Sudden death from cardiac causes, often due to ventricular fibrillation, claims at least 250,000 persons annually in the United States.
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The American Heart Association guidelines for advanced ...cardiac life support state that antiarrhythmic medications are “acceptable, probably helpful” for the treatment of ventricular fibrillation or pulseless ventricular tachycardia that persists after three or more shocks from an external defibrillator (often called “shock-refractory” ventricular fibrillation or tachycardia).
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This guarded recommendation reflects the limited evidence supporting the use of these agents, none of which have been convincingly demonstrated to improve the success of attempted resuscitation after cardiac arrest.
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CONTEXT Use of automated external defibrillators (AEDs) by
first arriving emergency medical technicians (EMTs) is advocated to
improve the outcome for out-of-hospital ventricular fibrillation (VF).
...However, adding AEDs to the emergency medical system in Seattle, Wash,
did not improve survival. Studies in animals have shown improved
outcomes when cardiopulmonary resuscitation (CPR) was administered
prior to an initial shock for VF of several minutes' duration. OBJECTIVE To evaluate the effects of providing 90 seconds of CPR
to persons with out-of-hospital VF prior to delivery of a shock by
first-arriving EMTs. DESIGN Observational, prospectively defined, population-based
study with 42 months of preintervention analysis (July 1, 1990-December
31, 1993) and 36 months of postintervention analysis (January 1,
1994-December 31, 1996). SETTING Seattle fire department–based, 2-tiered emergency medical
system. PARTICIPANTS A total of 639 patients treated for out-of-hospital
VF before the intervention and 478 after the intervention. INTERVENTION Modification of the protocol for use of AEDs,
emphasizing approximately 90 seconds of CPR prior to delivery of a
shock. MAIN OUTCOME MEASURES Survival and neurologic status at hospital
discharge determined by retrospective chart review as a function of
early (<4 minutes) and later (≥4 minutes) response intervals. RESULTS Survival improved from 24% (155/639) to 30% (142/478)
(P=.04). That benefit was predominantly in
patients for whom the initial response interval was 4 minutes or longer
(survival, 17% 56/321 before vs 27% 60/220 after;
P = .01). In a multivariate logistic model, adjusting for
differences in patient and resuscitation factors between the periods,
the protocol intervention was estimated to improve survival
significantly (odds ratio, 1.42; 95% confidence interval, 1.07-1.90;
P = .02). Overall, the proportion of victims who survived
with favorable neurologic recovery increased from 17% (106/634) to
23% (109/474) (P = .01). Among survivors, the proportion
having favorable neurologic function at hospital discharge increased
from 71% (106/150) to 79% (109/138) (P<.11). CONCLUSION The routine provision of approximately 90 seconds of
CPR prior to use of AED was associated with increased survival when
response intervals were 4 minutes or longer.
Electrical storm, multiple temporally related episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF), is a frequent problem among recipients of implantable cardioverter ...defibrillators (ICDs). However, insufficient data exist regarding its prognostic significance.
This analysis includes 457 patients who received an ICD in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and who were followed for 31 +/- 13 months. Electrical storm was defined as > or = 3 separate episodes of VT/VF within 24 hours. Characteristics and survival of patients surviving electrical storm (n = 90), those with VT/VF unrelated to electrical storm (n = 184), and the remaining patients (n = 183) were compared. The 3 groups differed in terms of ejection fraction, index arrhythmia, revascularization status, and baseline medication use. Survival was evaluated using time-dependent Cox modeling. Electrical storm occurred 9.2 +/- 11.5 months after ICD implantation, and most episodes (86%) were due to VT. Electrical storm was a significant risk factor for subsequent death, independent of ejection fraction and other prognostic variables (relative risk RR, 2.4; 95% confidence interval CI, 1.3 to 4.2; P = 0.003), but VT/VF unrelated to electrical storm was not (RR, 1.0; 95% CI, 0.6 to 1.7; P = 0.9). The risk of death was greatest 3 months after electrical storm (RR, 5.4; 95% Cl, 2.4 to 12.3; P = 0.0001) and diminished beyond this time (RR, 1.9; 95% CI, 1.0 to 3.6; P=0.04).
Electrical storm is an important, independent marker for subsequent death among ICD recipients, particularly in the first 3 months after its occurrence. However, the development of VT/VF unrelated to electrical storm does not seem to be associated with an increased risk of subsequent death.
Aims Three randomized trials of implantable cardioverter defibrillator (ICD) therapy vs medical treatment for the prevention of death in survivors of ventricular fibrillation or sustained ventricular ...tachycardia have been reported with what might appear to be different results. The present analysis was performed to obtain the most precise estimate of the efficacy of the ICD, compared to amiodarone, for prolonging survival in patients with malignant ventricular arrhythmia. Methods and Results Individual patient data from the Antiarrhythmics vs Implantable Defibrillator (AVID) study, the Cardiac Arrest Study Hamburg (CASH) and the Canadian Implantable Defibrillator Study (CIDS) were merged into a master database according to a pre-specified protocol. Proportional hazard modelling of individual patient data was used to estimate hazard ratios and to investigate subgroup interactions. Fixed effect meta-analysis techniques were also used to evaluate treatment effects and to assess heterogeneity across studies. The classic fixed effects meta-analysis showed that the estimates of ICD benefit from the three studies were consistent with each other (P heterogeneity=0·306). It also showed a significant reduction in death from any cause with the ICD; with a summary hazard ratio (ICD:amiodarone) of 0·72 (95% confidence interval 0·60, 0·87;P=0·0006). For the outcome of arrhythmic death, the hazard ratio was 0·50 (95% confidence interval 0·37, 0·67;P<0·0001). Survival was extended by a mean of 4·4 months by the ICD over a follow-up period of 6 years. Patients with left ventricular ejection fraction ≤35% derived significantly more benefit from ICD therapy than those with better preserved left ventricular function. Patients treated before the availability of non-thoracotomy ICD implants derived significantly less benefit from ICD therapy than those treated in the non-thoracotomy era. Conclusion Results from the three trials of the ICD vs amiodarone are consistent with each other. There is a 28% reduction in the relative risk of death with the ICD that is due almost entirely to a 50% reduction in arrhythmic death.
The NUDIX enzymes are involved in cellular metabolism and homeostasis, as well as mRNA processing. Although highly conserved throughout all organisms, their biological roles and biochemical ...redundancies remain largely unclear. To address this, we globally resolve their individual properties and inter-relationships. We purify 18 of the human NUDIX proteins and screen 52 substrates, providing a substrate redundancy map. Using crystal structures, we generate sequence alignment analyses revealing four major structural classes. To a certain extent, their substrate preference redundancies correlate with structural classes, thus linking structure and activity relationships. To elucidate interdependence among the NUDIX hydrolases, we pairwise deplete them generating an epistatic interaction map, evaluate cell cycle perturbations upon knockdown in normal and cancer cells, and analyse their protein and mRNA expression in normal and cancer tissues. Using a novel FUSION algorithm, we integrate all data creating a comprehensive NUDIX enzyme profile map, which will prove fundamental to understanding their biological functionality.
To develop a graphic model that describes survival from sudden out-of-hospital cardiac arrest as a function of time intervals to critical prehospital interventions.
From a cardiac arrest surveillance ...system in place since 1976 in King County, Washington, we selected 1,667 cardiac arrest patients with a high likelihood of survival: they had underlying heart disease, were in ventricular fibrillation, and had arrested before arrival of emergency medical services (EMS) personnel.
For each patient, we obtained the time intervals from collapse to CPR, to first defibrillatory shock, and to initiation of advanced cardiac life support (ACLS).
A multiple linear regression model fitting the data gave the following equation: survival rate = 67%-2.3% per minute to CPR-1.1% per minute to defibrillation-2.1% per minute to ACLS, which was significant at P < .001. The first term, 67%, represents the survival rate if all three interventions were to occur immediately on collapse. Without treatment (CPR, defibrillatory shock, or definitive care), the decline in survival rate is the sum of the three coefficients, or 5.5% per minute. Survival rates predicted by the model for given EMS response times approximated published observed rates for EMS systems in which paramedics respond with or without emergency medical technicians.
The model is useful in planning community EMS programs, comparing EMS systems, and showing how different arrival times within a system affect survival rate.
OBJECTIVES
This study evaluated the prognosis of patients resuscitated from ventricular tachycardia (VT) or ventricular fibrillation (VF) with a transient or correctable cause suspected as the cause ...of the VT/VF.
BACKGROUND
Patients resuscitated from VT/VF in whom a transient or correctable cause has been identified are thought to be at low risk for recurrence and often receive no primary treatment for their arrhythmias.
METHODS
In the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with a potentially transient or correctable cause of VT/VF were not eligible for randomization. The mortality of these patients was compared with the mortality of patients with a known high risk of recurrence of VT/VF in the AVID registry.
RESULTS
Compared with patients having high risk VT/VF, those with a transient or correctable cause for their presenting VT/VF were younger and had a higher left ventricular ejection fraction. These patients were more often treated with revascularization as the primary therapy, more commonly received a beta-blocker, less often required therapy for congestive heart failure and less commonly received either an antiarrhythmic drug or an implantable cardioverter defibrillator. Nevertheless, subsequent mortality of patients with a transient or correctable cause of VT/VF was no different or perhaps even worse than that of the primary VT/VF population.
CONCLUSIONS
Patients identified with a transient or correctable cause for their VT/VF remain at high risk for death. Further research is needed to define truly reversible causes of VT/VF. Meanwhile, these patients may require more aggressive evaluation, treatment and follow-up than is currently practiced.
The Dual-Chamber and VVI Implantable Defibrillator (DAVID) trial demonstrated a worse outcome in patients with implantable cardioverter-defibrillators (ICDs) programmed to DDDR at 70 bpm compared ...with patients who had ICDs programmed to VVI backup pacing at 40 bpm. Pacing was more frequent in the DDDR group.
The purpose of this study was to determine whether right ventricular pacing (RV) is an independent predictor of outcome in the DAVID trial.
We evaluated the relationship of percent RV pacing to the composite endpoint of death or hospitalization for congestive heart failure. Patients who had a 3-month follow-up and who had not yet reached an endpoint were included in the study. Using Cox regression analysis (VVI group N = 195; DDDR group N = 185), we examined multiple factors, including percent RV pacing at 3-month follow-up, that might be associated with adverse outcomes.
Percent RV pacing as a continuous variable was correlated with the primary endpoint. As a dichotomous variable, the best separation for predicting endpoints occurred with DDDR RV pacing > 40% vs DDDR RV pacing < or = 40% (P = .025). Patients with DDDR RV pacing < or = 40% had similar or better outcomes to the VVI backup group (P = .07). Correction for baseline variables predictive of the composite outcome in the (nonpaced) VVI group (use of nitrates, increased heart rate, and increased age) did not change the findings for RV pacing (P = .008). In contrast, atrial pacing was not predictive of worse outcomes.
These results suggest, but do not prove, a causal relationship between frequent RV pacing and adverse outcomes in patients with left ventricular ejection fraction < or = 40%.
Based on both animal studies and field studies of the process and intermediate outcomes related to cardiopulmonary resuscitation (CPR), we initiated a randomized trial of dispatcher-assisted CPR, ...with the intervention arm receiving instructions for chest compression only and the control arm receiving standard instructions for airway maintenance, ventilation, and chest compression. Of 241 patients randomized to chest compression instructions only, 35 survived (14.6%) compared with 29 of 279 (10.4%) patients in the control arm (p = .09). These results may have implications for future guidelines and teaching CPR.
These recommendations are presented to enhance the safety and efficacy of AEDs intended for public access. The task force recommends that manufacturers present developmental and validation data on ...their own devices, emphasizing high sensitivity for shockable rhythms and high specificity for nonshockable rhythms. Alternative defibrillation waveforms may reduce energy requirements, reducing the size and weight of the device. The highest levels of safety for public access defibrillation are needed. Safe and effective use of AEDs that are widely available and easily handled by nonmedical personnel has the potential to dramatically increase survival from cardiac arrest.
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