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Ann Thorac Surg 2005;80:599
© 2005 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Invited commentary

Service of Cardiovascular Surgery, Department of Surgery, University Hospital of Geneva, CH-1211 Geneva 14, Switzerland

(Email: beat.walpoth{at}hcuge.ch).

Intraoperative flow measurements have been used for quality control of arterial and venous bypass grafts, specifically in situations of off-pump surgery, when technical failures are more common [1]. Previous studies have shown differences between arterial and venous grafts, between the left and right coronary arteries, under resting conditions or after maximal vasodilation with adenosine or dipiridamole [2, 3]. The present study shows excellent results with regard to impaired intraoperative flow using several parameters of the transit time flow measurement technique. Although sensitivity of these various measures is high (96%), specificity is relatively low (76%). A ROC analysis (receiver operating analysis) might have allowed a better selection of cut-offs reducing sensitivity, but increasing specificity. Nevertheless, which surgeon uses this handful of various measurements and calculations intraoperatively, instead of using a simple cut-off value for mean bypass flow of <10 ml/min? In these low flow states all the other parameters are also abnormal. Since bypass flow is directly dependent on perfusion pressure, these values must be seen in the light of overall hemodynamics and not only as a single parameter. Other determinants of flow must be considered as well, such as graft diameter and length, size of the perfusion territory, competitive flow, peripheral vascular resistance, sympathetic stimulation (vasospasm), hematocrit, etc.

The reported differences between the flow parameters of the arterial bypass grafts to the left and to the right coronary territory reflects simple physiology, because the normal flow pattern of the right is systolic-dominant, whereas that of the left is diastolic-dominant depending on the size of the perfusion territory and the right ventricular pressure [4]. Thus, the reported differences to detect impairment of flow based on these criteria may not be helpful.

Certainly this paper underscores an important aspect of intraoperative flow measurements, thereby minimising technical graft failures and perioperative complications. In the presence of more and more elderly people with complex anatomic situations and the more common use of complete arterial graft revascularisation and off-pump surgery, the efforts of the authors have to be congratulated. Of interest is also the algorithm for the detection of graft failure based on intraoperative flow measurements. This may even simplify the decision-making of the surgeon. In the future, more surgeons should use these techniques to improve surgical outcome and reduce perioperative complications.

	References

Top References

 

1. Walpoth BH, Bosshard A, Genyk I, et al. Transit-time flow measurements for detection of early graft failure during myocardial revascularization Ann Thorac Surg 1998;66:1097-1100.[Abstract/Free Full Text]
2. Walpoth BH, Bosshard A, Neidhart P, Hess OM, Althaus U, Carrel T. Perfusion mismatch of internal mammary artery compared to saphenous vein grafts after myocardial revascularisationimplications for synthetic grafts. Int J Artif Organs 1999;22(6):461.
3. Walpoth BH, Schwab A, Bosshard A, Eckstein FS, Kipfer B, Hess OM, Carrel TP. Vascular remodelling of the IMA-graft early and late after bypass surgery Circulation 2001;104(Suppl. II):II-635.
4. Braunwald Eugene, et al. Braunwald’s Heart Disease. A Textbook of Cardiovascular Medicine. 2004.

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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Beat H. Walpoth Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Walpoth, B. H. Search for Related Content PubMed PubMed Citation Articles by Walpoth, B. H.