None listed
Conditions
Brief summary
The gold-standard treatment for people with critical narrowing (stenosis) of the vessels that supply blood to the heart muscle is coronary artery bypass graft surgery (CABG). CABG involves using conduit vessels harvested from other areas of the body to bypass the areas of critical stenosis. Constriction or blockage of the conduits are complications that commonly affect patients and increase the risk of heart attacks, repeat operations and death. We have hypothesised that the drug sildenafil may reduce the risk of conduit constriction or blockage. However, before a large scale trial can be undertaken, a critically appraised study protocol must be designed. A sensitive and feasible primary endpoint for this future study is yet to be identified. It is the main purpose of this feasibility study to identify such an endpoint. The MiraQ Cardiac system uses ultrasound to measure conduit patency in CABG patients and has been shown to be useful in detecting vessel constriction or blockage during CABG. It is possible that measurements of graft patency using the MiraQ Cardiac Unit could provide the sensitive and feasible primary endpoint that we have yet to establish for our future large scale study. The purpose of this feasibility study is thus: firstly, to determine the practicalities of MiraQ Cardiac-use during CABG; Secondly, to investigate whether measurement of conduit patency could be a sensitive and feasible primary endpoint in a future large-scale study; Lastly, whether the use of the MiraQ Cardiac technology can detect a difference in graft patency for patients who undergo a protocol simulating sildenafil's properties by repeat blood pressure cuff inflation and deflation during CABG.
Interventions
Exposure Group
Patients will have a manual brachial BP cuff applied to the arm not used for routine BP measurement. The BP cuff will be applied by another investigator at the time that median sternotomy is commenced. To induce remote ischaemic preconditioning and to simulate the actions of sildenafil, the cuff will be inflated to 180 mm·Hg for five minutes followed by five minutes of cuff deflation. Each patient will undergo three ten-minute inflation-deflation cycles before removal of the BP cu
Exposure Group Patients will have a manual brachial BP cuff applied to the arm not used for routine BP measurement. The BP cuff will be applied by another investigator at the time that median sternotomy is commenced. To induce remote ischaemic preconditioning and to simulate the actions of sildenafil, the cuff will be inflated to 180 mm·Hg for five minutes followed by five minutes of cuff deflation. Each patient will undergo three ten-minute inflation-deflation cycles before removal of the BP cuff and completion of the protocol. Comparison Group The BP cuff and sphygmomanometer will be kept with the anaesthetist and out of view of the operating surgeon. To ensure that the operating surgeon is blinded to the participant’s randomisation status, the BP cuff will be inflated (while unattached to the patient and at the time of median sternotomy) by another investigator to 180 mm·Hg for five minutes followed by five minutes of cuff deflation. The process will be repeated for three ten-minute inflation-deflation cycles and then the protocol will be completed. All Patients After completion of the anastomosis of the bypass grafts, a MiraQTM Cardiac probe will be introduced into the thoracic cavity and gently placed upon a graft immediately distal to the anastomoses. The procedure will be repeated for each anastomosis undertaken. The probe will be gently manipulated in order to obtain the best ultrasonographic view in consultation with the Responsible Clinician. A SCORECARD Investigator will then record the ultrasound measurements using the MiraQTM Cardiac touch screen. The probe will be gently removed from the thoracic cavity and the entire MiraQTM Cardiac Unit will be moved away from the operating field. Steps to be taken if there is Clinical Evidence of a Complication In the event that any graft displays a pulsatility index > 5 or a mean graft flow < 20 ·mL·min-1 the surgeon will be informed so that he can decide whether review of the graft(s) is required. These steps are in keeping with the current NICE Guidelines. Adherence There will be no strategies used to monitor adherence because a small sample size is being employed in this study.
Sponsors
University of Auckland
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Prevention
Masking
Blinded (masking used) (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
Patients will be eligible for recruitment if they meet all of the following inclusion criteria: (1) age greater than or equal to 18 years. (2) Admission to the cardiothoracic surgical unit (Auckland District Health Board, NZ) and expected coronary artery bypass graft surgery between 14 August 2016 and 14 October 2016. (3) Recommended and offered elective coronary artery bypass graft surgery. (4) Operating surgeon is the surgeon listed as an Investigator in this study.
Exclusion criteria
Patients will not be eligible for recruitment if they meet any of the following exclusion criteria: (1) Creatinine clearance less than or equal to 30 mL per minute. (2) Hepatic failure as determined by Child-Pugh class B or C. (3) BP less than or equal to 90/50 mm Hg. (4) Undergoing coronary artery bypass graft surgery revision. (5) Unable to provide informed consent. (6) Not eligible for public funding.
Outcome results
None listed