Internal Cardiac Defibrillation: Single and Sequential Pulses and a Variety of Lead Orientations

A sequential pulse system for internal cardiac defibrillation incorporating catheter and patch electrodes with two current pathways has been shown to reduce defibrillation threshold in comparison to the single pulse technique. The relative advantage of the sequential pulse over the single pulse technique with other lead systems is not known. We compared defibrillation thresholds using sequential and single pulses delivered to a variety of lead orientations with the same electrode surface areas, when possible. Defibrillation threshold totals determined in halothane-anesthetized open-chest pigs averaged: For the single pulse shock passed between (1) superior vena cava (SVC) and left ventricular apical patch (LVA), 27.2 +/- 9.1 joules (J) and (2) LV epicardial patch (LVE) to right ventricular epicardial (RVE) patch leads, 16.5 +/- 2.1 J; and for the sequential pulse shock with two pulses passed between: (1) the SVC to RV intracavitary apex (RVA) and a quadripolar catheter in the coronary sinus to the RVA, 11.6 +/- 1.0 J; (2) the SVC to LVA and the LVE to RVE, 9.6 +/- 1.3 J and (3) the SVC to RVA and the LVE to RVA, 8.9 +/- 0.4 J. Defibrillation thresholds for sequential pulse shocks were all significantly lower than either of the defibrillation thresholds for single pulse shocks (p less than 0.001). We conclude that the sequential pulse system provides a substantial reduction in defibrillation threshold over the single pulse regardless of the lead system when the surface area and pulse characteristics are controlled. Sequential pulse technique may be valuable in the design of an implantable automatic defibrillator.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sequential Pulse Countershock Between Two Transvenous Catheters: Feasibility, Safety, and Efficacy

We evaluated the feasibility, safety, and efficacy of sequential pulse countershock (SqCS) delivered solely through two endocardial catheters for the termination of ventricular tachycardia (VT) and fibrillation (VF) in patients undergoing electrophysiology studies (EPS). Thirty-four patients (31 men, 3 women) with a mean age of 56.8 +/- 10.1 years were studied. Etiology of VT/VF was ischemic heart disease (n = 26), cardiomyopathy (4) repaired tetralogy of Fallot (n = 1), heart transplant (n = 1), and no identifiable heart disease (n = 2). Catheters were positioned successfully in 29 patients. These were positioned in the right ventricular apex (RVA) and the coronary sinus (CS), respectively. The RVA electrode served as the common cathode for both pulses. The two electrodes located near the right atrium/superior vena cava junction served as anode for pulse 1 while the distal CS electrodes served as anode for pulse 2. Twenty-nine induced VT episodes with cycle length (CL) 220-370 msec were treated. SqCS successfully terminated 15 VT (100-500V) while 14 were accelerated or degenerated to VF. VTCL was longer in successful SqCS episodes than in those that were accelerated (285 +/- 17.3 vs 245 +/- 30.8 msec, P less than .003). Of 26 VF episodes, 21 were terminated with SqCS (500-900V) and 5 were terminated by transthoracic rescue shocks. On 2 occasions, failure to defibrillate was attributable to poor catheter position at the time of shock. No complications occurred. We conclude that SqCS delivered solely between endocardial catheter electrodes is feasible and effective using energy doses within the range of existing implantable cardioverter defibrillators.     

Effects of Time to Defibrillation and Subthreshold Preshocks on Defibrillation Success in Pigs

The purpose of this study was to examine the effects of: (1) time to defibrillation and (2) subthreshold preshocks on defibrillation success. We conducted two separate experiments in 19 anaesthetized, open-chested pigs. Defibrillation was attempted using the sequential pulse technique approximately 10 s after electrically induced ventricular fibrillation. Each sequential pulse shock consisted of two trapezoidal pulses (approximately 3 ms duration), separated by 0.2 ms. Current was delivered to three mesh electrodes (TX-7, Medtronic) sutured over the anterior right ventricle, posterior right ventricle, and lateral left ventricle. For each animal, defibrillation threshold (DFT) defined as the lowest delivered energy that defibrillated the heart, was measured twice and the average was designated as mean DFT. The energy at 1.4 times the specific mean DFT for each pig was designated as the test shock and 100 volts less than the mean DFT was designated as the preshock. In the first experiment, test shocks were delivered at five different fibrillation intervals (10, 20, 40, 60, and 90 s). Time to test shock delivery was randomized for 10 to 60 s, but, 90 s was always tested at the end of the study. Percentages of success at 10, 20, 40, 60, and 90 s were 94, 78, 94, 83, and 100%, respectively (p = NS). The 12 pigs in which all initial test shocks were successful were selected for the evaluation of post defibrillation arrhythmias. The cumulative incidence of complete heart block lasting at least 5 s were 8, 33, 83, 83, and 83%, respectively. The incidence of complete heart block increased significantly at 40 s (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison Between Two Versus Three Patches Single Pulse Shock Defibrillation in Pigs

The aim of the study was to test the hypothesis that defibrillation with a single pulse shock can be obtained at lower energy using three epicardial patches configuration (one cathode and two anodes) instead of the conventional two patches. The total surface area of the two- and three-patches configuration was the same (10 cm² vs 9.9 cm²). Epicardial spatial configuration was planned by using a computerized heart model. In ten anesthetized open-chest pigs, ventricular fibrillation was induced by using AC current through the mesh plaque epicardial custom-designed electrodes, and the minimum energy requirement for defibrillation was determined 15 seconds after the onset of stable ventricular fibrillation. Results were as follows (mean ± standard deviation):
Conclusions: three epicardial patches configuration significantly reduces energy requirements for defibrillation compared with two patches when single pulse shock is used.     

Sequential Shocks are Comparable to Single Shocks Employing Two Current Pathways for Internal Defibrillation in Dogs

Sequential pulse defibrillation using two current pathways was compared with single shocks simultaneously utilizing both pathways in 16 dogs to assess the effects of temporal summation. A cardioverter-defibrillator catheter was positioned via the external jugular vein with the distal 4 cm² shocking electrode located in the right ventricular apex and the proximal 8 cm² electrode located in the superior vena cava. Three electrode configurations were tested(1) single pulse, distal electrode (cathode) to proximal electrode and chest wall patch (common anode), (2) sequential 5 ms pulses with 1 ms interpulse delay, distal electrode (cathode] to proximal electrode (anode) followed by distal electrode (cathode) to chest wall patch (anode), and (3] sequential 10 ms pulses with I ms interpulse delay using same current pathways described for configuration 2. The lowest energies resulting in termination of AC induced ventricular fibrillation on four trials were 27.9. 26.6, and 42.3 joules respectively for configurations 1, 2, and 3. The mean energy levels were not significantly different for configurations 1 and 2, both of which were significantly lower than that for configuration 3. The lowest peak voltages terminating ventricular fibrillation on four trials were 595 ± 176, 521 ± 134 and 579 ± 171 volts for configuration 1, 2, and 3. The mean voltage level for configuration 2 was significantly lower than that for configurations 1 and 3, which were not significantly different. The mean calculated impedance for the pathway utilizing the catheter was 74.6 ±13.7 ohms, for the pathway utilizing the distal catheter electrode to the chest wall electrode was 102.9 ± 19.7 ohms, and for simultaneous discharge employing both current pathways was 65.0 ±11.3 ohms. In conclusion, for the lead system tested, sequential pulses were not associated with lower energies than single pulses delivered through the same pathways and therefore, temporal summation is comparable to a single shock for internal defibrillation.     

Effectiveness of Prehospital Dual Sequential Defibrillation for Refractory Ventricular Fibrillation and Ventricular Tachycardia Cardiac Arrest

Objective: Dual sequential defibrillation (DSD) — successive defibrillations with two defibrillators — offers a novel approach to refractory ventricular fibrillation (RVF) and tachycardia (VF/VT). While associated with rescue shock success, the effect of DSD upon out-of-hospital cardiac arrest (OHCA) is unknown. We evaluated the association of DSD with survival after refractory VF/VT OHCA. Methods: We used data from a large metropolitan fire-based EMS service. We included all adult OHCA during 2013–2016 with ≥3 standard defibrillations. Physicians authorized subsequent DSD use by two separate defibrillators (PhysioControl LIFEPAK® 12/15) with pads placed anterior-lateral and anterior-posterior. Evaluated outcomes included return of spontaneous circulation (ROSC), survival to hospital admission, survival to 72?hours, and survival to hospital discharge. Using multivariable logistic regression, we evaluated the association between defibrillation type and OHCA outcomes, adjusting for patient demographics and event characteristics. Results: We included 310 patients in the analysis, 71 patients receiving DSD and 239 receiving conventional defibrillation. Patient demographics and event characteristics were similar between both groups. ROSC was lower for DSD than standard defibrillation: 39.4% vs. 60.3%, adjusted OR 0.46 (95% CI: 0.25–0.87). There were no differences in survival to hospital admission (35.2% vs. 49.2%, adjusted OR 0.57 [95% CI: 0.30–1.08]), survival to 72?hours (21.4% vs. 32.3%, adjusted OR 0.52 [95% CI: 0.26–1.10]), or survival to hospital discharge (14.3% vs. 20.9%, adjusted OR 0.63 [95% CI: 0.27–1.45]). Conclusions: Compared with conventional defibrillation, DSD was associated with lower odds of prehospital ROSC. Defibrillation type was not associated with other OHCA endpoints. DSD may not be beneficial in refractory VF/VT OHCA.     

Biphasic Waveforms for Ventricular Defibrillation: Optimization of Total Pulse and Second Phase Durations

Waveform parameters may affect the efficacy of ventricular defibrillation. Certain biphasic pulse waveforms are more effective for ventricular defibrillation than monophasic waveforms, but the optimal biphasic waveform parameters have not been identified. The purpose of this study was to investigate the effects of total pulse duration and the duration of the second (negative) phase on voltage and energy defibrillation requirements using biphasic waveforms. Defibrillation efficacy was evaluated in an isolated rabbit heart model using the Langendorff technique. The biphasic waveform was a truncated exponential with the initial voltage of the second phase equal to 50% of the final voltage of the first phase. An up/down protocol was used to determine the 50% probability-of-success levels (E50) for delivered energy and initial voltage. First, using pulse waveforms with equal positive and negative phase durations, test waveforms with total durations of 4 nw (2 ms positive + 2 ms negative), 6 ms (3 + 3 ms), and 16 ms (8 + 8 ms) were compared to the control waveform of 8 ms (4+4 ms) in 30 experiments. Defibrillation voltage requirements with 4 ms (174 ± 56 V) were higher (P = 0.001) compared to 8 ms (127 ± 49 V). Defibrillation voltage requirements for the 6-ms and 16-ms waveforms were similar to the 8-ms control waveform. Delivered energies tended to be higher with the 4-ms waveform. A second series of 40 experiments were performed to compare monophasic (4+0 ms) and three asymmetric biphasic waveforms (4+2 ms, 4 + 8 ms, and 4 + 16 ms) to the symmetric control waveform (4+4 ms). The monophasic (2.15 ± 1.21 J) and the 4 + 16 ms waveform (1.86 ± 1.09 J) required higher energies (P ± 0.05) than the control waveform (1.24 ± 0.41 J and 0.87 ± 0.7 J, respectively). The monophasic waveform also resulted in greater voltage requirements (223 ± 64 V) compared to the control waveform (160 ± 26 V) (P = 0.02). Energy and voltage requirements were similar for the 4+2 ms and 4+8 ms waveforms compared to the control. Defibrillation requirements with biphasic waveforms were affected by total and second phase duration. For waveforms with equal phase durations, total durations between 6–16 ms resulted in the lowest values for defibrillation. For waveforms with variable second (negative) phase durations, durations ranging from 50%-200% of the first phase did not affect defibrillation efficacy.     

Effects of Autonomic Manipulation on Ventricular Fibrillation and Internal Cardiac Defibrillation Thresholds in Pigs

Autonomic tone may contribute to cardiac arrhythmogenesis and influence the efficacy of implantable defibrillators. Fifty-two anesthetized pigs were randomized to: (1) methacholine (n = 12); (2) nitroprusside (n = 12); (3) phenylephrine (n = 12); (4) carbachol (n = 8); and (5) saline (n = 8). Ventricular fibrillation threshold (VFT) and triplicate defibrillation thresholds (DFT) were obtained before and during each intervention. Mean (± SE) VFT was increased with: methacholine (76 ± 10.6 V vs 39 ± 7.1 V, P < 0.001); phenylephrine (68 ± 10.5 V vs 38 ± 6.2 V, P < 0.001); and carbachol (106 ± 11.5 V vs 30 ± 6.5 V, P < 0.0001). Nitroprusside and saline failed to alter VFT. Mean (± SE) DFT was decreased with: methacholine (7.7 ± 0.8 J vs 9.7 ± 0.8 J, P < 0.001); phenylephrine (9.8 ± 0.9 J vs 11.3 ± 1.0 1, P < 0.05); and carbachol (9.2 ± 0.7 J vs 12.2 ± 0.8), P < 0.0001), remaining unchanged following nitroprusside and saline infusion. Thus, modulation of autonomic tone modified arrhythmia susceptibility and the energy necessary for defibrillation, increased parasympathetic tone, increased VFT, and decreased DFT. Evaluation of autonomic balance, particularly parasympathetic tone, may be useful with the implantation of automatic defibrillators.     

Effective Defibrillation in Pigs Using Interleaved and Common Phase Sequential Biphasic Shocks

Previous studies have shown that low internal de/ibrillation threshoids (DFTs)can be attained by using two pairs of electrodes and combining hiphasic shocks with sequential timing. The purpose of this two-part study was to test the defibrillation efficacy of two new shock sequences, an interleaved biphasic. and a common phase sequential biphasic, that utilized two pairs of electrodes and were developed from the concept of sequential biphasic shocks. In the first part, defibriUation catheters were placed in the right ventricle and the superior vena cava of six anesthetized pigs. A small patch electrode was placed on the LV apex through a subxiphoid incision and a cutaneous patch was placed on the left thorax. The mean DFT energies for the interleaved biphasic (5.2 ± 0.4 J)and the common phase sequential biphasic waveforms (5.4 ± 0.4 J)were substantially less (P < 0.0001)than those for either the sequential monophasic (10.6 ± 1.0 J)or single biphasic waveforms (9.0 + 1.0 J). In (he second study, which used nine anesthetized pigs, the importance of phase reversal was demonstrated by the finding that Ihe DFT energy of a common phase sequential biphasic shock (6.2 ± 0.4 J)was much less than a common phase sequential monophasic shack (17.9 ± 1.3 J, P < 0.0001), furthermore, the average DFT for four common phase sequential biphasic configurations (5.7 ± 0.2 J)was much less than for a configuration that was similar except that current flow was not reversed in one phase so that no biphasic effect was present (19.7 ±1.2 J). The efficacy of common phase sequential biphasics was comparable to that of sequential biphasics. The effectiveness of sequential biphasics, interleaved biphasics, and common phase sequential biphasics is possibly due to two mechanisms: (A)an increase in the potential gradient during a later phase in regions that were low during the first phase, and (B)the exposure of most of the myocardium to a biphasic shock that reduces the minimum extracellular potential gradient needed to defibrillate.     

Defibrillation Threshold: A Simple and Quantitative Estimate of the Ability to Defibrillate

It has recently been shown that the probability of successful defibrillation as a function of energy has a sigmoidal dose-response relationship. Determination of a defibrillation "dose-response curve" is time consuming and requires multiple defibrillation attempts. On the other hand, determination of a defibrillation threshold is achieved rapidly and would be better suited to study the effect of interventions on the ability to defibrillate patients. We assessed the relationship of defibrillation threshold to the defibrillation "dose-response curve" in twelve open chest, halotbane anesthetized pigs. Ventricular fibrillation was induced electrically, and defibrillation was attempted by passing sequentiai puise shocks through an indwelling catheter and plaque electrodes. Defibrillation threshold was determined by decreasing the stored voltage of the initial shock until it failed to defibrillate the heart. Five different stored voltage levels distributed around defibrillation threshold were then randomly administered, six times for each level. A "dose-response curve" was obtained for each animal. Defibrillation threshold superimposed on the "dose-response curve" at 76 ± 7.2 percent (mean ± SEM) defibrillation success. Energy delivered at 1.5 times average defibrillation threshold was predicted to achieve 100 percent defibrillation success for a single shock in all animals. We conclude that defibrillation threshold provides a simple and quantitative estimate of the ability to defibrillate with a predictable relationship to the "dose-response curve."     

Optimal Truncation of Defibrillation Pulses

The statement that the optimal pulse for defibriliation has not yet been discovered implies that an ideal pulse exists, but that it is different in shape, duration, and energy as compared to pulses of today. The optimum pulse is that which can defibrillate with lowest energy. Reduction of energy can be reached twofold: by looking for a pulse duration with lowest energy threshold, and by finding the optimal truncation with lowest refibrillating effect. Assuming that there is also a rheobase in defibrillation below which no defibrillating but probably a refibrillating effect exists, the exponential pulse should be truncated if it intersects with the rheobase. Combining the fundamental law of electrostimulation with this boundary condition allows for the mathematical solution of the above problem of optimal energy. Defibrillation can be optimized with respect to pulse duration or tilt and to energy efficiency. The most important parameter in determining other optimized parameters such as output capacitor is the chronaxie. The calculations reveal that the "concept of constant energy" does not accurately describe defibrillation, that today's implantable cardioverter defibrillator devices possess refibrillating tilts, that pulse durations should he programmed to values between 4 and 10 msec, and that smaller output capacitors around 30 μF would minimize the energy requirements. Whether optimized monophasic pulses are inferior or equal to biphasic pulses needs further experimental studies.     

Influence of Ventricular Fibrillation Duration on Defibrillation Energy in Dogs Using Bidirectional Pulse Discharges

The automatic implantable defibrillator device typically discharges 5-30 seconds after detection of ventricular fibrillation. To investigate the importance of the duration of ventricular fibrillation on defibrillation, the effects of ventricular fibrillation durations of 5, 15, and 30 seconds on the energy requirements for successful internal defibrillation were compared in 15 closed chest dogs with internal electrodes. The electrode configuration utilized a transvenous right heart catheter with two electrodes and a precordial subcutaneous patch electrode, with a single bidirectional pulse discharged between the distal catheter electrode and the proximal catheter and patch electrodes. Curves of energy vs. percentage of successful defibrillation were constructed and logistic regression was used to derive 90% and 50% successful energy doses (ED90 and ED50). The mean ventricular fibrillation activation interval just prior to defibrillation was determined from discrete RV endocardial electrograms. Four dogs died during testing, all because of inability to defibrillate after 30 s of ventricular fibrillation. In the remaining 11 dogs, the ED90 increased from (mean +/- SD) 27 +/- 13J at 5 s to 41 +/- 14J at 30 s (p less than .01). The mean ventricular fibrillation activation interval decreased from 107 +/- 21 ms at 5 s to 95 +/- 18 ms at 30 s (p less than .01). In conclusion, the energy required for internal defibrillation in dogs using this electrode configuration increases with longer durations of ventricular fibrillation, and is associated with more rapid ventricular fibrillation activation intervals.     

Defibrillation Effects of Intravenous Nifekalant in Patients with Out-of-Hospital Ventricular Fibrillation

Nifekalant (NF), a pure K⁺ channel blocker developed in Japan, has been reported to be effective in the treatment of life-threatening ventricular arrhythmias. We studied its efficacy in 18 men and 4 women with out-of-hospital ventricular fibrillation (VF) admitted to our emergency department between August 2001 and March 2004. The number of DC shocks delivered for out-of-hospital VF, serum Na⁺ and K⁺, arterial blood pH, and base excess were compared in 8 patients treated with NF, 0.3 mg/kg i.v. followed by a continuous intravenous (group N) versus 14 patients treated with lidocaine, 2 mg/kg, i.v. (group C). The two groups were similar with respect to their baseline characteristics. Sinus rhythm returned in 5 of 8 patients in group N versus 2 of 14 patients in group C (P < 0.05). These seven patients were admitted to the intensive care unit, though all died within 1 month. The results of this study suggest that NF may be effective in defibrillation of out-of-hospital VF, though controlled studies are needed to confirm our observations.     

Double Sequential Defibrillation for Refractory Ventricular Fibrillation: A Case Report

Abstract

A 40-year-old male struck his chest against a pole during a basketball game and had sudden out-of-hospital cardiac arrest. After bystander cardiopulmonary resuscitation, fire and emergency medical services personnel provided six defibrillation attempts prior to emergency department arrival. A 7th attempt in the emergency department using a different vector was unsuccessful. On the 8th attempt, using a second defibrillator with defibrillator pads placed adjacent to the primary set of defibrillator pads, two shocks were administered in near simultaneous fashion. The double sequential defibrillation was successful and the patient had return of spontaneous circulation at the next pulse check. He recovered in the intensive care unit, was discharged home 1 month later, and continues to follow up in clinic over 1 year later with a Cerebral Performance Category score of 1 (short-term memory deficits).     

Temporal Stability of Sequential Pulse Defibrillation Threshold

We have shown that sequential pulse defibrillation threshold voltage and total delivered energy do not change with maturation of the electrode tissue interface for up to 12 weeks after implantation of two different electrode configurations. This result is important to predict the future performance of an implantable defibrillator that is tested only at implant.     

A Model of Ischemically Induced Ventricular Fibrillation for Comparison of Fixed-dose and Escalating-dose Defibrillation Strategies

OBJECTIVES: Fixed- and escalating-dose defibrillation protocols are both in clinical use. Clinical observations suggest that the probability of successful defibrillation is not constant across a population of patients with ventricular fibrillation (VF). Common animal models of electrically induced VF do not represent a clinical VF etiology or reproduce clinical heterogeneity in defibrillation probability. The authors hypothesized that a model of ischemically induced VF would exhibit heterogeneous defibrillation shock strength requirements and that an escalating-dose strategy would more effectively achieve prompt defibrillation. METHODS: Forty-six swine were randomized to fixed, lower-energy (150 J) transthoracic shocks (group 1) or escalating, higher-energy (200 J-300 J-360 J) shocks (group 2). VF was induced by balloon occlusion of a coronary artery. After 1 or 5 minutes of VF, countershocks with a biphasic waveform were administered. The primary endpoint was successful defibrillation (termination of VF for 5 seconds) with < or =3 shocks. RESULTS: VF was induced with occlusion or after reperfusion in 35 animals. Only five of 17 group 1 animals (29%, 95% CI = 10 to 56) could be defibrillated with < or =3 shocks; 15 of 18 group 2 animals (83%, 95% CI = 59 to 96) were defibrillated with < or =3 shocks (p < 0.002 vs. group 1). Nine of the group 1 animals (75%) that could not be defibrillated with 150-J shocks were rescued with < or =3 shocks ranging from 200 to 360 J. CONCLUSIONS: In this ischemic VF animal model, defibrillation shock strength requirements varied among individuals, and when defibrillation was difficult, an escalating-dose strategy was more effective for prompt defibrillation than fixed, lower-energy shocks.     

Comparison of Simultaneous Versus Sequential Defibrillation Pulsing Techniques Using a Nonthoracotomy System

The defibrillation threshold (DFT) using simultaneous (SIML) versus sequential (SEQ) pathways for shock delivery was compared in 16 patients with an implanted cardioverter defibrillator. All patients had three-lead nonthoracotomy systems (NTL) using a left chest subcutaneous patch, a right ventricular endocardial lead, and a lead in the coronary sinus (n = 5) or superior vena cava (n = 11). The DFT were determined 2–44 days (17 ± 17 days) after implantation. The DFT was defined as the lowest energy shock that resulted in successful defibrillation. The first pathway tested was SIML in 12 and SEQ in 4 patients with output beginning at or above the intraoperative DFT, routinely 18 J. The second pathway was tested beginning 2–4 J above the DFT of the first tested pathway. All shocks were delivered in 2–4 J decrement or increment steps. The SEQ pathway shocks resulted in a significantly lower DFT than SIML pathway shocks (14 ± 6 vs 18 ± 6 J; I < 0.01). There was no difference in the time delay after ventricular fibrillation initiation before shock delivery for the successful defibrillation between SIML versus SEQ pathways (7 ± 2 secs for both pathways). In 7 of 16 patients, defibrillation using SEQ pathway resulted in a > 5 J lowering of DFT, while only one patient had > 5 J lowering of DFT using SIML shocks (P <0.05). These results have important implications for selecting the optimal pathway for implantable cardioverter defibrillator therapy with a multilead NTL system.     

Treatment of Refractory Ventricular Fibrillation by Combined Internal (Epicardial) and External (Transthoracic) Defibrillation

This report describes a modified defibrillation technique used successfully in a patient with an implanted epicardial cardioverter defibrillator who developed refractory ventricular fibrillation. During operative testing at the time of generator replacement, two episodes of intractable ventricular fibrillation were terminated by using a combined internal (epicardial)-external (transthoracic) defibrillation system that delivered a 360-J shock between the anterior epicardial patch and a large posterior skin electrode.     

Double Sequential External Defibrillation and Survival from Out-of-Hospital Cardiac Arrest: A Case Report

Background: Patients who present in ventricular fibrillation are typically treated with cardiopulmonary resuscitation (CPR), epinephrine, antiarrhythmic medications, and defibrillation. Although these therapies have shown to be effective, some patients remain in a shockable rhythm. Double sequential external defibrillation has been described as a viable option for patients in refractory ventricular fibrillation. Objective: To describe the innovative use of two defibrillators used to deliver double sequential external defibrillation by paramedics in a case of refractory ventricular fibrillation resulting in prehospital return of spontaneous circulation and survival to hospital discharge with good neurologic function. Case: A 28-year-old female sustained a witnessed out-of-hospital cardiac arrest (OHCA). Bystander CPR was performed by her husband followed by paramedics providing high-quality CPR, antiarrhythmic medication, and 6 biphasic defibrillations using standard energy levels. Double sequential external defibrillation was applied and a return of spontaneous circulation was attained on scene and maintained through to arrival to the emergency department. Following admission to hospital the patient was diagnosed with long QT syndrome. An implantable cardioverter defibrillator was placed and the patient was discharged with a Cerebral Performance Category of 2 as well as a modified Rankin Scale of 2 after an 18-day hospital stay. The patient's functional status continued to improve post discharge. Conclusion: The addition of double sequential external defibrillation as part of a well-organized resuscitation effort may be a valid treatment option for OHCA patients who present in refractory ventricular fibrillation.