Ann Thorac Surg 2002;73:137
© 2002 The Society of Thoracic Surgeons
Invited commentary
Louis P. Perrault, MD, PhDa,
Roland G. Demaria, MDa
a Department of Surgery, Research Center, Montreal Heart Institute, 5000 Belanger St East, Montreal, PQ H1T 1C8, Canada
e-mail: lpperrau{at}icm.umontreal.ca
The main interest and originality of this clinical report resides in the long-term assessment of the functional properties of the pedicled internal thoracic artery (ITA) as a graft for coronary artery bypass surgery (CABG). Currently, perioperative assessment of ITA flow with Doppler flowmeters is performed routinely after performance of coronary bypasses to rule out anastomotic stenosis, insufficient inflow and flow compromise. However, the flow dynamics of ITA grafts at long term have not been studied previously.
This well designed study confirms that, although the native ITA presents a predominantly systolic flow pattern, when used as a pedicled graft, it switches to diastolic predominance which remains stable even 10 years after operation. This hemodynamic property could be responsible for the superior long-term patency results of ITA compared with saphenous vein or radial artery grafts.
However, other properties of the ITA may contribute to long-term patency; these include high endothelium-derived nitric oxide release, resistance to vasospasm, wide fenestrations of the internal elastic lamina, and low dependence on vasa vasorum for nutrition of the media. Favorable mechanical properties of the ITA wall could also be involved since the compliance mismatch between graft and target artery at the anastomotic site influences long-term patency results of bypasses. Measurement of the parietal compliance of the pedicled ITA is certainly of interest to understand how it affects long-term patency, compared with grafts, both pedicled and free, used in CABG surgery. The mechanical properties of the anastomosis technique (running suture versus interrupted) should also be looked into. These measurements require specific materials and expertise with high frequency ultrasound (20 MHz) and studies are already in progress by specialized teams with an interest in the biomechanics of arterial anastomosis and flow.
An understanding of both the hemodynamics and biomechanics of the ITA and of other conduits used as grafts for CABG will help surgeons make the selection of conduit (arterial versus venous, elastic versus muscular), type of graft (pedicled versus free, skeletonized versus not), site of inflow (in situ versus aortic versus artery-to-artery), relationship to the target coronary artery (critical stenosis versus mild) and outflow. Knowledge and integration of new insights into the physical, biochemical, anatomical and functional factors influencing successful outcome of bypass grafts will ensure superior long-term results of surgical myocardial revascularization.
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Flow dynamics in internal thoracic artery grafts 10 years after coronary artery bypass grafting
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