Our study has the advantage that it includes all out of hospital cardiac arrests caused by coronary heart disease in the age group studied over a period of nearly two million person years of observation, with necropsy verification in 86% of those who died. Our study needs to be distinguished from those that included only cases in which resuscitation had been attempted or that included arrests not caused by coronary heart disease.8,9,10,11
A limitation of the study is that people aged 76 years or older, an increasing proportion of patients, were excluded. Contemporary data from UK hospitals as recorded by the Myocardial Infarction National Audit Project (MINAP) show that nearly one third of hospital patients with acute myocardial infarction and one quarter of survivors of arrest in hospital are now over 75 years old.14
) Similar figures for arrests occurring outside hospital in busy public places are provided by the UK government led programme for rapid access defibrillation.6,7
In nearly 700 events, about 25% of the arrest victims and 15% of the survivors were aged 76 or older (M Colquhoun, personal communication).
Extrapolation of our results to the total UK population, with the assumption that we recorded only 75% of arrests and 85% of survivors, suggests that there would be more than 9000 arrests in a public place each year, about 8000 of which would be witnessed. Assuming similar success rates, there would be about 640 survivors in the UK annually, but we previously calculated12
that there would be three times as many (1920) if success rates would be improved to match those in the most successful overseas centres8,9
or those in one UK centre during the 1980s.15
To what extent public access defibrillation will improve matters is controversial,6,16
but other population based studies17,18
agree with ours that it can be applicable only to about 20% of out of hospital arrests (although slightly more for younger victims) (table 1) and it depends on what proportion of arrests occur in places where a defibrillator is available.19
At the time of writing, nearly all of the 700 defibrillators that have been provided under the UK national defibrillator scheme are at main line railway stations and airports.7
The UKHAS catchment area included no airports and three main line stations, and we knew of only one arrest that occurred at a station restaurant. As fire and police stations are much more widely distributed than ambulance stations, it is perhaps arguable that further devolution of defibrillation skills to fire service personnel or police,16
coupled with more intensive training of the public in basic life support, possibly starting in schools,20
may be of greater benefit than public access defibrillation for the wide variety of public places in which cardiac arrest can occur.
We believe that ours may be the first attempt to discover the presence or absence of premonitory symptoms before the arrest. We recorded premonitory symptoms in 72% of people who had a witnessed arrest at home and in whom the presence or absence of symptoms could be ascertained, and these appeared to have lasted for longer than 15 minutes in the majority. Although these people were older than those who had an arrest in a public place, they had no greater co-morbidity, and many may have returned home after the onset of premonitory symptoms. Had they sought help earlier, they would have transferred from the group with a 2% survival rate (nine of 464) (table 2) to the group whose arrest was witnessed by a doctor or paramedic, 101 patients in all, of whom 35 (35%) survived.
Public education campaigns to persuade the public to dial an emergency number in the event of new chest pain lasting 15 minutes or longer have had varying degrees of success but have shown on the whole that public behaviour, if not survival rates, can be modified.21
In a small study we showed a striking deficiency of public knowledge on the causes and treatment of heart attack, which was improved by distribution of booklets from doctors’ surgeries.22
Most of the earlier public education was attempted over a relatively short period through the media and it seems that, apart from better primary and secondary prevention, a longer more intensive educational effort is the most promising way by which the mortality burden of arrests occurring in the home can be alleviated.