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Differences in therapeutic consequences of exercise testing between a rural and an urban Danish county: population based study

Troels Niemann, research fellow ^a, Torsten Toftegaard Nielsen, professor in cardiology ^b, Niels Thorsgaard, specialist in internal medicine ^c, Jørgen Lous, assistant professor in general medicine ^d. 

^a Medical Research Unit of Ringkøbing County, 6950 Ringkøbing, Denmark, ^b Cardiology Department, Aarhus University Hospital, Skejby, 8200 Aarhus N, Denmark, ^c Medical Department, Herning Central Hospital, 7400 Herning, Denmark, ^d Institute of General Practice and Research Unit for General Practice, Aarhus University, 8000 Aarhus C, Denmark

Correspondence and requests for reprints to: T Niemann, Finsensgade 26, 7400 Herning, Denmark t.niemann{at}dadlnet.dk

Coronary angiography is the main diagnostic test for deciding whether to refer a patient for coronary revascularisation, but referral for coronary angiography may vary significantly among regions. ^{1 2} Regional differences have been explained by the fact that access to cardiac catheterisation facilities is associated with a higher likelihood of undergoing angiography. ^{3 4} We investigated the impact of exercise stress testing on decisions taken about patients suspected of having angina pectoris and the barriers to referral for coronary angiography.

	Subjects, methods, and results

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We identified all exercise tests and coronary angiography performed during 1996 in two Danish counties, Aarhus (urban) and Ringkøbing (rural), with five hospitals in each county. The total study population was about 900 000 inhabitants. Invasive cardiac facilities were available only in Aarhus but were for use of both counties. Data from the County Public Health Authorities on the number of admissions resulting from acute myocardial infarction and from the Danish National Board of Health on mortality from suspected ischaemic heart disease showed a similar or slightly higher prevalence of ischaemic heart disease in Ringkøbing in 1996.

A total of 2934 patients underwent bicycle exercise testing and 1691 patients underwent coronary angiography. Age adjusted rates of exercise testing were 3315 (urban) and 3183 (rural) per million inhabitants (rate ratio 1.04 (95% confidence interval 0.96 to 1.11)). Age adjusted angiography rates were 2162 (urban) and 1244 (rural) per one million inhabitants (1.74 (1.66 to 1.83)). Proportions of patients with an exercise test result that suggested disease (angina pectoris, severe ischaemia on electrocardiography, or decreased blood pressure) were similar among the 10 hospital catchment areas (table). The decision to refer for coronary angiography a patient who had a test result that suggested disease was taken either by a medical consultant at the local hospital or by a cardiology specialist (three in each county). Stratified for age, the relative risk of referral (urban versus rural) for angiography (if an exercise test result suggested disease) was 2.06 (1.39 to 3.05) for women and 1.27 (1.09 to 1.50) for men. Adjustment for history of myocardial infarction did not affect the relative risk. The highest proportion of patients (per million inhabitants) with a test result that suggested disease who were referred for angiography was 79%in the hospital catchment area 21 km from the angiography centre. The lowest proportion was 33%in two areas 128 km and 154 km away. A linear regression was significant (P<0.01) with a slope of 0.78.

	Comments

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Referral for coronary angiography in patients with a bicycle exercise test suggesting disease varied strongly with the distance from the angiography centre, showing that triage by medical consultants may constitute a barrier to referral for coronary angiography.

The two Danish counties in this study did not differ in their rates of exercise testing, and the doctors gave similar interpretations of the test results. No economic restrictions affected referral of patients from any of the local hospitals to the angiography centre, and both counties had similar policies on the management of healthcare problems.

The clear association between the distance to the coronary angiography service and the doctor's decision to refer the patient for coronary angiography presumably reflects different local medical cultures rather than problems with the transport of patients. Our data show that the medical specialist is a major barrier to referral for coronary angiography. The observed differences in practice between centres have implications for the organisation of the coronary angiography service, the diffusion of new technology, the use of guidelines, and continuing performance development. It is not known whether the observed differences in 1996 reflect appropriate or inappropriate use of medical resources; this issue deserves further investigation.

	Acknowledgments

We thank Professor Henrik Toft Sørensen for epidemiological support.

Contributors: TN and NT had the original idea, and TTN and JL helped to design the study. TN collected and analysed data and drafted the paper. TTN, NT, and JL helped to interpret the data and revise the paper. TN is guarantor for the study.

	Footnotes

Funding: A research grant from Ringkøbing County.

Competing interests: None declared.

This article is part of the BMJ's randomised controlled trial of open peer review. Documentation relating to the editorial decision making process is available on the BMJ's website

	References

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1.	Niemann T, Lous J, Thorsgaard N, Nielsen TT. Regional variations in the use of diagnostic coronary angiography. A one-year population-based study of all diagnostic coronary angiographies performed in a rural and an urban Danish county. Scand Cardiovasc J 2000; 34: 286-292[Medline].
2.	Gray D, Hampton JR. Variations in the use of coronary angiography in three cities in the Trent Region. Br Heart J 1994; 71: 474-478[Abstract/Free Full Text].
3.	Every NR, Larson EB, Litwin PE, Maynard C, Fihn SD, Eisenberg MS, et al. The association between on-site cardiac catherization facilities and the use of coronary angiography after acute myocardial infarction. N Engl J Med 1993; 329: 546-551[Abstract/Free Full Text].
4.	Pilote L, Califf RM, Sapp S, Miller DP, Mark DB, Weaver WD, et al. Regional variation across the United States in the management of acute myocardial infarction. GUSTO-1 Investigators. Global utilization of streptokinase and tissue plasminogen activator for occluded coronary arteries. N Engl J Med 1995; 333: 565-572[Abstract/Free Full Text].

(Accepted 17 January 2001)