Outcome after cardiac arrest outside hospital

Despite enormous efforts to improve survival during the past three decades, cardiac arrest outside hospital still makes a disproportionately large contribution to mortality in the Western world.¹,² So far, the only really valuable interventions have been cardiopulmonary resuscitation, often provided by a bystander, and rapid defibrillation, which is useful if the patient presents with ventricular fibrillation or ventricular tachycardia when emergency medical services arrive. The deployment of automated external defibrillators in selected sites, to be used by (trained) laypersons, has been described as a way to achieve faster defibrillation and improved survival after cardiac arrest outside hospital.³ Such plans may, however, result in limited success, given the current epidemiological developments.

In this issue (p 515) Pell and colleagues present a detailed breakdown of locations in Scotland where patients had cardiac arrests outside hospital over seven years and try to predict the impact of publicly accessible defibrillators on overall survival from cardiac arrest outside hospital.⁴ The prediction was made by using a statistical model in which survival among patients who were attended within three minutes after an emergency phone call was applied to patients who were suitable for public access defibrillation.

Pell and colleagues report data about locations and outcomes from almost 15 000 patients with cardiac arrest, which is impressive since previous reports often include considerably fewer patients. They conclude that most cardiac arrests outside hospital occur in patients' homes, which is not surprising. They estimate, however, that public access defibrillation would increase overall survival only from 5.0% to 6.5%, corresponding to 28-31 additional lives saved per year in Scotland. The authors conclude that public access defibrillation should not be preferred to defibrillation by the first responder and increased cardiopulmonary resuscitation by bystanders.

A similar study on location of cardiac arrest from King County, Seattle, found that of 7185 cardiac arrests occurring during a five year period, only 16% occurred in a public location.⁵ The authors estimated that 8-32 additional lives could be saved in Seattle in a five year period with public access defibrillation in the sites with the highest incidence of cardiac arrest. To increase survival further, tens of thousands of defibrillators would have to be deployed. For public access defibrillation to be successful it is necessary that the patient collapses in a public place, that the collapse is witnessed, that someone is willing to operate the defibrillator, and that the patient presents with an arrhythmia suitable for defibrillation—either ventricular fibrillation or pulseless ventricular tachycardia. Data from Gothenburg, the Swedish cardiac arrest registry (Johan Herlitz, personal communication, 2002), and Helsinki, however, show a trend in which the proportion of patients found in “shockable” arrhythmias declined overtly.⁶,⁷ As reported from Gothenburg in 1997, only slightly more than 30% of patients with cardiac arrest outside hospital presented in ventricular fibrillation on arrival of the ambulance, and the corresponding figure from Helsinki in 1999 was 48%.

The use of defibrillators by trained first responders—including policemen—has definitively proved its benefit in certain environments such as casinos or commercial airliners.^8–10 The possible benefit of defibrillators in the hands of untrained volunteer bystanders remains to be proved. The data from Pell and colleagues serve as a remainder of the fact that most patients with cardiac arrest outside hospital will never be within reach of publicly accessible defibrillators.⁴ A careful examination of the epidemiological conditions in the community, such as the one presented by Pell et al, is essential before considering implementation of a public access defibrillation programme.

The struggle to improve survival out of hospital encompasses several elements. Measures such as intensified primary and secondary prophylaxis among patients with coronary heart disease—including pharmacological treatment, coronary artery bypass grafting, and percutaneous transluminal coronary angioplasty—would probably have an impact. Moreover, increased awareness in the general population about medical emergencies, how to perform cardiopulmonary resuscitation, and how to alert the emergency medical services would strengthen the vulnerable chain of survival that these patients depend on.¹¹ Promising results from studies on prehospital thrombolytic treatment in patients with cardiac arrest outside hospital show that this could serve as a valuable and safe addition to current treatment.¹² One might, however, speculate that modern treatment prolongs the life of patients with advanced heart disease to such a degree that they more often present with unresuscitatable end stage heart disease when they are finally struck by cardiac arrest.

Papers p 515