Background Strategies to reduce DTB (door-to-balloon) time have been previously described. However, there is no well-established data-monitoring system that can be used for prompt feedback. The aims of this study were to use statistical process control (SPC) methodology to measure current processes, to provide real-time feedback on the impact of a change in service delivery and to identify individual outliers for specific investigation.

Methods A prospective study was conducted in a tertiary centre in North England. Data were collected for 841 consecutive STEMI patients from the local district undergoing PPCI. The impact on median DTB time after changes in protocols were prospectively determined.

Results Median DTB times fell significantly as a result of changes in protocol. The upper control limit (UCL) decreased from 209 to 86 min and narrower control limits indicated improved performance. The main outliers included patients presenting to the Accident and Emergency department and patients who developed STEMI while being treated in non-cardiology wards for other reasons (18.3% of the study population).

Conclusions SPC provides a statistically robust mechanism for assessing the effect of process redesign interventions, and in this context provides a clear visual representation of DTB times for individual patients. Identification of significant outliers allows investigation of any variation with a special cause. It allows a unit to identify when a system of service delivery, albeit stable, is inadequate and needs redesign and can monitor the impact of changes in protocol.