Results from Austria's nationwide public access defibrillation (ANPAD) programme collected over 2 years

AIM OF THE STUDY: To analyse 2 years of experience after introducing automated external defibrillators (AED) all over Austria. MATERIALS AND METHODS: This observational study evaluated the number of privately purchased devices and the rate of local bystander-triggered AED deployments from November 2002 to December 2004. As outcome measurements, the hospital discharge rate and neurological condition were recorded. Arrival times of the emergency medical service (EMS) on scene and the time intervals until shock decisions were made were calculated. Shock decisions were verified according to ECG downloads. Results were compared with historical data if applicable. RESULTS: During the study period, 1865 devices were installed. Seventy-three AED deployments were recorded. Eleven cases were excluded from the study because bystanders were part of the local EMS. Seventeen out of the remaining 62 (27%) compared to a historical 27 out of 623 (4.3%) individuals were discharged alive from hospital. Fourteen out of 26 (54%) patients who were found with a shockable rhythm survived to hospital discharge. Fifteen of our patients survived in good neurological condition (CPC I and II), two suffered from severe neurological deficit (CPC III and IV) and 45 people died. The median "call-to-AED advice interval" was 3.5 min (IQR 2-6 min; N=24). In two cases, the AED made inappropriate decisions because of artefacts. CONCLUSIONS: Compared to historical data, short 'intervals to shock' delivery and the frequent start of basic life support resulted in an increased hospital discharge rate in good neurological condition. Despite the relatively high number of installed devices, the number of patients reached remained small.     

Logarithm of the absolute correlations of the ECG waveform estimates duration of ventricular fibrillation and predicts successful defibrillation

BACKGROUND: Measures of the ventricular fibrillation (VF) waveform may enable better allocation of cardiac arrest treatment by discriminating which patients should receive immediate defibrillation versus alternate therapies such as CPR. We derive a new measure based on the 'roughness' of the VF waveform, the Logarithm of the Absolute Correlations (LAC), and assess and contrast how well the LAC and the previously published scaling exponent (ScE) predict the duration of VF and the likelihood of return of spontaneous circulation (ROSC) under both optimal experimental and commercial-defibrillator sampling conditions. METHODS AND RESULTS: We derived the LAC and ScE from two different populations-an animal study of 44 swine and a retrospective human sample of 158 out-of-hospital VF arrests treated with a commercial defibrillator. In the animal study, the LAC and ScE were calculated on 5s epochs of VF recorded at 1000samples/s and then down sampled to 125samples/s. In the human study, the LAC and ScE were calculated using 6s epochs recorded at 200samples/s that occurred immediately prior to the initial shock. We compared the LAC and ScE measures using the Spearman correlation coefficients (CC) and areas under the receiver operating characteristic curve (AUC). RESULTS: In the animal study, the LAC and ScE were highly correlated at 1000sample/s (CC=0.93) but not at 125samples/s (CC=-0.06). These correlations were reflected in how well the measures discriminated VF of 5min: AUC at 1000samples/s was similar for LAC compared to ScE (0.71 versus 0.76). However AUC at 125 samples was greater for LAC compared to ScE (0.75 versus 0.62). In the human study, the LAC measure was a better predictor of ROSC following initial defibrillation as reflected by an AUC of 0.77 for LAC compared to 0.57 for ScE. CONCLUSIONS: The LAC is an improvement over the ScE because the LAC retains its prognostic characteristics at lower ECG sampling rates typical of current clinical defibrillators. Hence, the LAC may have a role in better allocating treatment in resuscitation of VF cardiac arrest.     

Causes and clinical consequences of inappropriate shocks experienced by patients wearing a cardioverter-defibrillator

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