Homicide Manner-of-Death Classification in Arrest-Related Death.

ABSTRACT: Multiple studies have documented various factors that influence or determine forensic pathologist classification of manner of death. There do not appear to be any published studies on manner of death classification specifically regarding arrest-related deaths (ARDs). The goal of this study was to consider a large body of cases of nonfirearm ARDs to analyze the homicide classification with regards to numerous decedent and practitioner (medical examiner/coroner [ME/C]) variables. We analyzed 1145 US autopsy reports from the years 2006-2020, inclusive, and considered decedent variables of age, ethnicity, height, weight, body mass index, toxicology, and mention of a conducted electrical weapon and ME/C influence variables of gender, country region, and year. We found that the homicide classification likelihood increased by a factor of 1.04-1.05 per year, 1.34-1.37 for a female medical examiner, and 1.4-1.5 going from Southern states to Western states. There is an increasing trend for ME/C to label nonfirearm ARDs as homicides in the United States. The homicide classification is more common in Western states and less common in Southern states, and it was more common with a female ME/C.

Inhomogeneity and temporal effects in AutoPulse Assisted Prehospital International Resuscitation--an exception from consent trial terminated early.

BACKGROUND: The ASPIRE trial (AutoPulse Assisted Prehospital International Resuscitation) was multicenter exception from consent clinical trial that compared mechanical cardiopulmonary resuscitation (CPR) with a device (AutoPulse-CPR) to traditional manual CPR (manual-CPR) in out-of-hospital cardiac arrest. Enrollment was suspended early due to safety concerns. One site (site C) made a potentially important protocol change midtrial, and enrollment at that site was noted to be independently associated with outcome. METHODS: The study used a post hoc reanalysis of source data and documentation using standard statistical approaches evaluating for possible secular, temporal, and trial design, factors that may have related to the trial's outcome. RESULTS: The protocol change at site C also appears to have resulted in a delay in application of AutoPulse-CPR. Before and after the protocol change survival in patients receiving AutoPulse-CPR decreased from 19.6% to 4% (P = .024). Logistic regression analysis showed site C was significantly different (P = .008) from the remaining sites with respect to survival. Unlike site C, the other sites actually showed an increase over time in the primary end point of 4-hour survival (P = .008) favorable to AutoPulse-CPR. There did not appear to be significant safety (P = .42) nor efficacy concerns (P = .17) at these sites. CONCLUSIONS: The difference in survival that caused early suspension of ASPIRE appears to have been limited to one site after its protocols change. At the time the trial was suspended, the outcomes of patients at the other sites appear to have been trending in favor of the intervention.

Coronary blood flow produced by muscle contractions induced by intracardiac electrical CPR during ventricular fibrillation.

UNLABELLED: It has been reported that transthoracic electrical cardiopulmonary resuscitation (ECPR) generates coronary perfusion pressures (CPP) similar to manual chest compressions (MCC). We hypothesized that intracardiac ECPR produces similar CPP. METHODS: ECPR pulse train protocols were applied for 20 seconds in a porcine model following 10 seconds of ventricular fibrillation (VF), using a defibrillator housing electrode and a right ventricular coil (IC-ECPR). Each protocol consisted of 200-ms electrical pulse trains applied at a rate of 100 pulse trains/min. The protocols were grouped in skeletal-based versus cardiac-based stimulation measurements. CPP was recorded and compared to historical MCC values generated by a similar experimental design. CPP > 15 mm Hg at 30 seconds of VF following the application of an IC-ECPR protocol was defined as successful. RESULTS: Mean CPP for all intracardiac ECPR pulse train protocols at 30 seconds of VF was 14.8 +/- 3.8 mm Hg (n = 39). Mean CPP in seven successful skeletal-based IC-ECPR protocols was 19.4 +/- 3.2 mm Hg, and mean CPP in 10 successful cardiac-based IC-ECPR protocols was 17.4 +/- 2.1 mm Hg. Reported CPP for 15 MCC experiments at 30 seconds of VF was 22.9 +/- 9.4 mm Hg (P = 0.35 compared to skeletal-based IC-ECPR, P = 0.08 compared to cardiac-based IC-ECPR). CONCLUSIONS: Intracardiac applied electrical CPR produced observable skeletal muscle contractions, measurable pressure pulses, and coronary perfusion pressures similar to MCC during a brief episode of untreated VF.

Transthoracic application of electrical cardiopulmonary resuscitation for treatment of cardiac arrest.

OBJECTIVE: Observational studies have shown that muscular stimulation contracting the thoracic cage may produce coronary perfusion pressures equal to manual chest compressions. This study examined electrical cardiopulmonary resuscitation for coronary perfusion pressures during ventricular fibrillation in a porcine model of cardiac arrest. DESIGN: Prospective randomized controlled study. SETTING: University affiliated research institute. SUBJECTS: Domestic male pigs. INTERVENTIONS: In seven domestic male pigs (40 +/- 2 kg), ventricular fibrillation was induced electrically and untreated for 10 secs. For each ventricular fibrillation episode, one of 16 electrical cardiopulmonary resuscitation stimulation protocols (pulse trains) or manual chest compression was applied. Each compression protocol was applied for 20 secs, followed by a defibrillation shock. The experimental procedure was performed across one or more randomized complete blocks. The electrical cardiopulmonary resuscitation pulse trains were defined by four two-level factors: pulse width (0.15 and 7.5 msec), pulse period (15 and 30 msec), train width (50 and 200 msec), and train rate (60 or 120 compressions per min). Pulse trains comprised two groups, based on pulse width (skeletal-based, 0.15 msec; cardiac-based, 7.5 msec). MEASUREMENTS AND MAIN RESULTS: Train width was the significant design parameter for producing efficacious levels of coronary perfusion pressures for the skeletal-based electrical cardiopulmonary resuscitation pulse trains (p = 0.02). Both train width and train rate were significant design parameters for producing efficacious levels of coronary perfusion pressures for the cardiac-based electrical cardiopulmonary resuscitation pulse trains (p < 0.001, p = 0.5, respectively). Optimal skeletal-based and cardiac-based electrical cardiopulmonary resuscitation pulse trains were significantly better than ventricular fibrillation (p = 0.01, p = 0.01, respectively) and equivalent to manual chest compression (p = 0.2, p = 0.7, respectively) for sufficient coronary perfusion pressure levels. CONCLUSIONS: Optimal skeletal-based and cardiac-based electrical cardiopulmonary resuscitation pulse train parameters generated levels of coronary perfusion pressure significantly greater than ventricular fibrillation and comparable with manual chest compression over a short interval of untreated cardiac arrest.

A randomized controlled feasibility trial comparing safety and effectiveness of prehospital pacing versus conventional treatment: 'PrePACE'.

OBJECTIVE: To evaluate the feasibility of a prehospital randomized controlled trial comparing transcutaneous pacing (TCP) with dopamine for unstable bradycardia. METHODS: Unstable bradycardic patients who failed to respond to a fluid bolus and up to 3mg atropine were enrolled. The intervention was dopamine or TCP with crossover to dopamine if TCP failed. The primary outcome was survival to discharge or 30 days. Randomization compliance, safety, follow-up rates, primary outcome, and sample size requirements were assessed. RESULTS: Of 383 patients with unstable bradycardia, 151 (39%) failed to respond to atropine or fluid and were eligible for enrollment and 82 (55%) were correctly enrolled. Fifty-five (36%) of eligible patients could not be enrolled for practical reasons; 3 had advance directives, 32 met inclusion criteria on arrival at hospital and in 20 cases, paramedics chose not to enroll based on the circumstances of the case. The remaining 13 were missed cases; 8 were missing randomization envelopes and in 5, the paramedic forgot. Randomization compliance was 95% (78/82). Forty-two (51%) patients were randomized to TCP and seven of these crossed over to dopamine. Two cases were randomized but did not receive the intervention; either due to lack of time or loss of IV access. Three adverse events occurred in each group. Survival to discharge or 30 days in hospital was 70% (28/40) and 69% (29/42) in the dopamine and TCP groups, respectively with 100% follow up. To detect a 10% relative difference in 30 days survival between treatment arms, a sample size of 690 per group would be required. CONCLUSIONS: It is feasible to conduct a prehospital randomized controlled trial of TCP for unstable bradycardia and a definitive trial would require a multi-centre study.

Sensitivity and specificity of an automated external defibrillator algorithm designed for pediatric patients.

OBJECTIVE: Electrocardiographic (ECG) rhythm analysis algorithms for cardiac rhythm analysis in automated external defibrillators (AEDs) have been tested against pediatric patient rhythms (patients < or = 8 years old) using adult ECG algorithm criteria. However these adult algorithms may fail to detect non-shockable pediatric tachycardias because they do not account for the difference in the rates of normal sinus rhythm and typical tachyarrhythmias in childhood. METHODS: This study was designed to define shockable and non-shockable rhythm detection criteria specific to pediatric patients to create a pediatric rhythm database of annotated rhythms, to develop a pediatric-based AED rhythm analysis algorithm, and to test the algorithm's accuracy. Pediatric rhythm detection criteria were defined for coarse ventricular fibrillation, rapid ventricular tachycardia, and non-shockable rhythms, including pediatric supraventricular tachycardia. Pediatric rhythms were collected as sustained, classifiable, rhythms > or = 9 s in length, and were annotated by pediatric electrophysiologists as clinically shockable or non-shockable based on pediatric criteria. Rhythms were placed into a pediatric rhythm database; each rhythm was converted to digitally accessible, public-domain, MIT rhythm data format. The database was used to evaluate a pediatric-based AED rhythm analysis algorithm. RESULTS: Electrocardiographic rhythms from 198 children were recorded. There were 120 shockable rhythms from 49 patients (sensitivity; coarse ventricular fibrillation: 42 rhythms, 100%; rapid ventricular tachycardia: 78 rhythms, 94%), for combined sensitivity of 96.0% (115/120). There were 585 non-shockable rhythms from 155 patients (specificity normal sinus: 208 rhythms, 100%; asystole: 29 rhythms, 100%; supraventricular tachycardia: 161 rhythms, 99%; other arrhythmias: 187 rhythms, 100%), for combined specificity of 99.7% (583/585). Overall accuracy for shockable and non-shockable rhythms was 99.0% (702/709). CONCLUSIONS: New pediatric rhythm detection criteria were defined and analysis based on these criteria demonstrated both high sensitivity (coarse ventricular fibrillation, rapid ventricular tachycardia) and high specificity (non-shockable rhythms, including supraventricular tachycardia). A pediatric-based AED can detect shockable rhythms correctly, making it safe and exceptionally effective for children.

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

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

Reduced cardioversion thresholds for atrial fibrillation and flutter using the rectilinear biphasic waveform.

BACKGROUND: The RLB waveform has been shown to be superior in overall efficacy to the MDS waveform for cardioversion of AF in one prospective study and one large retrospective analysis. However, little is known about the efficacy of the RLB waveform at lower energies. OBJECTIVE: This study was undertaken to define the cardioversion thresholds for atrial fibrillation (AF) and flutter (FL) using the rectilinear biphasic (RLB) waveform and compare these to the cardioversion threshold using the conventional monophasic damped sine (MDS) waveform. METHODS: All patients underwent transthoracic cardioversion of persistent AF and FL. We performed step-up cardioversion thresholds for AF in 180 RLB patients and 38 MDS patients and compared those results. We also performed cardioversion threshold determinations in 39 RLB patients with typical right atrial FL. For the RLB patients, an initial energy setting of 5 Joules (J) was selected, with increasing energy steps until success, up to 200 J. The MDS energy sequence was 50 up to 360 J. RESULTS: The average selected energy threshold for AF using the RLB waveform was 70.6 J (median=50 J) versus 193.4 J (median=150 J) for the MDS waveform (p<0.001). For FL, the average cardioversion threshold using the RLB waveform was 33.2 J (median=20 J; p<0.001 vs. AF with the RLB waveform). CONCLUSIONS: Our results show that the transthoracic AF cardioversion threshold using the RLB waveform is significantly lower than the MDS waveform. As expected, the cardioversion threshold for FL was significantly lower than that of AF using the RLB waveform.

Comparison of the rectilinear biphasic waveform with the monophasic damped sine waveform for external cardioversion of atrial fibrillation and flutter.

External cardioversion using the monophasic damped sine (MDS) waveform is successful 70% to 94% of the time when using up to 360 J. The rectilinear biphasic (RLB) defibrillator has been shown to be superior in efficacy to the MDS waveform in atrial cardioversion in a small randomized study. This larger, retrospective study compares the results of the RLB waveform with those of the MDS waveform for cardioversion of atrial fibrillation (AF) and atrial flutter in a large cohort of patients. We performed 1,877 external cardioversion procedures in 1,361 patients for AF and atrial flutter by using the RLB defibrillator. We compared these results with those of the MDS defibrillator in 2,025 patients who underwent 2,818 cardioversion procedures. The overall success rates for the RLB defibrillator were 99.1% for AF and 99.2% for atrial flutter, and the corresponding success rates for the MDS defibrillator were 92.4% and 99.8% (p <0.001; RLB superior for AF). The median overall successful energy level for the MDS waveform was 200 J, whereas the corresponding RLB energy level was 100 J. Multivariate analyses demonstrated that underlying clinical conditions or use of antiarrhythmic drugs does not significantly affect overall success rates. Our results from >4,000 procedures confirmed and extended those of the previous report by showing a very high success rate for cardioversion of AF and atrial flutter using the RLB waveform. The MDS waveform was equally effective for atrial flutter but significantly less effective in terminating AF.

Medium voltage therapy for preventing and treating asystole and PEA in ICDs.

INTRODUCTION: Sudden cardiac death (SCD) takes up to 500,000 lives each year before a victim can even be treated. To address this the implantable cardioverter defibrillator (ICD) was developed to treat those identified at high risk of SCD. Unfortunately, there are a significant number of cases in which the ICD does not successfully return a victim to normal rhythm and effective perfusion of the blood. METHODS: The vast majority of cases that are not responsive to the ICD therapy require cardio-pulmonary resuscitation (CPR) according to current resuscitation guidelines. A novel electrical stimulus called medium voltage therapy (MVT) has shown efficacy in producing coronary and carotid blood flow during ventricular fibrillation. This report presents the case that the same stimulus may be effective and feasible for use in ICD patients that do not respond to their ICD therapy, or do not have a rhythm in which, an ICD shock is indicated. CONCLUSION: The inclusion of MVT technology in implantable devices may be effective in preparing the heart for successful defibrillation or in improving the metabolic condition of the heart to the extent that a pulsatile rhythm may spontaneously develop.

Medical device design process.

The current design process is a combination of methods from engineering disciplines, government regulatory agencies (domestic and international) and independent certification and compliance companies. The goal of the processes that have been developed is to be certain that a new product meets the users expectations, is safe and effective in providing its claimed benefits. As products have become more complex and particularly with regard to software control it has become increasingly more difficult to determine the safety and efficacy of a product by inspection or after the fact testing alone. In order to improve the ability of designers and auditors to ascertain the safety and efficacy of a product, the use of design controls has been adopted that specify a method of evaluating the design process at several key stages. This paper will describe some of the methods that are used for design controls intending to give the reader an overview of these methods in the context of medical products.

Comparison of rectilinear biphasic waveform with biphasic truncated exponential waveform in a pediatric defibrillation model.

OBJECTIVE: To compare the rectilinear biphasic waveform with a biphasic truncated exponential waveform for pediatric defibrillation. DESIGN: Prospective, randomized study. SETTING: Experimental laboratory of a university-affiliated research institute. SUBJECTS: Male domestic piglets (4-24 kg). INTERVENTIONS: Eleven piglets (4-8 kg), which represented a patient <1 yr old, and ten piglets (16-24 kg), which represented a pediatric patient between the ages of 2 and 8 yrs, were anesthetized, intubated, and mechanically ventilated. Ventricular fibrillation was induced and maintained for 30 secs, and a predetermined shock was then delivered to defibrillate. Following defibrillation, the animal was permitted to stabilize hemodynamically for 4 mins. Fifty shocks were applied to each animal using a randomization schedule based on a predetermined permutation of 50. The 50 shocks were 25 shocks for each rectilinear biphasic and biphasic truncated exponential waveforms, comprising five shocks at five energy settings. Each group of five shocks was fixed at a predetermined energy value, depending on the body weight of the animal. Dose-response curves were constructed using logistic regression. Aortic pressure, electrocardiogram, left ventricular pressure, and left ventricular pressure value of 40 mm Hg were continually measured. MEASUREMENTS AND MAIN RESULTS: Dose-response curves determined defibrillation thresholds at 50% (D50) and 90% (D90) probability of success. The rectilinear biphasic waveform defibrillated with <90% of the D50 and D90 energies required for a biphasic truncated exponential waveform. The rectilinear biphasic waveform also successfully defibrillated with significantly less energy per body weight and per heart weight compared with a biphasic truncated exponential waveform. CONCLUSIONS: The rectilinear biphasic waveform has superior defibrillation performance compared with a biphasic truncated exponential waveform in a piglet defibrillation model for young children.

Effects of biphasic waveforms on outcomes of cardiopulmonary resuscitation in a porcine model of prolonged cardiac arrest.

OBJECTIVES: The effects of two clinically available biphasic waveforms on the success of defibrillation and postresuscitation myocardial dysfunction after prolonged ventricular fibrillation were compared with two newly designed dual-path sequential and simultaneous rectilinear biphasic waveforms. Defibrillation via sequential pulses and encircling, overlapping multiple pathway may depolarize a larger myocardial mass and facilitate transthoracic defibrillation. DESIGN: Animal study. SETTING: Experimental laboratory. SUBJECTS: Thirty-two 40 +/- 3 kg pigs. INTERVENTIONS: Ventricular fibrillation was ischemically induced in 32 pigs. After 7 mins of untreated ventricular fibrillation, cardiopulmonary resuscitation was initiated and continued for 5 mins. Animals were then randomized to receive up to three shocks with a) single-path rectilinear biphasic waveform; b) single-path biphasic truncated exponential waveform; c) dual-path rectilinear biphasic sequential defibrillation; or d) dual-path rectilinear biphasic simultaneous defibrillation. MEASUREMENTS AND MAIN RESULTS: Rectilinear biphasic, dual-path sequential defibrillation, and simultaneous defibrillation had significantly fewer shocks (1.1 +/- 0.4, 1.4 +/- 0.5, 1.3 +/- 0.7, respectively) before restoration of spontaneous circulation than biphasic truncated exponential waveform (2.6 +/- 1.4, p < .005) and less postresuscitation myocardial dysfunction (p < .05). Also, dual-path sequential defibrillation had higher postresuscitation ejection fraction than rectilinear biphasic and dual-path simultaneous defibrillation (p < .005). CONCLUSIONS: The energy requirements for terminating ischemically induced ventricular fibrillation were significantly lower and minimized early postresuscitation myocardial dysfunction in the rectilinear biphasic, dual-path sequential defibrillation, and simultaneous defibrillation than the biphasic truncated exponential waveform. Dual-path sequential defibrillation had less postresuscitation myocardial dysfunction than rectilinear biphasic and dual-path simultaneous defibrillation, but at 72 hrs these differences were no longer significant.

Cardiac safety of neuromuscular incapacitating defensive devices.

Neuromuscular incapacitation (NMI) devices discharge a pulsed dose of electrical energy to cause muscle contraction and pain. Field data suggest electrical NMI devices present an extremely low risk of injury. One risk of delivering electricity to a human is the induction of ventricular fibrillation (VF). We hypothesized that inducing VF would require a significantly greater NMI discharge than a discharge output by fielded devices. The cardiac safety of NMI discharges was studied in nine pigs weighing 60 +/- 28 kg. The minimum fibrillating level was defined as the lowest discharge that induced VF at least once, the maximum safe level was defined as the highest discharge which could be applied five times without VF induction, and the VF threshold was defined as their average. A safety index was defined as the ratio of the VF threshold to the standard discharge level output by fielded NMI devices. A VF induction protocol was applied to each pig to estimate the VF threshold and safety index. The safety index for stored charge ranged from 15X to 42X as weight increased from 30 to 117 kg (P < 0.001). Discharge levels above standard discharge and weight were independently significant for predicting VF inducibility. The safety index for an NMI discharge was significantly and positively associated with weight. Discharge levels for standard electrical NMI devices have an extremely low probability of inducing VF.

Rectilinear biphasic waveform defibrillation of out-of-hospital cardiac arrest.

OBJECTIVE: The rectilinear biphasic (RLB) waveform has been shown to effectively defibrillate short-duration ventricular fibrillation (VF) at significantly lower energies than a monophasic damped sine (MDS) waveform. This article reports RLB waveform defibrillation effectiveness for patients presenting in VF during out-of-hospital cardiac arrest when compared with historical MDS effectiveness. METHODS: External RLB defibrillators were deployed in the Omaha Fire Department's emergency medical services (EMS) system. The RLB defibrillators delivered an escalating three-shock sequence of 120, 150, and 200 J. The results observed during the first year of full deployment were compared with the results observed during the previous year when only MDS defibrillators were deployed in the system. The MDS defibrillators delivered an escalating three-shock sequence of 200, 300, and 360 J. Defibrillation was defined as termination of VF for at least 5 seconds after a defibrillation shock. RESULTS: There were 141 adult patients presenting in VF without trauma during the first year using RLB defibrillators. By comparison, there were 153 adult patients during the comparable year using MDS defibrillators. The 120-J RLB shocks had a significantly higher first-shock rate of successful VF termination (67%, 95% CI: 59%-75%) compared with the initial 200-J MDS shocks (48%, 95% CI: 40%-57%, p < 0.0025; odds ratio 2.14 [1.33-3.42]). The number of patients who were defibrillated to a return of spontaneous circulation with a sinus rhythm was significantly greater (25%, 95% CI: 18%-33%) when using the RLB defibrillator compared with using the MDS defibrillator (15%, 95% CI: 10%-22%, p = 0.05; odds ratio 1.85 [1.04-3.31]). CONCLUSION: The RLB defibrillator terminated the VF of patients in out-of-hospital cardiac arrest with superior rates using significantly less energy compared with historical rates for a higher-energy MDS defibrillator.