Pressure trap created by vein valve closure and its role in graft stenosis

Abstract

Saphenous vein graft stenosis has become the leading cause of reoperation in coronary bypass operations. We investigated the role of vein valves in vein graft stenosis by studying 14 human saphenous veins placed in a simulator of the left side of the heart in parallel with the arterial system. The vein had a variable resistance and a capacitance simulating the distal vascular bed. The pressures at the proximal and distal ends of the vein and the venous flow were measured while the foUowing were changed: venous flow 200 to 0 m1/min, aortic pressure 150/120 to 80/60 mm Hg, cardiac output 3 to 5 L/min, and compliance of distal vascular bed 0 to 1 mI of air. The pressures at both ends of the vein From Heineman Medical Research Laboratory at the Carolinas Medical Center and the Sanger Clinic, Charlotte, N.C.

Improving Patency of Coronary Conduits "Valveless" Veins and/or Arterial Grafts

“…By decreasing endothelial wall stress, endothelial injury is reduced, thus atherosclerosis can be also reduced. Under the same conditions with reversed saphenous veins the "trap" phenomena were reconfirmed and documented in femro-popliteal bypasses 27 (Fig. 3).…”

“…Blood flow through the reversed venous valves has been extensively investigated. 26 Studies by Thubrikar et al 27 have documented the hemodynamic abnormalities of the existent valves as related closure, flow, and pressure. In different conditions of various systemic pressures and cardiac outputs, the valve offered no significant resistance to flow and pressure and it stayed open just like in any cylindrical tube would.…”

“…With gradually decreasing flow, the “trap” becomes more harmful generating more pressure, 27 simultaneously increasing the diastolic pressure gradient. This seems to be proportional to any given venous flow rate, highly influenced by compliance difference, the length to diameter, and wall thickness.…”

Posterior wall reinforcement in selected cases of graft to aorta end-to-side anastomosis

“…The performance appeared to be easy and the safety of the anastomosis appeared to be assured. Short-term results appear to be excellent and, based on our previous experiences with aortic wall reinforcement [1][2][3][4][5], we are quite confident that it will also work well in the long run.…”

One-Year Patency of Valvulotomized Vein Grafts Is Similar to That of Arterial Grafts

“…Furthermore, experimental data show improved flow behavior after valvulotomy. 5,6 There is also evidence of improved patency rates of valvulotomized vein grafts in the so-called horseshoe grafts, where one limb of these grafts has been used nonreversed and valvulotomized. 7 Most disadvantages of venous valves should have an impact on early patency, so the aim of our study was to evaluate whether early to midterm patency of vein grafts can be improved by systematic valvulotomy and further we wanted to prove whether flow rate can be changed by valvulotomy in the clinical setting.…”