Graft flow Measurement in Coronary Surgery during Aortic Cross-Clamp: a Possible Method to Study Coronary Pathophysiology
Gabriele Di Giammarco1, Daniele Marinelli1, Vladlen Basylev2, Arthur Mikulyak2, Valentina Mancini1, Tariq Mobariki1.
1University "G.D’Annunzio" Chieti-Pescara, Italy, CHIETI, Italy, 2Federal Center of Cardiovascular Surgery, Penza, Russian Federation.
OBJECTIVE: Intraoperative Transit-Time Flow Measurement (TTFM) if verified by imaging represents a unique tool for the study of the pathophysiology of coronary circulation. We sought to evaluate TTFM during coronary artery bypass grafting (CABG) under aortic cross-clamp and cardioplegic arrest comparing the MGF after clamp release and after protamine administration to check possible correlation in those different conditions and with a history of previous Myocardial Infarction (MI) on the territory of the Left Anterior Descending artery (LAD).
METHODS: We reviewed the prospectively collected intraoperative TTFM values and clinical charts of 57 patients form June 2016 to April 2017. Data are reported as median and 25th-75th percentile. Statistical analysis was performed using GraphPad Prism for Mac Ver 6.0.
RESULTS: The median MGF values measured during aortic cross-clamp were significantly higher than the MGF measured immediately after cross-clamp release and after protamine administration (35 ml/min (20-53) vs 15 ml/min (11-22) vs 20 ml/min (13-29) respectively; p=0.0003). Thirteen patients (22%) had a previous MI on the LAD territory. The median graft number per patient in the two groups was 2 (2-3; p=0,68). A strong correlation was found between the MGF of graft on LAD territory during aortic cross-clamp compared to the MGF recorded immediately after cross-clamp release in case of previous myocardial infarction (MI) in the same territory; the Spearman r coefficient was 0,73 (CI: 0,29 to 0,91; p=0,0056; Graph 1-A). No correlation was found in those without previous MI (Spearman r coefficient 0,27; CI -0,043 to 0,54; p= 0,088;Graph 1-B)
CONCLUSIONS: TTFM during cardioplegic arrest and aortic cross-clamp CABG proves a significant increase in myocardial blood flow demand related to very low coronary vascular resistance due to the absence of muscular contraction and microvascular tone modification. In addition there is a correlation between MGF during aortic cross clamp and the same parameter after clamp release in case of previous MI. This is the first study concerning in vivo observation of microvascular coronary circulation reaction during cardioplegic arrest in coronary surgery. The evaluation of scar extent using nuclear magnetic resonance can help to predict the expected flow after surgical revascularization.
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