Time changes in new cases of ischaemic heart disease in general practice

There are no recent studies of the presentation of ischaemic heart disease (IHD) in general practice. What information exists is derived from the secondary care setting, where seasonal and daily variation has been reported in admissions for IHD. There are epidemiological studies that show a falling incidence and mortality for IHD. It is not clear, however, if this is also the case in clinical general practice.

The aims of the present study were to (i) estimate the number of cases of IHD in general practice populations; (ii) determine the recorded diagnosis and time of first presentation of IHD during a 5 year period; and (iii) perform time series analysis on the above data.

The design of the study was a retrospective survey, using MIQUEST software, of computer databases in five general practices with a combined population of nearly 40,000 patients. The five practices were selected randomly from volunteering practices in the Trent Focus Collaborative Research Network. All patients with a new diagnosis of IHD recorded between January 1993 and December 1997 inclusive were included in the study. The number of new cases of IHD, the recorded diagnosis and time of first presentation of IHD were the main outcome measures.

A total of 644 new cases of IHD were identified during the study period: 54.0% 'angina pectoris', 26. 9% 'acute myocardial infarction', 18.8% 'ischaemic heart disease', 0. 3% 'coronary atherosclerosis'. Time series analysis reveals a seasonal and weekly pattern to new cases of IHD, with peak cases occurring in January and on Mondays/Fridays. A downward trend was detected for new cases of IHD (all diagnoses) over the 5 year period, and for new cases of IHD (excluding acute myocardial infarction). An upward trend was observed for new cases of acute myocardial infarction.

Presentation of IHD in general practice varies according to season and day of the week. The proportion of new cases recorded as 'angina pectoris' or 'ischaemic heart disease' is falling, and this decline masks a rise in the incidence recordings of 'acute myocardial infarction'.