Defibrillation Electrodes Research Articles

DefibViz: A Visualization Tool for the Assessment of Electrode Parameters on Transthoracic Defibrillation Thresholds

DefibViz is a software application developed for defibrillation simulation and visualization. It exploits both surface techniques and methods for the interactive exploration of volumetric datasets for the analysis of transthoracic defibrillation simulation results. DefibViz\ has a graphical user interface for the specification of the shape, size, position, and applied voltage of a defibrillator's electrodes. An option is provided for using 3-D slice plane widgets, which operate on the volumetric datasets, such that the distribution of the voltage gradient induced by an electric shock can be visually inspected in various tissues throughout the myocardium and torso. One goal of DefibViz is to enhance understanding of how electrode parameters relate to the change of the voltage gradient distribution throughout the heart, which may help lead to optimal defibrillator design. DefibViz; is significant, in that, it is built by using an open-source graphics and visualization framework providing a platform for subsequent modifiability and extensibility. Moreover, it integrates simulation and visualization techniques, which previously required the running of several independent software executables, into an enhanced, seamless, and comprehensive software application.

Abstract 2009: Matching the Transthoracic Defibrillation Vector to the Fibrillation Vector Improves Shock Success

Background: Depolarization of myocytes requires less energy when electrical current flows along the longitudinal axis compared to the transverse axis of myocytes. Since ventricular fibrillation (VF) amplitude in ECG leads reflects the functional electrical orientation of the majority of myocytes, we hypothesized that a defibrillation shock would be more effective if the shock vector was oriented along the functional electrical axis of the majority of myocytes, and this axis could be determined in real time from the relative amplitudes of the VF signal measured in three orthogonal ECG leads. Methods: In closed-chest, anesthetized, swine (22.0 ± SE0.8 kg, n=9), a new directional defibrillation device was used to simultaneously measure the VF amplitude through three orthogonal pairs of defibrillation electrodes: anterior-posterior, lateral-lateral, and superior-inferior. VF was electrically induced and persisted for 15 seconds. During defibrillation, the device identified the electrode pair that measured the largest or smallest peak amplitudes (+ or −) within the previous 100msec through which to deliver the shock. Defibrillation success for the electrodes measuring the largest or smallest VF amplitude was evaluated by delivering four 50J shocks for VF through each of these electrode pairs (in random order). The electrode pair measuring the largest VF signal amplitude was considered to be most closely aligned with the functional VF vector. Results: Fifty J shocks (n=37) delivered through the electrode pair measuring the largest VF signal amplitude had higher defibrillation success than 50J shocks (n=37) delivered through the electrodes measuring the smallest VF signal amplitude (62 ± 10% vs.19 ± 8%, p<0.05). Impedance and current were not different. Conclusions: By using a directional defibrillation device which instantaneously measures the peak VF signal amplitude in three pairs of orthogonally oriented defibrillation electrodes, it is feasible to determine which set of electrodes is oriented more favorably to the functional VF vector and to direct the shock through that set of electrodes. Matching the defibrillation vector to the fibrillation vector improves shock success.

Abstract 54: Preliminary Results With The Use Of Stat · Padz Pacing Electrode For Treatment Of Symptomatic Bradycardia In Emergency Department.

Background: Since the mid-1980’s transthoracic pacing has been a common temporary treatment for arrhythmias. Present external pacing technology requires the application of both multifunction defibrillation electrodes and separate leads for electrocardiogram (ECG) monitoring. Separate ECG leads are required as the current from the pacing pulse creates artifact in the signal that prevents one from distinguishing between pace-captured and non-captured rhythms when using the defibrillation electrode alone. Hypotheses: We hyothezised that Stat· padz MWP electrode, a transthoracic electrode that integrates the ECG electrodes into the defibrillation and pacing pad woud be abble to reconize captured and non-captured rhythms in a typical clinical setting of the syntomatic bradycardia. Methods: We conducted a prospective study at Emergency Department of a University Hospital. During October 2006 to April 2007, 28 patients with symptomatic bradycardia were include in the study. Comparison between monitoring by conventional electrode and Stat· padz MWP electrode was performed. After that was selected Lead II, and adjusted pacing rate and milliamps for the stimulation. Records and comparison of electrical capture was performed with the three lead conventional electrodes and Stat· padz MWP electrodes. Results: The mean electrocardiographic diagnoses was third degree atrio-ventricular block in 50% of patients, and the principal symptoms were presyncope in 82 %, symptoms of reduced cardiac output in 79% and syncope in 43%. Previous diagnoses were Hypertension in 57%, Chagas’s heart disease in 21%, Valvar heart disease in 14% and Dilated Cardiomyopathy in 18 %. Monitoring of cardiac rhythm, electrical and mechanical capture were obtained in 100 % of patients. The mean energy for capture was 69±18 milliamps. When compared the records of electrocardiographic capture with Stat· padz MWP electrode, it was equal than conventional electrodes in 46 % and better in 54 %. Conclusion: The Stat· padz MWP electrode has the feasibility of recognise capture and non-capture rhythms and to perform pacing function effectively. It presents the possibility of providing rapid treatment in patients with syntomatic bradycardia avoiding monitoring by conventional electrodes.

Incorrect Connectors Lead to Recall of Radiotranslucent Defibrillation Electrodes

Incorrect Connectors Lead to Recall of Radiotranslucent Defibrillation Electrodes

Twiddler-Syndrom bei einem links pektoral implantierten Defibrillator

Twiddler's syndrome describes a rare complication following implantation of a pacemaker/defibrillator and is characterized by spontaneous, repeated rotation of the generator in the subpectoral pocket. We describe the case of a 78-year-old man who presented with an exit block 7 months after defibrillator implantation. As cause, a 15-fold rotation of the defibrillator's generator around its own axis could be verified, which entailed dislocation of the defibrillator's electrode. Safe fixation of the electrode and generator in the subpectoral pocket is of paramount importance, particularly in patients with loose subcutaneous fatty tissue, to prevent this rare complication.

Endoscopy in patients with implanted electronic devices

Endoscopy in patients with implanted electronic devices

Intracardiac atrial defibrillation

Intravascular ventricular defibrillation and intravascular atrial defibrillation have many similarities. An important factor influencing the outcome of the shock is the potential gradient field created throughout the ventricles or the atria by the shock. A minimum potential gradient is required throughout the ventricles and probably the atria in order to defibrillate. The value of this minimum potential gradient is affected by several factors, including the duration, tilt, and number of phases of the waveform. For shock strengths near the defibrillation threshold, earliest activation following failed shocks arises in a region in which the potential gradient is low. The defibrillation threshold energy can be decreased by adding a third and even a fourth defibrillation electrode in regions where the shock potential gradient is low for the shock field created by the first two defibrillation electrodes and giving two sequential shocks, each through a different set of electrodes. However, the addition of more electrodes and sequential shocks complicates both the device and its implantation. Because patients are conscious when the atrial defibrillation shock is given, they experience pain during the shock, which is one of the main drawbacks of intravascular atrial defibrillation. Unfortunately, the pain threshold for defibrillation shocks is so low that a shock less than 1 J is uncomfortable and is not much less painful than shocks several times stronger. Therefore, even though electrode configurations exist that have lower atrial defibrillation threshold energy requirements than the atrial defibrillation threshold with standard defibrillation electrode configurations used in implantable cardioverter-defibrillators (ICDs) for ventricular defibrillation, they are not clinically practical because their shocks are almost as painful as with the standard ICD electrode configurations. Such electrode configurations would make the ICD more complicated, leading to greater difficulty and longer time required for implantation.

Assessment of CPR-D skills of nurses in Göteborg, Sweden and Espoo, Finland: Teaching leadership makes a difference

Construction of an effective in-hospital resuscitation programme is challenging. To document and analyse resuscitation skills assessment must provide reliable data. Benchmarking with a hospital having documented excellent results of in-hospital resuscitation is beneficial. The purpose of this study was to assess the resuscitation skills to facilitate construction of an educational programme. Nurses working in a university hospital Jorvi, Espoo (n=110), Finland and Sahlgrenska University Hospital, Göteborg (n=40), Sweden were compared. The nurses were trained in the same way in both hospitals except for the defining and teaching of leadership applied in Sahlgrenska. Jorvi nurses are not trained to be, nor do they act as, leaders in a resuscitation situation. Their cardiopulmonary resuscitation (CPR) skills using an automated external defibrillator (AED) were assessed using Objective Structured Clinical Examination (OSCE) which was build up as a case of cardiac arrest with ventricular fibrillation (VF) as the initial rhythm. The subjects were tested in pairs, each pair alone. Group-working skills were registered. All Sahlgrenska nurses, but only 49% of Jorvi nurses, were able to defibrillate. Seventy percent of the nurses working in the Sahlgrenska hospital (mean score 35/49) and 27% of the nurses in Jorvi (mean score 26/49) would have passed the OSCE test. Statistically significant differences were found in activating the alarm (P<0.001), activating the AED without delay (P<0.01), setting the lower defibrillation electrode correctly (P<0.001) and using the correct resuscitation technique (P<0.05). The group-working skills of Sahlgrenska nurses were also significantly better than those of Jorvi nurses. Assessment of CPR-D skills gave valuable information for further education in both hospitals. Defining and teaching leadership seems to improve resuscitation performance.

Novel rectangular biphasic and monophasic waveforms delivered by a radiofrequency-powered defibrillator compared with conventional capacitor-based waveforms in transvenous cardioversion of atrial fibrillation

To investigate the feasibility and efficacy of novel low-tilt biphasic waveforms in transvenous cardioversion of atrial fibrillation (AF), delivered by a radiofrequency-powered defibrillator. The investigation was performed in three phases in an animal model of AF: a feasibility and efficacy study (in 10 adult Large White Landrace swine), comparison with low-tilt monophasic and standard capacitor-based waveforms, and an assessment of sequential shocks delivered over several pathways (in 15 adult Suffolk sheep). Defibrillation electrodes were positioned transvenously under fluoroscopic control in the high lateral right atrium and distal coronary sinus. When multiple defibrillation pathways were tested, a third electrode was also attached to the lower interatrial septum. The electrodes were then connected to a radiofrequency (RF)-powered defibrillator or a standard defibrillator. After confirmation of successful induction of sustained AF, defibrillation was attempted. Percentage success was calculated from the effects of all shocks delivered to all the animals within each set of experiments. Of the low-tilt (RF) biphasic waveforms delivered during internal atrial cardioversion, 100% success was achieved with a 6/6 ms 100/-50 V waveform (1.45+/-0.01 J). This waveform was similar in efficacy to low-tilt (RF) monophasic waveforms (88 vs. 92% success, 1.58+/-0.01 vs. 2.67+/-0.03 J; P=NS; delivered energy 41% lower) and superior to equivalent voltage standard monophasic (50% success, 0.67+/-0.00 J; P<0.001) and biphasic waveforms (72% success, 0.69+/-0.00 J; P=0.03). Sequential shocks delivered over dual pathways did not improve the efficacy of low-tilt biphasic waveforms. A low-tilt biphasic waveform from a RF-powered defibrillator (6/6 ms 100/-50 V) is more efficacious than standard monophasic or biphasic waveforms (equivalent voltage) and is similar in efficacy to low-tilt monophasic waveforms.

An unconditionally stable numerical method for the Luo–Rudy 1 model used in simulations of defibrillation

Numerical simulations of defibrillation using the Bidomain model coupled to a model of membrane kinetics represent a serious numerical challenge. This is because very high voltages close to defibrillation electrodes demand that extreme time step restrictions be placed on standard numerical schemes, e.g. the forward Euler scheme. A common solution to this problem is to modify the cell model by simple if-tests applied to several equations and rate functions. These changes are motivated by numerical problems rather than physiology, and should therefore be avoided whenever possible. The purpose of this paper is to present a numerical scheme that handles the original model without modifications and which is unconditionally stable for the Luo–Rudy phase 1 model. This also shows that the cell model is mathematically well-behaved, even in the presence of very high voltages. Our theoretical results are illustrated by numerical computations.

Experimental verification of theoretical predictions concerning the optimum defibrillation waveform

The efficacy of electrical therapy at terminating ventricular fibrillation is highly dependent on the waveform used. We present experimental results which test one theory for defibrillation waveform dependence. Forty-four defibrillation waveforms (22 monophasic, 22 biphasic) were designed according to the theoretical construct of Fishier (2000). The waveforms were then tested on 67 male guinea pigs (46 for monophasic, 21 for biphasic waveforms) using a custom designed defibrillator and 12-mm subcutaneous disc electrodes. There was considerable agreement between the theoretical and experimental results. For example, as predicted, the ascending exponential waveform of 1 ms proved to be the most effective (86.4%) monophasic waveform, where efficacy is the number of successful shocks divided by the total number delivered. In addition, the efficacy decrease with duration increase was accurately predicted by the model for monophasic waveforms. For biphasic waveforms, as predicted by the model, when the first phase was optimized, an increase in second phase duration caused an increase in defibrillation efficacy (10 of 11 tested duration pairs). We conclude that the theoretical framework adequately explains the mechanism by which the defibrillation waveform affects efficacy for monophasic waveforms and, in at least one aspect, biphasic waveforms.

AB13-1: Evaluation of a novel ventricular support device with defibrillation capabilities

Surgical interventions, including passive restraining devices, can decrease ventricular dilation and improve heart failure. We tested an implantable ventricular support device consisting of a self-anchoring self-tensioning nitinol wireform harness containing 2 pair of integrated defibrillation electrodes (Paracor Medical) that connected to an ICD. The implant was placed on the epicardium of the left (LV) and right (RV) ventricles through a subxiphoid approach using an introducer and delivery system. We assessed the lead integrity, defibrillation threshold (DFT), hemodynamic responses, and histopathology following 42-180 days of implantation.

Lessons From the Failure and Recall of an Implantable Cardioverter-Defibrillator

Multiple clinical trials have shown that a properly functioning implantable cardioverter-defibrillator (ICD) is capable of interrupting sudden death caused by ventricular tachyarrhythmias. Unfortunately, ICDs are complex medical devices, and they do not always perform as expected. For example, only 5% of ICD batteries last >7 years, and most dual-chamber ICD models must be replaced for battery depletion every 3 to 5 years.1 Normal battery depletion, however, is reliably predicted by routine follow-up methods before an ICD fails. In contrast, electronic malfunctions are unpredictable and may not be detected by standard follow-up techniques before an ICD is unable to deliver effective therapy. Thus, sudden cardiac arrest or death may be the first and only sign that an ICD has failed.2 Recently, we reported the death of a 21-year-old patient who received a Prizm 2 DR model 1861 ICD pulse generator (Guidant, Inc) in 2001 to prevent sudden cardiac death resulting from hypertrophic cardiomyopathy.3 In March 2005, this young man experienced a witnessed arrest and could not be resuscitated. His ICD was returned to Guidant, which found that the device had failed during the delivery of a shock. The cause of failure was massive electronic damage caused by electrical overstress that occurred when a short circuit developed between a high-voltage wire and a tube used to test the housing during manufacturing (see the Figure). At the time of our patient’s death, Guidant had knowledge of 25 similar Prizm 2 DR model 1861 failures in patients, 3 of whom had required rescue defibrillation. Indeed, Guidant had first observed this mode of failure 3 years earlier, in February 2002, when 2 returned Prizm 2 DR pulse generators exhibited the same short circuiting that caused our patient’s device to fail. Guidant was sufficiently concerned about these failures that manufacturing changes were made …

Implantation of an “extracardiac” internal cardioverter defibrillator in a 6-month-old infant

In infants and small children, ICD implantation is a challenge due to technical limitations and a significant number of complications. This report describes ICD implantation in a 6-month-old infant (body weight 5.5 kg). A completely extracardiac defibrillation system was implanted using a transvenous lead subcutaneously in the back below the left scapula as the defibrillation electrode and an active-can device in the right upper abdomen. Defibrillation threshold of implantation was < or =10 J. During the follow-up of 3 months, 8 adequate ICD discharges were noted. The technique described seems feasible to facilitate ICD implantation in small infants.

Decreasing the time to defibrillation: A comparative study of defibrillator electrode designs

Introduction: Time to defibrillation ( T defib) is the most important modifiable factor affecting survival from cardiac arrest. Mortality increases by approximately 7–10% for each minute of defibrillation delay. The purpose of this study was to determine whether defibrillator electrode design complexity affects T defib. Methods: This was a randomized sequential design study utilizing a standardized ventricular fibrillation cardiac arrest model for CPR mannequins. We evaluated two common types of defibrillator electrode models: a single connector design and a double connector design that requires an adaptor. We compared the time required by cardiac arrest team leaders to apply the two types of defibrillator electrodes to a manikin, connect them to a defibrillator, and then deliver a first defibrillatory shock. The primary outcome was time to defibrillation. The secondary outcome was difficulty of application as perceived by the physician participants on a 10 cm visual analog scale. Results: Thirty-two residents performed a sequential assessment of both electrodes. The average T defib for the double connector model was 42.9 s longer than that of the single connector model (87.5 s versus 44.6 s, p < 0.001). As evaluated by the study participants, the single connector model was significantly easier to apply then the double connector model (1.3 cm versus 4.4 cm, p < 0.001). Conclusion: The single connector defibrillator electrode design was associated with a significantly shorter T defib than the double connector design. It also was judged to be easier to apply in this model. Ergonomic design of defibrillator electrodes can significantly impact time to defibrillation.

Impedance-gradient electrode reduces skin irritation induced by transthoracic defibrillation

A new type of disposable external defibrillation electrode has been developed to reduce the skin irritation commonly associated with defibrillation and synchronised cardioversion. This design employs an impedance gradient to reduce the proportion of current delivered to the electrode periphery. The temperature distribution under the new electrode was compared with that of four other types of commercially available electrodes after repeated high-energy biphasic defibrillation discharges to domestic swine. Skin temperature distributions were acquired using non-invasive thermography. Measurements of the maximum temperature rise at each electrode site, taken 3.6s after the fifth defibrillation discharge, demonstrated that the new impedance-gradient electrode produced 50-60% less skin heating than two of the three uniform-impedance electrode designs. Histological examination of erythematous sites excised 24 h after defibrillation quantified the associated skin damage using a scoring protocol developed for this study. In contrast to previous studies, histological examinations demonstrated second-degree skin burns following defibrillation. The new electrode design, however, induced 44-46% less skin damage than two of the traditional uniform-impedance electrodes.

Layperson positioning of defibrillation electrodes guided by pictorial instructions

Background : Correct positioning of defibrillation electrodes is essential to achieve sufficient transmyocardial current to depolarize a critical mass of myocardium, and thus terminate ventricular fibrillation (VF). Aim : To evaluate the pictures on the self-adhesive defibrillation electrodes in guiding laypersons to place the electrodes in the recommended position. Methods : Defibrillation electrodes from five manufactures (Access Cardio Systems, Schiller, Medtronic, Cardiac Science and Philips) were included in the study and compared with electrodes with a lateral view picture, designed for the study, showing the placement of the apical electrode. A total of 150 laypersons without any experience or training in use of a defibrillator participated in the study. The participants placed randomly selected electrodes on the chest of a resuscitation manikin without any guidance apart from the pictures on the electrodes. The distances of the electrodes from the recommended positions were measured. Results : The proportion of participants who placed both electrodes within 5 cm from recommended position varied from 8% to 36% with the different electrodes. Usually, the apical electrode was placed too anteriorly. Electrodes placed with help of the lateral instruction picture, (designed for the study), showing the placement of the apical electrode were placed significantly more often within 5 cm than any of the others (64%, 95% confidence interval 44–80, P < 0.05). Conclusions : The current practice in designing pictures on the electrodes does not seem to be optimal in showing the recommended position of the apical electrode as recommended by Guidelines 2000. It is suggested that by showing a lateral view in the instructions, success in placing the apical electrodes correctly can be improved.

Ergonomically Flawed Electrode Design Can Create Delays in Defibrillation

Cardiac arrest teams are designed to coordinate a timely response, especially to ventricular fibrillation arrest. Unfortunately, excessive delays may occur because the team may be slow to transport, set up, or activate defibrillation equipment. Delays in defibrillation should be viewed for what they are -a perilous source of medical error. Intuitively one would expect to attribute most defibrillation delays to human error. However, the tremendous impact that flawed equipment design has on medical system error in general is now being increasingly recognized.3 We seek to demonstrate through the following series that flawed defibrillation electrode design can lead directly to intolerable defibrillation delays.

Decreasing the time to defibrillation: A crossover comparative study of Quik-Combo and padpro defibrillator electrodes

Study objectives: Time to defibrillation is the most important factor affecting survival from cardiac arrest. Mortality increases by approximately 7% to 10% for each minute that defibrillation is delayed. Therefore, any improvement in time to defibrillation could have an important impact on clinical survival. Valuable progress in shortening the inhospital "chain of survival" has been achieved with the development of cardiac monitored beds, dedicated cardiac arrest teams, and strategic location of defibrillators throughout the hospital. However, the specific impact of defibrillator electrodes on time to defibrillation has not been analyzed. The purpose of this study is to determine whether the choice of defibrillator electrodes affects the time to defibrillation. Methods: This was a randomized crossover design study. It was approved by the institutional review board. Internal medicine and emergency resident physicians supervise cardiac arrest teams at many teaching hospitals, so they were selected to test this equipment. The residents were blinded to the intent of the study. We compared the time required by the residents to apply to the patient, then connect to a defibrillator, and then deliver a shock for 2 leading defibrillator electrodes, the Quik-Combo (Medtronic Physio-Control, Redmond, WA) and the Padpro (model 2516 Padpro LLC, Ann Arbor, MI). Under scripted direction of advanced cardiac life support–trained research nurses, they used the equipment during a standardized ventricular fibrillation cardiac arrest model using cardiopulmonary resuscitation mannequins. The independent variable was the choice of defibrillator electrode. Sequence of testing for the electrodes was block randomized to control for the confounding variable of learning. The primary outcome was time to defibrillation (total time elapsed from the beginning of cardiac arrest to delivery of a defibrillatory shock). The secondary outcome was the ease of application as assessed by the resident physicians with a 10-cm visual analog scale. The minimum required sample size was calculated to be 26 trials for each defibrillator electrode study group, assuming a 20% treatment effect between models (2-sided, for α=0.05 and β=0.2). Statistical significance was analyzed using Student's t test for continuous variables. Results: Thirty residents performed a crossover assessment of both electrodes. The average time to defibrillation for the Padpro was approximately double that of the Quik-Combo (88.2 seconds versus 44.5 seconds, P P Conclusion: The Quik-Combo defibrillator electrode significantly decreased the time to defibrillation and was judged to be easier to apply in this cardiac arrest model. The average time to defibrillation difference of 44 seconds when extrapolated to the clinical setting has important implications for patient survival and morbidity. International guidelines endorse a goal time of only 2 to 4 minutes from collapse until defibrillation. We demonstrate that the choice of defibrillator electrodes can significantly influence accomplishment of that goal. Cardiopulmonary resuscitation is a complex team task under highly stressful conditions. Regularly training on standardized equipment is essential for efficient cardiac arrest team performance. Hospital and emergency medical services authorities should select the most reliable and ergonomically simple equipment to minimize any delays in defibrillation.

Effect of rapid biphasic shock subpulse switching on ventricular defibrillation thresholds.

The aim of this study was to demonstrate that significant reductions in defibrillation threshold (DFT) can be achieved by rapidly switching defibrillation pulses within an overall biphasic envelope between multiple endovascular electrode sets. Defibrillation electrodes were implanted in four locations in nine anesthetized swine (41.7 +/- 8.7 kg). Electrodes were implanted into the right ventricular apex (RV), the superior vena cava (SVC), over the left pectoral region as a "hot can" (Can), and within the middle cardiac vein on the posterior left ventricular (LV) surface. The 50% DFT (level for which 50% of delivered shocks successfully defibrillated) for control shocks (7-ms first phase, 0.5-ms interpulse period, 4-ms second phase, RV- --> SVC+ + Can+) were determined to have energy of 20.5 +/- 5.5 J (mean +/- SD). Mean 50% DFTs were also determined for waveforms that split each phase of the same overall biphasic waveform between various electrode sets. Each phase was divided into 2, 3, 4, or 6 subpulses, the defibrillation shock was sequentially delivered to multiple electrode sets, and DFTs were determined (11.9 +/- 4.8 J, 11.7 +/- 2.9 J, 17.9 +/- 8.7 J, 16.7 +/- 6.1 J, respectively). DFT energy was statistically lower than the control (Wilcoxon sign rank test; P < 0.05) when each phase was divided into 2 or 3 subpulses. Rapid shock switching within an overall biphasic waveform between electrode sets including an electrode in the middle cardiac vein potentially can lower DFT energy by 40% or more.