Quantitative angiographic follow-up of the coronary Wallstent in native vessels and bypass grafts (European experience--March 1986 to March 1990).

The coronary stent has been investigated as an adjunct to percutaneous transluminal coronary angioplasty to obviate the problems of early occlusion and late restenosis. From March 1986 to March 1990, 265 patients (308 lesions) were implanted with the coronary Wallstent in 6 European centers. For this study, the patients were analyzed according to date of implantation (group 1, March 1986 to January 1988; group 2, February 1988 to March 1990) and vessel type (native arteries versus bypass grafts). Quantitative angiographic follow-up was performed in 82% of the study patients. The early in-hospital occlusion rate in the overall group was 15%. Group 1 patients had a 20% rate in contrast to 12% rate in group 2 (p = not significant [NS]). The early occlusion rate in native vessels and bypass grafts was 19 and 8%, respectively (p = 0.019). Restenosis was determined by 2 criteria (criterion 1, greater than or equal to 0.72 mm loss in minimal luminal diameter from poststent to follow-up; criterion 2, greater than or equal to 50% diameter stenosis at follow-up) within the stent and in the segments immediately proximal and distal to the stent. The restenosis rate with criterion 1 was 43% in the overall group of patients, 35% in group 1 versus 49% in group 2 (p = NS), and 34% in native vessels versus 54% in bypass grafts (p = 0.016). The second criterion was met by 27% of patients in the overall group, 21% in group 1 versus 32% in group 2 (p = NS), and 18% in native vessel versus 39% in bypass grafts (p = 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Preclotting of knitted Dacron prosthesis. A scanning electron microscope study.

A scanning electron microscope study of preclotting on knitted Dacron prosthesis is reported. Five steps of the interaction are well identified: (1) before any blood contact (virgin Dacron), (2) during the first 3 minutes (fibrin and platelet aggregates), (3) fifth minute of contact (clotting), (4) 15 minutes of contact with heparinized blood (thin fibrin network), and (5) the following minutes (invasion of fibrin, which enmeshes blood cells).

Technique for insertion of apicoaortic conduit.

A technique for insertion of an apicoaortic prosthesis is described. It provides a hemostatic aortic and ventricular anastomosis and can be performed with a minimum of bypass time and without interruption of coronary circulation. The technique requires no special instruments.

Arterial prosthesis of microporous expanded polytetrafluoroethylene for construction of aorta-pulmonary shunts.

A new arterial prosthesis made of polytetrafluoroethylene (OTFE) was evaluated in 10 infants with complex cyanotic congenital heart disease. All grafts used were 4 mm. in diameter and varied in length from 0.8 to 6 cm. The grafts were anastomosed to the main pulmonary artery or its bifurcation in 8 infants and to the right and left pulmonary arteries in one each. There were two early deaths, one of which was related to shunt failure. The advantages of a shunt to the main pulmonary artery are obvious, and the intraoperative procedure is facilitated with the prosthesis. Follow-up averages 9 months in the 8 survivors, and the patients have nearly doubled their preoperative weight. A shunt murmur is present in each case and the children have mild-to-moderate cyanosis at rest. Repeat aortograms in 2 patients, 8 and 10 months postoperatively, show a smooth graft without luminal narrowing. The aortic oxygen saturations were 73 per cent. The PTFE graft and/or anastomoses will not grow with the growth of the child and therefore may not accommodate growth by increased flow. This may prove to be a limiting factor in its long-term use in fants. We reserve the use of these grafts for infants with complex cyanotic defects undergoing emergency surgery or in older children in whom a conventional shunt is not possible or a previous shunt has failed.

Relief of congenital obstruction to left ventricular outflow with a ventricular-arotic prosthesis.

Hypoplasia of the aortic valve annulus and ascending aorta is a rare form of congenital aortic stenosis, with a poor prognosis. Replacement of the aortic valve and ascending aorta with a suitable prosthesis is feasible, but the hypoplastic valve annulus must also be enlarged if an adult-sized aortic valve is to be placed in the subcornary position. In an effort to develop a new method of surgical treatment for this congenital abnormality, we fabricated a prosthesis which can be interposed between the left ventricular apex and descending thoracic aorta. This prosthesis is coupled to a 25 mm. Dacron graft and xenograft valve and is lined with flocked Dacron fibrils to encourage formation of a stable biologic lining and prevent thrombus buildup. The prosthesis was implanted in a 22 year old male patient of the Children's Hospital Medical Center without difficulty. Postoperative cardiac catheterization idicated that all of the contrast material was ejected from the left ventricle through the prosthesis. The patient was discharged from the hospital taking sodium warfarin and remains entirely asymptomatic.

Complete repair of transposition of the great arteries with pulmonary atresia.

In this series of 13 patients undergoing repair of transposition of the great arteries with ventricular septal defect and pulmonary atresia, the operative risk and postoperative complications were greater than for repair of either transposition of the great arteries with ventricular septal defect and pulmonary stenosis or pulmonary arterial atresia with ventricular defect. Nevertheless, 6 of the 8 survivors improved clinically. Because operative and late mortality and morbidity rates are related to persistent right ventricular hypertension caused primarily by restricted pulmonary arterial outflow, results should be improved by performance of a preliminary systemic-pulmonary artery shunt for patients with hypoplastic pulmonary arteries and by use of the Hancock prosthesis, which has yielded lower gradients at both the proximal and distal anastomoses of the conduit. These improvements and the relief from cyanosis, exercise intolerance, and other symptoms seem to justify the continued application of surgical correction of transposition of the great arteries when associated with pulmonary atresia.

Processes human umbilical veins as arterial substitutes--evaluation in canine models.

Human umbilical cord vein segments have been used as vessel substitutes for damaged or occluded arteries, as aorto-coronary by-passes and as arterio-venous fistulae for dialysis. The Dardik-Biograft fixed with glutaraldehyde and the Mindich-Bioflow, fixed with ethanol and dialdehyde starch, are commercially available. They were implanted in dogs as replacements for a segment of the abdominal aorta. Post-implantation status was followed by angiography. They were evaluated after removal from sacrificed animals with the aid of scanning electron microscopy and histological techniques. Attention was focused on vessel patency, dimensional stability, integrity of the anastomosis line, lumen wall microstructure, evidence of suture damage and thrombus deposition pattern. Both types of grafts gave functional by-passes for at least until 6 months post-implantation. The Dardik-Biograft appeared more prone to thrombus formation near the anastomosis. Sparse cellular development was also noted. The Mindich-Bioflow gave rise to a prosthesis of superior thromboresistance which was more subject to mechanical damage.

Expanded polytetrafluoroethylene vascular prostheses seeded with enzymatically derived and cultured canine endothelial cells.

Thirteen adult dogs underwent thoracoabdominal bypass operations with 6 or 10 mm expanded polytetrafluoroethylene (PTFE) grafts 25 to 30 cm long. Eight experimental grafts were seeded with cultured autologous endothelial cells prior to implantation. Five unseeded grafts served as controls. Endothelial cells, derived from external jugular vein segments using 0.1% trypsin and 0.5% collagenase solutions, were cultivated for 14 days prior to seeding. Grafts were studied at 2 and 4 weeks after implantation. Endothelial linings in control grafts were restricted to limited anastomotic pannus ingrowths, never exceeding 10% of the graft surface. Experimental grafts demonstrated an endothelial surface coverage averaging 64% and 91% at 2 and 4 weeks, respectively. Generation of an early lining of endothelium in expanded PTFE grafts is possible in a canine model using cultured autologous cells.

An electric cutter for all surgical prostheses.

A new electric cutter for surgical prostheses has been developed and was compared with surgical scissors for efficacy. This comparison of the two methods was done by cutting the edges of nine popular prostheses. It was concluded from gross and microscopical results after pulling both edges of the grafts cut by the two methods that the electric cutter is much more effective for surgical prostheses.

Vein holder for coronary bypass surgery.

Two types of vein holder were designed to facilitate coronary bypass surgery. One is designed for vein graft-to-coronary artery anastomosis and is particularly useful for the side-to-side anastomosis in sequential grafting. The other is designed for vein graft-to-aorta anastomosis and enables anastomosis by one surgeon. The vein holder holds the vein graft in a three-dimensional position without the need of forceps, which protects the vein graft wall from crush injuries caused by vascular forceps.

Experimental assessment of newly devised transcatheter stent-graft for aortic dissection.

Despite recent advances, surgical results for Stanford type B dissection are not yet satisfactory because the procedure is so highly invasive. The aim of this study was to devise a new intraaortic (IA) graft that would offer less invasive treatment for type B dissection. To close the entry of type B dissections using transcatheter placement, we devised an IA graft (inner diameter, 15-20 mm; length, 40 to 60 mm) in which a self-expandable stent was covered with a thin, open-cell-structured polyurethane jacket. In acute animal experiments in which type B aortic dissections were prepared in 4 mongrel dogs, IA grafts were implanted to close the entry using a transfemoral catheter sheath, and closure of all the entries was confirmed by aortography. In chronic experiments, five IA grafts for normal descending aortas and one IA graft for an experimentally dissected aorta were implanted to observe histologic biocompatibility for up to 8 months. Histopathologic examination conducted at the projected sacrifice periods revealed that endothelialization of the luminal surface of the IA graft had begun as early as 1 month after implantation and was completed within 4 months. The prototype device that we developed may be promising as an effective, minimally invasive therapeutic intervention for closure of the entry site of type B dissection.

New approach to aortic dissection: development of an insertable aortic prosthesis.

We have developed a new aortic prosthesis with which we can replace or reinforce the aorta using a simple percutaneous technique. We have named the new prosthesis the shape-memory aortic prosthesis (SAP); it consists of a spiral-shaped nitinol stent and polyurethane tube. It can be compressed inside a 14F catheter at a low temperature and regain its original shape at above 30 degrees C. As a preliminary study, SAP sutureless grafting into the descending aorta was performed on 10 mongrel dogs. We found that when the proper diameter of SAP was applied, it functioned satisfactorily for 3 months or more. A percutaneous placement technique pertinent to the SAP also was developed and tried on 4 animals. Our procedure was applied to Stanford type B dissection models to close the entry point successfully. This newly developed SAP has potential to be applied to emergency cases of human aortic dissections.

Use of the doubly tapered graft for the creation of a systemic-pulmonary arterial shunt.

It is now possible to construct vascular grafts of expanded polytetrafluoroethylene having complex configurations. In this series of experiments a double tapered graft was used to create a bypass shunt between the aorta and the pulmonary artery in rhesus monkeys and between the aorta and the iliac artery in dogs. When the synthetic material was placed under a slight degree of tension, a high degree of patency was achieved in animals killed three to six months following implantation. The use of this approach in neonates with cyanotic congenital heart disease necessitating the creation of systemic-pulmonary artery shunts is suggested as a new method to achieve a controlled lumen size and an increased patency rate, while simultaneously decreasing the incidence of congestive heart failure or of late stricture of the pulmonary artery.

Superior late patency of small-diameter Dacron grafts seeded with omental microvascular cells: an experimental study.

The purpose of the study was to investigate the effect of omental microvascular cell seeding on the patency of small-diameter Dacron prostheses usable for coronary artery bypass grafting. In a canine carotid artery model, each dog (n = 64) received one seeded and one similar nonseeded Dacron prosthesis (internal diameter = 4 or 6 mm). Enzymatically harvested omental microvascular cells (omentum = 27.6 +/- 5.9 g [+/- the standard deviation]; range, 17 to 50 g) were seeded prior to implantation. The seeding density was 1.91 +/- 0.26 [+/- the standard error] x 10(6) cells/cm2 of graft surface. Dipyridamole (75 mg/d) and acetylsalicylic acid (325 mg/d) were administered orally for 4 weeks postoperatively. The prostheses were explanted between 2 and 52 weeks after placement. The results were assessed by angiography; light, scanning electron, and transmission electron microscopy; and morphometry. The seeded grafts developed a uniform luminal monolayer of endothelial cells with minimal platelet or cellular deposition. These grafts also had a significantly higher overall patency rate and significantly larger thrombus-free surface areas than the nonseeded grafts. The overall actuarial patency rates at 1 week, 5, 12, 26, and 52 weeks were 100%, 98%, 93%, 93%, and 93%, respectively, for seeded Dacron grafts and 100%, 91%, 61%, 54%, and 18%, respectively, for nonseeded grafts. The patency rates of Dacron grafts usable for coronary artery bypass grafting are significantly improved by seeding with omental microvascular cells in a canine model.

Lessons learned from the DIASTAT vascular access graft.

BACKGROUND: The vascular community continues to search for the ideal vascular access graft that will allow early cannulation and avoid temporary central venous catheters. METHODS: This is a review of the Cranley Surgical Associates' experience with the use of the Gore-Tex DIASTAT (W.L. Gore & Associates, Inc., Flagstaff, Arizona) vascular access graft in 20 patients compared with 20 control patients matched for age, sex and risk factors. RESULTS: Although the DIASTAT graft is touted for early accessibility and decreased need for central venous access, that was not found to be the case as 14 patients in the DIASTAT group received temporary access catheters. There was significantly more edema in the DIASTAT patients (P = 0.0048). Comparing the time to the first thrombosis or to revision revealed an average of 18 weeks for the DIASTAT group and 56 weeks for the control group. The length of time to thrombosis or revision was significantly longer in the control group (P = 0.0058). Comparison of the number of weeks of function and serviceability of the grafts revealed the average DIASTAT graft functioned for 34 weeks and that of the control group for an average of 70 weeks (P = 0.0131). Comparison of the two groups showed a significant increase in early thrombotic events (< 90 days) in the DIASTAT grafts (P = 0.0013). CONCLUSIONS: The DIASTAT vascular access graft does not appear to be the ideal hemodialysis access graft.

Evaluation of prosthetic grafts of different porosity for arterial reconstruction.

Autogenous jugular veins and Dacron grafts of different porosities were implanted as short bypass grafts around ligated femoral arteries in the dog. Patency rates for periods up to eight months were: vein, 79 per cent; DeBakey Dacron (lowest porosity), 39 per cent; Wesolowski Weavenit (imtermediate porosity), 56 per cent; high porosity Dacron, 8 per cent. The failure of sixteen of the twenty-four high porosity grafts was related to perigraft hematomas that occurred two to seven days after operation and later thrombosis. The higher the porosity of the graft, the better the healing pattern as evidenced by fibrous bonding of the inner and outer linings of the grafts through the interstices. In the spectrum of grafts with increasing porosity there is apparently an optimal porosity beyond which late bleeding counterbalances the better healing properties of the higher porosity graft.

Is the increasing use of prophylactic percutaneous IVC filters justified?

To determine whether the ease of percutaneous inferior vena cava (IVC) filter placement has led to an alteration of procedural indications, we reviewed the medical records of 150 patients who underwent 156 filter insertions from January 1986 through June 1993. Thirty-nine Greenfield filters were surgically inserted, while 117 percutaneous devices were placed in 111 patients. A comparison of these two groups showed that they had similar thromboembolic risks. Indications for surgical filter placement included pulmonary embolism (PE) prophylaxis (23%), PE with a contraindication to anticoagulation therapy (28%), and complication (26%) or failure (20%) of anticoagulation therapy. Indications for initial percutaneous placement included PE prophylaxis (56%), PE with a contraindication to anticoagulation therapy (27%), and complication (7%) or failure (9%) of anticoagulation therapy. Early mortality in the surgical and percutaneous groups was 26% and 27%, respectively. Ten percent of early deaths in the surgical group and 50% in the percutaneous group were associated with prophylactic insertions (P = 0.032). Associated morbidity was 8% in the surgical versus 24% in the percutaneous group (P = 0.036). The unrestricted use of prophylactic percutaneous IVC filters appears to have resulted in an increased procedure-related morbidity with no clear benefit in early patient survival. These findings suggest a need for improved patient selection.

Endovascular grafting for the treatment of abdominal aortic aneurysms.

Endovascular repair of an aortic aneurysm will allow aneurysm exclusion using a graft passed inside the aorta either percutaneously or from a small groin incision. Morbidity and mortality associated with this procedure should be decreased considerably. The first grafting systems currently being developed will be appropriate for repair of aneurysms of the abdominal and descending thoracic aorta that can be repaired using tube grafts. Several research groups have shown that endovascular grafting of the aorta can be accomplished successfully.

Doppler echocardiographic assessment of prosthetic aortic valve area: estimation with the continuity equation compared to the Gorlin formula.

Effective orifice area of 3 different designs of prosthetic valves implanted in the aortic position was determined by the continuity equation and the Gorlin formula using Doppler hemodynamic data. The orifice area by the two methods correlated well in the case of tilting disc prostheses (r = 0.75, P = 0.0001, n = 37, SEE = 0.17 cm2) but poorly in the case of bileaflet mechanical valves (r = 0.40, P = 0.17, n = 13) and ball-in-cage prostheses (r = 0.58, P = 0.06, n = 11). Estimation of prosthetic aortic valve area by the Gorlin formula is inappropriate in the latter two types of prostheses because of design-related variable empiric constant.