Variations in Use of Cardiology Services in a Health Authority: Comparison of Coronary Artery Revascularisation Rates with Prevalence of Angina and Coronary Mortality

Objective: To explore the relation between rates of coronary artery revascularisation and prevalence of angina to assess whether use of health services reflects need.

Design: Prevalence of angina symptoms determined by postal questionnaire on 16750 subjects (18 to 94 years). Comparison of data on use of coronary artery revascularisation with prevalence of symptoms and mortality from coronary heart disease.

Setting: Health authority with population of 530000.

Subjects: Patients admitted to hospital for coronary heart disease; patients who died; and patients undergoing angiography, angioplasty, or coronary artery bypass graft. Cohort of 491 people with symptoms from survey.

Main Outcome Measures: Pearson's product moment correlation coefficients for relation between variables.

Results: Overall, 4.0% (95% confidence interval 3.7% to 4.4%) of subjects had symptoms. Prevalences varied widely between electoral wards and were positively associated with Townsend score (r = 0.79; P < 0.001), as was mortality, but the correlation between admission rates and Townsend score was less clear (r = 0.47; P < 0.01). Revascularisation rate and Townsend score were not associated. The ratio of revascularisation to number experiencing symptoms was inversely related to Townsend score (r = 0.67; P < 0.001). The most deprived wards had only about half the number of revascularisations per head of population with angina than did the more affluent wards. In affluent wards 11% (13/116) of those with symptoms had coronary angiograms compared with only 4% (9/216) in poorer wards (chi 2 = 4.96; P = 0.026). Townsend score also inversely correlated with revascularisations per premature death from coronary heart disease (r = 0.55; P < 0.01) and revascularisations per admission for myocardial infarction (r = 0.47; P < 0.01).

Conclusion: The use of interventional cardiology services is not commensurate with need, thus exhibiting the inverse care law.