Cardiac Arrest Rhythm Research Articles

Avoiding the futility of resuscitation

Purpose: To identify patients who should not have resuscitation started or continued. Design: Multi-disciplinary prospective study. Subjects: Two hundred forty-one consecutive patients with cardiopulmonary arrests from January 1995 to February 1997 were evaluated, of which 200 were studied. Methods: Subjects were studied for age, sex, arrest location, CPR duration, recovery from arrest, hospital discharge, 6 weeks' survival, sepsis and co-morbid conditions. Results: Overall 69 (34.5%) recovered from the arrest, 24 (12.0%) left the hospital, and 17 (8.5%) survived 6 weeks. Of inpatients, 13.7% (16/117) were alive at 6 weeks in contrast to 1.2% (1/83) of field/emergency room (ER) arrests. Sepsis did not lessen the immediate recovery rate; however, none of 25 septic patients survived hospitalization. Outcomes were not different between men and women or regular floor and ICU/CCU arrests. Age of survivors was the same as non-survivors. Survivors were resuscitated for 18.7±16.5 min and non-survivors 33.1±18.4 min ( P=0.15). The initial rhythm of asystole or the presence of three or more co-morbid conditions had a negative prognosis. Conclusion: CPR survival is problematic, and it is especially poor in field/BR arrests. Emergency squads should terminate CPR for pulseless patients after communicating with the ER physician. Age is not a determinant of recovery or survival. Arrest outside of the hospital, sepsis, three or more co-morbid conditions, previous CPR, asystole or resuscitation for >25 min all decrease the chance of hospital discharge and survival. Instituting or continuing CPR in a great majority of these patients is futile. Families should be so advised.

Factors affecting survival after prehospital asystolic cardiac arrest in a Basic Life Support-Defibrillation system

Previous studies have shown a low but meaningful survival rate in cases of prehospital cardiac arrest with an initial rhythm of asystole. There may be, however, an identifiable subgroup in which resuscitation efforts are futile. This study identified potential field criteria for predicting 100% nonsurvival when the presenting rhythm is asystole in a Basic Life Support-Defibrillation (BLS-D) system. This prospective cohort study, a component of Phases I and II of the Ontario Prehospital Advanced Life Support (OPALS) Study, was conducted in 21 Ontario communities with BLS-D level of care, and included all adult arrests of presumed cardiac etiology according to the Utstein Style Guidelines. Analyses included descriptive and appropriate univariate tests, as well as multivariate stepwise logistic regression to determine predictors of survival. From 1991 to 1997, 9899 consecutive cardiac arrest cases with the following characteristics: male (67.2%), bystander-witnessed (44.7%), bystander CPR (14.2%), call response interval (CRI) </= 8 minutes (82%) and overall survival (4.3%) were enrolled. Of 9529 cases with available rhythm strip recordings, initial arrest rhythms were asystole in 40.8%, pulseless electrical activity in 21.2% and ventricular fibrillation or ventricular tachycardia in 38%. Of 3888 asystolic patients, 9 (0.2%) survived to discharge; 3 of these cases were unwitnessed arrests with no bystander CPR. There were no survivors if the CRI exceeded 8 minutes. Logistic regression analysis demonstrated that independent predictors of survival to admission were "CRI in minutes" (odds ratio [OR] = 0.87; 95% confidence interval [CI], 0.77-0.98) and "bystander-witnessed" (OR = 2.6; 95% CI, 1.5-4.4). In a BLS-D system, there is a very low but measurable survival rate for prehospital asystolic cardiac arrest. CRIs of over 8 minutes were associated with 100% nonsurvival, whereas unwitnessed arrests with no bystander CPR were not. These data add to the growing literature that will help guide ethical decision-making for protocol development in emergency medical services systems.

CPR-only survivors of out-of-hospital cardiac arrest: Implications for out-of-hospital care and cardiac arrest research methodology

Study objective: There is little evidence that cardiopulmonary resuscitation (CPR) alone may lead to the resuscitation of cardiac arrest victims with other than respiratory causes (eg, pediatric arrest, drowning, drug overdose). The objective of this study was to identify out-of-hospital cardiac arrest survivors resuscitated without defibrillation or advanced cardiac life support. Methods: This observational cohort included all adult survivors of out-of-hospital cardiac arrest of a cardiac cause from phases I and II of the Ontario Prehospital Advanced Life Support Study. During the study period, the system provided a basic life support/defibrillation level of care but no advanced life support. CPR-only patients were patients determined to be without vital signs by EMS personnel who regained a palpable pulse in the field with precordial thump or CPR only and then were admitted alive to the hospital. Six members of a 7-member expert review panel had to rate the patient as either probably or definitely having an out-of-hospital cardiac arrest, and a rhythm strip consistent with a cardiac arrest rhythm had to be present to be considered a patient. Criteria considered were witness status, citizen or first responder CPR, CPR duration, arrest rhythm and rate, and performance of precordial thump. Results: From January 1, 1991, to June 30, 1997, 9,667 patients with out-of-hospital cardiac arrest were treated. The overall survival rate to hospital discharge was 4.6%. There were 97 apparent CPR-only patients admitted to the hospital. Application of the inclusion criteria yielded 24 CPR-only patients who had true out-of-hospital cardiac arrest and 73 patients judged not to have cardiac arrest. Of the 24 true CPR-only patients admitted to the hospital, 15 patients were discharged alive, 10 patients were witnessed by bystanders, and 7 patients were witnessed by EMS personnel. The initial arrest rhythm was pulseless electrical activity in 9 patients, asystole in 12 patients, and ventricular tachycardia in 3 patients. One patient with ventricular tachycardia converted to sinus tachycardia with a single precordial thump. Conclusion: CPR-only survivors of true out-of-hospital cardiac arrest do exist; some victims of out-of-hospital cardiac arrest of primary cardiac cause can survive after provision of out-of-hospital basic life support care only. However, many patients found to be pulseless by means of out-of-hospital evaluation likely did not have a true cardiac arrest. This has implications for the survival rates of most, if not all, previous cardiac arrest reports. Survival rates from cardiac arrest may actually be lower if one excludes survivors who never had a true arrest. The absence of vital signs by out-of-hospital assessment alone is not adequate to include patients in research reports or quality evaluations for cardiac arrest. [De Maio VJ, Stiell IG, Spaite DW, Ward RE, Lyver MB, Field BJ, Munkley DP, Wells GA, for the OPALS Study Group. CPR-only survivors of out-of-hospital cardiac arrest: implications for out-of-hospital care and cardiac arrest research methodology. Ann Emerg Med. June 2001;37:602-608.]

Factors associated with sudden death of individuals requiring restraint for excited delirium

The purpose of this article is to identify and rank factors associated with sudden death of individuals requiring restraint for excited delirium. Eighteen cases of such deaths witnessed by emergency medical service (EMS) personnel are reported. The 18 cases reported were restrained with the wrists and ankles bound and attached behind the back. This restraint technique was also used for all 196 surviving excited delirium victims encountered during the study period. Unique to these data is a description of the initial cardiopulmonary arrest rhythm in 72% of the sudden death cases. Associated with all sudden death cases was struggle by the victim with forced restraint and cessation of struggling with labored or agonal breathing immediately before cardiopulmonary arrest. Also associated was stimulant drug use (78%), chronic disease (56%), and obesity (56%). The primary cardiac arrest rhythm of ventricular tachycardia was found in 1 of 13 victims with confirmed initial cardiac rhythms, with none found in ventricular fibrillation. Our findings indicate that unexpected sudden death when excited delirium victims are restrained in the out-of-hospital setting is not infrequent and can be associated with multiple predictable but usually uncontrollable factors.

Part 6: Advanced Cardiovascular Life Support

Part 6: Advanced Cardiovascular Life Support

Incidence, duration and survival of ventricular fibrillation in out-of-hospital cardiac arrest patients in Sweden

The chance of survival from ventricular fibrillation (VF) is up to ten times higher than those with other cardiac arrest rhythms. To calculate the effect of out-of-hospital resuscitation organisations on survival, it is necessary to know the percentage of cardiac arrest patients initially in VF and the relationship between delay time to defibrillation and survival. Aim: To study the incidence of VF at the time of cardiac arrest and on first ECG, the duration of VF and the relation between time to defibrillation and survival. Method: The Swedish Cardiac Arrest Registry has collected standardised reports on out-of-hospital cardiac arrests from ambulance organisations in Sweden, serving 60% of the Swedish population. Results: In 14 065 cases of out-of-hospital cardiac arrest collected between 1990 and 1995, resuscitation was attempted in 10 966 cases. Incidence: The first ECG showed VF in 43% of all patients. The incidence of VF at the time of cardiac arrest was estimated to be 60–70% in all patients and 80–85% in the cases with probable heart disease. Duration: The estimated disappearance rate of VF was slow. Thirty minutes after collapse ≈40% of the patients were in VF. Survival: Overall survival to 1 month was only 1.6% for patients with non-shockable rhythms and 9.5% for patients found in VF. With increasing time to defibrillation, the survival rate fell rapidly from ≈50% with a minimal delay to 5% at 15 min. Conclusions: This study suggests a high initial incidence of VF among out-of-hospital cardiac arrest patients and a slow rate of transformation into a non-shockable rhythm. The survival rate with very short delay times to defibrillation was ≈50%, but decreased rapidly as the delay increased.

Electrocardiographic evaluation of defibrillation shocks delivered to out-of-hospital sudden cardiac arrest patients

Objective: Following out-of-hospital defibrillation attempts, electrocardiographic instability challenges accurate assessment of defibrillation efficacy and post-shock rhythm. Presently, there is no precise definition of defibrillation efficacy in the out-of-hospital setting that is consistently used. The objective of this study was to characterize out-of-hospital cardiac arrest rhythms following low-energy biphasic and high-energy monophasic shocks in order to precisely define defibrillation efficacy and establish uniform criteria for the evaluation of shock performance. Methods: Automatic external defibrillators (AEDs) delivering 150 J impedance-compensating biphasic or 200–360 J monophasic damped sine waveform shocks were observed in a combined police and paramedic program. ECGs from 29 biphasic patients and 87 monophasic patients were classified as organized, asystole or VF at post-shock times of 3, 5, 10, 20 and 60 s. Results: Post-shock time ( P<0.0001) and shock waveform type ( P=0.02) affected the classification of post-shock rhythm. At each analysis time, there were more patients in VF following high-energy monophasic shocks than following 150 J biphasic shocks ( P<0.0001). The percentage of patients in VF increased with post-shock time. The rate of VF recurrence was not a function of shock type, indicating that refibrillation is largely a function of the patient’s underlying cardiac disease. Conclusion: Defibrillation should uniformly be defined as termination of VF for a minimum of 5-s after shock delivery. Rhythms should be reported at 5-s after shock delivery to assess early effects of the defibrillation shock and at 60-s after shock delivery to assess the interaction of the defibrillation therapy and factors such as post-shock myocardial dysfunction and the patient’s underlying cardiac disease.

The Universal Advanced Life Support Algorithm

Valid scientific evidence supports only three interventions as unequivocally effective in adult cardiac resuscitation: The universal algorithm presents these interventions simplistically and recommends a specific sequence that rescuers should follow. The sequence of interventions is based, whenever possible, on sound scientific information. But there is a paucity of convincing human data on some aspects of resuscitation. Until such time as new information becomes available, the working group made no changes to well-established procedures but suggested some modifications on educational rather than scientific grounds. Cardiac arrest rhythms can be divided into two subsets: ventricular fibrillation/pulseless ventricular tachycardia (VF/VT) and non-VF/VT. Non-VF/VT incorporates both asystole and pulseless electrical activity (PEA). The only difference in management between the two arrest rhythms is the need for rescuers to perform defibrillation for patients in VF/VT. Otherwise the actions and interventions are essentially the same: basic CPR, tracheal intubation, epinephrine administration, and correction of reversible causes. …

Circadian variation in sudden cardiac death: Effects of age, sex, and initial cardiac rhythm: Ann Emerg Med 1996; 27/1: 29–34

Abstract Study objective: Previous studies based on data obtained from vital statistics records have demonstrated circadian variation in the occurrence of sudden cardiac death. The purpose of this study was to examine the effects of age, sex, and initial cardiac rhythm on circadian variability in sudden cardiac death. Methods: This study employed a retrospective analysis of the records of adult patients with witnessed cardiac arrest who underwent resuscitation in an urban paramedic system during a 5-year period. Results: The records of 2,250 consecutive patients with witnessed cardiac arrest were reviewed. Spectral analysis was used to decompose the data into frequency components. A circadian variation in the occurrence of sudden cardiac death was demonstrated, with a low occurrence rate between midnight and 6 AM and a 2.4-fold increase between the rate at 6 AM and the rate at noon. The same circadian pattern was noted among both men and women, among both patients aged 18 to 70 and those older than 70 years, and among patients with various initial cardiac arrest rhythms (ventricular tachycardia or fibrillation, asystole, and electromechanical dissociation). However, the outcome of resuscitation in these patients (ie, the rate of successful resuscitation and the rate of survival) did not demonstrate circadian variation. Conclusion: Witnessed out-of-hospital sudden cardiac death demonstrated circadian variation, and this variability was observed regardless of the patient's age, sex, or initial cardiac arrest rhythm. The outcome of resuscitation did not show circadian variability. These results suggest a common pathophysiologic mechanism leading to sudden cardiac death. [Thakur RK, Hoffmann RG, Olson DW, Joshi R, Tresch DD, Aufderheide TP, Ip JH: Circadian variation in sudden cardiac death: Effects of age, sex, and initial cardiac rhythm. Ann Emerg Med January 1996;27;29-34.]

Safe performance of magnetic resonance imaging on five patients with permanent cardiac pacemakers.

Five patients with permanent cardiac pacemakers (Pacesetter models 261, 285, 2016, 2020, 2022) underwent magnetic resonance imaging (MRI). Only one patient (underlying rhythm asystole) was pacemaker dependent. A variety of pacing configurations (single and dual chamber; unipolar and bipolar; sensor and nonsensor driven) were scanned. A thorough evaluation of each pacing system was performed before and after scanning including determination of pacing and sensing thresholds. During MRI the patient was monitored using either ECG, pulse oximetry, or direct voice contact. In four patients heavy dressings were applied over the pacemaker pocket site. Patients were asked to report any symptoms experienced during MRI. The four nonpacemaker dependent patients remained in sinus rhythm throughout the MRI. During and after the MRI all pacemakers continued to function normally except for one transient pause of approximately 2 seconds (noted by pulse oximeter) toward the end of the scan. This occurred in a pacemaker dependent patient with a unipolar dual chamber device programmed DOO. No patient experienced any torque or heat sensation. When appropriate strategies are used our experience suggests that MRI may be performed, when necessary, with an acceptable risk-benefit ratio to the patient. It is unclear whether the isolated pause that was observed was due to the effect of the MRI, an artifact with the monitoring system, or oversensing by the pacemaker. Appropriate patient selection, close monitoring during the scan, and follow-up after MRI are of paramount importance. Further study is necessary to refine the appropriate strategies that could be used to consistently perform MRI safely in a selected pacemaker population.

CARDIAC ARREST

This article reviews the critical resuscitations necessary during prehospital and emergency department treatment of cardiac arrest. Standard therapy for cardiac arrest rhythms is presented. Novel pharmacologic agents, types of cardiopulmonary resuscitation, and circulatory-assist devices are discussed.

Circadian Variation in Sudden Cardiac Death: Effects of Age, Sex, and Initial Cardiac Rhythm

Study objective: Previous studies based on data obtained from vital statistics records have demonstrated circadian variation in the occurrence of sudden cardiac death. The purpose of this study was to examine the effects of age, sex, and initial cardiac rhythm on circadian variability in sudden cardiac death. Methods: This study employed a retrospective analysis of the records of adult patients with witnessed cardiac arrest who underwent resuscitation in an urban paramedic system during a 5-year period. Results: The records of 2,250 consecutive patients with witnessed cardiac arrest were reviewed. Spectral analysis was used to decompose the data into frequency components. A circadian variation in the occurrence of sudden cardiac death was demonstrated, with a low occurrence rate between midnight and 6 AM and a 2.4-fold increase between the rate at 6 AM and the rate at noon. The same circadian pattern was noted among both men and women, among both patients aged 18 to 70 and those older than 70 years, and among patients with various initial cardiac arrest rhythms (ventricular tachycardia or fibrillation, asystole, and electromechanical dissociation). However, the outcome of resuscitation in these patients (ie, the rate of successful resuscitation and the rate of survival) did not demonstrate circadian variation. Conclusion: Witnessed out-of-hospital sudden cardiac death demonstrated circadian variation, and this variability was observed regardless of the patient's age, sex, or initial cardiac arrest rhythm. The outcome of resuscitation did not show circadian variability. These results suggest a common pathophysiologic mechanism leading to sudden cardiac death. [Thakur RK, Hoffmann RG, Olson DW, Joshi R, Tresch DD, Aufderheide TP, Ip JH: Circadian variation in sudden cardiac death: Effects of age, sex, and initial cardiac rhythm. Ann Emerg Med January 1996;27;29-34.]

The Effect of the Total Cumulative Epinephrine Dose Administered During Human CPR on Hemodynamic, Oxygen Transport, and Utilization Variables in the Postresuscitation Period

Studies evaluating the dose of epinephrine required to optimize return of spontaneous circulation and survival after CPR have shown that doses greater than recommended by advanced cardiac life support (ACLS) improve coronary perfusion pressure and short-term resuscitation rates. Since survival has not improved, it is possible that higher doses of epinephrine may be physiologically detrimental in the postresuscitation period. The object of this study is to measure the effect of the total cumulative dose of epinephrine given during ACLS on the hemodynamic, oxygen transport, and utilization variables in the postresuscitation period. A prospective nonrandomized control trial of inception cohorts. A large urban emergency department and intensive care unit. Forty-nine successfully resuscitated witnessed, normothermic, nontraumatic, out-of-hospital patients, who had suffered cardiac arrests. All patients were treated according to ACLS guidelines; however, the epinephrine dose (0.01 to 0.2 mg/kg or 1 to 14 mg) was selected at the clinician's discretion and given through central venous access every 3 to 5 min. Hemodynamic, oxygen transport, and utilization variables were measured on a return of spontaneous circulation, and at least every 30 min thereafter under a standardized postresuscitation protocol. Hemodynamic, oxygen transport/utilization variables, and mortality in patients resuscitated from cardiac arrest. The total cumulative dose of epinephrine given during ACLS until a return of spontaneous circulation was recorded. A total cumulative epinephrine dose of 15 mg was found to best predict 24-h mortality. Of the 49 patients, 20 received less than 15 mg (group 1) and 29 received greater than 15 mg (group 2). Age, premorbid health status, sex, presenting rhythm, and duration of cardiac arrest were similar in both groups. The 24-h survival was 17 of 20 (85%) and 12 of 29 (41%) in group 1 and 2, respectively (p < 0.002). Over the first 6 h of the postresuscitation period, both groups had similar mean arterial pressure (MAP), mixed venous oxygen saturation, and systemic oxygen extraction ratio (all p > 0.1). Group 2, however, had a significantly lower cardiac index (CI), systemic oxygen consumption (VO2), and systemic oxygen delivery (DO2) (all p < 0.01). Systemic vascular resistance index (SVRI), initial and 6-h lactic acid levels were significantly higher in group 2 (all p < 0.03). The administration of all doses of epinephrine during the resuscitation of out-of-hospital cardiac arrest is associated with impairment of DO2 and VO2 in the postresuscitation period. Both duration and severity of these impairments correlate with the total cumulative epinephrine dose given during the resuscitation. Thus, inadvertent catecholamine toxicity represents a further complicating factor in the production of postresuscitation disease. Diagnostic and therapeutic interventions addressed toward mitigating these potentially reversible adverse effects may impact morbidity and mortality in out-of-hospital cardiac arrests.

Hypothermie majeure accidentelle

Two cases of severe accidental hypothermia (core temperature below 25 °C) are reported. Both occurred in an urban area during the same winter period. Both patients had the same age and similar clinical symptoms. In the first patient, the EEG, the echocardiography and the blood gases were in favour of a good tolerance of hypothermia, which led to choice a non aggressive rewarming method. The latter included the rewarming of inhaled gas mixture as well as i.v. fluids and gastro-intestinal lavage fluid. The outcome was uneventful. In the second patient, the visceral and biological consequences were more important (pH : 6.80, blood glucose concentration : 1.48 mmol · L −1, major coagulation disorders). Therefore a rapid rewarming via a cardiopulmonary bypass was preferred. The patient died from a prolonged shock with disseminated intravascular coagulation. The use of cardiopulmonary bypass which is essential in case of cardiac arrest rhythm, is controversial in case of severe hypothermia with a still beating heart.

Inter-rater agreement of paramedic rhythm labeling

Substantial inter-rater agreement is present in the labeling by paramedics of ventricular fibrillation and asystolic rhythms. Prospective, cross-sectional study. One hundred five practicing paramedics from nonvolunteer agencies who are advanced cardiac life support certified. Five static cardiac arrest rhythm strips, classified by Cummins' average peak amplitude method, were arranged into five different orders of presentation and placed into five booklets. The paramedics were instructed to label each rhythm ventricular fibrillation or asystole based on rhythm recognition, not on treatment plan. The overall kappa value for labeling the five rhythms was .63, indicating a moderate degree of inter-rater agreement. However, as the rhythm's amplitude decreased, the amount of inter-rater agreement also decreased. When the amplitude was approximately 1 mm, agreement was no different than chance; the proportion of paramedics labeling the rhythm ventricular fibrillation was .46 (95% confidence interval, .36, .56). Only a flat line (0 mm) demonstrated perfect inter-rater agreement, with no paramedic labeling the rhythm ventricular fibrillation. Inter-rater agreement of ventricular fibrillation rhythm labeling by paramedics in this emergency medical services system was amplitude dependent. An analysis of ventricular fibrillation rhythm data that does not address the degree of inter-rater agreement of rhythm labeling cannot ensure uniform reporting of out-of-hospital cardiac arrest data.

Methodology in cardiac arrest research symposium

On November 25, 1987, the mayor of Chicago sat working at his desk, when he suddenly slumped unresponsive to the floor. The mayor's bodyguards noted no puIse and started CPR immediately The chief paramedic officer for the city arrived in the mayor's office and began advanced cardiac life support procedures several minutes after the mayor's collapse, noting an ominous initial rhythm of asystole. Thirty-three minutes later, the mayor arrived at the emergency department at Northwestern Memorial Hospital, where a waiting cardiovascular team placed him on complete cardiac bypass and quickly moved him to the operating suites. However, despite these rapid and heroic efforts, Harold Washington became the second Chicago mayor in 15 years to die from cardiac arrest while in office. He was one of 3,500 Chicago citizens to die from cardiac arrest during that year; only 55 cardiac arrest victims survived to leave the hospital, resulting in an overall survival rate of less than 2%. ~ Had it not been for the fact that the mayor died, it might have been a perfect resuscitation. ''2 However, we must examine the facts squarely Very little has changed in the actual treatment of cardiac arrest over the last 15 years) Despite the fact that a few communities have survival rates of more than 15%, most communities' rates are closer to the 2% found in Chicago. Even in communities where 20% survival rates are found, the other 80% still die from cardiac arrest. The actual experience of most ED staff is far from encouraging. Many physicians have voiced skepticism regarding the usefulness of current treatment protocols and emergency medical services for cardiac arrest. Equally disturbing is the fact that most communities simply have no idea what their survival rates are because they do not measure them. Because the survival rate in Chicago was less than 2%, we were naturally interested in comparing our results with those from other communities. However, this was an impossible task due to the lack of uniform methodology

The accuracy of decision-making of a semi-automatic defibrillator during cardiac arrest

The accuracy of decision-making of a semi-automatic defibrillator was assessed at 57 cardiac arrests in 55 patients. The initial rhythm was ventricular fibrillation at 40 arrests and was correctly identified in 37 (sensitivity 92.5%). In the other 17 arrests initial rhythms were not ventricular fibrillation and 16 were correctly identified (specificity 94%). Continuous electrocardiographic recordings of the arrests were analysed in 8-12 s segments: of 432 segments showing ventricular fibrillation, 352 were correctly identified (sensitivity 81%); 3895 of 4139 segments showing rhythms other than ventricular fibrillation were correctly identified (specificity 94%). The percentage accuracy of detection of ventricular fibrillation varied from 0-100% (mean 91%) and for non-ventricular fibrillation from 51-100% (mean 92%). When 104 segments of ventricular fibrillation and 470 segments of non-ventricular fibrillation with cardiopulmonary resuscitation artefact were excluded from the analysis, a sensitivity of 91% and specificity of 96% were obtained. Thus the detection of cardiac arrest rhythms using a microprocessor based detection system for patients with cardiac arrest has a high sensitivity for ventricular fibrillation and specificity for non-ventricular fibrillation.

A review of pre‐hospital defibrillation by ambulance officers in Perth, Western Australia

Ventricular fibrillation (VF) is the most common presenting rhythm in cardiac arrest occurring outside hospitals. All cases of VF treated with a defibrillation-only protocol by ambulance officers were reviewed. Of the 231 cases entered into the study, 40 (22.7%) patients survived to 28 days after discharge from hospital. The proportion of survivors in this study is similar to that receiving full paramedic services. Further, where time to defribillation is short, the chance of survival improves. The key determinant in survival from VF occurring outside hospital appears to be how rapidly defibrillation can be initiated.

A new rhythm library for testing automatic external defibrillators: Performance of three devices

A library of arrhythmias obtained from patients with cardiac arrest was developed. Such a data base will permit both in vitro testing of the rhythm analysis system of automatic external defibrillators before clinical field trials are conducted and comparison of devices. Defibrillators equipped with voice/electrocardiographic tape recorders and used in the prehospital defibrillation programs in Iowa and King County, Washington provided the rhythm source. From these recordings, segments of ventricular fibrillation with minimal artifact and a duration of ≥6 s were selected. Segment of ventricular fibrillation (n = 102) were categorized by average peak amplitude as fine (1 to <3 mm), medium (3 to <7 mm), coarse (7 to <12 mm) and extra coarse (≥12 mm), and transcribed onto high fidelity videocassette tapes. Nonventricular fibrillation cardiac arrest rhythms (n = 144), which included wide complex idioventricular rhythms, ventricular and supraventricular tachycardias, asystole and artifact, were also transcribed.Automatic external defibrillators developed by three manufacturers reached a treat (shock) decision on 88 to 93% of the ventricular fibrillation rhythms and on 5 to 10% of the nonventricular fibrillation rhythms. The latter decisions were defined as false positive, though for many rapid nonventricular fibrillation rhythms, countershock may be the appropriate treatment response. There were no statistically significant differences among the three devices in the shock/no shock decisions. A variety of ventricular fibrillation arrhythmias and terminology to express the preclinical performance of automatic external defibrillators are defined. Three commercially available automatic external defibrillators appear to successfully identify ventricular fibrillation and nonventricular fibrillation rhythms. Although an arrhythmia library cannot substitute for clinical field trials, it may facilitate objective and consistent evaluation of automatic external defibrillator detection algorithms. Such evaluations should precede clinical use of new devices.

In-hospital cardiopulmonary resuscitation: prospective survey of management and outcome.

A sixteen-month prospective survey of in-hospital cardiac arrests indicated that of 168 patients who received cardiopulmonary resuscitation, 27 (16%) survived to leave hospital. Ninety-three per cent of these patients were ambulant and 81% were able to care for themselves. Poorest outcome was associated with initial rhythm of asystole, prolonged resuscitation and arrest in the Intensive Care Units. When compared with recent and past literature, these figures suggest that the incidence of successful outcome for cardiopulmonary resuscitation in hospitals has not changed significantly over the past twenty years.