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Ann Thorac Surg 2000;69:1301
© 2000 The Society of Thoracic Surgeons
a Division of Cardiovascular and Thoracic Surgery, University Hospital of Mont-Godinne, 1 av Therasse, B5530 Mont-Yuoir, Belgium
To the Editor
We thank Dr D’Ancona and associates for their interest in our work and congratulate them for their vast experience in off-pump coronary artery bypass grafting (CABG) and related flowmetry. Their comments address two different problems: (1) the intraoperative assessment of immediate graft patency and (2) the correlation between intraoperative flow-related variables and stenoses at midterm angiographic study.
Regarding the first point, they describe a large experience including 409 patients undergoing off-pump CABG [1]. All grafts were tested with transit time flowmeter and 3.2% of the grafts had to be revised for both low flow and abnormal flow curve pattern. We totally agree with their approach as we made similar observations using a dual-beam Doppler assessment in a series of 556 patients undergoing standard on-pump CABG [2]: detection of flow abnormalities prompted us to revise 29 of 1,512 distal anastomoses (2%). Moreover, in five saphenous vein grafts having low flow, intragraft injection of diluted papaverine resulted in an immediate and marked flow increase. We attributed the abnormality to a high resistance runoff bed and did not attempt to correct the anastomosis. This corroborates the observations made by D’Ancona and associates, who revised unnecessarily three grafts on the basis of low flow values but normal flow curves and pulsatility index. The dual-beam Doppler and transit time methods are simple, effective, and well-correlated methods to assess immediate graft patency [3]. As do D’Ancona and associates, we stress the paramount importance of detecting early graft failure, particularly in beating heart surgical procedures.
The second part of their comments relates to our publication dealing with intraoperative flow assessment and midterm coronary graft patency [4]. Our data indicated that increased resistance in the graft as measured intraoperatively was an independent variable associated with a reduced midterm patency rate. By contrast, we were unable to delineate a variable predicting late stenosis development. Indeed, the degree and localization of stenoses were very variable. Furthermore, growing of scar tissue and degeneration of a graft are difficult to predict simply on the basis of intraoperative hemodynamics because these factors are related to the patient risk factors and the type of conduit used. Finally, flow in the recipient coronary artery can compete with flow in the graft. D’Ancona and associates suppressed that limit of the method as all the proximal recipient arteries were snared to complete the distal anastomosis off-pump. Snaring of the proximal coronary artery is likely to enhance the graft specificity of the flow measurement. Nevertheless, we doubt that this additional manipulation could enhance the accuracy to predict late stenoses that are multifactorial in origin. In our series, all our grafts were implanted using on-pump conventional techniques and we never took the risk of snaring the proximal coronary arteries to assess intragraft flow.
In our opinion, early noninvasive detection of stenoses might be possible by developing approaches that combine specific hemodynamic assessment as suggested by D’Ancona and associates and morphometric methods using intraoperative coronary echography.
References
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