Dual cell seeding and the use of zymogen tissue plasminogen activator to improve cell retention on polytetrafluoroethylene grafts

OBJECTIVE

The purpose of this study was to enhance the retention of seeded endothelial cells (EC) on prosthetic vascular grafts. Dual-layer EC and smooth muscle cell (SMC) seeding and gene transfer of a zymogen tissue plasminogen activator gene (tPA) into seeded EC were studied.

METHODS

Polytetrafluoroethylene (PTFE) grafts were precoated with fibronectin, seeded with SMC followed by EC a day later, and then, 24 hours later, exposed to an in vitro flow system for 1 hour. Cell retention rates were determined for grafts seeded with EC only, a dual layer of EC on top of SMC, EC transduced with wild-type tPA, and EC transduced with zymogen tPA.

RESULTS

Seeding efficiency of PTFE pretreated with fibronectin was 260 +/- 8 cell/mm(2). After exposure to flow, only 39% +/- 14% of the EC were retained when EC were seeded alone, whereas 73% +/- 22% of EC remained on grafts when EC were seeded on top of SMC (P <.001, n = 10). The enzyme activity of a mutant zymogen tPA in absence of fibrin was 14 +/- 1 IU/mL, which is 3.6-fold lower than that in the presence of fibrin (50 +/- 19 IU/mL), whereas fibrin has no effect on the wild-type tPA activity. EC expressing a high level of wild-type tPA had a lower retention rate (37%) when compared with normal EC (45%). EC expressing the mutant zymogen tPA had an improved retention rate (54%, P =.001, n = 10) in absence of fibrin, whereas its retention rate was reduced to 43% when the cells were exposed to fibrin.

CONCLUSION

SMC seeded between EC and PTFE improves EC retention in vitro. Transduction of zymogen tPA increases thrombolytic ability of seeded cells with less adverse impact on cell retention than wild-type tPA.

Stent-assisted vascular anastomoses

A stent can be used to rapidly create a laminar end-to-end vascular anastomosis. To construct a stent-assisted vascular anastomosis (SAVA), 2 traction sutures 180 degrees apart are used to pull 1 conduit into another so that they overlap. A stent is balloon expanded to create a seal in the area of overlap. A SAVA takes 5 to 15 minutes to create. Essential to the procedure is proper sizing of the graft, stent, and balloon. The SAVA becomes reinforced internally by a neointima and externally by periadventitial scar tissue. No anastomotic leaks or pseudoaneurysms were observed in 13 patients (1 to 2.5 years; mean, 14 months), 6 adult mongrel dogs (6 months), and 5 growing pigs (5.5 months). Three of 9 upper-extremity basilic vein SAVAs (dialysis shunts) occluded (3, 9, and 13 months). Stent deformation was seen in all 3 despite protection by external graft rings. Within our follow-up interval, a balloon-expandable stent is an effective tool to use to rapidly join a vessel to a graft. Because the stent is deformable, a SAVA is not recommended in the extremity.

Staged thoracic and abdominal aortic aneurysm repair using stent graft technology and surgery in a patient with acute renal failure

A 52-year-old male presented with severe hypertension and acute renal failure. Carbon dioxide (CO(2)) angiography identified a saccular thoracic aortic aneurysm, right renal artery stenosis, left renal artery occlusion, an infrarenal aortic aneurysm, celiac artery, and inferior mesenteric artery (IMA) orificial stenoses. Via an anterior retroperitoneal approach, bilateral renal artery thromboendarterectomy, infrarenal aortic aneurysmectomy, and IMA reimplantation were performed. The patient's tortuous iliac arteries were straightened to permit future passage of a thoracic stent graft by mobilizing the aortic bifurcation and anastomosing it to a Dacron graft within 4 cm of the renal vessels. Two weeks later, a stent graft was placed via a femoral incision utilizing CO(2) angiography, successfully excluding the saccular thoracic aneurysm. Recovery from both procedures was quick, with rapid return of renal function, and alleviation of the hypertension. At 8 months follow-up, his renal arteries and aorta are patent.

Human macrovascular endothelial cells: optimization of culture conditions

The purpose of this study is to identify optimal culture conditions to support the proliferation of human macrovascular endothelial cells. Two cell lines were employed: human saphenous vein endothelial cells (HSVEC) and human umbilical vein endothelial cells (HUVEC). The influence of basal nutrient media (14 types), fetal bovine serum (FBS), and mitogens (three types) were investigated in relation to cell proliferation. Additionally, a variety of extracellular matrix (ECM) substrate-coated culture dishes were also tested. The most effective nutrient medium in augmenting cell proliferation was MCDB 131. Compared to the more commonly used M199 medium, MCDB 131 resulted in a 2.3-fold increase in cell proliferation. Media containing 20% FBS increased cell proliferation 7.5-fold compared to serum-free media. Among the mitogens tested, heparin (50 microg/ml) and endothelial cell growth supplement (ECGS) (50 microg/ml) significantly improved cell proliferation. Epithelial growth factor (EGF) provided no improvement in cell proliferation. There were no statistical differences in cell proliferation or morphology when endothelial cells were grown on uncoated culture plates compared to plates coated with ECM proteins: fibronectin, laminin, gelatin, or collagen types I and IV. The culture environment yielding maximal HSVEC and HUVEC proliferation is MCDB 131 nutrient medium supplemented with 2 mM glutamine, 20% FBS, 50 microg/ml heparin, and 50 microg/ml ECGS. The ECM substrate-coated culture dishes offer no advantage.

High efficiency in vitro gene transfer into vascular tissues using a pseudotyped retroviral vector without pseudotransduction

Murine leukemia virus (MuLV)-derived retroviral vectors have had limited application in vascular gene therapy because of low transduction efficiency of vascular tissues, both in vitro and in vivo. In this study, we compared the gene transfer efficiency of two retroviral vectors: amphotropic MuLV and a MuLV vector pseudotyped with the vesicular stomatitis virus G glycoprotein (VSV-G) envelope. Target vascular tissues included human endothelial cells (EC), smooth muscle cells (SMC) and saphenous veins (SV). Transduction efficiency of human EC and SMC was significantly higher for VSV-G pseudotyped MuLV vector (90%) than for Amphotropic MuLV (20%). Luminal surface en face analysis of transduced cultured SV showed a six- to 10-fold greater transduction efficiency with VSV-G pseudotyped MuLV. The tissue plasminogen activator (tPA) gene was transduced into EC using each vector. Four days following transduction, a 12-fold higher tPA antigen concentration and a 38-fold higher tPA enzymatic activity was measured from cells transduced with the VSV-G pseudotyped vectors as compared with the amphotropic MuLV. There was no detectable pseudotransduction (protein transfer) associated with the VSV-G MuLV vector. Both AZT inhibition of reverse transcriptase and cell division arrest by gamma irradiation inhibited transduction, indicating that viral transduction correlated with RNA reverse transcription and cell proliferation. MuLV pseudotyped with the VSV-G envelope glycoprotein is an effective retroviral vector for vascular gene therapy.

Retroviral vector-mediated transfer and expression of human tissue plasminogen activator cDNA in bovine brain endothelial cells

OBJECTIVES

Gene transfer of thrombolytic enzymes to vascular endothelial cells may influence the kinetics of intravascular thrombosis. This study defines the potential for gene transfer of tissue plasminogen activator (tPA) into bovine brain endothelial cells (BBEC).

METHODS

The retroviral vectors derived from murine leukemia virus (MuLV) were used to transfer human tPA cDNA to BBEC. The tPA activity, tPA antigen and tPA inhibitor 1 (PAI-1) antigen were determined in the supernatant of transduced (BBEC/tPA) cell cultures by an immunoassay.

RESULTS

The tPA antigen and enzymatic activity in cell culture supernatants of BBEC/tPA transduced cells were 75 ng/ml and 14 IU/ml after 4 days, that was 25 and 28-fold higher compared to the respective values in control cells. The PAI-1 antigen was not affected by tPA cDNA transfer. The Western blot assay of cell lysates confirmed that the majority of tPA in BBEC/tPA transduced cells was in the form of free tPA. While the maximal transduction efficiency of BBEC with an amphotropic MuLV vector was about 15%, a MuLV pseudotyped with vesicular stomatitis virus G glycoprotein envelope achieved high > 90% maximal transduction efficiency.

CONCLUSIONS

The fibrinolytic activity of brain endothelial cells can be enhanced by transferring human tPA cDNA. These findings provide an initial step in implementation of future studies that investigate the use of this technology as an adjunctive treatment for cerebrovascular disease.

Genetic engineering of stent grafts with a highly efficient pseudotyped retroviral vector

PURPOSE

The purpose of this study was first to compare the gene transfer efficiency of amphotrophic murine leukemia viral vector (ampho-MuLV) with the efficiency of MuLV pseudotyped with the vesicular stomatitis virus G glycoprotein (VSVG-MuLV) in tissue of vascular origin. The second purpose of this study was to determine cell retention after the implantation of genetically engineered stent grafts.

METHODS

Gene transfer efficiency was ascertained with the b-galactosidase assay. The target tissues included endothelial cells (ECs), smooth muscle cells (SMCs), and human saphenous veins (HSVs). Polyurethane stent grafts were suffused with lac Z-transduced ECs and SMCs that were harvested from porcine jugular vein. The grafts were implanted into the iliac artery of each pig whose jugular vein had been harvested. Cell retention was analyzed at 1 and 4 weeks with X-Gal staining.

RESULTS

VSVG-MuLV transduction efficiency exceeded that of ampho-MuLV in human ECs (VSVG-MuLV, n = 24, 89% +/- 6%; ampho-MuLV, n = 18, 14% +/- 6%; P <. 001), human SMCs (VSVG-MuLV, n = 5, 92% +/- 3%; ampho-MuLV, n = 4, 17% +/- 2%; P <.001), pig ECs (VSVG-MuLV, n = 4, 81% +/- 2%; ampho-MuLV, n = 4, 13% +/- 3%; P <.001), and pig SMCs (VSVG-MuLV, n = 5, 89% +/- 3%; ampho-MuLV, n = 4, 16% +/- 1%; P <.001). As much as a 10-fold higher transduction efficiency was observed with VSVG-MuLV in HSVs. After the stent graft implantation, the engineered cells were retained and proliferated on the stent membrane, with ingrowth into the underlying intima.

CONCLUSION

VSVG-MuLV significantly increased the gene transfer efficiency in vascular SMCs and ECs and in organ-cultured HSVs. The cells were retained and proliferated on stent grafts for the short term in the pig.

Combined carotid endarterectomy and coronary artery bypass grafting in asymptomatic carotid artery stenosis

The role of combined carotid endarterectomy (CEA) and coronary artery bypass grafting (CABG) in patients with severe asymptomatic carotid artery disease and concurrent symptomatic coronary artery disease is controversial. The objective of this report is to investigate the safety of combined CEA/CABG. The medical records of 30 patients who underwent combined CEA/CABG for coexistent asymptomatic carotid and symptomatic coronary artery occlusive disease were reviewed. All patients were scheduled for either elective or urgent myocardial revascularization due to their symptomatic coronary artery disease. Color-flow duplex scanning identified internal carotid artery stenosis of 80 to 99 per cent in 28 patients (93%) and 50 to 79 per cent in 2 patients (7%). Seventeen patients (57%) were male. The mean age was 64 +/- 10 years (range, 42-84 years). Contralateral internal carotid artery occlusion was present in four patients. Severe left main coronary artery disease was present in 12 patients (40%) and 7 patients (23%) had an ejection fraction of less than 50 per cent. There were no perioperative deaths or strokes. One patient suffered a myocardial infarction on postoperative day 1. This study demonstrates the safety of combined CEA/CABG for coexistent coronary and asymptomatic carotid disease. Using this surgical approach for critical coexistent disease may minimize the incidence of perioperative cerebrovascular complications in patients undergoing CABG.

Omental transfer for salvage of the moribund lower extremity

Use of omental flaps is well documented in soft tissue reconstruction of the head and neck, chest wall, and abdomen. Three cases of omental transfer for soft tissue reconstruction of the lower extremities are presented. In two patients, free vascularized omental flaps were used to cover deep soft tissue defects over the lower leg and in one patient, a pedicle flap was used to cover a deep groin defect extending into the hip joint. In all patients, use of an omental graft allowed revascularization and subsequent wound healing with good cosmetic results.

A preliminary analysis of medical futility decisionmaking: law and professional attitudes

Judicial decisions reviewed in this article indicate that courts have taken two disparate approaches to disputes over futility of treatment. To explore whether a consensus on medical futility is developing among hospitals, the authors conducted a nationwide survey of health care professionals at hospitals. Respondents assigned importance ratings to factors used in recent futility decisions made at their institutions. The resulting importance ratings showed significant variation by characteristics of the institution (comparing respondents from for-profit, not-for-profit, and government hospitals) and by profession of the respondent (comparing physicians and nurses). The respondents' judgments endorsed three distinct strategies for making futility decisions (i.e., emphasis on the patient's decision preferences, providing for the patient and family, and adhering to objective medical and social norms).

Histological response to stent graft therapy

BACKGROUND

The purpose of the present study was to examine the histological consequences of the endoluminal exclusion of blood flow effected with stent graft technology.

METHODS AND RESULTS

In 25-kg mongrel dogs, patulous vein patch infrarenal aortoplasty with iliac vein produces a fusiform abdominal aortic dilation (AAD). All aortic tributaries were preserved. Endoluminal exclusion via transfemoral placement of a thin-wall Dacron graft occurred 4 +/- 2 months later (n = 23). Balloon-expandable stents anchored the ends of the graft to the aorta. Hematoxylin and eosin, elastin van Gieson's, and Masson's trichrome staining was performed 6 and 12 months later at death. In control nongrafted AADs, the arterial portion of the AAD was lined by elastin -and collagen-rich intimal hyperplasia, and the venous portion developed medial hyperplasia containing collagen but little elastin. After stent graft placement, the stent struts and the graft were completely incorporated into an elastin-poor, collagen-rich neointima. Fibrosis of the vein patch was observed at 1 year. laminated thrombus did not form in the AAD until immediately after stent graft placement; flow arrest occurred in the space between the graft and the AAD intima despite the patent tributaries. At 6 and 12 months, microscopic recanalization was seen in this thrombus, although macroscopic flow was not discernible by duplex imaging or angiography. No AAD growth was measured.

CONCLUSIONS

Aortic dilation was not observed at 1 year after stent graft placement within AADs with patent side branches despite microscopic evidence of thrombus recanalization. A collagen-rich and elastin-poor neointima incorporated the entire stent graft.

Cytotoxic effect of photodynamic therapy with Photofrin II on intimal hyperplasia

This study evaluates the effect of photodynamic therapy using Photofrin II on prevention and treatment of intimal hyperplasia in a rabbit model of common carotid artery balloon injury. An established model was used. One week after injury (inhibition arm) or 6 weeks after injury (treatment arm), each common carotid artery was exposed to continuous external laser irradiation 48 hours after a 5 mg/kg intravenous dose of Photofrin II (fluency = 7.6 joules/cm2, lambda = 630 nm). Histologic evaluation was performed 6 weeks following therapy in the inhibition arm and 1 day, 1 week, and 6 weeks following therapy in the treatment arm. Each arm included four subgroups (N = 10/subgroup): control, drug only, laser only, and drug plus laser. The first two subgroups underwent sham reoperations without laser exposure. In the inhibition arm no effect was seen on intimal cell density or area stenosis 6 weeks after photodynamic therapy. In the treatment arm intimal cell density was markedly diminished in the drug plus laser subgroup sacrificed 1 day and 1 week (but not 6 weeks) after treatment as compared to the remaining subgroups. There was no significant impact on area of stenosis. A marked acute cytotoxic effect of photodynamic therapy on intimal hyperplasia was verified in vivo in the treatment arm. The extracellular matrix was not affected. Cellular repopulation of the treatment zone was observed. No sustained benefit was seen in either the inhibition or the treatment arm. Refinements in dosimetry will be necessary to achieve long-term benefits.

Results of endoluminal grafting in an experimental aortic aneurysm model

We studied the impact of an endoluminally placed stented aortic graft on the geometry of a surgically created abdominal aortic dilation (AAD) in nonatherosclerotic mongrel dogs. Patulous iliac vein patch infrarenal aortoplasty produced a fusiform AAD, doubling the aorta diameter. Lumbar and mesenteric aortic tributaries were preserved and no mural thrombus formed. AADs created in 23 dogs were endoluminally excluded through transfemoral placement of a thin-wall Dacron graft 4 +/- 2 months later. Balloon-expandable stents were used to anchor each end of the graft to the aorta. The graft was crimped radially in its body and longitudinally at its ends to provide longitudinal and radial expandability in these respective zones. Serial color duplex, angiography, and direct caliper measurements were made. Before graft placement, a 19% +/- 11% diameter growth was observed. At graft placement, flow arrest immediately occurred in the space between the graft and the AAD intima in all cases. Although microscopic recanalization of the thrombus in this space was seen at sacrifice 6 and 12 months later, no macroscopic duplex flow was imaged. A 10% +/- 11% reduction in AAD diameter was measured at 6 months (p < 0.001), with no further reduction at 12 months. Graft dimensions remained stable. No anastomotic leaks developed. AAD growth stopped during the first year after effective endoluminal exclusion in normotensive dogs despite patent side branches (< 1.5 mm internal diameter) and no mural thrombus at the time of graft placement. Whether microscopic recanalization of the thrombus that forms outside the graft has an impact after 1 year remains to be seen.

Photodynamic therapy. Cytotoxicity of aluminum phthalocyanine on intimal hyperplasia

OBJECTIVE

To study the cytotoxic effect of photodynamic therapy (PDT) on myointimal hyperplasia (MIH) in 120 New Zealand white rabbits using the chromophore chloroaluminum phthalocyanine tetrasulfonate (APtS).

DESIGN

A common carotid artery (CCA) injury model was used to initiate MIH. Photodynamic therapy was administered 1 week after injury (inhibition arm) or 6 weeks after injury (treatment arm). The inhibition arm CCAs were harvested 6 weeks after therapy. The treatment arm CCAs were harvested 1 week or 6 weeks after therapy. Each evaluation included four subgroups (n = 10 each): control, drug only, laser only, and drug plus laser.

INTERVENTIONS

An established CCA balloon injury model was used. Photodynamic therapy was administered by exposing CCAs to continuous external laser irradiation 30 minutes after treatment with a 2.5-mg/kg intravenous dose of APtS (fluence = 25 J/cm2, lambda = 672 nm). The control and drug-only subgroups received sham reoperations without laser exposure.

MAIN OUTCOME MEASURES

Following harvest, the CCAs were evaluated for area of stenosis and cell density.

RESULTS

In the inhibition arm, no PDT effect was seen on intimal cell density or area stenosis. In the treatment arm, intimal cell density was markedly diminished (P < .05) in the rabbits in the drug-laser group that were killed 1 week but not 6 weeks after PDT compared with rabbits in the control, drug-only, and laser-only groups. Area stenosis was not significantly affected by PDT.

CONCLUSIONS

Marked acute cytotoxicity of PDT on MIH was verified in vivo in the treatment arm. No sustained benefit of PDT was seen in the inhibition or the treatment arms. Refinements in dosimetry will be necessary to achieve long-term benefit of PDT for MIH.

Pitfalls in evaluation of photosensitizing agents: an example with Q-switch II dye

Photosensitizing agents potentiating laser therapy should have limited toxicity, no mutagenicity, stable spectral characteristics, and acceptable solubility when administered in vivo. Q-Switch II dye (QII) has been shown by others to be an effective chromophore for photodynamic therapy at 1051 nm in fibroblast cell culture. The objective of this study was to determine the spectral stability of QII in biological media and then to localize QII after administration in vivo. Spectral evaluation was performed between 250 and 1100 nm. QII dissolved in dimethyl sulfoxide (DMSO) rapidly lost its spectral characteristics, including its 1051-nm peak, when contacting water, minimal essential medium, human serum, organ surfaces, and intracellular fluid. One minute following intramuscular (IM) injection of 0.1 mg QII in 0.2 mL of DMSO, the dose precipitated as a discrete mass which was excised and reconstituted in DMSO. A new spectral pattern was seen, with no absorption between 850 and 1100 nm. Following intravenous (i.v.), (IM), or intraperitoneal (IP) injection, QII was not detected in any organ. Q-Switch II dye is not a suitable chromophore for in vivo photodynamic therapy at 1051 nm. Previous cell culture reports to the contrary did not account for the QII spectral change caused by biological media. Simple rapid assays are described to avoid this pitfall.

Endovascular surgery for peripheral arterial occlusive disease

Endovascular surgery includes angiography, balloon angioplasty, laser angioplasty, mechanical atherectomy and stent placement. Both diagnostic and therapeutic procedures are possible. The advantages of endovascular techniques include the ability to precisely and noninvasively remove an atherosclerotic lesion without producing damage to the surrounding vascular wall. Endovascular techniques have minimal complications, involve minimal blood loss and can be performed as outpatient procedures. Drawbacks include disappointingly high rates of restenosis, limitations on the type of lesion that can be treated successfully and only partial visualization of an atherosclerotic lesion with some devices.

Inhibition of intimal hyperplasia by photodynamic therapy using photofrin

Photodynamic therapy using photofrin and light energy inhibits human myofibroblast proliferation in cell culture. The purpose of this study is to evaluate its influence on intimal hyperplasia in vivo. Twenty New Zealand White rabbits underwent a standardized intimal injury to both common carotid arteries with a 2 Fr balloon catheter. One week later, half of the animals received photofrin (5 mg/kg) intravenously. The remaining 10 rabbits received no photofrin. Two days later, all neck incisions were reopened and a 1-cm segment of each of the 40 carotid arteries was exposed for 5 min to 80 mW of 630 nm light energy from a continuous wave tunable dye laser (fluence = 7.6 J/cm2). All vessels were harvested 5 weeks post-laser treatment following in vivo fixation with formalin. From each artery, separate cross-sections taken from both the lasered and non-lasered regions of each vessel were mounted and stained for histologic evaluation. Analyzed segments were then divided into four different treatment groups: group I segments consisted of arterial cross-sections which were taken from vessel regions that were injured but received neither photofrin nor laser treatment (group I, n = 20); group II segments also did not receive photofrin but were exposed to light energy (group II, n = 20); group III segments received photofrin but no light energy (group III, n = 20); and cross-sections in group IV were taken from those segments which received both photofrin and laser treatment. Using planimetry, the ratio of the area of intimal hyperplasia (IH) to the area enclosed by the internal elastic lamina (IEL) was measured for each specimen (IH/IEL).(ABSTRACT TRUNCATED AT 250 WORDS)

Endovascular surgery for peripheral arterial occlusive disease. A critical review

Endovascular surgery is a new multidisciplinary field that applies the recently innovated techniques of angioscopy, intraluminal ultrasound, balloon angioplasty, laser, mechanical atherectomy, and stents. This field can be defined as a diagnostic and therapeutic discipline that uses catheter-based systems to treat vascular disease. As such, it integrates the subspecialties of vascular surgery, interventional radiology, interventional cardiology, and biomedical engineering for the common purpose of improving arterial hemodynamics. Endovascular surgery offers many potential benefits: long incisions are replaced with a puncture wound, the need for postoperative intensive care is significantly reduced, major cardiac and pulmonary complications from general anesthesia are side stepped, and the dollar savings could be dramatic as the need for intensive care unit and in-hospital stay diminishes. Despite these technological advancements, endovascular surgery is still in its infancy and currently has limited applications. This review provides an updated summary of endovascular surgery today and addresses some of the obstacles still preventing its widespread use.

Intraoperative peripheral rotary atherectomy: early and late clinical results

Early and late clinical results of intraoperative peripheral atherectomy using the Auth Rotablator are analyzed. Twenty patients (15 males and 5 females age 39-89 years, mean 70 years) underwent 25 atherectomy procedures for peripheral arterial occlusive disease from August 1987 to October 1989. All patients underwent serial history, physical exam, and Doppler pressure measurements preoperatively and then postoperatively at 24 hours, one week, one month, and six months during a follow-up period of 15 to 41 months, mean 27 months. Preoperative and intraoperative completion follow-up arteriography was done in all cases and follow-up arteriography in 19 of 25 cases. Initial arteriographic success was achieved in 23/25 (92%) cases and in 39/41 (93%) arterial segments (superficial femoral artery 12/13, popliteal 14/15, tibial 12/13, profunda-femoral 1/1). Complications included intimal dissection (1), equipment breakage (2), minor emboli (3), major emboli with thigh skin loss (1), transient hemoglobinuria (4), wound hematoma (1), wound infection (1), and limb loss (1). Early thrombosis occurred in five cases to give an in-hospital success rate of 18/25 (72%). Primary patency was 66% at six months but only 12% at two years. Rotary atherectomy effectively recanalizes femoral, popliteal and tibial arteries. However, early thromboembolic complications occurred frequently, and the two year patency was dismal. Rotary atherectomy is not recommended for general use until problems of thromboemboli and intimal hyperplasia are solved.

Trends in endovascular surgery

Endovascular surgery is currently in its infancy. Much work is necessary before its full potential can be realized. Initial enthusiasm has appropriately turned into more sober, realistic cautiousness. This review summarizes experiences with angioscopy, IU, PTA, laser angioplasty, atherectomy, and stent placement. Solving the restenosis problem following endovascular interventions could significantly broaden the applications of endovascular surgery. The nursing challenges brought by this new field are not different from those of traditional vascular surgery and catheterization. Keeping up with the new technology as it quickly evolves and documenting clinical effectiveness probably require an endovascular nurse specialist in a center planning to do a great deal of procedures.

Prostacyclin production in the area of arterial endothelial denudation

The goal of this study was to quantify arterial prostacyclin (PGI2) synthesis and platelet aggregation in the immediate area of vessel injury. Twelve mongrel dogs whose platelets aggregated maximally to added arachidonic acid (AA) were equally divided into three groups. Controls received no drug while other dogs were treated with the platelet inhibitors aspirin (ASA) 3 mg/kg/day or BM 13.505 (BM), a thromboxane receptor antagonist, 25 mg/kg/day. After 3 days of treatment, the dogs underwent balloon catheter endothelial denudation of both carotid and femoral arteries. Blood was sampled from the first carotid artery just distal to the injury at 0, 1, 5, and 10 min after restoration of flow. Venous blood samples were also obtained at 1 and 2 weeks postoperatively. Dogs were sacrificed at 2 weeks and arterial rings from a proximal normal and a denuded region were excised and tested for PGI2 production in response to added AA. While control dogs showed no statistical change in AA-induced platelet aggregation postoperatively, there appeared to be a trend for enhanced responsiveness at 1 week. Aspirin and BM inhibited AA-induced aggregation completely in all samples at all timepoints. Levels of the stable metabolite of PGI2, 6-keto-PGF1 alpha, were determined by radioimmunoassay. In control dogs, baseline PGI2 levels were 72 +/- 17 pg/ml which increased to 479 +/- 20 pg/ml immediately after restoration of flow (P less than 0.001, Student t test) and returned to basal values in 10 min (85 +/- 5 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of PCO2-adjusted pH on the neonatal heart during hypothermic perfusion and ischemia

The effect of pH regulation on the function of the isolated neonatal heart during continuous hypothermic perfusion and arrest was tested in 3- to 6-day-old piglet hearts. Three groups of hearts were perfused from an adult support pig, with pH varied by a carbon dioxide/oxygen gas exchanger and temperature controlled by a heat exchanger. After control function studies were obtained at normothermia with a pH of 7.4, the hearts were cooled over 15 minutes to 10 degrees C. Hypothermic perfusion was maintained for 1 hour, followed by rewarming to 37 degrees C. In group 1 (n = 5), the alpha stat (neutral) model, the blood perfusate was maintained at a pH of 7.4 (calculated at 37 degrees C). In group 2, the alkaline model, the pH was maintained at 7.9, and in group 3, the pH-stat (acid) model, the pH was maintained at 7.0. In addition, the effect of 1 hour of hypothermic ischemia after hypothermic perfusion at a pH of 7.0 was evaluated in five hearts (group 4). After rewarming no significant difference was noted in functional recovery (group 1 = 93% +/- 5%, group 2 = 92% +/- 6%, group 3 = 96% +/- 5%, and group 4 = 95% +/- 2%), oxygen consumption, coronary resistance, lactate extraction, and myocardial extravascular water content. We conclude that neonatal heart function is resistant within the range of this study to changes in pH caused by changes in carbon dioxide tension during hypothermic perfusion and ischemia.

A rapid, accurate, noninvasive technique for diagnosing critical and subcritical stenoses in aortoiliac arteries

Accurate hemodynamic evaluation of the aortoiliac system for the purpose of determining the need for an inflow procedure currently requires invasive pressure measurements. This study was undertaken to evaluate a noninvasive technique with the aortofemoral transfer function. Twenty-eight human aortoiliac segments were studied with intraarterial pressure measurements, with and without papaverine injection, and by calculation of the Doppler-derived mean power frequency index obtained by digital signal processing of aortic and femoral spectra. The procedure is menu driven and can be performed by any duplex ultrasound technologist. This technique involves recording 20 aortic and 20 femoral Doppler signals, requiring less than 1 minute of data acquisition time. Intraarterial pressure measurements were used to classify arteries into the three following groups: (1) normal arteries, (2) arteries with subcritical stenoses, and (3) arteries with critical stenoses. The mean power frequency index of group 1 arteries (n = 7) was 0.63 +/- 0.04, of group 2 arteries (n = 6) was 0.46 +/- 0.02, and of group 3 arteries (n = 15) was 0.21 +/- 0.05. These mean power frequency index values were significantly different by analysis of variance (ANOVA) (p less than 0.0001). Each group could be differentiated from the other groups with a sensitivity of 0.83 to 1.00, a specificity of 1.00, and an accuracy of 0.92 to 1.00 compared to intraarterial pressure measurements, including papaverine testing. Measurement of the mean power frequency index is a rapid, noninvasive technique that diagnoses and quantifies aortoiliac stenoses with an accuracy similar to intraarterial pressure measurements.

Hollenhorst plaques: retinal manifestations and the role of carotid endarterectomy

The ocular examinations and hospital records of 64 patients with Hollenhorst plaques were retrospectively reviewed to document any associated visual defects and to determine if carotid endarterectomy prevented the occurrence of new plaques or symptoms. One hundred nine Hollenhorst plaques were seen in 75 eyes; 18 had multiple plaques simultaneously. Visual field defects were noted in 14 eyes, four of which corresponded to the location of Hollenhorst plaques. Twenty-eight carotid endarterectomies were performed ipsilateral to a Hollenhorst plaque: 24 patients had no symptoms; four patients developed new ipsilateral asymptomatic Hollenhorst plaques at 1 to 50 months after operation. Two late strokes occurred, one of which was ipsilateral to a new Hollenhorst plaque, during a mean follow-up of 50 months (range 8 to 102 months). Thirty-seven eyes with asymptomatic Hollenhorst plaques did not undergo ipsilateral operation. Two eyes developed new Hollenhorst plaques during a mean follow-up of 23 months (range 1 to 132 months). Eight eyes in patients with no symptoms had multiple Hollenhorst plaques, one of which was associated with a subsequent stroke. Of the 29 eyes with a single Hollenhorst plaque, one subsequently experienced an ipsilateral stroke, and another had a transient ischemic attack (1 and 3 years later, respectively). Visual field defects infrequently corresponded to locations of Hollenhorst plaques. The cerebral hemisphere ipsilateral to asymptomatic plaques had a slightly increased risk of subsequent transient ischemic attack or stroke compared to the contralateral side without Hollenhorst plaques. The number of simultaneous Hollenhorst plaques in the retinal circulation did not predict clinical outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Hollenhorst plaques: retinal manifestations and the role of carotid endarterectomy

The ocular examinations and hospital records of 64 patients with Hollenhorst plaques were retrospectively reviewed to document any associated visual defects and to determine if carotid endarterectomy prevented the occurrence of new plaques or symptoms. One hundred nine Hollenhorst plaques were seen in 75 eyes; 18 had multiple plaques simultaneously. Visual field defects were noted in 14 eyes, four of which corresponded to the location of Hollenhorst plaques. Twenty-eight carotid endarterectomies were performed ipsilateral to a Hollenhorst plaque: 24 patients had no symptoms; four patients developed new ipsilateral asymptomatic Hollenhorst plaques at 1 to 50 months after operation. Two late strokes occurred, one of which was ipsilateral to a new Hollenhorst plaque, during a mean follow-up of 50 months (range 8 to 102 months). Thirty-seven eyes with asymptomatic Hollenhorst plaques did not undergo ipsilateral operation. Two eyes developed new Hollenhorst plaques during a mean follow-up of 23 months (range 1 to 132 months). Eight eyes in patients with no symptoms had multiple Hollenhorst plaques, one of which was associated with a subsequent stroke. Of the 29 eyes with a single Hollenhorst plaque, one subsequently experienced an ipsilateral stroke, and another had a transient ischemic attack (1 and 3 years later, respectively). Visual field defects infrequently corresponded to locations of Hollenhorst plaques. The cerebral hemisphere ipsilateral to asymptomatic plaques had a slightly increased risk of subsequent transient ischemic attack or stroke compared to the contralateral side without Hollenhorst plaques. The number of simultaneous Hollenhorst plaques in the retinal circulation did not predict clinical outcome.(ABSTRACT TRUNCATED AT 250 WORDS)