The performance of commercially available sealed Dacron vascular grafts in intraarterial thrombolytic therapy.

The purpose of this study was to assess whether two commercially available, sealed arterial prostheses would tolerate catheter directed, intraarterial thrombolytic therapy. Sealed vascular grafts were implanted in 12 mongrel dogs for 3, 4, and 6 week intervals as iliac artery interposition grafts. This allowed direct comparison of two types of sealed grafts in the same animal. The indications for graft failure consisted of clinically evident bleeding, transluminal extravasation, or anastomotic leakage of contrast medium documented by angiography. Thrombolytic therapy (urokinase) was delivered immediately proximal to the grafts in the distal aorta, thereby exposing the intraluminal surfaces to urokinase delivered directly from the catheter tip, as well as to the accumulated systemic levels of urokinase and urokinase activated plasmin. There was no evidence of postoperative bleeding or extravasation of contrast medium during any follow-up arteriogram in any animal. There was no discernible extravasation of contrast medium noted at the anastomotic sites. At the time of explantation, no graft demonstrated any evidence of subclinical extravasation, such as separation of the external capsule from the abluminal surface of the graft. It is concluded that it appears safe to use thrombolytic therapy in these grafts as early as 3 weeks postimplantation.

Delayed exposure to pulsatile shear stress improves retention of human saphenous vein endothelial cells on seeded ePTFE grafts.

Since significant loss of endothelial cells (ECs) from the surface of a seeded prosthetic graft occurs after implantation, improved cell retention following exposure to flow should increase the likelihood of long-term success with this technology. An in vitro pulsatile flow circuit was developed to study the effects of two variables on cell retention: cell density at the time of seeding and postseeding incubation time. Fibronectin-coated ePTFE grafts (4 mm x 5 cm) were seeded with human saphenous vein ECs at two densities, confluent (1 x 10(5) cells/cm2) or subconfluent (2 x 10(4)), and incubated in vitro for varying time intervals (90 min, 1, 3, or 7 days). Test grafts were exposed to 90 min of pulsatile flow in an in vitro flow circuit, then fixed, and stained, and in situ cell counts (cells/cm2) were determined for nine representative fields per graft. Paired control grafts were treated identically but were not exposed to flow. Cell retention was calculated using the formula: % retention = cells/cm2 perfused graft divided by cells/cm2 control graft. Grafts exposed to flow 90 min after seeding demonstrated significantly lower cell retention when compared to later time points. When cells were seeded at confluent density, maximal retention (92 +/- 3%) occurred 24 hr after seeding. Prolonged culture of cells seeded on ePTFE grafts at confluent density resulted in increased cell loss. In contrast, on grafts seeded at subconfluent density, retention improved as cells grew to confluence (16 +/- 4.5% initially to 82 +/- 7% at 7 days).(ABSTRACT TRUNCATED AT 250 WORDS)

Limb salvage and selectivity.

In a group of properly prepared poor risk patients with advanced atherosclerosis of both the aortoiliac and femoropopliteal segments, a combined procedure, extra-anatomic bypass with an extended profundoplasty, was used for successful salvage of their ischemic--mean calf pressure=27 millimeters of mercury--limbs. Prediction of success versus failure could be determined on neither clinical nor angiographic-anatomic grounds but was possible using two simple measurements: a large aortoiliac differential pressure--deltaP--between inflow pressure obtained from a standard arm cuff and outflow pressure measured directly from the femoral artery, 89.3 millimeters of mercury versus 33.2 millimeters of mercury, p less than 0.001, and a potentially adequate outflow bed as determined by the percentage drop in outflow [(deltaPo/Po) per cent] upon papaverine injection, 36.3 versus 11.3 per cent, p less than 0.001. These values became an important part of the selection scheme developed in the approach to 24 ischemic limbs.

Noninvasive assessment of the peripheral vascular system.

Forty-five limbs varying clinically from normal through moderate to severely ischemic were studied by noninvasive measurements of both arterial blood pressure and perfusion. From the values plotted on a two-coordinate system, they arranged themselves well into three clinical categories: (1) normal, (2) intermittent claudication, and (3) ischemia or ulceration and rest pain. Good clinical responses to arterial reconstruction were corroborated by postoperative measurements. Reinforcing the results of one measurement with those of the other has provided an objective, numerical, and graphic basis for decisions regarding the advisability of angiography or arterial reconstructive procedures or both. To date, almost 400 patients have been evaluated by these techniques.

Indirect near-infrared spectrophotometric determination of silicate by the 2-amino-4-chlorobenzenethiol method.

An indirect near-infrared spectrophotometric method for the determination of silicate, based on the absorbance of an equivalent amount of molybdenum-2-amino-4-chlorobenzenethiol complex in chloroform solution, has been developed. The green chloroform solution has an absorbance maximum at 715 nm. The development of the spectrophotometric method for the determination of silicate included a study of a buffer system for the purpose of maintaining the pH within a narrow optimum pH range, complex stability, effect of diverse ions, and conformity to Beer's law. The limit of detection is 0.034 mug of silicon per ml of aqueous heteropoly acid solution.