Cost comparison
| Control group Mean±SD in £ (n=70) | Procedural-refinement group Mean±SD in £ (n=89) | Mean difference in £ | P value | |
| Total | 29 923±12 168 | 26 343±6399 | −3580 | 0.001 |
| Fixed costs | 1324±1070 | 803±454 | −521 | <0.001 |
| Semifixed | 9975±8132 | 5262±2971 | −4713 | <0.001 |
| Variable | 18 625±6250 | 20 278±4431 | +1653 | 0.004 |
| Costs of special interest | ||||
| Procedural costs (implantation) | 17 308±6023 | 19 398±4291 | +2090 | <0.001 |
| Intensive care unit | 1838±3001 | 200±574 | −1638 | <0.001 |
| Ward | 1603±2083 | 1342±1267 | −261 | 0.519 |
| Drugs | 445±313 | 232±144 | −213 | <0.001 |
Costs were categorised into fixed, semi-fixed and variable costs based on acute health clinical costing standards28 provided by Healthcare Financial Management Association in the UK (www.hfma.org.uk). Fixed costs are not affected by in-year changes in activity such as rent and rates. Semi-fixed costs are fixed for a given level of activity but change in steps when activity levels exceed or fall below these given levels; nursing costs are an example. Variable costs are costs that vary with changes in activity,for example, devices (valve, closure device etc.). Non-parametric test used (Mann-Whitney U test).