This single-centre, prospective observational feasibility and safety study will enrol 190 consecutive adults undergoing elective isolated coronary artery bypass grafting (CABG) at Nanjing Drum Tower Hospital. The study aims to evaluate the feasibility and safety of intraoperative ultrasound for the quantitative assessment of native coronary artery and bypass graft blood flow.
Transit-time flow measurement will be performed as part of routine intraoperative graft assessment. Additional ultrasound measurements will be obtained from major native coronary arteries before and after revascularisation and from bypass grafts after restoration of blood flow. The ultrasound findings will be collected for research purposes and will not influence graft revision or other intraoperative clinical decisions.
The co-primary outcomes are the participant-level technical success rate of the protocol-defined intraoperative ultrasound assessment and the incidence of adverse events related to the ultrasound device or measurement procedure. Secondary outcomes include agreement between ultrasound and transit-time flow measurements, changes in native coronary artery blood flow after revascularisation, measurement repeatability, and exploratory associations between intraoperative flow parameters and postoperative cardiac function and myocardial injury biomarkers. Participants will be followed for 30 ± 7 days after surgery.
Aged 18 years or older.
Confirmed coronary artery disease and scheduled to undergo elective isolated coronary artery bypass grafting at Nanjing Drum Tower Hospital.
Able and willing to provide written informed consent before any study-specific procedures are performed.
Urgent, emergency, or salvage coronary artery bypass grafting.
Prolonged preoperative fasting, as defined in the study protocol, or inability to maintain adequate oral intake without enteral or parenteral nutritional support.
History of malignancy.
Body weight below 50 kg.
The study population will consist of adults undergoing elective isolated coronary artery bypass grafting in the Department of Cardiac Surgery at Nanjing Drum Tower Hospital. Consecutive patients meeting the eligibility criteria will be screened and enrolled after providing written informed consent.
Cohort
Prospective
Intraoperative Ultrasound Blood Flow Measurement
Diagnostic testIntraoperative ultrasound measurements of major native coronary arteries will be obtained before and after revascularisation, followed by measurements of individual bypass grafts after restoration of blood flow. Recorded variables will include blood flow velocity, volumetric blood flow and other protocol-defined quantitative parameters. The findings will be collected for research purposes and will not guide graft revision or other intraoperative clinical decisions.
Participant-Level Technical Success Rate of the Protocol-Defined Intraoperative Ultrasound Assessment
The proportion of enrolled participants with analysable quantitative flow parameters obtained from ultrasound measurements of at least two major native coronary arteries both before and after revascularisation and from all protocol-specified independent bypass grafts. Failure to initiate or complete a protocol-defined measurement, visualise a required target vessel, obtain a stable flow signal, or generate analysable data will be classified as technical failure and retained in the denominator.
Incidence of Adverse Events Related to the Intraoperative Ultrasound Device or Measurement Procedure
The proportion of participants with any adverse event judged by the investigator as possibly, probably, or definitely related to the intraoperative ultrasound device or measurement procedure. Prespecified events of special interest include a new or worsened sustained arrhythmia requiring treatment; clinically significant haemodynamic instability; bleeding or tissue injury attributable to probe contact or manipulation; native coronary artery, graft, or anastomotic injury; interruption or clinically meaningful prolongation of surgery attributable to ultrasound measurement; device malfunction posing a patient safety risk; and other related events as judged by the investigator.
Agreement Between Intraoperative Ultrasound and Transit-Time Flow Measurements
Agreement between comparable bypass graft blood flow parameters obtained using intraoperative ultrasound and transit-time flow measurement will be evaluated in grafts with analysable paired measurements using intraclass correlation coefficients and Bland-Altman analysis.
Mean Within-Vessel Change in Ultrasound-Derived Volumetric Blood Flow of Native Coronary Arteries Before and After Revascularisation
Volumetric blood flow will be measured in the same analysable segments of the left anterior descending, left circumflex, and right coronary arteries immediately before revascularisation and after completion of graft anastomoses following haemodynamic stabilisation. For each analysable native coronary artery, the within-vessel change will be calculated as post-revascularisation volumetric blood flow minus pre-revascularisation volumetric blood flow. The native coronary artery will be the unit of analysis, and the mean of all analysable vessel-level change values will be reported in mL/min. Positive values indicate increased blood flow after revascularisation.
Repeatability of Intraoperative Ultrasound Blood Flow Measurements
Repeatability of intraoperative ultrasound-derived quantitative blood flow parameters will be evaluated using repeated measurements obtained at the same vascular measurement site. Intraclass correlation coefficients, coefficients of variation, repeatability coefficients, and Bland-Altman limits of agreement will be calculated.
Association of Intraoperative Blood Flow Parameters With Postoperative Cardiac Function and Myocardial Injury Biomarkers
Associations between intraoperative ultrasound-derived native coronary artery and bypass graft blood flow parameters and postoperative measures of cardiac function, cardiac structure, and myocardial injury will be explored. Planned measures include left ventricular ejection fraction, left ventricular end-diastolic diameter, B-type natriuretic peptide or N-terminal pro-B-type natriuretic peptide, cardiac troponin T or cardiac troponin I, and other protocol-defined measures.
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