Advice
The technology
The technology
MiraQ cardiac (Medistim) combines transit time flow measurement (TTFM) and high-frequency ultrasound (HFUS) modalities within a single system. Surgical findings can be documented through flow tracing and images provided by the system. It is intended for intraoperative quality assessment of graft blood flow during coronary artery bypass graft (CABG) surgery. The system consists of 2 probes. The L15 HFUS imaging probe has a frequency range of 11 MHz to 18 MHz and provides high-resolution images that allow the surgeon to assess morphology, including the cannulation or clamping site of the aorta, and to evaluate the completed bypass anastomosis. The TTFM probe uses transit time technology to accurately measure blood flow intraoperatively. It measures 3 parameters of transit time flow (mean blood flow in ml per minute, pulsatility index and diastolic filling percentage) to assess graft blood flow and check graft patency. A microcomputer with a touchscreen mounted on a moveable trolley is used to control the probes and store their outputs.
There is another version available, the MiraQ TTFM system, that does not include HFUS. This version has been evaluated separately in NICE's medical technologies guidance on MiraQ for assessing graft flow during CABG surgery and is not part of this briefing.
Innovations
The company claims that the L15 imaging probe is designed to improve near-field imaging using HFUS and is applied directly to the cardiac tissue. The company also claims that intraoperative quality assessment and surgical guidance using HFUS is more likely to lead to a positive outcome and decrease the chance for additional surgical reinterventions.
Current care pathway
Coronary artery disease is a common cause of symptoms, disability and death. It is caused by atherosclerosis, which leads to stenosis or occlusion of the coronary arteries. NICE's guideline on stable angina: management recommends that revascularisation of the blocked coronary arteries using CABG or percutaneous coronary interventions should be considered in people whose symptoms are not satisfactorily controlled by medical treatment.
CABG surgery aims to bypass narrowed or blocked segments of the coronary arteries using grafts. Grafts are usually constructed from lengths of the patient's own long saphenous vein or internal mammary artery, although other blood vessels are also used.
Cardiac surgeons use a variety of techniques to avoid technical problems during CABG surgery, but assessment of graft flow is usually subjective. Techniques used vary according to the graft used, the surgical technique, and the surgeon's individual preference. They include the surgeon assessing resistance and perfusion beyond a graft by flushing fluid through it before restoring flow, and observing and palpating grafts for pulsation when blood flow has been re-established.
The following publications have been identified as relevant to this care pathway:
Population, setting and intended user
The MiraQ cardiac TTFM and HFUS system is intended for use in people with coronary artery disease undergoing CABG surgery.
The technology is used by cardiovascular surgeons, with nurses operating the system. It is used in tertiary care during cardiac surgery.
The company states that both the surgeon and the operator of the MiraQ cardiac system need to be trained in using the system. The training is provided by the company and is included in the cost of the device.
Costs
Resource consequences
The company states that MiraQ cardiac with TTFM and HFUS is used in 6 NHS trusts.
The company claims that using the MiraQ cardiac TTFM and HFUS system reduces postoperative deaths and re-hospitalisations when compared with both CABG surgery alone and CABG surgery with the MiraQ TTFM system.
The company states that there are no practical difficulties or changes in facilities and infrastructure associated with adopting MiraQ. It is a standalone system that only needs an electrical output socket.