Common brachiocephalic trunk: strategies for revascularization

BACKGROUND

A common brachiocephalic trunk, in which both common carotid arteries and the right subclavian artery arise from a single trunk off the arch, is a normal variant of aortic arch branching that occurs in approximately 10% of the population. Because three of the four primary sources of cerebral blood flow arise from a single aortic branch, stenosis or occlusion of a common trunk can cause severe ischemic consequences. Common trunk revascularization has been described, but there have been no reports focusing on the management options for occlusive disease of this vascular anatomy.

METHODS

A retrospective review of our experience with innominate artery revascularization identified 6 patients who underwent revascularization of a common brachiocephalic trunk between 1977 and 1997. All patients were symptomatic, with either total occlusion (n = 3) or critical stenosis (n = 3) caused by atherosclerosis (n = 5) or Takayasu's arteritis (n = 1). Revascularization was achieved by a prosthetic bypass graft from the ascending aorta to the innominate or left common carotid arteries or both (n = 5); or transarterial endarterectomy (n = 1). Concomitant endarterectomy of branch vessels was performed in 3 patients.

RESULTS

There was one perioperative death from myocardial infarction, and one perioperative stroke, with death occurring 1 month after hospital discharge. One patient developed cerebral hyperperfusion syndrome 1 week after endarterectomy that resolved without sequelae with antihypertensive medications. During a follow-up period ranging from 1 to 20 years, there was one late death from congestive heart failure 5 years after operation. All surviving patients are alive and free from symptomatic recurrence.

CONCLUSIONS

Revascularization for occlusive disease of a common brachiocephalic trunk can be achieved with effective and durable relief of symptoms using either a prosthetic bypass graft or endarterectomy. However, neurologic complications in 2 patients, which were fatal in 1, attest to the potential cerebral ischemic threat posed by occlusive disease of a common brachiocephalic trunk.

Abdominal aortic aneurysm in high-risk patients: short- to intermediate-term results of endovascular repair

PURPOSE

To assess the safety and efficacy of endovascular repair of abdominal aortic aneurysm in high-risk patients during the short to intermediate term.

MATERIALS AND METHODS

Endovascular aneurysm repair was performed in 50 patients considered too high risk for conventional repair. Stent-grafts were inserted through surgically exposed femoral arteries with fluoroscopic guidance. The anesthetic technique was epidural in 36 patients, general in 12, and local in two. Aortouniiliac stent-grafts were inserted in 42 patients and aortoaortic in eight.

RESULTS

There were no deaths and no conversions to open surgical repair. The primary success rate (complete aneurysm exclusion according to CT criteria) was 88% (44 of 50). The secondary, clinical, and continuing success rates were all 98% (49 of 50). Surgical time was 196 minutes +/- 67 (mean +/- SD), blood loss was 284 mL +/- 386, and volume of contrast material administered was 153 mL +/- 64. The time from the end of the surgery to resumption of a normal diet was 0.58 days +/- 0.56, to ambulation was 1.22 days +/- 0.77, and to discharge from the hospital was 3.63 days +/- 1.60. Wound problems accounted for the majority of complications. There were no instances of pulmonary failure, renal failure, stent-graft migration, or late leakage.

CONCLUSION

Endovascular repair of abdominal aortic aneurysm is feasible in two-thirds of high-risk patients, with a low mortality and high success rate during the short to intermediate term.

Surgical management of subclavian-vein effort thrombosis as a result of thoracic outlet compression

BACKGROUND

There is considerable variability and controversy in the current management of subclavian-vein effort thrombosis. The purpose of this study was to determine the long-term effectiveness and the functional outcome of our preferred treatment strategy of early thrombolysis/recanalization and prompt extensive supraclavicular decompression.

PATIENTS AND METHODS

Thirty-three patients who ranged in age from 15 to 60 years underwent operative decompression of 34 primary subclavian-vein thromboses, one of which was bilateral. There were 21 patients with acute thrombosis 7 of whom had had prior unsuccessful balloon venoplasty, 1 with stent placement and 8 patients with chronic/recurrent thrombosis 5 of whom had had 9 unsuccessful prior operations for attempted decompression. Four patients had high-grade symptomatic stenosis and positional occlusion. A supraclavicular approach was used in 32 cases and, in 23 cases, was complemented by an infraclavicular (n = 21) or transaxillary (n = 2) incision. Complete subclavian-vein decompression was achieved by first-rib resection (n = 31), scalenectomy (n = 33), and circumferential venolysis (n = 34).

RESULTS

Follow-up was obtained in 30 patients at a mean of 31 months. Twenty of the 21 patients with acute thrombosis had a complete resolution of symptoms with a return to full activity; the other patient was lost to follow-up. Four of the 8 patients with chronic thrombosis reported a mild relief of symptoms but still had limitations of activities of daily living. All of the patients with high-grade symptomatic stenosis with positional occlusion had a complete relief of symptoms and a return to full activity.

CONCLUSION

The optimal management of acute effort thrombosis of the subclavian vein includes anticoagulation therapy, thrombolysis/recanalization, confirmatory positional venography, and early supraclavicular decompression of the subclavian vein. In the patients with chronic subclavian-vein thrombosis and positional venographic evidence of compression of first-rib bypass graft collaterals, the initial anticoagulation therapy should be followed by the surgical decompression of the collaterals. The supraclavicular approach alone or with an infraclavicular incision provides optimal exposure for scalenectomy, total first-rib resection, and circumferential venolysis.

Innominate artery reconstruction: over 3 decades of experience

SUMMARY BACKGROUND DATA

Symptomatic atherosclerotic occlusive disease of the innominate artery is a threatening disease pattern that offers a major challenge in achieving definitive surgical repair. To assess the evolution of treatment strategies and their outcomes for this disease, the authors undertook a review of the cumulative experience for more than 3 decades at one institution.

METHODS

Between 1960 and 1997, 94 patients (mean age, 62 years) underwent direct innominate artery revascularization for occlusive atherosclerotic disease to relieve neurologic (n = 85) and/or right upper extremity (n = 26) symptoms or asymptomatic critical stenosis (n = 3). The pattern of atherosclerotic involvement revealed by angiography included critical stenosis (n = 77), complete occlusion (n = 10), and moderate stenosis with plaque ulceration (n = 7). A common brachiocephalic trunk was present in five patients. Transsternal (n = 68) or transcervical (n = 4) innominate endarterectomy was performed in 72 patients and bypass grafting in 22. Forty-one patients underwent concomitant endarterectomy or bypass of innominate branches or adjacent arch vessels, and 3 had coronary bypass grafting.

RESULTS

There were three perioperative deaths (3%), all due to cardiac causes. Postoperative morbidity included four strokes (three resolved), two myocardial infarctions, two transient ischemic attacks, and one sternal dehiscence. Follow-up ranged from 8 months to 20 years. Postoperative actuarial survival rate was 96% at 1 year, 85% at 5 years, and 67% at 10 years. Freedom from recurrence requiring reoperation was 100% at 1 year, 99% at 5 years, and 97% at 10 years.

CONCLUSIONS

Innominate artery reconstruction is safe and durable when either endarterectomy or prosthetic bypass is used. The anatomic variation and disease distribution permit endarterectomy for most patients. The technique of innominate endarterectomy can be extended safely to outflow and adjacent vessels.

Femoral artery exposure for endovascular aneurysm repair through oblique incisions

PURPOSE

To offer an alternative technique for accessing the femoral artery prior to endovascular grafting.

TECHNIQUE

An oblique incision is made over the medial half of the inguinal ligament and continues to the femoral sheath, which is opened longitudinally. The distal external iliac artery and proximal common femoral artery are isolated. A tiny stab wound is made distal to the primary wound for femoral artery puncture and catheter access.

CONCLUSIONS

Using an oblique incision at the level of the inguinal ligament optimizes exposure for endograft insertion and may minimize the frequency of serious wound complications.

Endovascular repair of abdominal aortic aneurysm: getting out of trouble

The standard techniques of endovascular aneurysm repair sometimes fail to produce atraumatic stent-graft delivery of hemostatic implantation, and additional maneuvers are required to avoid conversion to open repair. Between June 1996 and May 1997 elective endovascular aneurysm repair was performed in 33 high risk patients, using a Z-stent-based prosthesis. Challenging anatomic features included: short neck (< 15 mm) in four cases, angulated neck (> 60 degrees) in seven, iliac aneurysm in six, and iliac tortuosity (> 80 degrees) in 24. There were no deaths, no renal failure, no pulmonary failure, no graft thrombosis, no migration, and no conversions to open surgery. Deviations from standard technique were required to treat iliac artery dissection, iliac artery stenosis, and leaks resulting from proximal stent malalignment, proximal stent malposition, and distal stent malposition. The necessary adjunctive maneuvers included: additional stent placement, additional stent-graft placement, and balloon dilatation. Mean operating time was 191 +/- 72 min, mean contrast volume was 148 +/- 76 ml, and mean blood loss was 314 +/- 427 ml. Mean time from operation to discharge from the hospital was 3.5 +/- 1.67 days. These short-term results demonstrate that endovascular aneurysm repair is safe and effective in high risk patients, only if adjunctive maneuvers are available to supplement standard technique.

In situ autogenous reconstruction of the thoracoabdominal aorta and branches for treatment of an infected thoracoabdominal aortobifemoral bypass graft

Graft infection is an uncommon but potentially lethal complication of prosthetic aortic repair. We describe a novel technique for upper abdominal aortic and visceral revascularization after percutaneous drainage and antibiotics failed to cure a thoracofemoral prosthetic graft infection. One week after axillofemoral and femorofemoral bypass grafting, the infected thoracoabdominal graft was removed and a bifurcated iliac artery autograft was used to replace the upper abdominal aorta and revascularize the abdominal viscera. The infected graft was removed from the thorax and retroperitoneum, the infection resolved, and the patient remained well until his death of lung cancer 9 years later.

Reoperation for recurrent chronic visceral ischemia

PURPOSE

Recurrent visceral ischemia after a failed visceral revascularization occurs in up to one third of patients, yet no comprehensive report has described the management of this problem. The purpose of this study was to examine the presentation, surgical management, and outcome of patients with recurrent visceral ischemia.

METHODS

Between 1959 and 1997, 109 patients underwent primary visceral revascularization at the University of California, San Francisco. Nineteen patients (17.4%) had recurrent visceral ischemia (12 chronic visceral ischemia, seven acute visceral ischemia). Fourteen additional patients with recurrent chronic visceral ischemia were referred after failed primary revascularization (two patients underwent multiple operations before referral). Thirty visceral reoperations were performed for recurrent visceral ischemia in 24 patients (10 patients with recurrence at University of California, San Francisco, 14 referred patients). Symptom-free and overall survival rates were determined by life table analysis.

RESULTS

Of seven patients (6.4%) who had recurrent acute visceral ischemia, six (85.7%) died of bowel infarction. Twelve patients (11%) had recurrent chronic visceral ischemia. Patients with recurrent chronic visceral ischemia received their diagnoses earlier and lost less weight than at their initial presentation (p = 0.004 and 0.001, respectively). Recurrent ischemia was associated with younger age, greater weight loss, and modification of surgical technique at the time of initial operation (p = 0.5, 0.009, and 0.02, respectively). For 20 (90.9%) of the 22 first reoperations, antegrade aortovisceral bypass (n = 10) or transaortic visceral endarterectomy (n = 10) was used. Multiple techniques (four antegrade bypass, two retrograde bypass, one endarterectomy, one anastomotic revision) were used in the eight second or third reoperations. Postoperative mortality and complication rates were 6.7% and 33.3%, respectively. Symptoms recurred in six of 22 patients (27.3%) after the first reoperation, three of whom were cured or improved after additional reoperations. The life table symptom-free survival rate after reoperation was 77.3% and 62.8% at 1 and 5 years, respectively. The life table overall survival rate after reoperation was 74.6% at 5 years.

CONCLUSIONS

Recurrent visceral ischemia is not uncommon after primary visceral revascularization. These results show that reoperation for recurrent chronic visceral ischemia can be accomplished safely and effectively with established revascularization techniques. Furthermore, after repeat visceral revascularization patients achieve durable relief of symptoms and have life expectancy rates comparable with those of patients who undergo primary visceral revascularization.

Improved retroviral transduction efficiency of vascular cells in vitro and in vivo during clinically relevant incubation periods using centrifugation to increase viral titers

Vascular cells are an important target for gene transfer because of their potential to deliver gene products both locally and systemically. Direct retroviral gene transfer to vascular cells in vivo has been limited by inefficient rates of transduction. We hypothesized that vascular cell transduction efficiency (TE), during short retroviral incubation periods, is significantly improved in vitro and in vivo using centrifugation to increase viral titer. Furthermore, we hypothesized a linear relationship between concentration of viable viral particles (measured as colony-forming units (CFUs)/cell) and retroviral TE during short incubation periods. Cultured rat pulmonary artery endothelial cells (RPAECs), rat aortic smooth muscle cells (RSMCs), and human iliac artery endothelial cells (HIAECs) demonstrated a strong correlation between TE and high concentrations of virus (> 100 CFU/cell) during retroviral incubation periods of 10 to 60 minutes. High titers, and thereby high concentrations, were achieved by centrifugation and resuspension in a fraction of the original volume. Titers was consistently increased tenfold, for a twentyfold increase in concentration by volume. A 20-minute incubation with a Moloney murine leukemia-derived retroviral vector coding for human placental alkaline phosphatase, pLJhpAP, at a concentration of 1150 CFU/cell yielded TEs of 10.6% +/- 0.7%, 40.4% +/- 1.6%, and 15.1% +/- 2.0% for RPAECs, RSMCs, and HIAECs, respectively. A similar effect was shown using the Moloney murine leukemia-derived MFGlacZ retroviral vector, coding for Escherichia coli beta-galactosidase. Increased titer and concentration had no effect on target cell viability, as shown by trypan blue exclusion. Although RSMCs had the most cells transduced in a given incubation period (p < 0.05), RPAECs had the highest replication rate (p < 0.05), suggesting the importance of factors other than cell cycle on retroviral TEs during short, clinically relevant incubation periods. In subsequent in vivo experiments, gene transfer was achieved in the rat carotid artery during a 20-minute incubation period infusing the concentrated pLJhpAP retrovirus after carotid balloon injury. Rats infused with virus 2 days after balloon injury exhibited hpAP activity (0 to 10 cells/section/rat) in the neointima of five out of six rats. Rats infused 4 days after balloon injury exhibited hpAP activity (0 to 25 cells/section/rat) in the media and adventitia of five out of five rats. Control rats that received the balloon injury alone or the balloon injury and unconcentrated retrovirus exhibited zero hpAP activity. We conclude that the TE of retroviral-mediated gene transfer to vascular cells in vitro and in vivo can be improved during short, clinically relevant incubation periods using centrifugation to increase retroviral titer, and thereby concentration of viable viral particles.

Visceral artery aneurysms

Visceral artery aneurysms are an uncommon form of vascular disease that have a significant potential for rupture or erosion into an adjacent viscera, resulting in life-threatening hemorrhage. During the last decade, hepatic artery aneurysms have become the most commonly reported visceral artery aneurysm. This change likely reflects the increased use of percutaneous diagnostic and therapeutic biliary procedures, as well as increased use of diagnostic computed tomography after blunt abdominal trauma. A second significant development is the increased use of percutaneous catheter-based therapy in the management of visceral artery aneurysms. Nonetheless, a continued aggressive approach to the diagnosis and management of these unusual aneurysms remains warranted.

Induction of angiogenesis by lidocaine and basic fibroblast growth factor: a model for in vivo retroviral-mediated gene therapy

A strategy of direct, in vivo retroviral-mediated gene therapy targeting capillary endothelial cells must provide an environment of active angiogenesis. Both lidocaine and basic fibroblast growth factor (bFGF) promote angiogenesis, but the angiogenic response invoked by these substances in normal skeletal muscle has not been fully characterized. We sought to characterize these agents' angiogenic effects in anterior tibialis muscles of male Sprague-Dawley rats. An injection of either 1% lidocaine with 1:100,000 epinephrine or alternate-day injections of bFGF (0.025 or 0.25 microgram) with or without heparin were tested (n = 6 muscles/condition). Rats were sacrificed 4, 7, 10, or 12 days later and muscles were evaluated histologically to determine the number of proliferating cells using 5-bromo-2'-deoxycytidine (BrdC) and evaluated for capillary density using Griffonia simplicifolia I (GSI) lectin. At all time points, lidocaine produced at least 20-fold greater capillary density and cellular proliferation than PBS control (P < 0.0001). Injections of high-dosage bFGF produced more than fivefold greater capillary density than control injections at 7 and 10 days (P < 0.001), and more than twofold greater proliferation at 4, 7, and 12 days (P < 0.001). Capillary density returned to control levels 12 days following bFGF administration, whereas it remained well above control levels for 12 days after lidocaine administration. To confirm that lidocaine can be utilized in gene therapy strategies targeting vascular endothelium and skeletal muscle fibers, concentrated pLJ retrovirus containing cDNA for the heat-stable human placental alkaline phosphatase (hpAP) marker gene was infused into the rat hindlimb vasculature 4 days post-lidocaine administration. Rats receiving pLJhpAP retrovirus demonstrated significant hpAP transgene expression in endothelial cells and myocytes 21 days after the lidocaine injection (n = 6 muscles). In contrast, controls receiving pLJhpAP infusion without prior lidocaine administration failed to demonstrate any hpAP transgene expression. Lidocaine treatment evokes a substantially higher proliferative response than bFGF and, importantly, a durable angiogenic response in skeletal muscle. Thus, lidocaine is an ideal agent to induce angiogenesis in preparation for direct in vivo retroviral-mediated gene therapy targeting vascular endothelium.

Tissue plasminogen activator increases canine endothelial cell proliferation rate through a plasmin-independent, receptor-mediated mechanism

BACKGROUND

Tissue plasminogen activator (tPA) is elevated in cancer patients and is thought to promote tumor angiogenesis by facilitating endothelial cell migration through plasmin-mediated degradation of extracellular matrix. Due to the presence of an epidermal growth factor (EGF)-finger domain in the tPA A-chain and the existence of an endothelial cell (EC) receptor that binds this domain, it was hypothesized that tPA has a direct receptor-mediated effect on EC proliferation, independent of plasmin.

METHODS AND RESULTS

Using cultured canine ECs, tPA (7.25 microg/ml, approximately 107 nM) increased proliferation as much as 50 and 170% in the absence and presence of growth factors, respectively. tPA-induced increases in EC proliferation occurred independent of plasmin generation, as the plasmin inhibitor, aprotinin (10 microg/ml) did not inhibit tPA-induced proliferation. However, tPA-induced proliferation was inhibited dose-dependently to a maximum of 78% using a monoclonal antibody against the tPA EGF-finger domain. This antibody, known to inhibit tPA binding to its receptor, did not inhibit tPA-induced plasmin generation. To investigate the role of potential signal transduction pathways, ECs were exposed to lavendustin A, a tyrosine kinase inhibitor, at 33.5 microM (IC50 for basic fibroblast growth factor). Lavendustin A did not inhibit tPA-induced EC proliferation. However, Rp-cAMP, an inhibitor of cAMP-dependent kinases, specifically inhibited tPA-induced EC proliferation in a dose-dependent manner (IC50 = 50.5 microM). Pertussis toxin at maximal concentrations for this system (0.5 ng/ml) did not inhibit tPA-induced EC proliferation.

CONCLUSION

These results lend support to the hypothesis that tPA may have a direct receptor-mediated effect on EC proliferation and that this effect occurs independent of plasmin and may be dependent upon protein kinase A activity.

Retroviral-mediated transduction of endothelial cells with the lac Z gene impairs cellular proliferation in vitro and graft endothelialization in vivo

PURPOSE

An endothelialized lumen within a synthetic graft that expresses recombinant proteins with anticoagulant or antiproliferative activity has the potential to improve graft function. However, preliminary data suggest that genetic modification of endothelial cells (ECs) impairs their proliferation. The purpose of this investigation was to test the hypothesis that retroviral transduction of cultured ECs with the lac Z gene encoding for beta-galactosidase would decrease EC proliferation in vitro and graft endothelialization in vivo.

METHODS

In vitro studies compared canine EC proliferation over a 14-day period among early-passage ECs (two and three) and late-passage ECs (six and nine) transduced with the BAG vector (containing the lac Z gene and the neomycin resistance gene), ECs transduced with the neomycin resistance gene only, the nontransduced ECs. In vivo canine studies assessed endothelialization of expanded polytetrafluoroethylene thoracoabdominal grafts seeded with autologous lac Z-transduced ECs (n = 7) or nontransduced ECs (n = 3) compared with that of nonseeded grafts (n = 3). Histochemical staining and DNA polymerase chain reaction was used 6 weeks after implantation to detect the presence of the lac Z gene in the grafts' cellular linings and perigraft tissues. Endothelialization was assessed by light microscopy and electron microscopy.

RESULTS

Proliferation of late-passage lac Z-transduced ECs in vitro was significantly decreased compared with neomycin resistance-transduced ECs or nontransduced ECs. Among early-passage ECs smaller but significant decreases in proliferation were noted among lac Z-transduced cells compared with nontransduced cells. Six of seven expanded polytetrafluoroethylene grafts seeded with transduced ECs showed lac Z gene expression. Lac Z gene expression was not found on grafts seeded with nontransduced ECs or nonseeded grafts. The endothelialized luminal surface area was significantly less in grafts seeded with lac Z-transduced ECs compared with grafts seeded with nontransduced ECs.

CONCLUSIONS

Retroviral-mediated transduction of canine ECs with the lac Z gene encoding for beta-galactosidase impairs EC proliferation in vitro and the ability of transduced ECs to form a confluent EC monolayer on the luminal surface of synthetic grafts in vivo.

Systemic delivery of the interleukin-1 receptor antagonist protein using a new strategy of direct adenoviral-mediated gene transfer to skeletal muscle capillary endothelium in the isolated rat hindlimb

Current gene therapy strategies using adenoviral vectors to target the lung or liver have been complicated by an acute inflammatory response that can result in loss of transgene expression as well as tissue injury and necrosis. Skeletal muscle comprises 40% of total body weight; it possesses a high density, accessible capillary network that is resistant to injury and thus may be a logical target for adenoviral vectors. We hypothesized that adenoviral transduction of the rat skeletal muscle capillary bed during vascular isolation would achieve efficient gene transfer sufficient to achieve systemic serum levels of a recombinant protein without significant tissue injury. During vascular isolation of the hindleg, a replication-incompetent adenovirus (Ad) encoding for either the marker gene, human placental alkaline phosphatase (hpAP), or interleukin-1 receptor antagonist (IL-1ra) was infused and subsequently flushed from the circulation after a 30-min dwell period. Gene transfer over a 10(9)-10(12) particle/ml range to the gastrocnemius capillary endothelium and muscle fibers was highly efficient and titer-dependent, reaching maximum transduction rates of 71 +/- 7% and 25 +/- 5%, respectively, 5 days after gene transfer (n = 3-8 rats/group, p < 0.05). hpAP transgene expression was barely detectable at 14 days. No significant tissue injury or necrosis of the skeletal muscle was observed at 5 and 14 days, and distant organ gene transfer was minimal or absent. Gastrocnemius muscle from rats (n = 4) given Ad-IL-1ra had 241 +/- 66 pg IL-1ra/mg protein at 5 days, while those given Ad-hpAP, negative control (n = 3) had 35 +/- 14 pg IL-1ra/mg protein (p < 0.05). Ad-IL-1ra rats (n = 4) had serum levels of 185 +/- 20 pg/ml IL-1ra at 5 days whereas Ad-hpAP control rats (n = 5) had no IL-1ra detectable (p < 0.0001). Athymic rats given Ad-IL-1ra (n = 6) had serum levels of 493 +/- 62 pg/ml IL-1ra 14 days after transduction, and IL-1ra was detected for up to 98 days. Sera from Ad-IL-1ra athymic rats significantly inhibited IL-1 beta-induced (1 ng/ml) prostaglandin E2 (PGE2) production from cultured endothelial cells by 82 +/- 2% (p < 0.001). Thus, this gene transfer strategy is the first to result in substantial transduction of both skeletal muscle capillary endothelium and fibers, sufficient to achieve pharmacologic levels of IL-1ra. Although no acute tissue injury or necrosis was observed, persistence of transgene expression in athymic rats suggests that loss of expression in normal rats was by an immune-mediated mechanism.

PKH26 and 125I-PKH95: characterization and efficacy as labels for in vitro and in vivo endothelial cell localization and tracking

PKH26, a fluorescent cell label, and PKH95, a 125 I-radioactive cell label, are both potentially valuable endothelial cell labels because they bind irreversibly within cell membranes. These labels would be particularly well suited to tract transplanted endothelial cells in vivo. However, no previous studies documenting lack of transfer of the label to unlabeled endothelial cells, as well as the effect of the label on endothelial cell function, have been undertaken. The purpose of this study was to determine the optimal method of endothelial cell (EC) labeling with PKH26 and PKH95, whether significant to EC-to-EC transfer of the label occurs, the effects of these labels on EC proliferation and membrane function, and the feasibility of using these labels for long-term quantitative EC tracking in vivo. Canine ECs in confluent monolayers or in cell suspension were labeled by exposure to 1.0 or 5.0 microM PKH26 for 1, 3, or 5 min. Cell viability was determined by trypan blue exclusion. The percentage of cells labeled and their fluorescence intensity were determined in a fluorescent-activated cell sorter (FACS). Effect of the label on cell function was assessed by measuring EC proliferation rates as well as intercellular adhesion molecule (ICAM) expression before and after induction with tumor necrosis factor (TNF). To determine if transfer of the label occurs, both labeled and nonlabeled ECs were grown in coculture and subjected to FACS analysis. For in vivo cell tracking, doubly labeled ECs were injected into the femoral artery of rat hind-limbs, and whole-body tissue analysis was undertaken to determine labeled-EC distribution at 60 days. Endothelial cells were labeled with equal efficacy as monolayers or in suspension. Labeling had no effect on EC proliferation rates nor on TNF-induced upregulation of ICAM expression. Coculture experiments revealed no significant label transfer to nonlabeled ECs. In vivo cell tracking studies documented that 8% of label remained within the skeletal muscle capillaries at 60 days after injection. PKH26 and PKH95 labels incorporate stably into EC membranes, do not alter endothelial cell function, and provide a precise means for quantitative EC tracking and histologic localization both in vitro and in vivo. These labels should prove to be very useful for studies of endothelial cell biology and transplantation.

Effects of retroviral-mediated tissue plasminogen activator gene transfer and expression on adherence and proliferation of canine endothelial cells seeded onto expanded polytetrafluoroethylene

PURPOSE

Seeding prosthetic arterial grafts with genetically modified endothelial cells (ECs) has the potential to substantially improve graft function. However, preliminary applications suggest that grafts seeded with retrovirally transduced ECs yield a significantly lower percent surface coverage than those seeded with nontransduced ECs. The objective of this study was to test the hypothesis that canine ECs transduced with the human tissue plasminogen activator (tPA) gene would have a lower rate of adherence to pretreated expanded polytetrafluoroethylene (ePTFE) both in vitro and in vivo and that they would proliferate at a slower rate on pretreated ePTFE in vitro.

METHODS

Early passage ECs derived from canine external jugular vein were transduced with the retroviral MFG vector containing the gene for human tPA. ECs exposed to media alone served as controls. Iodine 125-labeled ECs were seeded in vitro onto ePTFE graft segments pretreated with canine whole blood, fibronectin (50 micrograms/ml), or media alone, and the percent of ECs adherent at 1 hour were determined (n = 3). Additional tPA-transduced and -nontransduced ECs were grown for 10 days on either fibronectin (50 micrograms/ml)-pretreated ePTFE wafers or tissue culture plastic pretreated with gelatin (1%) or fibronectin (50 micrograms/ml), and the EC proliferation rates were determined (n = 3). Furthermore, 125I-labeled ECs were seeded onto fibronectin (50 micrograms/ml)-pretreated ePTFE graft segments implanted as carotid and femoral artery interposition grafts (n = 3). The grafts were harvested after 1 hour, and the percent of ECs adherent was determined.

RESULTS

Human tPA was detected by immunohistochemical staining in 61% +/- 5% of the transduced ECs and was expressed at 35.4 +/- 12.9 ng/hr/10(6) cells. Fibronectin and whole blood pretreatment of the ePTFE grafts led to greater EC adherence in vitro than did media alone (90.9% +/- 5.3% vs 77.8% +/- 5.8% vs 4.7% +/- 1.1%, p < or = 0.05). No significant difference in the rates of adherence or proliferation was seen in vitro between the transduced and nontransduced ECs. No significant difference in proliferation was found for the transduced ECs on the three matrices tested in vitro. In contrast, adherence of the transduced ECs in vivo was significantly lower than that of nontransduced ECs (64.7% +/- 2.1% vs 73.7% +/- 4.1%, p < or = 0.05) 1 hour after implantation.

CONCLUSIONS

Lower rates of surface endothelialization by genetically modified ECs in vivo do not appear to be due to an impaired capacity to initially adhere or proliferate on the synthetic graft but may result from decreased adherence after exposure to in vivo hemodynamic forces.

Variability in measurement of abdominal aortic aneurysms. Abdominal Aortic Aneurysm Detection and Management Veterans Administration Cooperative Study Group

PURPOSE

The purpose of this study was to report interobserver and intraobserver variability of computed tomography (CT) measurements of abdominal aortic aneurysm (AAA) diameter and agreement between CT and ultrasonography observed in the course of a large, multicenter, randomized trial on the management of small AAAs.

METHODS

CT measurements of AAA diameter from participating centers were compared with measurements made from the same scan by a central laboratory. Blinded central remeasurement of a randomly selected subset of these CT scans was used to assess intraobserver variability. Agreement between AAA measurements by CT and ultrasonography done within 30 days of each other was also assessed.

RESULTS

For interobserver pairs of local and central CT measurements of AAA diameter (n = 806), the difference was 0.2 cm or less in 65% of pairs, but 17% differed by at least 0.5 cm. For intraobserver pairs of central CT remeasurements (n = 70), 90% differed by 0.2 cm or less, 70% were within 0.1 cm, and only one differed by 0.5 cm. Of 258 ultrasound-measured and central CT pairs, the difference was 0.2 cm or less in 44% and at least 0.5 cm in 33%. Ultrasound measurements were smaller than central CT measurements by an average of 0.27 cm (p < 0.0001). Local CT and ultrasound measurements showed a marked preference for recording by half centimeter.

CONCLUSIONS

A high degree of precision is possible in CT measurement of AAA diameter, but this precision may not be obtained in practice because of differences in measurement techniques. Differences between imaging modalities increase variability further. Variations in AAA measurement of 0.5 cm or more are not uncommon, and this should be taken into account in management decisions. Efforts to reduce variation in measurement are warranted and might include (1) seeking agreement between surgeons and radiologists on a precise definition of AAA diameter, (2) limiting the number of radiologists who measure AAAs, and (3) use of calipers and magnifying glass for CT measurements.

Inhibition of aortic aneurysm development in blotchy mice by beta adrenergic blockade independent of altered lysyl oxidase activity

PURPOSE

This study was designed to define the effects of beta-adrenergic blockade on aortic lysyl oxidase (LO), an enzyme responsible for elastin and collagen cross-linking, and aneurysm formation in the blotchy mouse. It was hypothesized that beta-blockade would inhibit the development of aneurysms because of its hemodynamic effect rather than a direct effect on LO activity.

METHODS

Three groups of mice were studied: group I--normal littermates of blotchy mice; group II--untreated blotchy mice; group III--blotchy mice given either propranolol, atenolol, or nadolol. Data from the three different beta blocker-treated animals, group III, were statistically identical and were combined for analysis. The study was concluded when the mice were 4 months of age. At that time systolic blood pressure, heart rate, and aortic diameters were measured, and the entire aorta from each mouse was subjected to a bioassay for LO activity.

RESULTS

Group I normal mice had an aortic arch diameter of 0.10 +/- 0.02 cm. Group II blotchy mice developed aortic arch aneurysms with a diameter of 0.21 +/- 0.03 cm. In Group III, beta blockade reduced the aortic arch diameter in blotchy mice to 0.11 +/- 0.03 cm. Mean heart rate in group III beta-blocked mice was reduced 25% compared with group I normal mice, and 18% compared with group II untreated blotchy mice. Blood pressures were similar in all three groups. Group II blotchy mice exhibited approximately half of the aortic LO activity (2.43 +/- 0.57 cpm/micrograms protein) noted in group I normal mice (5.82 +/- 1.06 cpm/micrograms protein). Aortic LO activity in group III blotchy mice remained low (2.09 +/- 0.85 cpm/micrograms protein) despite administration of beta-blockers.

CONCLUSIONS

This is the first study to document an actual decrease in the level of aortic LO activity in blotchy mouse. beta-Blockade inhibits development of aortic aneurysms in blotchy mice. This is associated with a reduction in heart rate, but not by alterations in LO activity.

Gadolinium-enhanced magnetic resonance angiography of abdominal aortic aneurysms

PURPOSE

The objective of this study was to assess the usefulness of gadolinum-enhanced magnetic resonance angiography (MRA) for defining anatomic features relevant to performing aortic surgery for aneurysmal disease.

METHODS

Anatomic data defined by MRA, including abdominal aortic aneurysm (AAA) size and character, as well as the status of the celiac, mesenteric, renal, and iliac arteries, were correlated with angiography, ultrasonography, computed tomography, or operative data in 43 patients. Five MRA sequences were obtained in an hour-long examination optimized for aortoiliac, splanchnic, and renal artery imaging at 1.5 T in a body coil. Four of the sequences were performed during or after infusion of gadolinium to improve image quality.

RESULTS

MRA correctly defined the maximum aneurysm diameter, as well as its proximal and distal extent in all patients. MRA detected 33 of 35 significant stenoses among 153 splanchnic, renal, or iliac branches examined (sensitivity = 94% and specificity = 98%). MRA did not resolve the degree of aortic branch stenotic disease sufficiently to precisely grade its severity. MRA did not reliably define the status of the inferior mesenteric artery, lumbar arteries or internal iliac arteries. One ruptured AAA and one inflammatory AAA were correctly diagnosed by MRA. No patient had a contrast reaction or contrast-induced renal toxicity related to administration of gadolinium.

CONCLUSION

Gadolinium-enhanced MRA of AAA provides appropriate, essential anatomic information for aortic reconstructive surgery in a 1-hour examination devoid of contrast-related renal toxicity or catheterization-related complications attending conventional arteriography.

Pediatric renovascular hypertension: a thirty-year experience of operative treatment

PURPOSE

This study was undertaken to characterize the changing operative treatment of pediatric renovascular hypertension and subsequent outcomes in a 30-year experience at a single institution.

METHODS

Clinical data were analyzed on 57 pediatric patients, 24 girls and 33 boys, ranging in age from 10 months to 17 years, who underwent operations for renovascular hypertension from 1963 to 1993 at the University of Michigan. Renal artery disease included atypical medial-perimedial dysplasia, often with secondary intimal fibroplasia (88%), and inflammatory mural fibrosis (12%). Abdominal aortic narrowings affected 15 patients. Data were categorized into three chronologic eras (I:1963-1972, II:1973-1980, and III:1981-1993) to allow identification of therapeutic trends.

RESULTS

Primary surgical procedures were undertaken 74 times. Ex vivo reconstruction was necessary once. Primary operations included aortorenal bypass with autogenous vein grafts (n = 26) or internal iliac artery grafts (n = 7); iliorenal bypass with vein grafts (n = 2); renal artery resection beyond the stenosis and reimplantation into the aorta (n = 10), the main renal artery (n = 2), an adjacent segmental renal artery (n = 3), or the superior mesenteric artery (n = 3); renal artery resection and reanastomosis (n = 3); focal renal arterioplasty (n = 2); operative dilation (n = 7); splenorenal bypass (n = 2); and primary nephrectomy (n = 7). Among 23 primary operations performed in era I, 56.5% were aortorenal bypasses with vein grafts, but in era III this form of revascularization represented only 3% of 33 primary operations. No reimplantations were performed in era I, whereas reimplantations accounted for 51.5% of era III procedures. Thirteen patients underwent staged or concomitant aortic reconstructions with thoracoabdominal aortoaortic bypass grafts (n = 5) or patch aortoplasty (n = 8). Fourteen patients underwent a total of 20 secondary operations, including seven secondary nephrectomies. Operative therapy benefited 98% of these children: hypertension was cured in 45 (79%), improved in 11 (19%), and unchanged in one (2%). There were no operative deaths.

CONCLUSIONS

Contemporary surgical management emphasizes direct reimplantation of main renal arteries into the aorta, reimplantation of segmental arteries into adjacent renal arteries, patch aortoplasty for associated abdominal aortic coarctations, and single-stage revascularizations. Pediatric patients with renovascular hypertension clearly benefit from carefully executed operative therapy.

Transplantation of lac-Z-transduced microvascular endothelial cells into the skeletal muscle capillary bed of the rat hindlimb occurs independent of the duration of femoral artery occlusion after injection of cells

The skeletal muscle capillary bed may be an ideal recipient site for transplantation of genetically modified autologous endothelial cells and thus provide a basis for a technique of somatic gene therapy that would be applicable to a variety of acquired and inherited human diseases. The purpose of this study was to test the hypothesis that adhesion of lac-Z-transduced microvascular endothelial cells (MVEC) in the skeletal muscle capillary bed in vivo is dependent on the duration of arterial occlusion after injection of the transduced MVEC. MVEC derived from the abdominal fat pad of syngeneic rats (Wistar F-455) were transfected with the BAG vector, a replication-incompetent retroviral vector containing the lac-Z gene for beta-galactosidase and the Tn5 gene for selection of the transduced cells by the neomycin analogue, G418. lac-Z-transduced MVEC were radiolabeled with 125I-PKH-95, and, after the femoral artery was occluded for 10 min, these cells (1 to 2 x 10(6)) were injected intraarterially into the rat hindlimb. In the experimental groups the femoral artery clamp was removed at 0, 60, or 120 min after injection. A control group without pre- or postinjection femoral arterial occlusion was also studied. Adhesion of MVEC in the skeletal muscle capillary bed (mean percentage of injected 125I activity) was determined in groups of 4 rats at 1 day, 1 week, and 1 month after injection. Adhesion of the transduced MVEC did not increase as the duration of femoral artery occlusion after injection was increased.(ABSTRACT TRUNCATED AT 250 WORDS)