1. Vascular Conduits & Flow dynamics
Dr. Nalaka Gunawansa
Consultant Vascular and Transplant surgeon
National Institute for Nephrology, Dialysis & Transplantation –

2. Vascular Conduit ?
An artificial channel / connection between two different vessels or parts of the same vessel.

5. For steady laminar flow of a Newtonian fluid through a cylindrical tube, the flow rate is directly proportional to the pressure drop, fourth power of radius of tube and inversely to the length and viscosity of fluid

8. Types of Vascular Conduits.
autologous
Biological
Cryo-preserved
Dacron
Prosthetic
Polytetraflouroethylene
(PTFE)
Endografts - - stents/ stent grafts

9. Venous Conduits. Autologous-
Cryo preserved – cadaveric / xeno (porcine)
Reversed
Non-reversed
In situ

10. Autologous venous conduits.
A venous graft taken from the patient's own body.
eg – 1. Greater Saphenous vein –
-Most frequently used autologous vein graft.
2.Lesser Saphenous vein –
-used as an alternative to GSV where this is unsuitable or has been harvested previously.
3.Arm veins -
-where there is no suitable leg vein available but there is a strong indication for the use of vein rather than prosthetic material
-Cephalic and basilic veins
Composite grafts

11. Cryo Preserved Venous Conduits
In infected fields
Where the autologous vein is not available or not suitable.
Dimethyl sulfoxiude and chondroitin sulfate
are current cryoprotectants.
Specific complications,
- aneurysmal degeneration
- late rejection leading to thrombosis

12. Vein graft handling
Pre-operative
mapping

13. Reversed / insituVenous Conduits
Insitu – Valves surgically destroyed with intraluminal cutting valvutome

14. Arterial Conduits
internal mammary, radial and hypogastric arteries are the most durable and best performing vascular conduits.
In cardiac bypass surgeries

15. Prosthetic Conduits Types - Polyethylene (PET) - Dacron
-Poly tetra fluro ethylene - PTFE
Indications
- Autologous unavailable/ non patent.
- Replace the thoracic and abdominal aorta, arch vessels, the iliac artery, and common femoral arteries. for either aneurismal or occlusive disease
Complications
-Thrombosis
-Compliance mismatch
-Infection

16. Dacron Conduits Available in woven or knitted forms
woven material reduced porosity less leakage
Stiffer
knitted graft looser construction more flexible
excessive blood leakage
prevented by impregnation
impregnated with Silver, Rifampicin, heparin to be used when there is high risk of graft infection.

17. Polytetraflouroethylene (PTFE) Conduits
Smooth surface – less thrombogenic than Dacron
Prone to kinking
external reinforcing
rings to prevent kinking

20. Endo – prosthetic grafts

21. The ‘ideal’ graft Non biodegradable Non thrombogenic Non carcinogenic
Cheap
Long shelf life
durable
Pliable and allowing body movement
Easy to handle / suture
Self sealing
Mechanically inert
Hydrophobic
Resistant to infection