Fig 4.

Distribution of mortality risk. This distribution displays the predicted mortality risk in 1058 patients who received reperfusion therapy for ST elevation myocardial infarction at 28 US hospitals from the lowest risk (0th centile) to the highest risk (100th centile). Mortality risk is calculated using the individual patients’ clinical and electrocardiographic variables and a validated logistic regression equation.⁶⁸ The dotted red line indicates that the average mortality risk is about 6%. However, about three quarters of patients have a risk lower than the average risk, and the typical (median) risk patient has a risk that is around half the average risk. The quarter of patients at lowest risk have only a 1% probability of 30 day mortality, so an invasive procedure such as percutaneous coronary intervention, is unlikely to reduce the risk of mortality any further in these patients. However, the quarter of patients at highest risk have substantial potential for benefit. In a conventional clinical trial, these patients with highly different risks are collapsed into a single overall population, even though benefit-harm trade-offs may differ greatly. This risk distribution is typical of trials with a low outcome rate, when a reasonably good multivariable predictive model is available to describe risk.⁶⁷