Mechanical determinants of graft kinking.

Vascular grafts can be twisted inadvertently during implantation. If twisted excessively, they may kink and obstruct flow. In this study, in vitro experiments were performed to identify the mechanical factors that determine graft kinking.

Chronic loading and extension increases the acute breaking strength of polypropylene sutures.

Polypropylene sutures provide satisfactory strength for construction of vascular anastomoses, but occasionally they break. Experimental studies show that they break at reduced forces when they are subjected to chronic loads. Moreover, in patients, sutures are subject to acute loads superimposed on chronic loads.

Mechanics of end-to-end artery-to-PTFE graft anastomoses.

On some occasions vascular surgeons are called upon to construct an end-to-end anastomosis using prosthetic graft material. If a spatulated anastomosis is not fashioned, three important variables that are under the surgeon's control could affect anastomotic dimensions: (1) selection of graft material, (2) graft size relative to the native vessel, and (3) suture technique. Accordingly, studies were performed on 36 nonspatulated, end-to-end artery-to-polytetrafluoroethylene (PTFE) grafts to evaluate the effects of graft size and suture technique on anastomotic dimensions.

Mechanics of spatulated end-to-end artery-to-vein anastomoses.

It previously has been shown that in straight end-to-end artery-to-vein anastomoses, maximum dimensions are obtained with an interrupted suture line. Nearly equivalent dimensions are obtained with a continuous compliant polybutester suture (Novafil), and the smallest dimensions are obtained with a continuous noncompliant polypropylene suture (Surgilene). The present study was undertaken to examine these suture techniques in a spatulated or beveled anastomosis in living dogs.

Effect of pulsatile pressure on the breaking strength and movement of Prolene sutures.

Purpose: Most studies of sutures used in vascular surgery have used steadily applied loads. But in vivo, sutures are subject to pulsatile pressures. Pulsatile pressures could weaken sutures, or they could be beneficial by helping to slide the suture, thereby equilibrating the tension between unevenly tightened loops.

Intimal hyperplasia following thrombectomy versus thrombolysis in occluded vein grafts.

Although the histologic effects of balloon catheter thromboembolectomy in arteries are well described, little is known about its effects on arterialized vein grafts. A chronic canine model was used to compare the intimal hyperplasia that develops following balloon catheter thrombectomy versus thrombolytic therapy when each treatment was used to open experimentally occluded reversed autogenous vein grafts. Eleven of 12 dogs survived to the time of graft thrombosis and treatment.

Venous flow through coiled and noncoiled umbilical cords. Effects of external compression, twisting and longitudinal stretching.

Objective: To examine the association between umbilical cord coiling and perinatal morbidity.

Study Design: Ten umbilical cord segments, six coiled and four noncoiled, were categorized according to Strong's coiling index and were examined experimentally. The umbilical arteries and vein were perfused, pressurized, placed in a saline bath at 37 degrees C and subjected to compression, twisting and stretching while measuring venous flow.

Influence of suture technique and suture material selection on the mechanics of end-to-end and end-to-side anastomoses.

Experiments were performed in dogs to evaluate the mechanics of 26 end-to-end and 42 end-to-side artery-vein graft anastomoses constructed with continuous polypropylene sutures (Surgilene; Davis & Geck, Division of American Cyanamid Co., Danbury, Conn.), continuous polybutester sutures (Novafil; Davis & Geck), and interrupted stitches with either suture material.

Failure of elastin or collagen as possible critical connective tissue alterations underlying aneurysmal dilatation.

Previous studies in the authors' laboratory have demonstrated that degradation of arterial elastin produces vessel dilatation, decreased vessel distensibility, and vessel elongation which can cause tortuosity. By contrast, degradation of collagen produces increased vessel distensibility and rupture. However, neither degradation of elastin nor of collagen produced the true gross enlargement characteristic of human aneurysms.

Estimating the elastic modulus of non-atherosclerotic elastic arteries.

Background: Non-invasive measurements of the diameter and wall thickness of arteries in vivo, combined with recordings of pressure, permit the assessment of some mechanical aspects of arteries in vivo. However, arteries are anisotropic cylinders with complex elastic properties which can only be determined by a detailed evaluation. Many of the parameters required to calculate the anisotropic circumferential elastic modulus cannot be obtained in patients in vivo, or can be obtained only with difficulty.

Balloon embolectomy catheter-induced arterial injury: a comparison of four catheters.

This study compared four brands of balloon embolectomy catheters with respect to their mechanical characteristics and the histologic responses they elicit. Seventy-two 4F Becton-Dickinson, Edwards, Electro-Catheter, and Shiley catheters were studied. In vitro studies of penetration forces demonstrated that the forces required for arterial puncture were greatest for Shiley (295 +/- 22 gm) and least for Edwards catheter tips (217 +/- 11 gm) (p less than 0.

Longitudinal retractive force in pressurized dog and human arteries.

Experiments were performed to examine longitudinal retractive force in pressurized arteries in vitro. This force opposes vessel elongation and prevents the development of tortuosity. Common carotid arteries were excised from six adult dogs and external iliac arteries were excised from six elderly male humans at autopsy.

Early myointimal hyperplasia after balloon catheter embolectomy: effect of shear forces and multiple withdrawals.

Arterial stenosis occurring after balloon catheter embolectomy may be caused by myointimal hyperplasia (MIH). This study investigated the effects of shear force and repeated catheter withdrawals on the development of MIH after embolectomy. The procedures were performed in the common carotid and common femoral arteries of 18 anesthetized dogs.