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PubMed2004

Analysis of mortality events in the Multicenter Automatic Defibrillator Implantation Trial (MADIT-II).

OBJECTIVES: The purpose of this study was to determine the efficacy of implantable cardiac defibrillator (ICD) therapy in preventing sudden cardiac death (SCD) in post-infarction patients with advanced left ventricular (LV) dysfunction. BACKGROUND: The Multicenter Automatic Defibrillator Implantation Trial (MADIT-II) randomized 1,232 post-infarction patients with an ejection fraction of < or =30% to ICD or conventional therapy. In the ICD group, there was a 31% decrease in the risk of total mortality. However, a better understanding of the mode of death is desirable in order to refine therapeutic interventions in high-risk populations. METHODS: We evaluated the 202 deaths, using a variation of the Hinkle-Thaler classification system as well as a clinical classification system to determine the incidence of SCD and the incidence of cardiac death due to progressive LV failure. RESULTS: The SCD rates were 10.0% in the conventional group and 3.8% in the ICD group (p < 0.01). The hazard ratio for the risk of SCD in the ICD group compared with the conventional therapy group was 0.33 (95% confidence interval 0.20 to 0.53, p < 0.0001). The ICD had no meaningful effect on non-sudden death (p = 0.32). The effect of defibrillator therapy in reducing SCD was similar in subgroup analyses stratified according to relevant baseline characteristics. CONCLUSIONS: The decrease in mortality with ICD therapy in MADIT-II is entirely due to a reduction in SCD, with similar reductions in SCD in a spectrum of subgroups stratified according to relevant baseline characteristics.

Aged↗
PubMed2004

Susceptibility of automated external defibrillators to train overhead lines and metro third rails.

INTRODUCTION: Immediate accessibility to automated external defibrillators (AED) is recommended for highly frequented public areas. In train terminals and metro stations electromagnetic interference (EMI) is present. In preparation for a public access defibrillation (PAD) programme in this environment possible effects on AED safety and accuracy were studied. METHODS: In typical public transportation settings 11 different AED models were bench tested for their sensitivity and specificity of ECG analysis with shockable and nonshockable rhythms provided by an ECG simulator. The devices were exposed to the electromagnetic interference of a rail system operating with 15 kV alternating current (ac) with a frequency of 16 2/3 Hz and a subway system powered with 750 V direct current (dc). AED cables were setup parallel and perpendicular to the tracks, the tests were carried out at 3 m distance from the rails in an empty station and with incoming trains. RESULTS: A total of 5280 tests were recorded, each device was tested a total of 480 times. Fifteen kilovolts 16 2/3 Hz ac interfered more than 750 V dc with the tachyarrhythmia detection systems (P < 0.0001). An AED setup with electrode cables perpendicular to track and power line reduced interference (P < 0.0001), while incoming trains had no significant effect on ECG analysis (P = 0.19). Depending on the AED model, sensitivity ranged from 60 to 100% and specificity from 54 to 100%, representing a positive likelihood-ratio from 1.3 to 241 and a negative likelihood-ratio from 0.7 to 0.0. In the public transportation setting tested, four AED models were unsuitable for automated defibrillation as these devices demonstrated an unacceptable performance in respect of accuracy and safety. In the train setting two devices performed with an accuracy of 57 and 65%. One AED recommended shocks for sinus rhythm at normal frequency. In the metro setting one AED did not advise shocks for ventricular tachycardia. CONCLUSION: Shock advisory systems of some AED models are susceptible to electromagnetic interference, especially in terminals with 15 kV 16 2/3 Hz ac power supplies. Interference is minimized, if patient position is parallel and electrode cables are perpendicular to overhead line. The choice of AED model for train or metro stations depends on its lack of susceptibility to typical electromagnetic interference.

Defibrillators↗
PubMed2005

Localization of out-of-hospital cardiac arrest in Goteborg 1994-2002 and implications for public access defibrillation.

PURPOSE: The purpose of this study was to report the locality of out-of-hospital cardiac arrest (OHCA) in the city of Goteborg and to identify implications for public access defibrillation (PAD). METHODS: Ambulance run reports for the years 1994-2002 were studied retrospectively and manually to establish the location of the cardiac arrest. RESULTS: The location could be identified in 2194 of 2197 patients (99.9%). One thousand four hundred and twenty-nine (65%) of the arrests took place in the victims' homes. Two hundred eighty-five (13%) were outdoors and 57 (3%) in cars. Fifty-one (2%) took place en route in ambulances. These arrests were regarded not to be generally suitable for PAD. One hundred thirty-five (6%) of the arrests happened in a public building. Eighteen of these 135 were in 15 different general practitioners' offices. A ferry terminal had 11 cardiac arrests. One hundred fifty (7%) of the arrests took place in different care facilities. Twenty-one (1%) patients had their cardiac arrest in public transport locations. Twenty-two (1%) patients arrested at work in 20 different sites. In total, 17% of the cardiac arrests were regarded as generally suitable for PAD. Several sites with more than one cardiac arrest in five years could be identified and 54 patients (2.5%) had their cardiac arrest in these high-incidence sites. CONCLUSION: Among patients suffering from out-of-hospital cardiac arrest in Goteborg in whom resuscitation efforts were attempted 17% of all cardiac arrests were regarded as generally suitable for PAD. According to previous suggestions, the indication for public access defibrillation is in a place with a reasonable probability of use of one AED in 5 years. Several high-incidence sites that probably would benefit from defibrillator availability could be identified, and 54 patients (2.5%) arrested in these sites.

Defibrillators↗
PubMed2005

Out-of-hospital cardiac arrest rectilinear biphasic to monophasic damped sine defibrillation waveforms with advanced life support intervention trial (ORBIT).

BACKGROUND: Although biphasic defibrillation waveforms appear to be superior to monophasic waveforms in terminating VF, their relative benefits in out-of-hospital resuscitation are incompletely understood. Prior comparisons of defibrillation waveform efficacy in out-of-hospital cardiac arrest (OHCA) are confined to patients presenting in a shockable rhythm and resuscitated by first responder (basic life support). This effectiveness study compared monophasic and biphasic defibrillation waveform for conversion of ventricular arrhythmias in all OHCA treated with advance life support (ALS). METHODS AND RESULTS: This prospective randomized controlled trial compared the rectilinear biphasic (RLB) waveform with the monophasic damped sine (MDS) waveform, using step-up energy levels. The study enrolled OHCA patients requiring at least one shock delivered by ALS providers, regardless of initial presenting rhythm. Shock success was defined as conversion at 5s to organized rhythm after one to three escalating shocks. We report efficacy results for the cohort of patients treated by ALS paramedics who presented with an initially shockable rhythm who had not received a shock from a first responder (MDS: n=83; RLB: n=86). Shock success within the first three ascending energy shocks for RLB (120, 150, 200J) was superior to MDS (200, 300, 360J) for patients initially presenting in a shockable rhythm (52% versus 34%, p=0.01). First shock conversion was 23% and12%, for RLB and MDS, respectively (p=0.07). There were no significant differences in return of spontaneous circulation (47% versus 47%), survival to 24h (31% versus 27%), and survival to discharge (9% versus 7%). Mean 24h survival rates of bystander witnessed events showed differences between waveforms in the early circulatory phase at 4-10 min post event (mean (S.D.) RLB 0.45 (0.07) versus MDS 0.31 (0.06), p=0.0002) and demonstrated decline as time to first shock increased to 20 min. CONCLUSION: Shock success to an organized rhythm comparing step-up protocol for energy settings demonstrated the RLB waveform was superior to MDS in ALS treatment of OHCA. Survival rates for both waveforms are consistent with current theories on the circulatory and metabolic phases of out-of-hospital cardiac arrest.

Adult↗
PubMed2006

In-hospital cardiac resuscitation outside the ICU by nursing staff equipped with automated external defibrillators--the first 500 cases.

BACKGROUND: Since nursing staff in the hospital are frequently the first to witness a cardiac arrest, they may play a central role in the effective management of in-hospital cardiac arrest. In this retrospective study the first 500 in-hospital cardiac arrests in non-monitored areas, which were treated initially by nursing staff equipped with automated external defibrillators (AEDs) are reported. METHODS AND RESULTS: Between April 2001 and December 2004, 500 in-hospital cardiac arrest calls were made: there were false arrests in 61 patients, so a total of 439 patients (88%) were evaluated using the Utstein style of data collection. ROSC occurred in 256 patients (58%), 125 (28%) were discharged from hospital and 95 (22%) were still alive 6 months after discharge. Among the 73 patients with VF/VT 63 (86%) had ROSC, 34 (47%) were discharged from hospital and 28 (38%) were alive after 6 months. The chance of survival was not influenced by the time between the call of the arrest team and the 1st defibrillation but was slightly higher with physicians as in-hospital first responders (p=0.078). In contrast, 366 patients with non-VF/VT, 193 (53%) had ROSC, but only 91 (25%) were discharged from hospital and 67 (18%) were alive after 6 months. The risk of dying was significantly higher in patients with non-VF/VT (p<0.001), and there was a trend to a higher risk ratio in patients older than 65 years and in patients with non-witnessed cardiac arrest (p=0.056 and 0.079, respectively). CONCLUSION: This observational study supports the concept of hospital-wide first responder resuscitation performed by nursing staff before the arrival of the CPR-team. Among these patients survival rate was higher in those with VF/VT defibrillated at an early stage. Consequently, it may be assumed that patients may die unnecessarily due to sudden cardiac arrest if proper in-hospital resuscitation programmes are not available.

Aged↗
PubMed2003

Use of antiarrhythmics and implantable cardioverter-defibrillators in congestive heart failure.

As much as half of the mortality in patients with congestive heart failure (CHF) resulting from left ventricular systolic dysfunction is attributable to sudden cardiac death. Thus, the identification of risk and prevention of sudden death are important components of treating this population of patients. Antiarrhythmic drugs have been shown to be either neutral or harmful when studied in patients with prior myocardial infarction and impaired left ventricular function. Amiodarone, when studied in patients with CHF, may be of benefit. This benefit may be more pronounced in patients with nonischemic cardiomyopathy. Implantable cardioverter defibrillators (ICDs) are of clear benefit when used in the primary and secondary prevention of sudden death in selected populations. Studies soon to be completed should clarify the role of the cardioverter-defibrillator in patients with CHF. Antiarrhythmic medications are often used in conjunction with ICDs for a variety of reasons. However, these drugs have the potential to adversely affect defibrillator function, and knowledge of these effects is important when using this strategy.

Anti-Arrhythmia Agents↗
PubMed1996

Sensing lead-related complications in patients with transvenous implantable cardioverter-defibrillators.

The widespread use of the redesigned Endotak lead (CPI, St. Paul, Minnesota), which combines transvenous pacing, sensing, and defibrillation on a single transvenous lead in patients receiving transvenous implantable cardioverter-defibrillators (ICDs), has reduced morbidity and shortened length of hospital stay after ICD implantation. We describe the incidence and management of Endotak sensing lead-related failures in a series of 348 consecutive patients from 4 institutions who underwent implantation between 1990 and 1995. We retrospectively reviewed the databases for patients receiving an ICD with an Endotak lead for the incidence of lead-related sensing abnormalities. Ten patients (2.8%) with lead-related sensing abnormalities were detected at a mean of 15 +/- 11 months after ICD implantation. Sensing abnormalities were detected in 6 patients after they received inappropriate shocks. Noise or oversensing was noted in 7 patients from interrogation of the devices' data logs. Eight patients had a new transvenous sensing lead placed, 1 patient had a new Endotak lead placed, and 1 had a chronic pacemaker sensing lead converted to function as a sensing lead. No further sensing problems were noted in 8 of 10 patients during a mean follow-up of 14 +/- 8 months. The site of the sensing lead failure was localized to the subrectus pocket in 5 patients and to the clavicle-first rib area in 3 patients; it was undetermined and presumed to be in the clavicle-first rib area in the other 2 patients. One patient had late failure of the defibrillation lead. We conclude that Endotak sensing lead failure does not require insertion of a new Endotak lead, but can be managed with close follow-up and insertion of a new transvenous sensing lead. Endotak lead fractures are frequently localized to the ICD pocket.

Aged↗
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↗
PubMed1997

Clinical predictors of transvenous defibrillation energy requirements.

Nonthoracotomy and, more recently, transvenous lead systems have become routine for initial implantable cardioverter-defibrillator (ICD) placement. Previous studies of clinical predictors of nonthoracotomy defibrillation energy requirements evaluated multiple complex lead systems that included subcutaneous patches. However, the predictors of an adequate transvenous defibrillation threshold (DFT) have not been assessed previously. Accordingly, the present study is a prospective evaluation of DFT using a uniform testing protocol in 119 consecutive patients undergoing ICD implantation with a single transvenous lead. For each patient, 38 parameters were assessed including standard clinical, echocardiographic, and radiographic measures. An adequate monophasic DFT (< or =20 J) was achieved in 76% of patients. Multivariable analysis revealed 3 independent factors predictive of a high threshold: preoperative amiodarone use (odds ratio = 5.8, p < or =0.002), echocardiographic measures of left ventricular dilation (odds ratio = 0.47, p < or =0.005) and body size (odds ratio = 0.51, p < or =0.006). Patients receiving amiodarone who also had left ventricular dilation constitute a group at considerable (69%) risk for having a high DFT. In contrast, patients with neither of these risk factors have only an 11% chance of having a high threshold. We conclude that an adequate transvenous DFT can be predicted from simple clinical parameters.

Amiodarone↗
PubMed1997

Clinical predictors of defibrillation energy requirements.

In implantable cardioverter-defibrillator therapy with endocardial lead systems, certain clinical variables are associated with defibrillation energy requirements. Because of the weak correlation coefficients, these variables cannot predict defibrillation thresholds in individual patients.

Age Factors↗
PubMed1997

Clinical predictors of transvenous biphasic defibrillation thresholds.

Transvenous lead systems have become routine for defibrillator placement. However, previous studies of clinical predictors of an adequate nonthoracotomy defibrillation threshold (DFT) evaluated monophasic waveforms or more complex lead systems, including subcutaneous patches. Accordingly, this study is a prospective evaluation of the predictors of an adequate biphasic DFT in 114 consecutive patients undergoing cardioverter-defibrillator implantation with a single transvenous lead. For each subject, 38 parameters were assessed, including standard demographic, electrocardiographic, echocardiographic, and radiographic measurements. An adequate DFT (< or =20 J) was achieved in 92% of patients. Multivariable analysis revealed 2 independent factors predictive of a high threshold: echocardiographic measurements of left ventricular dilation (odds ratio = 0.16, 95% confidence interval 0.05 to 0.53, p = 0.003) and body size (odds ratio = 0.36, 95% confidence interval 0.17 to 0.73; p = 0.005). No patient with a normal left ventricular end-diastolic dimension had a high DFT, whereas 14% (9 of 66) of those with left ventricular dilation had elevated thresholds. When the DFT cutoff was lowered to 15 J, as is necessary with some downsized pulse generators, an adequate threshold was observed in 84% of patients and the same 2 independent predictors of high thresholds were found. These results indicate that an adequate transvenous DFT can be predicted from simple clinical parameters.

Aged↗
PubMed1999

Use of the prophylactic implantable cardioverter defibrillator for patients with normal hearts.

About 10-20% of patients dying suddenly and unexpectedly do not have structural heart disease. The major causes of sudden death in this population are acute ischemia, the syndrome of right bundle branch block, and ST-elevation from V1 to V3, the long QT-syndrome, and the Wolff-Parkinson-While syndrome. In some patients, none of these syndromes can be recognized and ventricular fibrillation is classified as idiopathic. There are good preventive and therapeutic methods against acute ischemia and there are also curative treatments for the Wolff-Parkinson-White syndrome. Patients with idiopathic ventricular fibrillation cannot be recognized beforehand. However, there are electrocardiographic and genetic markers for the Brugada syndrome and the long QT syndrome. It is, therefore, justified to discuss the possible role of the prophylactic defibrillator to prevent sudden death in these 2 syndromes for which no effective treatment exists. Patients with Brugada syndrome have a high incidence of sudden death, and prophylactic defibrillators are indicated in patients with inducible arrhythmias at electrophysiologic study, irrespective of symptoms. On the contrary, the incidence of sudden death in the long QT syndrome is very low, making prophylactic defibrillator implantation not cost-effective.

Bundle-Branch Block↗
PubMed2000

Effect of ethanol on defibrillation energy requirements in humans.

The purpose of this double-blind study was to determine the effect of intravenous ethanol administration on defibrillation efficacy in 18 patients with an implantable defibrillator. The equivalent of 60 ml of 100 proof ethanol did not impair defibrillation efficacy.

Aged↗
PubMed2001

Implantable cardioverter defibrillator patch erosion in a heart transplant patient.

A 57-year-old man who had received an automatic implantable cardioverter defibrillator and subsequent orthotopic heart transplant presented to medical attention for hemoptysis. The hemoptysis was caused by the migration of the left ventricular patch of the automatic implantable cardioverter defibrillator, which had been left in place at the time of orthotopic heart transplant. The patch had eroded into the left lung. We recommend that implantable cardioverter defibrillators be removed completely at the time of heart transplantation to prevent subsequent complications.

Defibrillators, Implantable↗
PubMed1999

Pectoral implantation of single-lead implantable cardioverter-defibrillators in patients without transvenous access.

With the introduction of the single-lead "Active-Can" implantable cardioverter-defibrillators, the implantation of the internal defibrillators has become a technically easy procedure. With these systems lowest defibrillation thresholds are achieved with a very low complication rate. For patients with thrombosis of both subclavian veins, however, a transvenous implantation technique is not possible. These patients are still equipped with epicardial patch electrodes. This article describes an alternative technique for implantation of this system in such patients, eliminating the need for epicardial patches and related complications.

Defibrillators, Implantable↗
PubMed1995

Radiological appearances of implantable defibrillator systems.

Implantable defibrillator systems have been used in over 20,000 patients worldwide. Such systems use a variety of different electrodes and the identification of these and the recognition of associated problems with them presents a challenge to the radiologist. The appearance of currently available implantable defibrillation systems and the use of radiological examination in patient follow-up and system troubleshooting is discussed based on our experience with a large population of patients receiving these devices. Radiological examination is excellent for demonstrating displacement of distortion of defibrillation electrodes, but in our experience is ineffective for the identification of lead conductor fractures.

Defibrillators, Implantable↗
PubMed2001

The implantable cardioverter defibrillator.

Implantable cardioverter defibrillators (ICDs) have evolved from the treatment of last resort to the gold standard therapy for patients at high risk for ventricular tachyarrhythmias. High-risk patients include those who have survived life-threatening arrhythmias, and individuals with cardiac diseases who are at risk for such arrhythmias, but are symptomless. Use of an ICD will affect the patient's quality of life. Some drugs can substantially affect defibrillator function and efficacy, and possible drug-device interactions should be considered. Patients with ICDs may encounter cell phones, antitheft detectors, and many other sources of potential electromagnetic Interference. In addition to treating ventricular tachyarrhythmias, new defibrillators provide full featured dual chamber pacing, and could treat atrial arrhythmias, and congestive heart failure by means of biventricular pacing.

Arrhythmias, Cardiac↗
PubMed2003

Echocardiographic changes and predictors of arrhythmia recurrence after long-term use of the atrial defibrillator.

BACKGROUND: The patient-activated atrial defibrillator allows patients to cardiovert themselves from atrial fibrillation soon after the onset of symptoms. The long-term effects of early cardioversion from persistent atrial fibrillation on left ventricular performance and left atrial size are unknown. METHODS: Eighteen patients, mean age 63.4, 83% male, had the Jewel((R)) AF atrial defibrillator implanted for persistent atrial fibrillation only. Transthoracic echocardiography was performed 3-monthly following implant. Parasternal long axis measurements were taken using conventional M-mode techniques. RESULTS: Over follow-up of 28.0+/-9 months, 377 episodes of persistent atrial fibrillation were terminated by patient-activated cardioversion (median 15 per patient). Echocardiographic measurements at implant were; left atrium 44+/-6 mm, left ventricular end-diastolic diameter 49+/-7 mm, left ventricular end-systolic diameter 34+/-7 mm, fractional shortening 33+/-10% and ejection fraction 65+/-17%. After 1 year there had been a significant decrease in mean left atrial size to 41+/-6 mm (P=0.02) and an increase in mean ejection fraction to 73+/-8% (P=0.04). At long-term follow-up however, all parameters reverted to pre-implant levels. Baseline echocardiographic variables did not predict which patients would demonstrate serial increases in sinus rhythm duration between shocks during long-term follow-up. Patients on antiarrhythmic drug therapy however were more likely to demonstrate "sinus rhythm begetting sinus rhythm". CONCLUSIONS: Use of the atrial defibrillator for spontaneous persistent atrial fibrillation is associated with a medium-term (1 year) reduction in left atrial size and an increase in ejection fraction. These changes were not maintained in the long-term. Synergistic therapy with antiarrhythmic drugs may prolong periods of sinus rhythm between arrhythmia recurrences.

Adult↗