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PubMed1993

[Cardiac pacemakers and implantable cardioverter-defibrillators in the perioperative phase].

Recent developments have changed the techniques and indications for different methods of temporary cardiac pacing. Temporary transvenous pacing involves endocardial right ventricular stimulation by a bipolar electrode, introduced directly via a vein, or through a "paceport" pulmonary artery catheter. A "multipurpose" pulmonary artery catheter permits both atrial and ventricular sensing and pacing. Noninvasive transcutaneous cardiac pacing is safe, fast, and easily applicable. However, pain and discomfort from cutaneous nerve or muscle stimulation may be intolerable for unsedated patients. Transoesophageal cardiac pacing is usually successful only for atrial stimulation, e.g., in sinus node bradycardia, but is not indicated in patients with impaired AV-conduction. In patients with implanted pacemakers, temporary cardiac pacing can both impair or improve the haemodynamic situation. Implanted pacemakers should always be checked following surgery involving electrocautery. Preoperatively, rate-responsive pacemakers should be re-programmed so as to avoid activation of the rate-responsive function. Automatic implantable cardioverter-defibrillators should be deactivated to avoid delivery of inappropriate shocks. In patients with implanted epicardial patch electrodes, transthoracic defibrillation can be difficult with routine defibrillation protocols and may require positioning of the paddles on the lateral chest wall. However, emergency noninvasive transcutaneous cardiac pacing is possible in such patients with normal thresholds.

Arrhythmias, Cardiac↗
PubMed2003

Long-term outcomes of out-of-hospital cardiac arrest after successful early defibrillation.

BACKGROUND: Mortality after out-of-hospital cardiac arrest from ventricular fibrillation is high. Programs focusing on early defibrillation have improved the rate of survival to hospital discharge. We conducted a population-based analysis of the long-term outcome and quality of life of survivors. METHODS: All patients who had an out-of-hospital cardiac arrest between November 1990 and January 2001 who received early defibrillation for ventricular fibrillation in Olmsted County, Minnesota, were included. The survival rate was compared with that of an age-, sex-, and disease-matched (2:1) control population of residents who had not had an out-of-hospital cardiac arrest and with that of age- and sex-matched controls from the general U.S. population. The quality of life was assessed with use of the Medical Outcomes Study 36-item Short-Form General Health Survey (SF-36) and compared with U.S. population norms. RESULTS: Of 200 patients who presented with an out-of-hospital cardiac arrest with ventricular fibrillation, 145 (72 percent) survived to hospital admission (7 died in the emergency department) and 79 (40 percent) were neurologically intact (good overall capability or moderate overall disability) at discharge. The mean (+/-SD) length of follow-up was 4.8+/-3.0 years. Nineteen patients died after discharge from the hospital. The expected five-year survival rate (79 percent) was identical to that among age-, sex-, and disease-matched controls (P=0.68) but lower than that among the age- and sex-matched U.S. population (86 percent, P=0.02). Fifty patients completed SF-36 surveys at the end of follow-up, and the majority had a nearly normal quality of life, with the exception of reduced vitality. CONCLUSIONS: Long-term survival among patients who have undergone rapid defibrillation after out-of-hospital cardiac arrest is similar to that among age-, sex-, and disease-matched patients who did not have out-of-hospital cardiac arrest. The quality of life among the majority of survivors is similar to that of the general population.

Aged↗
PubMed2004

Public-access defibrillation and survival after out-of-hospital cardiac arrest.

BACKGROUND: The rate of survival after out-of-hospital cardiac arrest is low. It is not known whether this rate will increase if laypersons are trained to attempt defibrillation with the use of automated external defibrillators (AEDs). METHODS: We conducted a prospective, community-based, multicenter clinical trial in which we randomly assigned community units (e.g., shopping malls and apartment complexes) to a structured and monitored emergency-response system involving lay volunteers trained in cardiopulmonary resuscitation (CPR) alone or in CPR and the use of AEDs. The primary outcome was survival to hospital discharge. RESULTS: More than 19,000 volunteer responders from 993 community units in 24 North American regions participated. The two study groups had similar unit and volunteer characteristics. Patients with treated out-of-hospital cardiac arrest in the two groups were similar in age (mean, 69.8 years), proportion of men (67 percent), rate of cardiac arrest in a public location (70 percent), and rate of witnessed cardiac arrest (72 percent). No inappropriate shocks were delivered. There were more survivors to hospital discharge in the units assigned to have volunteers trained in CPR plus the use of AEDs (30 survivors among 128 arrests) than there were in the units assigned to have volunteers trained only in CPR (15 among 107; P=0.03; relative risk, 2.0; 95 percent confidence interval, 1.07 to 3.77); there were only 2 survivors in residential complexes. Functional status at hospital discharge did not differ between the two groups. CONCLUSIONS: Training and equipping volunteers to attempt early defibrillation within a structured response system can increase the number of survivors to hospital discharge after out-of-hospital cardiac arrest in public locations. Trained laypersons can use AEDs safely and effectively.

Adolescent↗
PubMedDate not supplied

Modelling transthoracic defibrillation waveforms.

Recent investigations connected with implantable defibrillators yielded new data on heart electrophysiology, resulting in reassessment of existing and advancing of new types of electrical impulses. Different electrical equivalent circuits were proposed for modelling intracardiac and transthoracic defibrillation pulse waveforms, comprising generator, electrode interface and tissue resistances. We attempted modelling of the transmembrane voltage Vm time course, induced by different applied voltage Vs waveforms, taking into account only the shapes and the relative Vs and Vm amplitudes. The excitable cell membrane impedance Zm was modelled with higher resistance and lower capacitance, so that a shunting effect on the generator and tissue resistances was avoided. The result was a very simple equivalent circuit. We proposed criteria for efficient defibrillation pulse waveforms yielding a straightforward approach to model existing and new pulses and to assess their efficiency.

Biomedical Engineering↗
PubMed1995

Superior vena cava syndrome after implantation of a transvenous cardioverter defibrillator.

Superior vena cava syndrome is a rare, but nevertheless well known complication of permanent pacemaker implantation. Nowadays cardioverter defibrillators are also routinely implanted transvenously. A superior vena cava syndrome occurred in a 48-year-old female 2 years after implantation of cardioverter defibrillator. The clinical problem, in the presence of a predisposing thrombophilic condition (circulating lupus anticoagulant), resolved only partially after treatment with thrombolytics and oral anticoagulation. This syndrome should be recognized as a possible important complication of defibrillator therapy and requires lifelong anticoagulation.

Defibrillators, Implantable↗
PubMed1995

Randomized comparison of aspirin and phenprocoumon for prevention of right-sided thromboembolic complications associated with transvenous defibrillation leads.

Death due to pulmonary embolism caused by thrombosis formation along a pacing wire has been reported in patients with antibradycardia pacemakers. The purpose of this prospective and randomized study was to evaluate the effects of prophylactically assigned aspirin (100 mg per day) or phenprocoumon (a coumarin derivative) on the incidence of right-sided thromboembolic complications associated with transvenous defibrillation leads. Multiplane transoesophageal echocardiography and pulmonary scintigraphy were performed in 62 consecutive patients immediately and 6 +/- 2 months after transvenous defibrillator implantation. Aspirin or phenprocoumon was administered to the patients in a randomized and parallel manner. By means of multiplane transoesophageal echocardiography and pulmonary scintigraphy no thromboembolic events were observed immediately after transvenous defibrillator implantation. After 6 +/- 2 months, however, multiplane transoesophageal echocardiography disclosed thrombi on the transvenous leads in 13 of 62 patients (21%) despite antithrombotic therapy. At the same time, pulmonary scintigraphy did not reveal any defects compatible with pulmonary embolism. Although thrombi occurred in only four patients treated with phenprocoumon, but in nine patients receiving aspirin, this difference was statistically insignificant. Other variables associated with the occurrence of thrombosis formation were not identified. One fatal intracranial haemorrhage occurred in the phenprocoumon group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

At what time are implantable defibrillator shocks delivered? Evidence for individual circadian variance in sudden cardiac death.

BACKGROUND: As in myocardial infarction and transient ischaemia, out-of-hospital sudden cardiac death has an increased morning incidence. However, sudden death occurring in hospital is evenly distributed over the 24 h period suggesting that there might be subgroups of patients with atypical circadian patterns of sudden death. Patients who received an implantable defibrillator constitute an ideal group for studies of circadian patterns of sudden death since this generation of devices are able to store the exact time when defibrillation occurred. METHODS: The distribution of sudden death aborted by the implantable defibrillator was analysed during the 24 h period for 87 presumed appropriate shocks delivered in a group of 22 patients, 18 men and four women, 58.7 +/- 11.9 years old and with a mean left ventricular ejection fraction of 39.4 +/- 17.6%. RESULTS: Each patient received an average of 4.42 +/- 3.04 shocks during a mean follow-up of 9.4 +/- 5.6 months. Apart from a clear tendency for shocks to occur during the morning hours (42% of total shocks), five of 16 patients who received multiple shocks also showed a trend to repeat the shocks around the same period during the day. CONCLUSION: Our results support the accepted view that changes in autonomic tone in the early morning play a role in the circadian variations of sudden death. Sudden death not only occurs more frequently in the morning hours, but it also clusters in certain periods for individual patients.

Adult↗
PubMed1993

Postoperative arrhythmias and the role for implantable cardioverter-defibrillators.

Arrhythmias are seen frequently in the early postoperative phase of coronary artery surgery. Ventricular ectopic beats and atrial fibrillation are the most common rhythm disturbances and they offer the greatest management challenges. Yet despite the lack of good clinical trial data, few new studies have been initiated and reported in recent years. Recent reviews have given a better picture of the epidemiology of atrial fibrillation, but as yet there is little of practical use for the clinician. Magnesium, which looks so promising in the treatment of patients with acute myocardial infarction, offers no preventative action against postoperative atrial fibrillation. Implantable cardioverter-defibrillators have brought a new "surgical" procedure to arrhythmia management, but with the development of transvenous systems, implantation of these devices may revert from the surgeon to the cardiologist. Implantable cardioverter-defibrillators have dramatically reduced interest in map-directed antiarrhythmic surgery, yet recent work suggests that abandoning such techniques would be inappropriate. Implantable cardioverter-defibrillators and map-guided surgery must evolve together; neither can replace the other.

Anti-Arrhythmia Agents↗
PubMed1998

A review of the implantable cardioverter defibrillator trials.

Clinical ventricular tachycardia and ventricular fibrillation are associated with a high recurrence rate, and through the 1980s and the early 1990s a variety of therapies have been proposed including the implantable cardioverter defibrillator (ICD). Over the past decade it has been recognized that prospective randomized trials are imperative if the proper role for any therapy is to be defined. The Antiarrhythmic Versus Implantable Defibrillator (AVID) trial recently was concluded and helped define the role of the ICD in high-risk patients. Other trials are studying patients at high risk for sudden death who have not yet had a clinical event. The recently concluded Multicenter Automatic Defibrillator Implantation Trial and CABG Patch Trial helped determine the proper role of the ICD in various pre-event high-risk subsets. These trials are summarized in detail.

Arrhythmias, Cardiac↗
PubMed2001

Use of implantable pacemakers and implantable defibrillators in hypertrophic cardiomyopathy.

Recent data have emerged to help guide the use of implantable pacemakers and implantable defibrillators in patients who have hypertrophic cardiomyopathy (HCM). Controlled studies of the use of dual chamber pacemakers to treat outflow tract obstruction in HCM have shown little benefit, and have raised the possibility that earlier favorable reports were demonstrating an element of placebo effect. In particular, there is no recent support for earlier claims of regression of ventricular hypertrophy from chronic dual chamber pacing. Several reports have added to our understanding of the risk factors for sudden death in HCM. A normal blood pressure response to exercise appears to identify a subset of patients at low risk for sudden death. In a recent study of a large number of HCM patients, the risk of sudden death was found to be directly proportional to the extent of left ventricular hypertrophy. There is accumulating evidence that the implantable defibrillator is highly effective in terminating malignant ventricular arrhythmias in HCM patients, and HCM patients thought to be at significant risk for sudden death should be offered defibrillator implantation.

Arrhythmias, Cardiac↗
PubMed2004

Pacemaker and defibrillator lead extraction.

PURPOSE OF REVIEW: Continued growth in the elderly population and expanding indications have resulted in a progressive increase in the number of implants of pacemakers and defibrillators. Concomitant with these expanding numbers, more leads require removal, due especially to mechanical dysfunction, the need to upgrade to more complex devices, or local or systemic infection. Further, leads have become more complex, particularly for defibrillator systems, resulting in the development of powered extraction sheaths to expedite their removal. For these reasons, it is important to understand the expanding indications, procedural aspects, and limitations of arrhythmia device extraction. RECENT FINDINGS: Expanded indications for lead extraction include upgrade to more complex systems, particularly pacemaker to defibrillator or biventricular device, extraction through occluded vasculature to produce a conduit for reimplantation, more frequent removal due to vascular overload with multiple leads, and a finite frequency of infection, occurring particularly with device replacement or revision. Powered sheaths now include laser and electrocautery systems, both improving the ease of lead explantation. SUMMARY: Complication rates remain low but constant with extraction of larger numbers of leads using new technologies. Expansion of the use of biventricular systems, with implantation of coronary sinus electrodes, will continue to challenge lead extraction in terms of technology and safety. Design of leads that are easier to remove remains of paramount importance.

Arrhythmias, Cardiac↗
PubMed2004

Recent advances in pacemaker and implantable defibrillator therapy for young patients.

PURPOSE OF REVIEW: This review is intended to highlight major clinical advances over the past year related to (1). biventricular pacing as a treatment for dilated myopathy, (2). growing clinical experience with implantable cardioverter defibrillators in pediatrics, (3). technical advances in standard antibradycardia pacing, and (4). an appraisal of the newly updated ACC/AHA/NASPE guidelines for device implant in children and adolescents. RECENT FINDINGS: Complex rhythm devices are being used more frequently in children. Biventricular pacing to improve ventricular contractility is a rapidly evolving technology that has now been applied to children and young adults with intraventricular conduction delay, such as bundle branch block after cardiac surgery. Implantable defibrillators are also being used for an expanding list of conditions, although lead dysfunction is seen as a fairly common complication in active young patients. Guidelines for device implantation have been developed, but the weight of evidence remains somewhat limited by the paucity of pediatric data in this field. SUMMARY: Thanks to refinements in lead design and generator technology, coupled with rapidly expanding clinical indications, pacemakers and implantable defibrillators have become increasingly important components of cardiac therapy for young patients. Expanded multicenter clinical studies will be needed to develop more objective guidelines for use of this advanced technology.

Adolescent↗
PubMed2004

Assessment and management of patients with pacemakers and implantable cardioverter defibrillators.

OBJECTIVE: To review the design and function of pacemakers and implantable cardioverter defibrillators with particular attention to those aspects that are of clinical relevance to perioperative and critical care physicians. MAIN POINTS: Pacemakers and implantable cardioverter defibrillators are complex devices that interact with cardiac function in ways that can significantly influence hemodynamics. A basic appreciation of device technology is essential to understanding both the normal patterns of pacemaker and implantable cardioverter defibrillator usage and the ways in which iatrogenic influences may result in adverse outcomes. The most important concern for pacemaker patients who enter the hospital is exposure to electromagnetic interference. Exposure is mainly from surgical cautery, but other sources are also present. With awareness of these concerns and an understanding of how to prevent adverse interactions, it is possible to safely care for these patients in the critical care setting. Despite recommended precautions, undesirable outcomes may occur and the clinician must be prepared to intervene in an appropriate manner to prevent patient injury.

Critical Care↗
PubMed2006

Thoracic impedance changes measured via defibrillator pads can monitor ventilation in critically ill patients and during cardiopulmonary resuscitation.

OBJECTIVE: Monitoring of ventilation performance during cardiopulmonary resuscitation would be desirable to improve the quality of cardiopulmonary resuscitation. To investigate the potential for measuring ventilation rate and inspiration time, we calculated the correlation in waveform between transthoracic impedance measured via defibrillator pads and tidal volume given by a ventilator. DESIGN: Clinical study. SETTING: Emergency department of a tertiary care university hospital. PATIENTS: A convenience sample of mechanical ventilated patients (n = 32), cardiac arrest patients (n = 20), and patients after restoration of spontaneous circulation (n = 31) older than 18 were eligible. INTERVENTIONS: The Heartstart 4000SP defibrillator (Laerdal Medical Cooperation, Stavanger, Norway) with additional capabilities of recording thoracic impedance changes was used. MEASUREMENTS AND MAIN RESULTS: The relationship between impedance change and tidal volume (impedance coefficient) was calculated. The mean (sd) correlations between the impedance waveform and the tidal volume waveform in the patient groups studied were .971 (.027), .969 (.032), and .967 (.035), respectively. The mean (sd) impedance coefficient for all patients in the study was .00194 (.0078) Omega/mL, and the mean (sd) specific (weight-corrected) impedance coefficient was .152 (.048) Omega/kg/mL. The measured thorax impedance change for different tidal volumes (400-1000 mL) was approximately linear. CONCLUSIONS: The impedance sensor of a defibrillator is accurate in identifying tidal volumes, when chest compressions are interrupted. This also allows quantifying ventilation rates and inspiration times. However this technology, at its present state, provides only limited practical means for exact tidal volume estimation.

Adult↗
PubMed2004

Implantable cardioverter defibrillator therapy in postinfarction patients.

PURPOSE OF REVIEW: In the past few years, new clinical trials were conducted to determine the effectiveness of implantable cardioverter defibrillators (ICDs) for prevention of mortality in patients with ischemic and nonischemic cardiomyopathies. This paper aims to provide an overview of the current state of knowledge regarding ICD therapy in postinfarction patients. RECENT FINDINGS: Postinfarction patients with severe left ventricular dysfunction are at high risk of sudden cardiac death. Antiarrhythmic therapy does not improve survival in such patients and, therefore, ICDs emerged as treatment of choice for both primary and secondary prevention of mortality after MI. The MADIT (Multicenter Automatic Defibrillator Implantation Trial) and MUSTT (Multicenter Unsustained Tachycardia Trial) trials were the first primary prevention ICD trials documenting a substantial reduction in mortality with an ICD in postinfarction patients with depressed ejection fraction, nonsustained ventricular tachycardia, and inducible sustained ventricular tachycardia. The recently completed MADIT II trial broadened indications for prophylactic use of ICD in postinfarction patients with ejection fraction of 30% or less without a requirement for additional risk stratifiers. The benefit from ICD therapy in patients with low ejection fraction was recently confirmed by results from the SCD-HeFT (Sudden Cardiac Death in Heart Failure) and COMPANION (Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure) trials. SUMMARY: Recent clinical trials established ICD as an important therapeutic modality for primary and secondary prevention of mortality in postinfarction patients.

Death, Sudden, Cardiac↗
PubMed2005

Sudden cardiac death in division I collegiate athletics: analysis of automated external defibrillator utilization in National Collegiate Athletic Association division I athletic programs.

OBJECTIVE: To determine current outcomes of automated external defibrillator (AED) interventions in sports medicine programs in National Collegiate Athletic Association (NCAA) division I athletics. DESIGN: Qualitative scripted telephone interview with all positive responders to prior NCAA division I-wide study on AED utilization and implementation. SETTING: NCAA division I sports medicine programs. Head athletic trainers were the main data source. PARTICIPANTS: All positive responders to a previously published study on AED implementation in the NCAA division I sports medicine community. Positive responders were those that indicated that they had used their departmental AEDs in a sudden cardiac death (SCD) scenario. MAIN OUTCOME MEASUREMENTS: Survival to hospital discharge was the main outcome sought. When available, additional outcomes were time to defibrillation, time to notification of athletic training staff, EMS response time, location of event, and sudden cardiac victim type (i.e., student, coach, fan). RESULTS: Sixteen departments that previously reported having had an SCD event at their institution responded to this follow-up telephone survey. Twenty percent of AED uses were attributed to student athletes, with 33% of utilizations for athletic department staff and 47% for fans. Defibrillation was actually administered in 53% of AED unit applications. Time to shock was an average of 3.4 minutes, with average EMS response time of 8.2 minutes for those events without EMS on site. Reported survival to hospital discharge in this university athletic department setting for SCD was 0% for students, 75% for staff, 57% for fans, and 61% overall. CONCLUSIONS: The results of this study demonstrate the need for NCAA division 1 athletic sports medicine programs to examine, and possibly expand, the traditional scope of practice of caring primarily for student athletes to include the larger community of sports participants comprised of athletes, departmental staff, and spectators. Athletic department AED programs were extremely successfully at increasing survival of SCD far above national prehospital standards, mainly in the nonathletic population. Further study is also necessary in the realm of AED placement, maintenance, and training of staff.

Chi-Square Distribution↗
PubMed2005

Ejection fraction and QRS width as predictors of event rates in patients with implantable cardioverter defibrillators.

OBJECTIVES: The Multicenter Automatic Defibrillator Implantation Trial II in 2002 recommended implantable cardioverter defibrillators (ICDs) prophylactically for all patients with a prior myocardial infarction and ejection fraction (EF) of 30% or less. In June of 2003, the Centers for Medicare and Medicaid Services approved reimbursement for ICD placement in patients with an EF of 30% or less who have a QRS interval greater than 120 ms. The purpose of this study was therefore to determine the value of QRS duration in predicting the occurrence of ventricular arrhythmias within the first year after ICD implantation. These ICDs were placed over the past 5 years for various indications. METHODS: EF cut points of 30% or less and 31% or greater and QRS duration of 120 ms or less and 121 ms or greater were used to assess the risk of events. RESULTS: There was a significant increase in events in subjects with EF of 30% or less, compared with patients with EF of 31% or greater (P < 0.05), and there was a trend toward increased likelihood of arrhythmias in patients with widened QRS width. CONCLUSIONS: This study confirms the conclusion of the Multicenter Automatic Defibrillator Implantation Trial II and implies that the Centers for Medicare and Medicaid Services criteria for reimbursement may not be scientifically valid.

Aged↗
PubMed2001

Defibrillation via the elimination of spiral turbulence in a model for ventricular fibrillation.

Ventricular fibrillation, the major reason behind sudden cardiac death, is turbulent cardiac electrical activity in which rapid, irregular disturbances in the spatiotemporal electrical activation of the heart make it incapable of any concerted pumping action. Methods of controlling ventricular fibrillation include electrical defibrillation as well as injected medication. Electrical defibrillation, though widely used, involves subjecting the whole heart to massive, and often counterproductive, electrical shocks. We propose a defibrillation method that uses a very low-amplitude shock (of order mV) applied for a brief duration (of order 100 ms) and over a coarse mesh of lines on our model ventricle.

Defibrillators, Implantable↗