Pre-Operative Eligibility for Minimally Invasive Coronary Artery Bypass Grafting: An Examination of Epicardial Adipose Using Computed Tomography
Kate Dillon1, Marjorie Johnson1, Ian Chan2, Bob Kiaii3.
1Western University, London, ON, Canada, 2Western University, London Health Sciences Centre Department of Radiology, London, ON, Canada, 3Western University, London Health Sciences Centre Divison of Cardiac Surgery, London, ON, Canada.
OBJECTIVE: One of the primary concerns necessitating conversion to a conventional full-sternotomy coronary artery bypass procedure from a robotic-assisted endoscopic single-vessel small thoracotomy (endo-SVST), is the inability to visualize the left anterior descending (LAD) coronary artery within the surrounding epicardial adipose tissue using the endoscopic camera. The purpose of this study is to determine if the analysis of anatomical properties of the epicardial adipose tissue, along with anthropometric parameters examined using patient data and pre-operative computed tomography (CT) images, is able to predict and thus reduce the need for intraoperative conversion based on effective pre-operative exclusion criteria.
METHODS: Retrospective analysis of patient pre-operative CT angiography scans from both converted (n=13) and successful robotic-assisted (n=13) procedures was performed. Where possible, measurements of thoracic cavity dimensions and epicardial adipose tissue thickness were acquired from axial slices, at the most accessible segment of the LAD, in the fourth anterior intercostal space. An independent-samples Student T Test (α=0.05) was performed using SPSS.
RESULTS: Results indicate that patients who successfully underwent the endo-SVST procedure (mean thickness: 5.0±2.0 mm) had significantly less epicardial adipose tissue (34%, p=0.03) overlying the LAD in the transverse (Fig 1. LAD to Pericardium (II)) measurement than those who were converted to the full-sternotomy approach intra-operatively (mean thickness: 7.6±3.3 mm). Using this mean thickness as the baseline for exclusion reduces the conversion rate for this group by 46%. Preliminary data suggest that no significant differences exist between the two groups with respect to the remaining epicardial adipose tissue and anthropometric data.
CONCLUSIONS: The addition of CT measurements of the epicardial adipose tissue overlying the LAD may enhance pre-operative surgical planning for the endo-SVST procedure, thereby reducing the instances of procedural changes, which have been shown to lead to higher patient morbidity, along with increased operative time and costs.
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