Elsevier

Resuscitation

Volume 44, Issue 1, March 2000, Pages 7-17
Resuscitation

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

https://doi.org/10.1016/S0300-9572(99)00155-0Get rights and content

Abstract

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.

Introduction

Death from cardiac disease is the most common cause of mortality in western countries. Approximately two-thirds of these deaths occur outside hospital [1]. In addition, large numbers of people suffer sudden death from other causes, like suicide, lung disease and drowning.

A large proportion of these persons could be resuscitated with an optimal emergency service organisation. The chance of survival is up to ten times higher for those patients suffering from ventricular fibrillation (VF) compared with those with asystole or pulseless electrical activity (PEA) patients [2]. To estimate the possible effect of out-of-hospital resuscitation organisations on survival, it is therefore necessary to know the percentage of cardiac arrest patients who are initially in VF.

In the numerous reports on out-of-hospital cardiac arrest, there is wide variation in the reported incidence of VF [3]. In almost all of these reports, the calculation is based on the first rhythm analysis after the arrival of the ambulance, with various delays in the time from the cardiac arrest. This underestimates the true incidence of VF, as, in many cases, the initial VF has deteriorated into asystole.

The aim of this study was to indirectly try to analyse the initial incidence and duration of VF based on observations at first ECG recording and the estimated interval between collapse and this recording. Furthermore, we aimed at evaluating the relation between time to defibrillation and survival in out-of-hospital cardiac arrest patients.

Section snippets

Ambulance registry

This study is based on material collected within the Swedish ambulance cardiac arrest registry. The registry was started in 1990 by a few ambulance systems and has successively been joined by more. To date, the registry is based on reports from ≈60% of the ambulance systems in Sweden and includes 5 million of the total of 8.5 million inhabitants in Sweden.

Most of the ambulance organisations included serve communities with <100 000 inhabitants and only recently have the larger cities, i.e.

Results

The age and sex distribution of the patients are given in Fig. 1. The median age was 70 years and the age range was 2–101 years. In all, 28% of the victims were females. The proportion of females increased with age. One hundred and forty patients were children under 10 years of age.

In 70% of the cases the arrest was witnessed; in 60% by bystanders and in 10% by the ambulance crew. Bystander CPR was initiated in 32%. The average time from collapse to first ECG was 14 min.

Discussion

The data from the Swedish Cardiac Arrest Registry are collected from the majority of the ambulance systems in the country. They are likely to reflect the national standard of care for out-of-hospital cardiac arrest patients fairly well.

Limitations of the study

No validation of adherence to the protocol was performed. Instead, a questionnaire was administered to all the medical directors of the participating ambulance organisations, asking them to estimate the accuracy of the representation of the study population. This was expressed as the percentage of the patients they estimated were omitted from the study in their own district. Percentage values in this survey varied from 0 to 30% (mean 5%). This means that one could estimate that the study

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 for patients with VF and very short delay times was ≈50%, but fell rapidly as the delay increased.

Acknowledgements

This study was carried out for the Swedish Cardiac Arrest Registry. Participating ambulance district physicians: Å Andren-Sandberg MD, L-Å Augustsson MD, S Berglind MD, J Bennis MD, U Björnstig MD, K Brunnhage MD, J Castenhag MD, B Eriksson MD, A Elvin MD, B Engerström MD, L Engerström MD, M Erlandsson MD, L Fernandez MD, J Fischer MD, B Gustavsson MD, S Hagman MD, M Helfner MD, H Huldt MD, M Johansson MD, R Johansson MD, M Kjeldgaard MD, M Larsson MD, Ö Lennander MD, S Leward MD, T Lindgren

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