| Abstract
| - Objective: In recent years, there has been increasing use of analytical and graphical methods to assist the monitoring of outcomes in adult cardiac surgery. In this paper, we present extensions to the basic VLAD methodology that add flexibility and assist in its interpretation. Methods: Using techniques from probability theory, we have devised graphical tools whereby deviations from expected outcomes can be monitored to see how likely they are to have occurred by chance. The methods are based upon pre-operative assessments of risk and use exact analytical techniques. Results: These tools allow deviations from expected outcomes to be readily assessed and compared with the distribution of chance outcomes. Appropriate colour coding allows interpretation in terms of a temperature gradient. Conclusions: Exact analysis methods based on the use of pre-operative risk assessment provide a useful means for assisting the interpretation of VLAD charts. Such analysis has the advantage that it is applicable even for relatively short series of operations. Also, it takes specific account of the heterogeneity of case mix when quantifying the variability that is expected. By displaying the overall history of outcomes in a visually intuitive manner, it complements the more formal tools for detecting isolated good and bad runs that are available.
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