Elsevier

Resuscitation

Volume 81, Issue 8, August 2010, Pages 956-961
Resuscitation

Clinical paper
Incidence and outcomes of out-of-hospital cardiac arrest with shock-resistant ventricular fibrillation: Data from a large population-based cohort

https://doi.org/10.1016/j.resuscitation.2010.04.015Get rights and content

Abstract

Background

The increasing survival rates after out-of-hospital cardiac arrests (OHCA) are due mainly to improvements in the first 3 steps of the chain of survival. The aim of this study was to describe the temporal trends of OHCA incidence and outcomes with shock-resistant ventricular fibrillation (VF) requiring advanced life support procedures.

Methods

All our subjects were persons aged 18 years or more who had suffered OHCA of presumed cardiac etiology, were witnessed by bystanders, treated by emergency medical service (EMS), and had VF as initial rhythm. Our study was conducted in Osaka Prefecture, Japan from May 1, 1998 through December 31, 2006. Data were collected by EMS personnel using an Utstein-style database. We evaluated the temporal trends of incidence and outcomes of shock-resistant VF.

Results

During the study period, there were 8782 witnessed OHCA cases of presumed cardiac etiology. Among them, 1733 had VF as an initial rhythm, 392 of whom were shock-resistant. While the age-adjusted annual incidence of witnessed VF increased from 2.0 to 3.3 per 100,000 inhabitants, that of shock-resistant VF underwent little change during the study period. The proportion of shock-resistant VF among witnessed VF decreased from 37.0% to 19.0%. Neurologically intact 1-month survival rates after shock-resistant VF remained low at 5.6% even in 2006.

Conclusion

The actual incidence of shock-resistant VF has remained unchanged, and their outcomes continue to be dismal. Further efforts are required to reduce the mortality rates of such shock-resistant VF to achieve improved survival after OHCA.

Introduction

Sudden cardiac arrest is one of the leading causes of death in the industrialized world,1 with approximately 50,000 events occurring every year in Japan.2 We previously reported a continuous increase in survival after out-of-hospital cardiac arrest (OHCA) with improvements in the chain of survival.3 However, overall neurologically favorable 1-month survival after witnessed OHCAs of cardiac origin remained at 7% and was 16.5% for witnessed ventricular fibrillation (VF) in 2006.3

The increasing survival rate was due mainly to improvements in the first 3 steps of the chain of survival.3, 4 However, if spontaneous circulation did not return by the basic life support (BLS), we had to utilize advanced life support (ALS) measures.5 There are several reports suggesting the benefits of anti-arrhythmic medication, early percutaneous coronary intervention (PCI), extracorporeal life support, and therapeutic hypothermia.6, 7, 8, 9, 10, 11 However, how many and what types of OHCA patients fail to achieve a return of spontaneous circulation (ROSC) by BLS, and how well they are able to recover after such intensive care remains unknown.

The Utstein Osaka Project, begun in 1998, is a large ongoing, prospective population-based cohort study of OHCA in Osaka, Japan, that covers a population of 8.8 million.3, 12, 13, 14, 15 The aim of this study was to describe the temporal trends in the incidence and outcomes of OHCA with shock-resistant VF based on this cohort.

Section snippets

Target area

The target area for this study was Osaka Prefecture in Japan, which has an area of 1897 km2 (October 2006) and a residential population of 8,817,166 inhabitants (2005 Population census of Japan).16 Males make up 48.5% of the population, 18.5% of whom are 65 years old or older. Study subjects aged 18 years or more number 7,306,544.

Study patients

We enrolled all adults aged 18 years or more who suffered OHCA of presumed cardiac etiology, were witnessed by bystanders, treated by an emergency medical service

VF cardiac arrests in Osaka

A total of 45,512 adult OHCAs were documented during the study period of 8 years and 8 months. Resuscitation was attempted in 42,873, with 25,026 presumed to be of cardiac origin. Among these cardiac OHCAs, 8782 were witnessed by bystanders, 1733 of whom (20%) had VF (including pulseless VT), 2167 (25%) pulseless electrical activity (PEA), and 4789 (55%) asystole as the initial rhythm. We could not obtain data on the initial rhythm for 93 (1%) of cases.

Among 1733 patients with VF, 1546 (89%)

Discussion

Our principle finding was that shock-resistant VF had been decreasing in proportion among initial VF, but that the actual incidence had been stable, with outcomes remaining dismal. This is the first study to estimate how many patients had persistent VF upon hospital arrival against pre-hospital care, and how poor their outcomes were. It was quite important to determine the actual conditions of shock- or BLS-resistant VF who needs ALS treatments, including anti-arrhythmic therapy for OHCA. Our

Conclusions

This population-based study of the Utstein Osaka Project showed that though the proportion of shock-resistant VF among initial rhythm VF has been decreasing, its actual incidence has remained unchanged and its outcomes are still dismal. Further efforts in both BLS and ALS are required to reduce the mortality of such shock-resistant VF to achieve better survival after OHCA.

Conflict of interest statement

None.

Role of funding source

This study was supported by a grant-in-aid for university and society collaboration from the Ministry of Education, Culture, Sports, Science and Technology of Japan (Nos. 11794023 and 19390459) and by Health and Labour Sciences research grants (H19-Shinkin-003 and H19-Iryou-Ippan-006) from the Ministry of Health, Labour, and Welfare.

Acknowledgements

We are deeply grateful to Kikushi Katsurada, Tokihiko Yamamoto, Hiroshi Nonogi, Masami Imanishi, Akihiko Hirakawa, Toshimasa Hayashi and the other members of the Utstein Osaka Project for their contribution as its steering committee to the organization, coordination, and oversight of this study. Chika Nishiyama, Kayo Tanigawa, and Tetsuhisa Kitamura provided support for the data analyses. Motohiro Tsuruwa and Kyohtoh Go cooperated to initiate multi-institutional research groups. The following

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