Patient delay in calling for help: the weakest link in the chain of survival?

On average, one third of cases of myocardial infarction (MI) are fatal before hospitalisation and most of the deaths have occurred within four hours of the onset of acute symptoms. The very high pre-hospital mortality is particularly a problem in younger patients as over 90% of the deaths in those less than 55 years old occur before they come to hospital, whereas in the 70–74 year age group 67% of the deaths occur outside hospital. A greater emphasis on pre-hospital care has more potential for reducing the mortality from acute MI than further development of hospital based treatments. The delay between the time of onset of symptoms and the time at which the patient comes under medical attention is a major determinant of prognosis in acute MI; the largest single component of the delay is that taken by the patient deciding to summon help. In the UK heart attack study, lives saved per thousand patients treated were 107 for patients coming under care within one hour of onset, compared with 31 for those coming under care at 4–12 hours and 21 if the delay was 12 hours or greater. Reducing delay optimises the benefit of thrombolytic treatment and is also crucially important for improving outcome in patients who develop ventricular fibrillation. Currently only about 25% of all infarct patients receive thrombolytic treatment and this number would increase significantly if delays were shortened. Delaying the administration of thrombolysis by 30 minutes, particularly in the early hours of acute MI, reduces life expectancy by an average of one year.