5.1 The economic evidence for the MiraQ system comprised a new cost analysis to assess the cost savings to the NHS of introducing the MiraQ system for assessing graft flow during coronary artery bypass graft (CABG) surgery, compared against clinical assessment.
5.2 In the base-case analysis, the equipment cost for the MiraQ system was about £111 per procedure and the additional time for measuring flow in 3 grafts was 2.35 minutes. The equipment costs were based on the VeriQ 2011 console (purchase cost £32,000 with an anticipated life span of 10 years) and an average use of 1.7 probes per procedure (£1,582 per PS probe, which is recommended for up to 30 uses). The costs per patient were based on the purchase cost of a MiraQ system divided by 220 days' use per year over its life expectancy, including annual maintenance costs. Annual maintenance costs are payable from the end of year 2 at £1,800 per year. It was assumed that the annual maintenance costs for the remaining 8 years would be averaged over the 10-year life expectancy of the equipment. All time costs in the model were based on the salaries of a CABG team comprising 2 cardiothoracic surgeons, 1 anaesthetist, 1 cardiac perfusionist and 2 cardiac nurses.
5.3 The cost model evaluated the cost savings of using the MiraQ system compared with clinical assessment alone in assessing graft flow in all patients having CABG. The outcomes considered in the model are complications associated with the CABG surgery.
5.4 The consequences of using the MiraQ system were based on results from 2 studies (Kieser et al.  and Becit et al. ). In the base-case analysis, use of the MiraQ system was associated with an increase of 6.6% in the graft revision rate (a 2.3% increase in minor revisions and a 4.3% increase in major revisions). Costs were based on the time taken by the CABG team to perform the revisions. The cost of the time taken to perform a minor revision was estimated to be £11, and for major revisions, £180.
5.5 The perioperative events included in the cost analysis were: incidence of postoperative myocardial infarction and the associated rehabilitation costs; use of intra-aortic balloon pumping; incidence and treatment costs of intraoperative re-exploration for bleeding; and incidence and treatment costs of deep sternal infection. The rates of these events for CABG with and without the MiraQ system were based on Becit et al. (2007). The base-case analysis compared a 0% postoperative myocardial infarction rate for patients assessed clinically and with VeriQ versus a 5% rate for patients who had clinical assessment alone. The treatment costs of postoperative myocardial infarction and associated rehabilitation costs were estimated to be £1,667 per patient. The cost of treatment by intra-aortic balloon pumping was estimated to be £2,657 per episode. The base-case analysis compared a 1% rate for intra-aortic balloon pumping for patients assessed clinically and with VeriQ versus a 7% rate for patients who had clinical assessment alone. There was no difference in the rate of intraoperative re-exploration of bleeding and incidence of deep sternal infection between the arms of the model. No adverse event costs as a result of using the VeriQ system were included in the model because none have been reported.
5.6 The cost saving associated with the MiraQ system in the base case was £115 per patient based on purchase of a VeriQ 2011 console (£32,000), using a PS probe (£1,582 for 30 uses), and annual maintenance costs (£1,800) payable at the end of year 2.
5.7 The sensitivity analysis based on the parameters and ranges identified by the manufacturer showed that estimates of cost saving for the MiraQ system are robust. The key drivers of the cost saving were the reduction in the rate of postoperative myocardial infarction and the reduction in use of intra-aortic balloon pumping associated with the use of the MiraQ system. The highest cost saving obtained in the sensitivity analysis was £323 per patient and was associated with 0% use of intra-aortic balloon pumping in patients assessed with the MiraQ system compared with a usage rate of 14% in patients assessed without the MiraQ system. The lowest cost saving, of £38 per patient, was obtained for a 2.5% postoperative myocardial infarction rate. The only case in which use of the MiraQ system was not cost saving (when the cost per patient was £45) was when there was no change in the usage rate of intra-aortic balloon pumping in either arm of the model (3.5%). The external assessment centre advised that this is a pessimistic view and that the MiraQ system is likely to be cost saving when used appropriately.
5.8 The committee considered that the assumptions made in the cost model were realistic and that the range of savings calculated for the use of MiraQ was likely to be realised in practice.
5.9 The committee noted that the manufacturer's cost model did not include potential cost savings from reductions in intensive therapy unit stay and reduced readmission rates. The cost savings associated with the MiraQ system may therefore have been underestimated.
5.10 The committee also noted that the manufacturer's estimated usage of the MiraQ system at 1 patient per day for 220 days per year was likely to be conservative. The committee was advised that on average 3 to 4 CABG operations are performed per day in a cardiac operating theatre in the UK. Increased annual use of a MiraQ system is expected to reduce the estimated equipment cost per procedure because the capital cost of the VeriQ system will be divided across more procedures.
5.11 The committee considered that the reductions in perioperative myocardial infarction rate to zero and of intra-aortic balloon pump use from 7% to 1% when using the MiraQ system compared with clinical assessment alone in the base case were likely to be overestimates. This would tend to reduce the estimated cost savings of the MiraQ system. However, the committee noted that sensitivity analysis showed that if using the MiraQ system had no impact on the postoperative myocardial infarction rate or led to only a small change in intra-aortic balloon pumping rates (of less than 2%), the MiraQ system remained cost saving compared with clinical assessment alone, resulting in a saving to the NHS.
5.12 For the guidance review, the external assessment centre revised the model to reflect 2017 costs (original guidance values are given in brackets). The main parameter changes were the cost of the MiraQ console £34,000 (£32,000) and probes £1,481 (£1,582) with 50 uses (30 uses). These costs resulted in a MiraQ system cost of about £141 (£111) per procedure. The cost of the time taken to perform a minor revision was estimated to be £24 (£11), and for major revisions, £396 (£180). Treatment costs of postoperative myocardial infarction and associated rehabilitation costs were estimated to be £2031 (£1,667) per patient and treatment cost by intra-aortic balloon pumping was estimated to be £2,574 (£2,657) per episode. Base-case results for the 2017 revised model shows the cost saving associated with the MiraQ system was £141 (£115) per patient. Further details of the 2017 revised model are in the revised model summary .