Rationale and design of the Home Automatic External Defibrillator Trial (HAT).

Most cardiac arrests occur in the home, where emergency medical services (EMS) systems are challenged to provide timely care. Because a large proportion of sudden cardiac arrests (SCAs) are due to ventricular tachycardia or ventricular fibrillation, home use of an automated external defibrillator (AED) might offer an opportunity to decrease mortality in those at risk. Predicting who will have a cardiac arrest in the general population is difficult. Individuals at high risk are usually easily identified and may become candidates for implantable cardioverter defibrillators. It is within the population at lower risk where home AEDs may be most useful. The purpose of the Home Automatic External Defibrillator Trial (HAT) is to test whether providing home access to an AED can improve survival in patients at modest risk of SCA, such as those surviving an anterior myocardial infarction but in whom implantable cardioverter defibrillator therapy is not deemed necessary. Between January 23, 2003, and October 20, 2005, 7001 patients were enrolled, with completion of follow-up scheduled for September 30, 2007. Randomization was conducted in a 1:1 fashion between control therapy, comprising the standard lay response to SCA (calling the EMS and performing cardiopulmonary resuscitation), and the use of an AED first, followed by calling the EMS and performing cardiopulmonary resuscitation. The primary end point is all-cause mortality. Secondary outcomes include survival from SCA (witnessed and unwitnessed, in home and out of home), incremental cost-effectiveness, and quality of life measures for both the patient and the spouse/companion. The results of the trial should be available in mid 2008.

Assessment of a three-phase model of out-of-hospital cardiac arrest in patients with ventricular fibrillation.

AIM: Cardiac arrest with ventricular fibrillation (VF) has been divided into three phases in which phase-specific therapy may improve outcome. The aim of this study was to assess the relationship between call-to-shock time, bystander CPR (BCPR), and cardiac arrest outcomes. METHODS: In a retrospective analysis of prospectively-acquired data from witnessed VF out-of-hospital cardiac arrests (OHCA), patients were classified as phases 1, 2, or 3 based on call-to-shock time (<5, 5-8, and >8 min) and further stratified based on performance of BCPR. Groups were compared with regard to survival, neurological outcome, and restoration of spontaneous circulation (ROSC) with defibrillation only (no ALS interventions to achieve sustained ROSC). RESULTS: Survival, neurologically intact survival, and ROSC with defibrillation were different between phases 1 and 2 (p=0.014 and p=0.005, p<0.01) but not between phases 2 and 3. Patients were further classified as having received BCPR (N=111) or no BCPR (N=107). Neurologically intact survival with and without BCPR, respectively, was 61% versus 72% (phase 1), 44% versus 41% (phase 2), and 42% versus 29% (phase 3). ROSC with defibrillation only with and without BCPR, respectively, was 64% versus 56% (phase 1), 37.0% versus 29% (phase 2), and 33% versus 8% (phase 3). ROSC with defibrillation alone was statistically higher in univariate analysis in phase 3 with BCPR (p=0.033) but not in multivariate analysis (p=0.068). CONCLUSIONS: BCPR did not significantly improve survival in any phase of OHCA, though there was a trend toward increased neurologically intact survival and increased ROSC with defibrillation alone in phase 3.

Preventing sudden death with n-3 (omega-3) fatty acids and defibrillators.

BACKGROUND: Because interventions that prevent and treat events due to cardiovascular disease are applied to different, but overlapping, segments of the population, it can be difficult to estimate their effectiveness if formal calculations are not available. METHODS: Markov chain analysis, including sensitivity analysis, was used with a hypothetical population resembling that of Olmsted County, MN, aged 30 to 84 in the year 2000 to compare the estimated impact of three interventions to prevent sudden death: (1) raising blood levels of n-3 (omega-3) fatty acids, (2) distributing automated external defibrillators (AEDs), and (3) implanting cardioverter defibrillators (ICDs) in appropriate candidates. The analysis was performed in 2004, 2005, and 2006. RESULTS: Raising median n-3 fatty acid levels would be expected to lower total mortality by 6.4% (range from sensitivity analysis = 1.6% to 10.3%). Distributing AEDs would be expected to lower total mortality by 0.8% (0.2% to 1.3%), and implanting ICDs would be expected to lower total mortality by 3.3% (0.6% to 8.7%). Three fourths of the reduction in total mortality due to n-3 fatty acid augmentation would accrue from raising n-3 fatty acid levels in the healthy population. CONCLUSIONS: Based on central values of candidacy and efficacy, raising n-3 fatty acid levels would have about eight times the impact of distributing AEDs and two times the impact of implanting ICDs. Raising n-3 fatty acid levels would also reduce rates of sudden death among the subpopulation that does not qualify for ICDs.