A review of telemedicine in vascular surgery.

Telemedicine refers to the delivery of medical care through telecommunications and has been utilized by many medical specialists. In its basic form, telemedicine can involve the use of a telephone or fax. More advanced forms are the transmission of still images, often referred to as "store-and-forward" technology, or real-time two-way interactive video. The former is possible over existing phone lines or the Internet and has enjoyed success in visually oriented disciplines such as radiology and dermatology. The latter requires high bandwidth communication lines and is therefore considerably more expensive. This article reviews the use of telemedicine as applied specifically to vascular surgery. Initial studies indicate that store-and-forward technology can be used to adequately assess and treat wounds in vascular patients. A recent study reported the use of two-way interactive video for remote assessment of a wide variety of vascular patients. Diagnosis and treatment recommendations by the remote physician were found to be comparable to conventional on-site examinations. Patient satisfaction with the telemedicine examination was noted to be extremely high. In conclusion, telemedicine, although not commonly used in vascular surgery, has the potential of increasing patient access to specialty care, while decreasing patient or physician travel. The use of telemedicine in vascular surgery will likely continue to expand as technology improves and costs decrease.

Enoxaparin treatment in high-risk trauma patients limits the utility of surveillance venous duplex scanning.

OBJECTIVE: The value of surveillance venous duplex scanning for detecting unsuspected deep venous thrombosis (DVT) in trauma patients who are receiving enoxaparin prophylaxis is open to question. This study was undertaken to determine whether enoxaparin reduced the clinical utility of surveillance scanning and whether management of these patients was altered by findings of the scans. METHODS: The medical records of trauma patients who met defined criteria for high DVT risk, admitted during 30 consecutive months, were reviewed. These patients received enoxaparin 30 mg every 12 hours for the duration of their admissions. Per protocol, surveillance lower extremity venous duplex scans were performed within 72 hours of enoxaparin administration and then weekly until patients were discharged from the hospital. The records were reviewed for thromboembolic events (DVT or pulmonary embolism [PE]), patient location and ambulatory status, therapeutic interventions (systemic anticoagulation, vena cava filter), and complications of enoxaparin therapy. RESULTS: A total 241 patients underwent 513 venous duplex examinations (1-13 per patient). Eight patients had DVT on the initial scan; seven of these patients were asymptomatic. Five were treated with anticoagulation and/or vena cava filter placement. Of the 233 patients with initially negative duplex scan results, five patients (2%) developed clinically unsuspected lower extremity DVT while hospitalized. All of these five patients were in an intensive care unit. Three of the five patients had no change in treatment. Two of the five underwent anticoagulation, and one vena cava filter was placed. PE occurred in two hospitalized patients, one of whom was ambulatory, with negative duplex scan results. After hospital discharge, six other patients had symptomatic DVT or PE despite in-hospital scans with negative results. Complications associated with enoxaparin included hemorrhage (2) and thrombocytopenia (8). CONCLUSIONS: After initial negative scan results, repeat surveillance duplex scanning during hospitalization detected a low incidence (2%) of DVT in high-risk patients. Furthermore, the detection of unsuspected DVT altered the clinical management of less than 1% of the patients tested. Thus, after a venous duplex scan with negative results and initiation of enoxaparin prophylaxis, subsequent surveillance duplex examinations are not warranted in asymptomatic trauma patients.

Surgical management of thrombotic acute intestinal ischemia.

OBJECTIVE: To evaluate the University of Kentucky experience in treating acute intestinal ischemia to elucidate factors that contribute to survival. SUMMARY BACKGROUND DATA: Acute intestinal ischemia is reported to have a poor prognosis, with survival rates ranging from 0% to 40%. This is based on several reports, most of which were published more than a decade ago. Remarkably, there is a paucity of recent studies that report on current outcome for acute mesenteric ischemia. METHODS: A comparative retrospective analysis was performed on patients who were diagnosed with acute intestinal ischemia between May 1993 and July 2000. Patients were divided into two cohorts: nonthrombotic and thrombotic causes. The latter cohort was subdivided into three etiologic subsets: arterial embolism, arterial thrombosis, and venous thrombosis. Patient demographics, clinical characteristics, risk factors, surgical procedures, and survival were analyzed. Survival was compared with a collated historical series. RESULTS: Acute intestinal ischemia was diagnosed in 170 patients. The etiologies were nonthrombotic (102/170, 60%), thrombotic (58/170, 34%), or indeterminate (10/170, 6%). In the thrombotic cohort, arterial embolism accounted for 38% (22/58) of the cases, arterial thrombosis for 36% (21/58), and venous thrombosis for 26% (15/58). Patients with venous thrombosis were younger. Venous thrombosis was observed more often in men; arterial thrombosis was more frequent in women. The survival rate was 87% in the venous thrombosis group versus 41% and 38% for arterial embolism and thrombosis, respectively. Compared with the collated historical series, the survival rate was 52% versus 25%. CONCLUSIONS: These results indicate that the prognosis for patients with acute intestinal ischemia is substantially better than previously reported.

Telemedicine in vascular surgery: does it work?

Telemedicine (TM) using closed-circuit television systems allows specialists to evaluate patients at remote sites. Because an integral part of the vascular examination involves palpation of peripheral pulses the applicability of TM for the evaluation of vascular surgery patients is open to question. This study was carried out to test the hypothesis that TM is as effective as direct patient examination for the development of a care plan in vascular patients. Sixty-four vascular evaluations were done in 32 patients. The patients presented with a variety of vascular problems and were seen in regularly scheduled rural outreach vascular clinics. Two faculty vascular surgeons evaluated each patient; one was on site and the second, using TM, remained at the medical center. Each surgeon was blinded to the other's findings. The TM physician was aided by a nonphysician assistant, who obtained blood pressures, utilized a continuous-wave Doppler probe, positioned the patient, and operated the TM equipment. The results of each surgeon's evaluations were compared. Patient and physician satisfaction with the TM evaluation was appraised by questionnaires. Eight patients were seen for initial evaluations; 24 patients were seen for follow-up visits. Patients were seen with a variety of diagnoses, including aneurysm (seven), cerebrovascular disease (five), lower extremity occlusive disease (13), multiple vascular problems (three), and other disease (four). The average duration for the TM and on-site evaluations were 20.6+/-1.4 and 19.0+/-1.3 minutes, respectively (P = not significant). Physician concordance, as determined by treatment recommendations, was the same in 29 (91%) patients. Physician confidence in the ability to obtain an accurate history via TM was rated as excellent in 97 per cent; confidence in the TM physical examination was rated as excellent in 70 per cent. All patients rated the TM evaluation as the "same as" or "better than" the on-site examination, and all indicated a preference for being seen locally using TM as opposed to traveling to a regional medical center. We conclude that the TM evaluation of vascular patients is accurate and is as effective as on-site evaluations for a variety of vascular problems. Important adjuncts to enhance the success of a TM evaluation are physician experience with the technology and the presence of a knowledgeable on-site assistant. This technology can be easily adapted to other clinical situations.

The migratory response to platelet-derived growth factor of smooth muscle cells isolated from synthetic vascular grafts in a canine model.

OBJECTIVE: Previous studies on smooth muscle cells (SMCs) harvested from implanted synthetic grafts demonstrate increased production of platelet-derived growth factor (PDGF) but decreased proliferative response compared with aortic SMCs. The purpose of this study was to determine the migratory response of graft versus aortic SMCs. METHODS: Thoracoabdominal grafts were implanted in beagles. The SMCs were harvested from the graft and infrarenal aorta. Migration was determined with the use of a razor-scrape assay and computerized image analysis. RESULTS: The mean distance migrated and the number of cells that migrated were greater in graft SMCs at baseline (185 +/- 18 micrometer and 108 +/- 17 cells) compared with aortic cells (110 +/- 10 micrometer and 42 +/- 5 cells)(P <.05). Baseline differences persisted after treatment with antibodies to PDGF. The addition of PDGF (10 ng/mL) resulted in increased migration in both graft (229 +/- 23 micrometer and 146 +/- 20 cells) and aortic SMCs (130 +/- 9 micrometer and 70 +/- 5 cells) compared with baseline (P <.05). The relative increase in response to PDGF was similar between the two groups (P = not significant). CONCLUSIONS: Graft SMCs differ phenotypically from aortic SMCs; they exhibit increased basal migration that is independent of autocrine stimulation by PDGF. In contrast to their blunted proliferative response, graft SMCs have a similar migratory response to PDGF compared with aortic SMCs.

The proliferative response to platelet-derived growth factor of smooth muscle cells isolated from synthetic vascular grafts in a canine model.

OBJECTIVE: Previous studies on graft healing have shown increased platelet-derived growth factor (PDGF) production in graft segments versus native aortic segments. The purpose of this study was to characterize the proliferative response of graft smooth muscle cells (SMCs) to PDGF. METHODS: Thoracoabdominal grafts were implanted in beagles. SMCs were harvested from the graft and the proximal and distal aortas. Basal proliferation was assessed with growth curves in primary culture. The proliferative response to PDGF then was compared with [3H]thymidine uptake studies and cell counts. Finally, PDGF receptors were characterized with radio-labeled ligand binding assays. RESULTS: The growth curves showed that the graft SMCs entered log-phase growth 2 days earlier than did the aortic SMCs. Stimulation of quiescent early-passage graft SMCs with PDGF (10 ng/mL) resulted in a 1.7 +/- 0.1-fold increase in [3H]thymidine incorporation, which was significantly less than that of the SMCs from both the proximal aorta (11.8 +/- 3.0) and the distal aorta (10. 2 +/- 1.9; P <.5). Similarly, the 1.1 +/- 0.1-fold increase in graft SMC cell number was significantly less than the increases for both proximal (2.8 +/- 0.5) and distal (2.9 +/- 0.8) aortic SMCs (P <.5). Binding studies on quiescent first-passage cells showed fewer PDGF receptors available for binding in the graft SMCs (185 +/- 70 fmol/million cells) as compared with both the proximal (419 +/- 147 fmol/million cells) and the distal (387 +/- 112 fmol/million cells) aortas (P <.5). Binding affinity was similar for the three groups. CONCLUSION: Graft SMCs exist in a chronic proliferative state but exhibit a decreased proliferative response to PDGF and have fewer receptors available for binding PDGF than do aortic SMCs in vitro.

Platelet-derived growth factor production by cells from Dacron grafts implanted in a canine model.

PURPOSE: Previous studies of grafts implanted in dogs documented a time-dependent increase in platelet-derived growth factor (PDGF) production that correlated with inner-capsule thickness. The purpose of this study was to identify the cells in vascular grafts that produce PDGF. METHODS: Dacron thoracoabdominal grafts were seeded with autologous endothelial cells (ECs), implanted in 11 beagles, and removed after 4 or 20 weeks. ECs and smooth muscle cells (SMCs) were cultured from grafts and adjacent aorta, and PDGF in the conditioned media was measured by radioreceptor assay. The PDGF A-chain mRNA level in freshly harvested cells was assessed using reverse transcriptase, followed by polymerase chain reaction, and expressed as a ratio of glyceraldehyde-3-phosphate dehydrogenase signal. Localization of PDGF A-chain and B-chain protein was also examined with immunohistochemical analysis. RESULTS: Graft and aortic ECs in primary culture did not produce significantly different amounts of PDGF in 72 hours, averaging 368 +/- 160 and 340 +/- 81 pg/microgram DNA, respectively. Graft SMCs in primary culture produced significantly more PDGF than aortic SMCs (584 +/- 343 and 113 +/- 94 pg/microgram DNA, respectively; p < 0.01). Graft SMC PDGF secretion remained greater than aortic SMC PDGF secretion through at least six cell passages. PDGF A-chain mRNA levels were not significantly different for aortic or graft ECs. The PDGF A-chain mRNA level was significantly higher for graft SMCs than aortic SMCs (2.44 +/- 0.67 and 1.45 +/- 0.57 pg/microgram, respectively; p < 0.03). Immunocytochemical analysis detected PDGF A-chain and B-chain protein in the ECs from both native aorta and graft as well as the subendothelial SMCs in the graft, but not in the SMCs of the native aorta. CONCLUSIONS: These results suggest that graft SMCs are functionally altered, producing more PDGF than aortic SMCs. PDGF produced by graft SMCs may contribute to the development of intimal hyperplasia.

Inhibition of smooth muscle cell proliferation and migration in vitro by antisense oligonucleotide to c-myb.

PURPOSE: Smooth muscle cell (SMC) migration and proliferation are prominent features of intimal hyperplasia. Previous studies have shown that inhibition of c-myb inhibits arterial SMC proliferation. Our goal was to evaluate the effect of an antisense oligonucleotide targeted to c-myb on the proliferation and migration of SMC explanted from synthetic vascular grafts. METHODS: SMCs were enzymatically removed from aortas and Dacron grafts explanted from dogs (n = 5). For proliferation studies, quiescent SMCs were incubated with either 0.0, 0.5, 5.0, or 10.0 microM antisense (GTGTCGGGGTCTCCGGGC) or sense (GCCCGGAGACCCCGACAC) oligonucleotides to c-myb. Proliferation was measured after 24 hours by incorporation of [3H]thymidine. Migration was assessed 24 hours after a razor injury. RESULTS: Antisense to c-myb consistently inhibited proliferation and migration of both native aortic and graft SMCs in a dose-dependent fashion. At a concentration of 10 microM antisense oligonucleotide, aortic and graft SMC proliferation rates were 32% +/- 20% and 56% +/- 9% of control samples, respectively. At 25 microM antisense, the number of migrating aortic and graft SMCs decreased to 41.9% +/- 26.8% and 51.9% +/- 34.1% of control samples, respectively. CONCLUSIONS: Our results suggest that antisense oligonucleotides to c-myb may be useful in the inhibition of SMC proliferation and migration associated with development of intimal hyperplasia.

Pseudoaneurysm of the external carotid artery following radical neck dissection and irradiation: a case report and review of the literature.

A 54-year-old man developed a pseudoaneurysm of the left external carotid artery 8 years after concluding treatment for squamous cell carcinoma of the tongue. Treatment included radiation therapy, radical neck dissection and a myocutaneous pectoralis major flap. Percutaneous transcatheter embolization resulted in thrombosis of the pseudoaneurysm. A review of the literature yielded only six other reported cases of pseudoaneurysm of the external carotid artery proper.

Elastin is increased in abdominal aortic aneurysms.

The decrease in elastin concentration in abdominal aortic aneurysm (AAA) has been ascribed to elastolysis. The discordant response of the elastin and collagen genes in AAA suggests a different explanation: dilution of elastin because of higher levels of synthesis of collagen and other matrix proteins. The purpose of this study was to determine circumferential content of elastin, collagen, and total protein in aneurysmal (AAA), atherosclerotic, and normal (NL) infrarenal aorta. Standard serial extraction techniques of complete 1-cm rings of midinfrarenal aortic tissue were used to remove soluble protein, calcium, and lipids. Hydroxyproline (collagen), desmosine/isodesmosine (elastin), and total amino acid (total protein) content were determined by amino acid analysis. Means values (+/- SEM) were compared by ANOVA. Circumferential content of desmosine/isodesmosine was increased 2.5-fold in AAA compared to NL (P < 0.05). Collagen and total protein were increased 5.7- and 4.7-fold, respectively (P < 0.05). There was a high degree of correlation between circumference and collagen content (r = 0.89). These data demonstrate that significant synthesis of matrix proteins accompanies aortic dilatation. While both elastin and collagen are increased, there is a much greater increase in circumferential collagen content than elastin content. These data do not preclude proteolysis as a factor in AAA but suggest that the decrease in elastin concentration results from dilution of elastin by a greater increase in the synthesis of other matrix proteins and that synthesis is an important factor in AAA formation.

Abdominal aortic aneurysms are associated with altered matrix proteins of the nonaneurysmal aortic segments.

PURPOSE: Abdominal aortic aneurysms (AAA) are associated with diffuse arteriomegaly and peripheral aneurysms, suggesting a generalized process. Elastin and collagen are the key structural proteins of the aorta, and their relative content is markedly altered in tissue from AAA. Our purpose was to investigate elastin and collagen content in the proximal, nonaneurysmal segments of aortas with infrarenal AAA. METHODS: After extraction of lipid, calcium, and soluble proteins, hydroxyproline (collagen) and desmosine-isodesmosine (elastin) contents were determined by high-performance liquid chromatography in the ascending and descending thoracic, supraceliac, and suprarenal aorta. By repeated measures of analysis of covariance, collagen was found to be increased throughout the aorta in AAA as compared with normal aorta or aorta with atherosclerotic occlusive disease. This difference remained significant when adjustments were made for group differences in age and degree of atherosclerosis. This increase in collagen content results in a dilutional decrease in elastin concentration. These data demonstrate that the same matrix protein alterations found in AAA tissue occur throughout the aorta, differing only in magnitude in the aneurysmal and nonaneurysmal segments. These data suggest that aneurysm formation may related to alterations in the regulation of elastin and collagen.

Rational approach to postoperative transfusion in high-risk patients.

An appropriate threshold for transfusion in patients with coronary artery disease has not been defined. Our purpose was to determine: (1) the effects of preoperative volume loading; (2) postoperative function and oxygen delivery (DO2); (3) an appropriate transfusion threshold based on observed DO2 in high-risk patients undergoing abdominal aortic aneurysm (AAA) repair, bypass of aortoiliac disease (AOD), distal bypass, or carotid endarterectomy (CEA). Preoperative volume loading increased cardiac output (CO) in all groups by 15% to 22%. Postoperative CO was unchanged from optimal preoperative values except in the CEA group, in which it decreased. Systemic vascular resistance decreased in the AAA and AOD groups. The decrease in postoperative DO2 in all groups (25% to 31%) was related to a decrease in hemoglobin. Despite marginal (less than 11 mL/kg/min) postoperative DO2 in more than a third of patients, there was no compensatory increase in CO. Thus, after optimization of function by volume loading, red cell transfusion may be the only way to increase DO2. Hemoglobin levels of 10 to 12 g/dL may be required for adequate DO2 when ventricular function is markedly impaired.

Soluble factors modulate changes in collagen gene expression in abdominal aortic aneurysms.

BACKGROUND: Although increased procollagen gene expression and synthesis have been implicated in the progression of abdominal aortic aneurysms (AAA), factors modulating this change have not been identified. Furthermore, it is not known whether the increase in AAA procollagen expression is specific to this disease or also occurs in tissue affected by atherosclerotic occlusive disease (AOD). If paracrine rather than autocrine factors are responsible for increased gene expression in AAA, this effect should be transferable to target smooth muscle cells through conditioned media. Our objectives were to determine 1 alpha (I) procollagen messenger RNA levels in AOD tissue compared with normal and AAA and to determine whether differences noted in tissue procollagen gene expression could be transferred through conditioned media from normal, AOD, and AAA tissues to target smooth muscle cells in primary culture. METHODS: Normal, AOD, and AAA tissue was used for tissue RNA extraction or was minced and washed with serum-free media (4 degrees C) x 30 minutes and the media applied to human aortic smooth muscle cells (SMC) in primary culture for 36 hours. Total RNA from tissue and SMC exposed to conditioned media was analyzed by Northern and dot blot analysis for 1 alpha (I) procollagen. RESULTS: Relative tissue 1 alpha (I) procollagen levels were not increased in AOD (0.23 +/- 0.05) as compared with normal (0.17 +/- 0.03); both were decreased compared with AAA (0.53 +/- 0.07; p < 0.01). The 1 alpha (I) procollagen levels in SMC exposed to conditioned media from AAA (1.73 +/- 0.15) were increased (p < 0.05) compared with AOD (1.10 +/- 0.12) and normal (1.16 +/- 0.16). CONCLUSIONS: There is no increase in tissue AOD procollagen gene expression. The ability to transfer the same relative patterns of gene expression from tissue to target SMC with conditioned media suggests that paracrine, rather than autocrine, factors modulate procollagen expression in AAA tissues.

Elastin and fibrillin mRNA and protein levels in the ontogeny of normal human aorta.

Elastin associated microfibrils (EAMF) are ubiquitous connective tissue structures that are believed to provide tensile strength and flexibility to numerous tissues. In this study the ontogeny of EAMF in normal human aorta was examined using immunohistochemical analysis of fibrillin, an EAMF component, and mRNA levels of fibrillin and elastin. Specimens of infra-renal aorta from ages 11 months to 44 years were obtained following organ procurement. Decreasing amounts, as judged by computer digitized image analysis, of immunoreactive fibrillin when compared to elastin auto-fluorescence were observed in aortic sections with increasing age. Elastase treatment would un-mask the anti-fibrillin reactive epitope reinforcing the suggestion that EAMF act as a "scaffold" for elastin deposition. Northern and dot blot hybridizations demonstrated a decrease in relative fibrillin message levels with increasing age. The abundance of fibrillin in relation to elastin may suggest a role for EAMF independent of their association with elastin.