Use of cumulative mortality adjusted for case mix in patients with acute myocardial infarction for early detection of variation in clinical practice.
20 hospitals across the former Yorkshire region.
All 2153 consecutive patients with confirmed acute myocardial infarction identified during three months.
Main outcome measures
Variable life-adjusted displays showing cumulative differences between observed and expected mortality of patients; expected mortality calculated from risk model based on admission characteristics of age, heart rate, and systolic blood pressure.
The performance of two individual hospitals over three months was examined as an example. One, the smallest district hospital in the region, had a series of 30 consecutive patients but had five more deaths than predicted. The variable life-adjusted display showed minimal variation from that predicted for the first 15 patients followed by a run of unexpectedly high mortality. The second example was the main tertiary referral centre for the region, which admitted 188 consecutive patients. The display showed a period of apparently poor performance followed by substantial improvement, where the plot rose steadily from a cumulative net lives saved of −4 to 7. These variations in patient outcome are unlikely to have been revealed during conventional audit practice.
Variable life-adjusted display has been integrated into surgical care as a graphical display of risk-adjusted survival for individual surgeons or centres. In combination with a simple risk model, it may have a role in monitoring performance and outcome in patients with acute myocardial infarction.
What is already known on this topicThe national service framework for coronary artery disease requires minimal standards of care and audit of patients with acute myocardial infarction but does not integrate clinical status into the audit toolPredictive models using only a few factors to adjust for case mix are easy to use and may be as accurate as more complicated methodsEarly identification of variations in patient outcome is not revealed by block audit, and, instead, a continuous monitoring process is requiredWhat this study addsUsing just patients' age, blood pressure, and heart rate to adjust for case mix, a continuous plot can be derived to compare observed and expected outcome for patients with acute myocardial infarctionThis method of monitoring outcome over time can be used as an early warning system to allow more detailed audit to be performed