Circumstances and causes of out-of-hospital cardiac arrest in sudden death survivors

Objective—To study the circumstances and medical profile of out-of-hospital sudden cardiac arrest (SCA) patients in whom resuscitation was attempted by the ambulance service, and to identify causes of SCA in survivors and factors that influence resuscitation success rate.
Methods—During a five year period (1991-95) all cases of out-of-hospital SCA between the ages of 20 and 75 years and living in the Maastricht area in the Netherlands were studied. Information was gathered about the circumstances of SCA, as well as medical history for all patients in whom resuscitation was attempted by the ambulance personnel. Causes of SCA in survivors were studied and logistic regression analysis was performed to identify factors associated with survival.
Results—Of 288 SCA patients in whom cardiopulmonary resuscitation (CPR) and advanced life support were applied, 47 (16%) were discharged alive from the hospital. Their mean (SD) age was 58 (11) years, 37 (79%) were men, and 24 (51%) had a history of cardiac disease. Acute myocardial infarction was diagnosed in 24 (51%) of the survivors; seven with and 17 without a history of cardiac disease. Ventricular fibrillation (VF) or ventricular tachycardia (VT) as the first documented rhythm was significantly positively associated with survival (odds ratio (OR) 5.7, 95% confidence interval (CI) 2.1 to 15.9). A time interval of less than four minutes between the moment of collapse and the start of resuscitation, and an ambulance delay time of less than eight minutes were significantly positively associated with survival (OR 3.3, 95% CI 1.3 to 8.6, and OR, 3.6, 95% CI 1.3 to 10.5, respectively). A history of cardiac disease was negatively associated with survival (OR 0.46, 95% CI 0.21 to 0.98).
Conclusions—Acute myocardial infarction was the underlying mechanism of SCA in most of the survivors, especially in those without a history of cardiac disease. CPR within four minutes, an ambulance delay time less than eight minutes, and VT or VF diagnosed by the paramedics were positively associated with success.

Keywords: cardiac arrest;  sudden death;  cardiopulmonary resuscitation;  paramedics     

Clinical and genetic evaluation after sudden cardiac arrest

Sudden cardiac arrest (SCA) and sudden cardiac death (SCD) can be attributed to cardiac, respiratory, metabolic, and toxicologic etiologies. Most cases of SCD are caused by coronary artery disease and approximately 40% of cardiac arrests are unexplained. Inherited arrythmias and cardiomyopathies are important contributors to SCA and SCD. Identifying an inherited condition after such an event not only has important ramifications for the individual, but also for relatives who may be at risk for the familial condition. This review will provide an overview of inherited cardiovascular disorders than can predispose to SCA/SCD, review the diagnostic evaluation for an individual and/or family after an SCA/SCD, and discuss the role of genetic testing.     

Long-term follow-up of sudden cardiac arrest survivors and electrophysiologically guided antiarrhythmic therapy

Sudden cardiac arrest survivors have a high risk of suffering from recurrent arrhythmic events. Recent studies have shown that these patients have a significantly decreased mortality rate, if they are supplied with an implantable cardioverter/defibrillator (ICD). The aim of this study was to evaluate the long-term prognosis of patients with electrophysiologically guided antiarrhythmic drug therapy in comparison to patients with ICD. 204 consecutive survivors of sudden cardiac arrest were enrolled in this study. All patients were examined with an initial electrophysiologic study (EPS) with programmed ventricular stimulation. Patients were treated with antiarrhythmic drugs (if the inducible tachycardia was suppressed) or with the implantation of an ICD. The maximal follow-up period was 120 months, the mean period was 53.3 +/- 31.4 months (ICD) versus 60.3 +/- 35.5 months (EPS, nonsignificant). Patients with ICD showed an overall mortality rate of 14.6%, whereas EPS-guided patients had a mortality rate of 43.2% (p < 0.001). The cardiac and arrhythmogenic mortality rates were significantly lower in the ICD group (12 vs. 43%, p < 0.01, and 1 vs. 16%, p < 0.001, respectively). A reduction of the mortality risk was observed in the ICD group by up to 61% (all-cause mortality), 52% (cardiac mortality) and 97.2% (arrhythmogenic mortality). In arrhythmic event survivors with ICD, arrhythmic and overall mortality rates are significantly lower compared to patients with an EPS-guided drug therapy. In the secondary prevention of sudden cardiac death, ICD should be the first choice of antiarrhythmic therapy.     

Genetics of sudden cardiac arrest

Sudden cardiac arrest (SCA) due to ventricular arrhythmias is a major cause of mortality in western populations with up to 450,000 deaths in the United States each year. Although environmental factors clearly contribute to the determinants of SCA, familial aggregation studies and advances in the molecular genetics of inherited arrhythmias suggest that genetic factors confer susceptibility to SCA in the general population. Research in this area typically has focused on association of common genetic variants with intermediate phenotypes that predispose to SCA risk, such as QT interval, but few studies have examined genetic risk factors for SCA. We review the evidence for genetic susceptibility to SCA in the general population and focus on the studies published to date that have explored genetic risk factors.     

Comparison of heart rate variability in survivors and nonsurvivors of sudden cardiac arrest.

Imbalances in autonomic nervous system function have been posed as a possible mechanism that produces ventricular fibrillation and sudden cardiac arrest in patients with cardiovascular disease. Heart rate (HR) variability is described in survivors and nonsurvivors of sudden cardiac arrest within 48 hours after resuscitation using time and frequency domain analytic approaches. HR data were collected using 24-hour ambulatory electro-cardiograms in 16 survivors and 5 nonsurvivors of sudden cardiac arrest, and 5 control subjects. Survivors of sudden cardiac arrest were followed for 1 year, with recurrent cardiac events occurring in 4 patients who died within that year. Analysis of 24-hour electrocardiograms demonstrated that control subjects had the highest HR variability (standard deviation of all RR intervals = 155.2 +/- 54 ms), with nonsurvivors demonstrating the lowest HR variability (standard deviation of all RR intervals = 52.3 +/- 6.1 ms) and survivors of sudden cardiac arrest falling between the other 2 groups (standard deviation of all RR intervals = 78 +/- 25.5 ms, p less than or equal to 0.0000). Two other indexes of HR variability (mean number of beat to beat differences in RR intervals greater than 50 ms/hour and root-mean-square of successive differences in RR intervals) did not demonstrate the expected pattern in this sample, indicating that perhaps patterns of HR variability differ between groups of patients with cardiovascular disorders. Spectral analytic methods demonstrated that survivors of sudden cardiac arrest had reduced low- and high-frequency spectral power, whereas nonsurvivors demonstrated a loss of both low- and high-frequency spectral power.(ABSTRACT TRUNCATED AT 250 WORDS)     

心脏骤停和心脏性猝死

心脏性猝死(SCD)是目前社会关注的热点问题.2005年WHO的数据表明,在全球死于心脑血管疾病的约1700万人群中,40%～50%是SCD.SCD虽然有多种定义,但目前一般认为是在1 h内出现的由于心血管原因导致的非预期死亡事件或无目击者的死亡事件.心脏骤停(SCA)不等同于SCD,SCA如果救治失败会引起真正的SCD.     

Care of sudden cardiac death survivors: the aberrant cardiac patients

Caring for survivors of sudden cardiac death presents nursing with a challenge. Although many of these individuals' needs are similar to those of other patients with cardiac disease, some are different. This article investigates the role of the nurse in providing care for these unique clients. To increase the nurse's understanding, sudden cardiac death is defined, its pathophysiology described, and the current medical management detailed. The unique nursing care needs of these individuals are outlined and suggestions for nursing interventions are presented. By providing comprehensive physical and emotional support to these individuals, recovery and return to a high-quality life will be facilitated.     

Clinical evaluation of the internal automatic cardioverter-defibrillator in survivors of sudden cardiac death

An R-wave synchronous implantable automatic cardioverter-defibrillator (IACD) was evaluated in 12 patients with repeated episodes of cardiac arrest who remained refractory to medical and surgical therapy. Seven men and 5 women, average age 61 years, surgically received a complete IACD system. Coronary artery disease was found in 11 and the prolonged Q-T syndrome in 1. The average ejection fraction was 34%, and 6 patients had severe congestive heart failure (New York Heart Association class III or IV).

The IACD is a completely implantable unit consisting of 2 bipolar lead systems. One system uses a lead in the superior vena cava and on the left ventricular apex through which the cardioverting pulse is delivered. The second system employs a close bipolar lead implanted in the ventricle for sensing rate. After the onset of ventricular tachycardia or fibrillation, the IACD automatically delivers approximately 25 J.

Postoperative electrophysiologic study in 10 and spontaneous ventricular tachycardia in 1 patient demonstrated appropriate IACD function and successful conversion in all with an average of 18 ± 4 seconds. The induced arrhythmias were ventricular tachycardia (160 to 300 beats/min) in 9 and ventricular fibrillation in 1.

These data demonstrate that ventricular tachycardia, not ventricular fibrillation, was the predominant rhythm induced during programmed ventricular stimulation in these survivors of cardiac arrest and that the IACD effectively responded to a wide range of ventricular tachycardia rates as well as ventricular fibrillation. Use of the IACD offers an effective means of therapy for some patients who otherwise may not have survived.     

Management of survivors of out-of-hospital cardiac arrest

Sudden cardiac death is a major cause of death in the western world. Since a 1-year recurrence rate of 30% is expected in survivors of sudden death, treatment is mandatory. If an apparent cause (e.g. proarrhythmia or acute ischemia) exists, treatment is generally directed at its alleviation. However, in most patients no obvious cause is found. Both noninvasive and invasive diagnostic procedures are employed to uncover treatable etiologies. If a treatable cause is not found, an electrophysiological study may be employed to tailor antiarrhythmic therapy. At this point, many patients still cannot be offered an adequate antiarrhythmic treatment. For these patients, amiodarone, antiarrhythmic surgery or an implantable defibrillator may be appropriate options. Algorithms for diagnostic and therapeutic interventions in survivors of sudden cardiac death are delineated.     

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.     

Post-resuscitation care for survivors of cardiac arrest

Cardiac arrest can occur following a myriad of clinical conditions. With advancement of medical science and improvements in Emergency Medical Services systems, the rate of return of spontaneous circulation for patients who suffer an out-of-hospital cardiac arrest (OHCA) continues to increase. Managing these patients is challenging and requires a structured approach including stabilization of cardiopulmonary status, early consideration of neuroprotective strategies, identifying and managing the etiology of arrest and initiating treatment to prevent recurrence. This requires a closely coordinated multidisciplinary team effort. In this article, we will review the initial management of survivors of OHCA, highlighting advances and ongoing controversies.     

Decision making in prehospital sudden cardiac arrest

Many studies of prehospital resuscitation report on selected populations. We examined a series of 445 unselected nontraumatic cardiac arrests. Emergency cardiac care (ECC) was not initiated in 126 (28%). ECC was begun in 319 (78%), but was terminated in 132 (33%). Ninety-four (21%) were admitted to the hospital with palpable pulses and organized rhythm (successful resuscitation/save rate for patients presenting in ventricular fibrillation was 50%/25%. Multivariate regression analysis was used to identify the relative importance of significant variables in predicting survival, and the analysis identified the presence of ventricular fibrillation, short paramedic response times, and short paramedic treatment times.     

Survival after sudden cardiac arrest in hospital

Although there are many reports on sudden cardiac arrest occurring outside the hospital, little is known about the precise prognostic factors that determine the outcome after cardiopulmonary resuscitation. Clinical information before and immediately after sudden cardiac arrest is frequently incomplete because the event occurs outside the hospital. We studied 90 consecutive patients with sudden and unexpected cardiac arrest who were resuscitated in the general ward of our hospital. Twenty-five (28%) were discharged from the hospital. Multivariate analysis revealed that the promptness of initiation of CPR, age, severity of cardiac dysfunction, time and the type of arrhythmia are of significance in relation to survival. To evaluate long-term survival after hospital cardiac arrest, we analyzed long-term follow-up data accumulated during a 16 year period. In the group of 25 patients in our study, there have been a total of 10 deaths (40%). Five of the 10 deaths resulted from recurrent cardiac arrest and 1 was a noncardiac death. There was a high rate of recurrence of cardiac arrest in the first year following resuscitation, especially among the cardiomyopathy patients.     

Cognitive impairment in survivors of out-of-hospital cardiac arrest

Background

The huge importance of rapid provision of care, especially early defibrillation, for survival of out-of-hospital cardiac arrest (OHCA) is well known. This prospective cohort study investigated cognitive functioning of OHCA survivors in relation to the time-related elements of the resuscitation.

Methods

Fifty-seven consecutive survivors, from a cohort of 308 witnessed OHCA patients with ventricular fibrillation as the initial rhythm, underwent extensive neuropsychologic examination, including tests of memory, attention, and executive functioning, 6 months after the resuscitation. Time-related aspects of the resuscitation were collected on scene. Cognitive functioning was studied in relation to the administration of cardiopulmonary resuscitation (CPR) prior to ambulance arrival, and time from collapse to start of CPR, defibrillation, and return of spontaneous circulation (ROSC).

Results

Depending of the test, between 11% and 28% of survivors were cognitively impaired, while 58% scored unimpaired for all tests. Daily life activities were limited in 19% of the patients. Patients who received CPR prior to arrival of the ambulance showed a trend towards overall better cognitive functioning and significant better immediate memory and visuomotor tracking (P = .03 and P < .01). We found a weak correlation between the time to CPR, time to defibrillation, or time to ROSC and cognitive functioning.

Conclusions

The majority of survivors of OHCA with ventricular fibrillation as the initial rhythm are cognitively unimpaired. Long delays to ROSC are compatible with good cognitive outcome. Initiation and cessation of resuscitation efforts should not be based on the duration of circulatory arrest.     

Angiographic coronary morphology in survivors of cardiac arrest

Autopsy studies in victims of sudden coronary death revealed intramyocardial platelet aggregates with microscopic myonecrosis downstream from ruptured atherosclerotic plaques. Ruptured plaques usually manifest angiographically as irregularly bordered (type II) lesions. To investigate the possible pathogenic role of ruptured plaques in arrhythmic death, we analyzed clinical, angiographic, and electrophysiologic data from 49 survivors of cardiac arrest without acute myocardial infarction. All patients had greater than or equal to 50% stenoses of greater than or equal to one coronary artery; 16 had type II morphology, and 33 did not. Type II morphology was more prevalent in patients without inducible sustained monomorphic ventricular tachycardia (11 of 22 or 50%) than in those with it (five of 27 or 19%), p less than 0.05, and patients without akinetic or dyskinetic segments (eight of 14 or 57%) than in those with them (eight of 34 or 24%), p less than 0.06. Thus type II morphology is more prevalent in patients without a demonstrable anatomic and/or electrophysiologic substrate for reentrant ventricular tachycardia, indirectly implicating ruptured plaques in the pathogenesis of cardiac arrest in this subset of patients.     

Predicting defibrillation success in sudden cardiac arrest patients

Although the importance of quality cardiopulmonary resuscitation (CPR) and its link to survival is still emphasized, there has been recent debate about the balance between CPR and defibrillation, particularly for long response times. Defibrillation shocks for ventricular fibrillation (VF) of recently perfused hearts have high success for the return of spontaneous circulation (ROSC), but hearts with depleted adenosine triphosphate (ATP) stores have low recovery rates. Since quality CPR has been shown to both slow the degradation process and restore cardiac viability, a measurement of patient condition to optimize the timing of defibrillation shocks may improve outcomes compared to time-based protocols. Researchers have proposed numerous predictive features of VF and shockable ventricular tachycardia (VT) which can be computed from the electrocardiogram (ECG) signal to distinguish between the rhythms which convert to spontaneous circulation and those which do not. We looked at the shock-success prediction performance of thirteen of these features on a single evaluation database including the recordings from 116 out-of-hospital cardiac arrest patients which were collected for a separate study using defibrillators in ambulances and medical centers in 4 European regions and the US between March 2002 and September 2004. A total of 469 shocks preceded by VF or shockable VT rhythm episodes were identified in the recordings. Based on the experts' annotation for the post-shock rhythm, the shocks were categorized to result in either pulsatile (ROSC) or non-pulsatile (no-ROSC) rhythm. The features were calculated on a 4-second ECG segment prior to the shock delivery. These features examined were: Mean Amplitude, Average Peak-Peak Amplitude, Amplitude Range, Amplitude Spectrum Analysis (AMSA), Peak Frequency, Centroid Frequency, Spectral Flatness Measure (SFM), Energy, Max Power, Centroid Power, Power Spectrum Analysis (PSA), Mean Slope, and Median Slope. Statistical hypothesis tests (two-tailed t-test and Wilcoxon with 5% significance level) were applied to determine if the means and medians of these features were significantly different between the ROSC and no-ROSC groups. The ROC curve was computed for each feature, and Area Under the Curve (AUC) was calculated. Specificity (Sp) with Sensitivity (Se) held at 90% as well as Se with Sp held at 90% was also computed. All features showed statistically different mean and median values between the ROSC and no-ROSC groups with all p-values less than 0.0001. The AUC was >76% for all features. For Sp = 90%, the Se range was 33–45%; for Se = 90%, the Sp range was 49–63%. The features showed good shock-success prediction performance. We believe that a defibrillator employing a clinical decision tool based on these features has the potential to improve overall survival from cardiac arrest.