S Nicholls*, P McElduff and J W Leitch.

Department of Cardiovascular Medicine, John Hunter Hospital and University of Newcastle, Newcastle.

Background: The use of beta blockers is suboptimal following myocardial infarction, but the reasons for underutilisation of beta blockers are unclear. The aim of this study was to assess factors responsible for underuse of beta blockers in two geographic regions to determine the influence of community and hospital prescribing practice.

Method: The World Health Organisation's MONICA project collected clinical data and followup on patients with suspected or proven ischaemic events in 40 geographic regions. Between 1985 and 1993 patients in Perth (4503) and Newcastle (1776) were enrolled in the MONICA study with definite myocardial infarction and survived to hospital discharge. Medication use prior to admission and on discharge was analysed.

Results: Beta blocker use at the time of hospital admission was nearly identical in both regions (21% of patients with AMI). During hospital admission, beta blockers were commenced nearly twice as frequently in Perth than in Newcastle (66% v 36%) and more patients were discharged on beta blocker therapy in Perth (68% v 45%). In both areas, the use of beta blockers at hospital discharge increased significantly over the study period. Factors associated with underuse of beta blockers included admission to hospital in the Newcastle region (OR 0.3, 95% CI 0.3-0.3), history of previous myocardial infarction (OR 0.6, CI 0.5-0.7), diabetes (OR 0.6, CI 0.5-0.8) and concomitant use of diuretics (OR 0.5, CI 0.4-0.6) and calcium channel antagonists (OR 0.7, CI 0.5-0.8).

Conclusion: The underuse of beta blockers following myocardial infarction was strongly related to hospital prescribing patterns and not to community use prior to admission. Underuse occurred in patients with diabetes and markers of ventricular dysfunction who stand to benefit most from this therapy following myocardial infarction.

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