Thrombolytic eligibility in acute myocardial infarction patients admitted to Norwegian hospitals1,2

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Abstract

We characterised the population of acute myocardial infarction patients admitted to Norwegian hospitals and quantified the actual use and potential maximal use of thrombolytic therapy. Data were collected by medical record review of all acute myocardial infarction patients discharged from hospital in April and May 1993 in Health region 1. The clinical population differed significantly from the patients recruited to the thrombolytic clinical trials. Patients were more likely to have ST depression on admission (23% vs. 7%) and to be over 74 years (42% vs. 10%) than in the trials. A fifth of patients presented more than 12 h after symptom onset (or time indeterminate). Thrombolysis was given to 32% of patients, mainly utilising streptokinase. Late presentation or diagnostic difficulty appeared to be the main reasons for non- thrombolysis. Approximately 50% of the clinical population were eligible for thrombolysis. Eligibility for thrombolytic therapy was therefore severely restricted by the presenting characteristics of the clinical population. Substantial numbers of patients belonged to subgroups where the reported benefit from thrombolysis is equivocal. Uncertainty remains on the extrapolation of the trials evidence to those subgroups who were under-represented in the clinical trials.

Introduction

Several large randomised clinical trials of thrombolytic therapy in acute myocardial infarction have reported substantial reductions in mortality 1, 2, 3, 4. A recent systematic overview has reported an 18% (95% confidence interval 13–23%) proportional reduction in 35-day-mortality [5]. Despite this convincing evidence in favour of thrombolysis, studies have concluded that less than half, and in some studies considerably less than half, of all acute myocardial infarction patients receive thrombolytic treatment 6, 7, 8. Patients recruited to trials are a selected group and may differ from typical patients in their characteristics and suitability for treatment. The translation of published evidence into routine practice may therefore be limited by the eligibility of patients in the typical population for the tested therapy.

The aim of the study was to identify the current use and potential maximal use of thrombolytic therapy in the clinical population of acute myocardial infarction patients admitted to Norwegian hospitals.

Section snippets

Study sample

The study population was Health region 1 comprising the counties of Oslo, Hedmark and Oppland in eastern Norway. This region has a population of about 850 000 representing 20% of all Norwegian inhabitants. Half of the study population was urban (Oslo) and half mainly rural. All ten hospitals treating emergency patients in the region participated. Necessary approval for the study was obtained locally. Data were collected from all hospitals on all patients with the discharge diagnosis of acute

Patient characteristics

Patient characteristics and past medical history of the 487 consecutive patients in this sample are shown in Table 1. The initial diagnosis of definite or suspected acute myocardial infarction was made in 88% of patients and 90% of the total were admitted to a coronary care unit. A fifth of patients presented more than 12 h after symptom onset and only 61% of patients were admitted within 6 h. Significant differences between this clinical population and the fibrinolytic trials population are

Discussion

The population of acute myocardial infarction patients admitted to hospital in Norway differs substantially from the patients who were enrolled in the thrombolytic clinical trials. This difference is particularly apparent in the significantly higher prevalence of ST depression on admission in this study sample. There has been much discussion as to which ECG patterns warrant administration of thrombolytic agents. Most data have been collected from the ISIS-2 trial which showed significant

Acknowledgements

The European Secondary Prevention Study was funded within the BIOMED 1 programme of the European Union.European Secondary Prevention Study Group:C Hagn (Austria), R Kala (Finland), A Leizorowicz (France), NB Karatzas (Greece), D Vasiliauskas (Lithuania), Å Reikvam (Norway), R Seabra Gomes (Portugal), A Agusti (Spain), L Wilhelmsen (Sweden), J Schilling (Switzerland), K Woods, D Ketley (United Kingdom).We thank the following for their participation: Dr E Arnesen, Central Hospital of Hedmark,

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Cited by (4)

  • Consequences of overutilization and underutilization of thrombolytic therapy in clinical practice

    2001, Journal of the American College of Cardiology
    Citation Excerpt :

    In a recent European study, the corresponding figure was 20% (14). Numerous other studies have, in agreement, shown that only 33% to 50% (5,15)of patients eligible for thrombolytic therapy do receive the treatment. The 35-day mortality among all our patients treated with thrombolysis was 8.2%.

1

For the European Secondary Prevention Study Group. Members of the Group are listed at the end of the paper.

2

Some of the data in this paper presented in the following abstract: Reikvam, Å., Ketley, D., Woods, K.L. Reasons for the assumed underutilisation of thrombolytic therapy in acute myocardial infarction. Norwegian Journal of Epidemiology 1995; 2 suppl: p 30.

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