Elsevier

The Lancet

Volume 352, Issue 9127, 15 August 1998, Pages 507-514
The Lancet

Articles
Variations between countries in invasive cardiac procedures and outcomes in patients with suspected unstable angina or myocardial infarction without initial ST elevation*

https://doi.org/10.1016/S0140-6736(97)11162-XGet rights and content

Summary

Background

There are wide variations between countries in the use of invasive cardiac catheterisation and revascularisation procedures for patients with acute ischaemic syndromes. We studied the relation between rates of such procedures and rates of cardiovascular death, myocardial infarction, stroke, refractory angina, and major bleeding in a prospective, registry-based study in six countries with widely varying intervention rates.

Methods

7987 consecutive patients presenting with unstable angina or suspected myocardial infarction without ST-segment elevation were recruited prospectively from 95 hospitals in six countries and followed up for 6 months.

Findings

The rates of all procedures were highest in patients in Brazil and the USA, intermediate in Canada and Australia, and lowest in Hungary and Poland. There were no significant differences in rates of cardiovascular death or myocardial infarction among these countries (4·7% overall [range 3·7-5·6] at 7 days; 11% overall [9-12] at 6 months). For the countries with the highest rates of invasive procedures (59%) versus the rest (21%) there was no difference in rate of cardiovascular death or myocardial infarction (adjusted odds ratio 0·88 at 7 days and 1·0 at 6 months). Rates of stroke were higher in Brazil and the USA than in the countries with lower intervention rates (adjusted odds ratio at 7 days 3·0, p=0·012; at 6 months 1·8, p=0·004) but rates of refractory angina at 7 days (0·7, p<0·001) and readmission for unstable angina at 6 months were lower (0·70, 0·63; both p<0·001). Comparison of results for hospitals without cardiac-catheterisation facilities and for those with such facilities gave adjusted odds ratios for cardiovascular death, myocardial infarction, or stroke at 6 months of 0·83 (10·6% vs 12·5%, p=0·05) and for refractory angina of 1·25 (19·3% vs 16·1%, p=0·09).

Interpretation

Higher rates of invasive and revascularisation procedures were associated with lower rates of refractory angina or readmission for unstable angina, no apparent reducton in cardiovascular death or myocardial infarction, but with higher rates of stroke. Randomised trials should assess the relative impact of conservative and more aggressive approaches to invasive cardiac procedures and revascularisations in patients with unstable angina.

Introduction

Patients with unstable angina or suspected non-Q-wave myocardial infarction are at high risk of death, myocardial infarction, or severe ischaemia despite current pharmacological therapy.1 There is a growing trend for routine early coronary angiography in these patients, with the expectation that early revascularisation in appropriate patients will prevent adverse outcomes. Other physicians adopt a more conservative approach and refer patients for angiography only if symptoms are refractory or if there is clear evidence of provocable ischaemia. These differing practice patterns are influenced by such factors as the beliefs of physicians and availability of catheterisation facilities. Two randomised trials2, 3 in patients with acute myocardial infarction or unstable angina compared the strategy of an early aggressive invasive approach with a conservative approach and showed no significant difference in outcomes (although in one there was a non-significant 25% excess in death or myocardial infarction with the more aggressive approach). In these trials, however, even the conservatively treated groups had high rates of catheterisation, which could have decreased the power of the studies to show any difference in effect between the strategies.

Investigation of the impact of differing approaches to the management of patients with ischaemic syndromes can be approached in another way. This approach is to compare the outcomes of patients managed in centres or countries without readily available catheterisation facilities (where only a few selected patients are referred for the procedure) with outcomes in centres or countries where such facilities are readily available (where there is likely to be a greater and earlier use of procedures). Most previous studies (all of myocardial infarction) with this design have used administrative databases (many of which do not include detailed characteristics of patients) or have been carried out within a single country (thus a broad range of practice styles cannot be contrasted).4, 5

To overcome these limitations, we set up a large prospective study in six countries to examine variations in patterns of invasive strategies, their relation to the patient's risk, and clinical outcomes. The countries and hospitals included were expected to represent a broad range of practice patterns with respect to use of invasive procedures. This study had two main aims. The first was to compare outcomes for patients with acute ischaemic syndromes in countries with a more aggressive use of catheterisation and in those with a more conservative approach. The second aim was to compare outcomes for patients admitted initially to hospitals with cardiac-catheterisation facilities and for those admitted to hospitals without such facilities.

Section snippets

Patients

95 hospitals in Australia, Brazil, Canada, the USA, Hungary, and Poland took part in the study. Each hospital enrolled consecutive eligible patients during their participation in the study (1995-96). Eligibility criteria were: admission to hospital (coronary-care unit, intermediate coronary-care unit, cardiology ward, or emergency department ward) with acute ischaemic cardiac chest pain within 48 h of onset; and, if there were no electrocardiographic (ECG) changes at presentation, a history of

Results

The study enrolled 7987 patients from 95 hospitals in six countries.

Discussion

Despite wide variations in the proportion of patients undergoing invasive procedures among the countries we studied, there was no evidence of better prognosis in countries with a more aggressive approach. Indeed, in the two countries with the highest intervention rates (Brazil and USA), there was a significant excess in stroke and major bleeding. However, these differences seemed to be largely related to the availability of cardiac-catheterisation facilities and easier access to invasive

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