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PubMed2003

Automated external defibrillators (AEDs).

Automated external defibrillators, or AEDs, will automatically analyze a patient's ECG and, if needed, deliver a defibrillating shock to the heart. We sometimes refer to these devices as AED-only devices or stand-alone AEDs. The basic function of AEDs is similar to that of defibrillator/monitors, but AEDs lack their advanced capabilities and generally don't allow manual defibrillation. A device that functions strictly as an AED is intended to be used by basic users only. Such devices are often referred to as public access defibrillators. In this Evaluation, we present our findings for a newly evaluated model, the Zoll AED Plus. We also summarize our findings for the previously evaluated model that is still on the market and describe other AEDs that are also available but that we haven't evaluated. We rate the models collectively for first-responder use and public access defibrillation (PAD) applications.

Cardiopulmonary Resuscitation↗
PubMed1992

Defibrillation and cardioversion.

To optimize the success of defibrillation, the clinician needs to minimize impedance, choose the proper energy level, apply the proper interface, select the appropriate paddle size, and deliver the shock at the earliest possible time. Other factors that may contribute to effective defibrillation include defibrillation during exhalation, maintenance of an effective airway, and correction of electrolyte abnormalities. Open chest defibrillation can be achieved at a lower dose of between 10 J and 20 J. Automated external defibrillators have increased survival of prehospital arrests. Cardioversion can generally be accomplished safely either as an elective or emergent procedure. Selection of the proper indications, protection of the airway, anticoagulation if necessary, correction of digitalis toxicity, and the utilization of adjuvant therapy ensure an optimal outcome.

Anti-Arrhythmia Agents↗
PubMed2004

Facilitating internal cardioversion of chronic atrial fibrillation with ibutilide--predictors of atrial defibrillation-threshold decrease.

BACKGROUND: Internal atrial cardioversion has been successfully used in the treatment of atrial fibrillation. The object of this study was to depict the effect of ibutilide on sinus rhythm restoration and internal atrial defibrillation threshold in patients with chronic atrial fibrillation. MATERIAL/METHODS: Twenty-four patients (14 men and 10 women, mean age 63.16+/-8.55 years) with chronic atrial fibrillation were cardioverted using a single-lead system. The distal coil of the defibrillator catheter was placed in the coronary sinus and the proximal coil at the junction of the superior vena cava and the high right atrium. Synchronized biphasic shocks were applied using a step-up protocol from 1 to 30 joules until sinus rhythm was restored. In all patients with successful cardioversion, atrial fibrillation was reinduced and second cardioversion was attempted after intravenous administration of 1 mg ibutilide. RESULTS: Successful internal cardioversion was achieved in 22 (91.6%) and 23 (95.83%) patients before and after ibutilide administration, respectively. The amount of energy given was reduced from 13.89+/-11.44 to 8.28+/-9.64 joules (p=0.0001). Variables associated with the reduction of the defibrillation threshold after ibutilide administration were: duration of the last episode of atrial fibrillation (p=0.008), time since the first episode of atrial fibrillation (p=0.002), body mass index (p=0.01), ejection fraction (p=0.025), male gender (p=0.001), and diameter of the left atrium (p=0.028). CONCLUSIONS: Internal atrial defibrillation after ibutilide administration is a safe and effective method for sinus rhythm restoration, with concurrent significant reduction of the atrial defibrillation threshold.

Aged↗
PubMed1992

[Semiautomated defibrillator. Experiences with the use in ambulances in a rural district].

Early defibrillation has been shown to be the single most effective intervention in resuscitation from sudden cardiac death. The new semi-automated defibrillators are safe and easy to use and are effective and precise instruments for interpreting cardiac rhythm. In our rural area, ambulance staff received six hours training in the use of a semi-automated defibrillator (Heartstart 2000, Laerdal Medical) before the apparatus was installed in the ambulance. During the first year after installation, eight cases of cardiac arrest were treated by the ambulance staff. Four patients received defibrillation, two of whom were resuscitated successfully. Increased local interest in treatment of cardiac arrest, including increased awareness of the need to provide early resuscitation, has strengthened the chain of response, where the procurement of a semi-automated defibrillator represents a link that seems to have improved the prognosis for patients with cardiac arrest in our district.

Aged↗
PubMed2006

[Hilbert transform analysis of the relation between ventricular fibrillation voltage and the outcome of defibrillation shocks].

The objective of this study is to evaluate the correlation between the absolute ventricular fibrillation voltage (AVFV) computed from electrocardiogram (ECG) and the outcome of defibrillation shocks. Orthogonal ECG (sagittal, x; transverse, y; and longitudinal, z) was recorded from 11 dogs during 10 seconds of electrically induced ventricular fibrillation followed by defibrillation shocks with 50% probability of success. The transvenous two-leads defibrillation system was used to deliver defibrillation shocks. The envelope voltage was estimated by using the Hilbert transform. The comparison of the envelope voltages between 236 successful trials and 249 unsuccessful trials did not show any consistent and statistically significant differences. In contrast with the previously reported correlation, the moving average of AVFV was not higher in the successful trials. In the Z direction, the successful trials had lower voltage than did the unsuccessful trials (P < 0.05). These results suggest that the absolute voltage of ECG during ventricular fibrillation is not robustly correlated with the outcome of defibrillation shocks.

Animals↗
PubMed1987

[Long-term clinical results of the implantable automatic defibrillator].

Between October 1982 and May 1986, 12 patients were implanted with an automatic defibrillator AID-B; 7 had coronary artery disease, 2 had dilated cardiomyopathies and 3 had torsades de pointe with or without long QT intervals. Five patients had a thoracic approach with a left ventricular patch and implantation of a right atrial endocavitary electrode. Thereafter a subcostal approach was used with 2 patch electrodes. Two of the first 5 patients rejected the device, but this complication was not observed in the remaining 7 cases. The threshold of defibrillation was greater than 25 joules in 1 case out of 5 with a patch and endocavitary electrode. This threshold was less than 25 joules in all patients with 2 patch electrodes. The AID-B was triggered in less than 20 seconds. One patient died of pulmonary embolism 8 days after implantation; 2 others had a temporary aggravation of their arrhythmias. There were no cases of inappropriate activation of the AID-B device during follow up: 5 patients had no arrhythmia or defibrillation. The 6 others had 2 to 35 defibrillations with documented arrhythmias before or after defibrillation. One patient suffered a sudden death after exhaustion of the device which had functioned on two occasions but had not been replaced for economic reasons. The technique of implantation has been simplified, so limiting local complications. This device is reliable and represents an effective palliative treatment of sudden death due to ventricular arrhythmias.

Adult↗
PubMed1986

Energy requirements for defibrillation.

Available clinical data indicate that an initial shock energy of 200 J will defibrillate the majority of patients. There is no advantage in starting at a higher energy, and lower energy shocks may be safer. Measurements of transthoracic impedance may permit the use of even lower energy levels for initial shocks. If the initial shock fails to defibrillate it should be repeated immediately, at the same energy level, and then increased if defibrillation is still not achieved. If the initial shock defibrillates but refibrillation occurs later there is no reason to increase the energy; it should be repeated at 200 J. We suggest the following energy selection algorithm for defibrillation (VF = ventricular fibrillation): (Formula: see text).

Electric Countershock↗
PubMedDate not supplied

Optimization of epicardial electrode size and implant site for reduced sequential pulse defibrillation thresholds.

The influence of epicardial electrode surface area and implant site on sequential pulse defibrillation threshold was investigated in four isolated heart preparations. Electrodes with surface areas of 2.5, 5.0, and 10.0 cm2 were each sutured, in random order, to the epicardial surface of the isolated heart at each of four sites: mid-ventral left ventricle (LV); mid-dorsal LV; lateral-apical LV; and lateral-basal LV. The epicardial electrode is one of the electrodes in a three-electrode, two-current pathway, sequential pulse system. The first two electrodes, which are catheter-mounted, are located in the right ventricular apex (RVA) and superior vena cava (SVC). In sequential pulse defibrillation, one shock is delivered from the SVC to the RVA, followed 1 msec later by a second shock delivered from the third electrode to the RVA. Sequential pulse defibrillation threshold was obtained with each epicardial electrode used at each site. A single-pulse (SVC to RVA) catheter threshold was also obtained in each heart. The overall mean sequential pulse threshold was 47 per cent less than the mean single-pulse threshold (P less than 0.001). Increasing patch size reduced sequential pulse threshold (P less than 0.03), but no significant effect of patch location could be demonstrated. It is concluded that sequential pulse defibrillation is superior to single-pulse catheter defibrillation and that increasing epicardial patch size is advantageous, although patch location does not influence thresholds in the isolated heart.

Animals↗
PubMed1994

ECRI responds to FDA Safety Alert on Laerdal automated external defibrillators.

PROBLEM: On January 26, 1994, FDA issued a Safety Alert to directors of emergency medical services (EMS) and emergency healthcare provider organizations concerning automated external defibrillators (AEDs) manufactured by Laerdal Manufacturing Corp. The Safety Alert listed problems with three different Laerdal AED models: 1. Heartstart 1000 (Laerdal's fully automated unit): Failure to recognize and treat ventricular fibrillation. FDA did not provide a recommendation to prevent this problem, but requested that any deaths, serious injuries, or serious illnesses involving Laerdal defibrillators (or other devices) be reported. 2. Heartstart 1000s (a semiautomated version of the 1000): Delivery of a second, unnecessary shock after a normal sinus rhythm had been restored by a first shock. FDA recommended that users of this model check the patient for evidence of a pulse and breathing before allowing the machine to deliver a second or repeated shocks. 3. Heartstart 3000: Keypad malfunction, faulty battery connection, and defective optocoupler components. Other than recommending that all defibrillators, regardless of type or brand, be tested at the beginning of each shift and that they undergo all periodic maintenance recommended by the manufacturer, FDA did not provide specific recommendations to address these problems. CONCLUSIONS: ECRI has several concerns with the FDA's Safety Alert: It does not adequately characterize the frequency or severity of the problems listed and provides a specific recommendation for only one. The specific recommendation provided for the Heartstart 1000s instructs EMS systems using this model to abandon established, successful practices and to adopt a new procedure that contradicts the American Heart Association's (AHA) protocol for AED use and could cause confusion and an increased risk of operator shock. It has caused enough concern that some EMS systems have taken Laerdal AEDs out of service or have hesitated to place new units into service. Unless alternative defibrillators are used, this will prevent patients from receiving the potentially lifesaving therapy of early defibrillation and can lead to unnecessary loss of life. The FDA Safety Alert is intended to raise the awareness of safe and effective use of medical devices; it does not have the force of law.

Clinical Protocols↗
PubMed1994

Pediatric defibrillation: current flow is improved by using "adult" electrode paddles.

OBJECTIVE: Current flow, the major determinant of defibrillation success, depends on delivered energy and transthoracic impedance. Previous experimental data suggest that transthoracic impedance is higher using "pediatric" electrode paddles compared to the larger "adult" electrode paddles. There are few data from actual shocks to support the experimental studies. The purpose of this study was to measure transthoracic impedance during actual shock delivery and to determine the optimal electrode paddle size for pediatric defibrillation and cardioversion. METHODS: We prospectively evaluated all shocks of < or = 20 joules given to pediatric patients at the University of Iowa from 1988 to 1992. Data collected included energy selected by the operator, energy delivered by the defibrillator, peak current flow and transthoracic impedance. Data were analyzed by unpaired t test and linear regression. RESULTS: Fifty-five shocks were delivered to 20 patients, age newborn to 8 years. Thirty-seven shocks were given with "pediatric" electrode paddles (surface area 21 cm2) and 18 with "adult" electrode paddles (surface area 83 cm2). Selected energy correlated well with delivered energy (r = .98, P < .0001). Delivered energy using "pediatric" electrodes did not differ from that delivered with "adult" electrodes (8.0 +/- 0.9 joules vs 10.5 +/- 1.2 joules P > .1). However transthoracic impedance was significantly higher with "pediatric" electrodes (78.1 +/- 4.4 ohms vs 54.6 +/- 2.7 ohms P < .0008), resulting in lower peak current flow through "pediatric" electrode paddles (6.2 +/- 0.5 amps vs 8.7 +/- 0.5 amps P < .002). There was no correlation between joules/kg and peak current flow (r = .26, P > .05). CONCLUSION: Use of "pediatric" electrode paddles results in higher transthoracic impedance and thus lower peak current flow. In pediatric defibrillation, larger "adult" electrode paddles should be used as soon as chest size permits (approximately 10 kg). Lower transthoracic impedance results in higher current flow that facilitates cardioversion and defibrillation.

Child↗
PubMed1993

Role of heart mass in the developmental changes of ventricular fibrillation threshold and spontaneous defibrillation in young dogs.

In the course of studying developmental changes of induction and maintenance of ventricular fibrillation in canine pups, we have documented that at about the third week of age, hearts reach a critical point where ventricular fibrillation may become both inducible and sustainable, thus forming the basis for cardiac arrhythmic death. Since age-related variations of cardiac mass may account for these findings, this study was conducted to systematically investigate the role of changing heart mass on the induction and maintenance of ventricular fibrillation in the canine heart, during the early postnatal development. Repetitive determinations of ventricular fibrillation threshold and individual incidence of spontaneous defibrillation were obtained in 87 puppies 1-6 weeks old, from litters of varied body size breeds, studied at weekly intervals. Overall, ventricular fibrillation threshold correlated positively with ventricular weight (VFTmA = 3.30 + 1.27 Vwtg, r = 0.71). However the slopes were steeper and correlations were stronger for the first, second and sixth week and nonsignificant in the fourth and fifth weeks. The ventricular fibrillation to ventricular weight ratio also varied with age (P < 0.01). Spontaneous defibrillation occurred at least once in 68 of the puppies (78%). In general, spontaneous defibrillation was more likely to occur in hearts weighing less than 9 grams (P < 0.01), but the overall correlation of the decreasing defibrillation incidence to increasing weight was weak (SDF % = 48.6-0.90 Vwtg, r = 0.106). Spontaneous defibrillation was not observed at any age or weight in two litters, totaling 9 puppies.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1995

[New approach for defibrillation after cardiac reoperation].

Cardiac reoperations are associated with several complications such as ventricular lacerations, major vessel trauma, and ventricular arrhythmias. As it is impossible to defibrillate before ending the pericardial dissection, this latter complication increases the mortality rate in the perioperative period. In those instances, the self-adhesive electrode pads for external defibrillation were proven effective for cardioversion and defibrillation, even in the presence of adherences. In our institution, these electrode pads are compulsory for all patients requiring cardiac reoperation. The apex pad covers the cardiac apex in the V5 and V6 electrode derivations, while the posterior pad is placed over the right infrascapular area, which reduces the risk of hazardous current concentration. In addition, it does not obstruct the operative site and the pads can be connected to a R2 cable adaptor compatible with regular leading defibrillating systems. The electrode pads were tested on 132 of the 508 patients (26%) requiring cardiac surgery during a 6-month period. Eighteen of these cases (14%) required one or more defibrillating during the operation. The benefits of using this system (R2 Corporation, Skokie, Ill) include: a smaller dissection, reduced blood loss, lower numbers of blood transfusions, and decreased operating time. When the electrode pads remain in place during the patient's transfer to the intensive care unit and the first hours thereafter, they can be used again this time to control arrhythmia complications after the surgery.

Cardiac Surgical Procedures↗
PubMed1998

Intra-atrial defibrillation of human atrial fibrillation.

Low-energy intra-atrial defibrillation is a new therapeutic option for restoring sinus rhythm in patients with atrial fibrillation (AF). The success rate is quite high when right atrium-coronary sinus or right atrium-pulmonary artery electrode configurations are used, although the former is associated with a slightly lower defibrillation threshold. Several issues regarding the safety and tolerability of the procedure remain unresolved. Our experience and that of others indicate that low-energy intra-atrial cardioversion is safe even during exercise, provided the shock is well synchronized with the QRS and the preshock RR interval is > 500 msec. Reported defibrillation thresholds in patients with persistent AF range from 4 to 8 J, and shocks of this type inevitably are associated with some degree of discomfort. Measures aimed at lowering the defibrillation threshold (e.g., use of biphasic waveforms, antiarrhythmic pretreatment, and use of a single effective shock, as opposed to the multiple shocks delivered in research settings) can be expected to increase patient tolerance and extend the indications for low-energy intra-atrial cardioversion. The procedure currently is indicated for patients with persistent AF who are resistant to external defibrillation unable or unwilling to undergo general anesthesia. The procedure could be expanded to patients affected by obesity in whom the efficacy of external cardioversion is lower.

Atrial Fibrillation↗
PubMed2005

Comparison of efficacy of implanted cardioverter-defibrillator in patients with versus without diabetes mellitus.

In the second Multicenter Automatic Defibrillator Implantation Trial, patients with a previous myocardial infarction and left ventricular ejection fraction < or =0.30 benefited significantly from prophylactic implantable cardioverter-defibrillator (ICD) placement. Diabetic patients who had a myocardial infarction had a worse prognosis compared with nondiabetics. The present study used data from the second Multicenter Automatic Defibrillator Implantation Trial to assess the efficacy of ICD placement on survival in diabetic patients. Of the 1,232 patients in the second Multicenter Automatic Defibrillator Implantation Trial, 489 were characterized as diabetic. They were more likely to be New York Heart Association class II to IV, be hypertensive, have renal dysfunction, have an increased body mass index, and to take diuretic drugs. Diabetic patients had a 24% greater adjusted risk of death than nondiabetic patients. The hazard ratio (HR) for the risk of death in patients treated with the ICD compared with conventional therapy was similar in diabetics (HR 0.61; 95% confidence interval [CI] 0.38 to 0.98) and nondiabetics (HR 0.71; 95% CI 0.49 to 1.05), with no evidence of interaction. Thus, diabetic patients derive a similar benefit from ICD therapy despite being sicker and having a higher mortality rate overall.

Aged↗
PubMed2001

"Stable" ventricular tachycardia is not a benign rhythm : insights from the antiarrhythmics versus implantable defibrillators (AVID) registry.

BACKGROUND: Sustained ventricular tachycardia (VT) can be unstable, can be associated with serious symptoms, or can be stable and relatively free of symptoms. Patients with unstable VT are at high risk for sudden death and are best treated with an implantable defibrillator. The prognosis of patients with stable VT is controversial, and it is unknown whether implantable cardioverter-defibrillator therapy is beneficial. METHODS AND RESULTS: Screening for the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial identified patients with both stable and unstable VT. Both groups were included in a registry, and their clinical characteristics and discharge treatments were recorded. Mortality data were obtained through the National Death Index. The mortality in 440 patients with stable VT tended to be greater than that observed in 1029 patients presenting with unstable VT (33.6% versus 27.6% at 3 years; relative risk [RR]=1.22; P:=0.07). After adjustment for baseline and treatment differences, the RR was little changed (RR=1.25, P:=0.06). CONCLUSIONS: Sustained VT without serious symptoms or hemodynamic compromise is associated with a high mortality rate and may be a marker for a substrate capable of producing a more malignant arrhythmia. Implantable cardioverter-defibrillator therapy may be indicated in patients presenting with stable VT.

Aged↗
PubMed1995

Implantable cardioverter-defibrillator patch shunting effect manifestations on the body surface map.

The purpose of this study was to demonstrate the known shunting effect of implantable cardioverter-defibrillator patches using the body surface map. Using a 32-lead body surface mapping computer system (Corazonix Predictor, Oklahoma City, OK) we recorded body surface potential maps both prior to and 7 days after implantable cardioverter-defibrillator patch placement in a patient during right ventricular pacing at 60 beats/minute. This study demonstrated a marked shunting effect from the patches to the body surface during electrical depolarization as well as repolarization. In addition, patch orientation and configuration were evaluated by this method. Specifically, the waveforms were affected by the presence of insulator patches. This may be an important explanation, which may prevent appropriate transthoracic defibrillation using standard configurations. Further research is necessary to elucidate the true effect of the depolarization and repolarization waveform and defibrillator patches.

Aged↗
PubMed2006

Cesarean section in a patient with familial cardiomyopathy and a cardioverter-defibrillator.

PURPOSE: To describe the impact of maternal automatic implantable cardioverter-defibrillator (AICD) therapy on pregnancy outcome, and discuss the clinical rationale for regional anesthesia in parturients with AICDs. CLINICAL FEATURES: A 20-yr-old primigravida with a history of familial cardiomyopathy and AICD placement presented at 39 weeks gestational age for elective labour induction. Ultimately, the patient underwent a Cesarean section for a failed induction. Her AICD was deactivated during the peripartum period, although the pacing function remained active as she had an underlying heart rhythm of less than 34 beat.min(-1). The patient had continuous electrocardiogram monitoring via an external defibrillating unit to which she remained connected by external defibrillator pads. Labour analgesia and surgical anesthesia were provided with a lumbar epidural dosed with varying concentrations of bupivacaine. This management resulted in an excellent maternal and fetal outcome. CONCLUSIONS: Automatic implantable cardioverter-defibrillators are being utilized more frequently in the obstetric population, and appear compatible with good fetal outcomes. Experience with the anesthetic management of these patients is markedly limited - primarily involving reports of general anesthesia for Cesarean section. Epidural anesthesia, however, offers distinct advantages in this patient population including easy conversion from labour analgesia to surgical anesthesia, preservation of fetal-maternal hemodynamics, prevention of increases in plasma catecholamines due to labour or operative pain, and, finally, possible direct suppression of arrhythmias by pharmacologically-active plasma levels of local anesthetic.

Adult↗
PubMed2005

[First responder defibrillation in the LAGO-die Therme--results and experiences].

The use of automated external defibrillator (AED) by persons other than paramedics and emergency medical technicians is advocated by several US- and European organizations. However, at the present time it is still unclear to identify public places with a high incidence of out-of-hospital cardiac arrest. There are few data on the potential impact of public access defibrillators on survival after out-of-hospital cardiac arrest in sporting arenas or water parks. Therefore, we studied prospectively incidence of out-of-hospital cardiac arrest in the LAGO-die Therme in Herne. This is one of the most important swimming parks in Europe and member of the European Waterpark Association EWA. Eight AEDs were placed in the waterpark LAGO-die Therme. The locations where the defibrillators were stored were chosen to make possible a target interval of 60 seconds from collapse to first defibrillation. Twenty waterpark officers were instructed in cardiopulmonary resuscitation and in the use of the AED. During November 16, 2001 and December 31, 2004, 2.05 Mio. visitors were counted in the LAGO. Out-of-hospital cardiac arrest occurred in none of them. AED were used in two visitors with non arrhythmogenic syncope, no shock was delivered. Questionaires were done in 588 visitors (336 males, 252 females, mean age 38+21 years) in 2002 and in 579 visitors (322 males, 257 females, mean age 37+/-25 years) in 2004. In 2002, 77% of the visitors noticed the AED and, therefore, 49% performed more sporting activities. In addition, in 2004, AED was noticed by 480 visitors (83%) and 277 visitors (48%) did more sporting activities. There were no significant differences between 2002 and 2004 (p=ns). Despite no out-of-hospital cardiac arrest in the waterpark during the 3 year follow- up, it seems reasonable to install AED in sporting places with thousands of visitors per year.

Adult↗