A Series Of Research On The Blood Flow Of Grafts In Coronary Artery Bypass Grafting

Objectives1. To study the relationship between the degree of stenosis of Left Anterior Descending Artery (LAD) and the blood flow of Left Internal Mammary Artery (LIMA) anastomosed to LAD in Off-pump Coronary Artery Bypass Grafting (OPCAB).2. To compare the blood flow of LIMA measured immediately after its anastomosis to LAD and that measured before chest closure in OPCAB.3. To compare the patency rate of grafts between Conventional Coronary Artery Bypass Grafting (CCABG) and OPCAB.4. To investigate the patency rate of grafts with mean blood flow less than 10ml/min.5. To compare the patency rate of LIMA and saphenous vein (SV) graft in CABG.6. To define referential criteria of parameters of graft's blood flow in CABGPatient and methodsA total of 299 patients (pts) underwent intraoperativehemodynamic assessment of the grafts in CABG using Transit-Time Flowmeter (TTFM). LIMA was routinely bypassed to LAD and SV to the other target vessels with sequential fashion when anastomoses were no less than two. Several parameters in terms of mean blood flow, systolic blood flow, diastolic blood flow, Pulsatility Index (PI) and the real time flow wave were recorded.In the first part, 169 cases underwent OPCAB were divided into two groups according to the degree of stenosis of LAD ( 75% or 90%?). Blood flow of LIMA was measured immediately after completion of anstamosis.In the second part, to determine the dynamic change of LIMA's blood flow in OPCAB, 65 LIMAs were assessed immediately after anstomosis and before chest closure which were accordingly defined as early group and late group.In the third part, the characteristics of blood flow of grafts including LIMA and SV in 296 pts was compared in order to show if the patency rate of grafts could be influenced by cardiopulmonary bypass (OPCAB group and CCABG group).In the fourth part, 41 grafts, involving LIMA and SV, with mean blood flow no more than 10ml/min, which was thought by experience to be lower than preferable value, were studied by injection of papaverine directly into SV or LIMA pedicle and the blood flow before and after the intervention with vasodilatation agent was compared for the purpose of determining the association of low mean blood flow and patency rate.In the fifth part, patency rate between LIMA and SV in 296 pts was compared to demonstrate whether the type of conduit was a influencing factor for patency.In the sixth part, referential criteria of parameters of graft'sblood flow in CABG were defined after analyzing parameters mentioned above on the basis of the data from the total 299 pts.ResultsBlood flow of LIMA was significantly influenced by the degree of stenosis of LAD. The higher degree the larger flow which could imply the competition of blood flow between graft and native vessel. Dynamic change of blood flow of LIMA occured along with time according to the significant alteration of some parameters while the others remained unchanged significantly. In the third part, some parameters of blood flow were significantly different between OPCAB group and CCABG group, but this couldn't indicate a significant difference of the patency of grafts between the two groups. Low blood flow of grafts could be significantly increased by injection of papaverine, which implied that low flow was not definitely associated with technique problem of anastomosis but might be the result of some other factors like spasm of grafts or poor run-off of native vessel. Significant difference of patency rate between LIMA and SV could not be made in spite of difference with significance of some parameters. After comparison of all parameters it seemed that PI might be the best to reflect the patency of graft. The value of PI below 5 is acceptable.Conclusions1. The blood flow of LIMA anstomosed to LAD in OPCAB is positively related to the degree of stenosis of LAD.2. The blood flow of LIMA in OPCAB has dynamic alteration after grafted to LAD.3. The patenc...