable cardioverter defibrillator (ICD) lead infection is a rare condition with reported incidence of 0.2% to 16%. It usually presents with persistent bacteremia or fever of unknown origin and requires high clinical suspicion for diagnosis. Whenever ICD lead infection is suspected, transesophageal echocardiography is the diagnostic technique of choice for detection and characterization of the lesions. Lead infections are extremely difficult to manage conservatively and surgical removal of the entire defibrillator system is recommended along with antimicrobial therapy. We describe a case of recurrent staphylococci bacteremia due to an ICD lead infection in a patient with arrhythmogenic right ventricular dysplasia.

Adult↗
PubMed2006

The Rhythm ID Going Head to Head Trial (RIGHT): design of a randomized trial comparing competitive rhythm discrimination algorithms in implantable cardioverter defibrillators.

BACKGROUND: The implantable cardioverter defibrillator (ICD) has become primary therapy for the prevention of sudden death. One of the major morbidities of ICD use remains inappropriate therapy for supraventricular arrhythmias (SVA). Detection enhancements have increased therapy specificity, but their impact on inappropriate therapy is not well studied. Moreover, ICD manufacturers have developed unique algorithms to meet this goal, with no previous clinical direct comparisons. RIGHT is a randomized, prospective study that will assess the differential efficacy of ICDs from two different manufacturers. It is the first trial to compare directly competitive ICD rhythm discrimination algorithms on a large scale. OBJECTIVE: The primary objective of this study is to assess arrhythmia discrimination in Guidant versus Medtronic ICDs by comparing the time to first inappropriate therapy after the predischarge visit. METHODS: The study will enroll approximately 2,000 patients in 100 centers. Patients will be randomized to Guidant or Medtronic using a permuted block design, stratified by center and by single/dual chamber device types. Patients will receive a commercially available Guidant VITALITY 2 family ICD with Rhythm ID or a Medtronic ICD using the Enhanced PR Logic or Wavelet discrimination algorithms, and will be followed according to the schedule shown until a common closing date with a minimum follow-up of 12 months. All events will be reviewed by an independent committee to determine the appropriateness of rhythm classification and therapy delivery. CONCLUSION: RIGHT is the first randomized, large scale, head-to-head comparison of ICD discrimination algorithms.

Algorithms↗
PubMed2004

Placebo-controlled, randomized clinical trial of azimilide for prevention of ventricular tachyarrhythmias in patients with an implantable cardioverter defibrillator.

BACKGROUND: Although implanted cardioverter defibrillators (ICDs) effectively treat sustained ventricular tachyarrhythmias, up to 50% of ICD recipients eventually require concomitant antiarrhythmic drug therapy to prevent symptomatic arrhythmia recurrences and hence reduce the number of device therapies. METHODS AND RESULTS: A total of 633 ICD recipients were enrolled in a randomized, double-blind, placebo-controlled study to evaluate the effect of daily doses of 75 or 125 mg of azimilide on recurrent symptomatic ventricular tachyarrhythmias and ICD therapies. Total all-cause shocks plus symptomatic ventricular tachycardia (VT) terminated by antitachycardia pacing (ATP) were significantly reduced by azimilide, with relative risk reductions of 57% (hazard ratio [HR]=0.43, 95% CI 0.26 to 0.69, P=0.0006) and 47% (HR=0.53, 95% CI 0.34 to 0.83, P=0.0053) at 75- and 125-mg doses, respectively. The reductions in all-cause shocks with both doses of azimilide did not achieve statistical significance. The incidence of all appropriate ICD therapies (shocks or ATP-terminated VT) was reduced significantly among patients taking 75 mg of azimilide (HR=0.52, 95% CI 0.30 to 0.89, P=0.017) and those taking 125 mg of azimilide (HR=0.38, 95% CI 0.22 to 0.65, P=0.0004). Five patients in the azimilide groups and 1 patient in the placebo group had torsade de pointes; all were successfully treated by the device. One patient taking 75 mg of azimilide had severe but reversible neutropenia. CONCLUSIONS: Azimilide significantly reduced the recurrence of VT or ventricular fibrillation terminated by shocks or ATP in ICD patients, thereby reducing the burden of symptomatic ventricular tachyarrhythmia.

Anti-Arrhythmia Agents↗
PubMed1992

Elderly care. Automatic implantable cardioverter defibrillators.

The automatic implantable cardioverter defibrillators (AICD) is a commonly accepted treatment for an increasing number of elderly clients at high risk for ventricular dysrhythmias and sudden cardiac death. With increasingly successful use of AICDs, a unique group of gerontological patients has emerged with special physical, educational, psychosocial, and emotional needs. Gerontological nurses will encounter these clients in acute care settings as well as in home health care, nursing homes, senior citizen centers, and adult day health-care centers. Nurses need basic information about AICDs to plan for the continued care, teaching, guidance, and reassurance of these clients and their families.

Aged↗
PubMed2005

Psychosocial issues of patients with implantable cardioverter defibrillators.

Use of implantable cardioverter defibrillators has become standard therapy for patients at high risk for life-threatening ventricular arrhythmias. Although acceptance of the device is generally high among patients and their families, quality of life and psychosocial issues associated with use of the defibrillators deserve greater attention to improve outcomes. Psychosocial issues, their ramifications, and theory-and evidence-based approaches to improving outcomes are described.

Defibrillators, Implantable↗
PubMed2004

The effects of age on quality of life in implantable cardioverter defibrillator recipients.

BACKGROUND: The implantable cardioverter defibrillator shows superiority over conventional pharmacological therapy. The implantable cardioverter defibrillator has been implanted with increasing frequency in patients who are either at risk for or have experienced a life-threatening dysrhythmia. Implantable cardioverter defibrillator recipients experience a myriad of physical, emotional and social adjustments, with little being known about the impact of age on trajectory. AIMS, OBJECTIVES AND DESIGN: Therefore the purpose of the study is to examine the effects of age on health status, quality of life, and mood states of implantable cardioverter defibrillator recipients during the first year after implantation using a repeated measures design. METHODS: A comparison of implantable cardioverter defibrillator patients' scores with other samples, both ill and well, are discussed to see how the two implantable cardioverter defibrillator age groups compare on the various measures. Human subjects approval was obtained from the institutional review board. RESULTS: Seventy subjects, 51 males and 19 females, were recruited. There were 31 subjects between the ages of 21 and 62 years, mean age of 51 years, that comprised the younger age group, and 39 subjects between the ages of 67 and 84 years, mean age of 74 years, that comprised the older age group. Each subject completed the Medical Outcomes SF-36, the Ferrans and Powers Quality of Life Index, and the Profile of Moods States at time of implantable cardioverter defibrillator implantation, and 6 and 12 months later. CONCLUSIONS: The older age group was as expected less physically active, less satisfied with their physical functioning, and had slightly more anxiety at 6 and 12 months than the younger counterparts. The younger implantable cardioverter defibrillator recipients demonstrated some improvements over time in the perception of their physical adjustment and anxiety. RELEVANCE TO CLINICAL PRACTICE: Comparison of the SF-36 with other populations with or without a medical condition revealed scores below norms in physical health for both groups, and only slightly higher than patients with heart failure for the older group.

Activities of Daily Living↗