An aortic aneurysm model for the evaluation of endovascular exclusion prostheses

PURPOSE

The purpose of this study was to develop an aortic aneurysm (AA) model with a predictable tendency for rupture for the evaluation of the efficacy of endovascular prostheses in preventing rupture and their long-term outcome after implantation.

METHODS

An infrarenal AA measuring two to three times the diameter of the proximal aorta was created in 18 dogs with a full-thickness patch of jejunum. Seven dogs were allowed to survive without aneurysm exclusion. In 11 dogs the aneurysm was immediately excluded with a stented 8 mm Dacron graft mounted in a 14F delivery system introduced through the femoral artery with aortographic guidance. The pressure differential between the aorta and the excluded aneurysm was measured, and angiography, necropsy, and histologic examination were performed at 3- and 6-month survival.

RESULTS

All animals survived aneurysm implantation. Without aneurysm exclusion, six dogs died of rupture within 1 to 6 days of surgery. In three dogs the exclusion failed because of graft-to-aorta size mismatch or misplacement demonstrated on angiography and by a low pressure differential between the aorta and the aneurysm (< 5 mm Hg); all three dogs died of rupture within 4 days. In eight dogs the aneurysm was successfully excluded on the basis of angiography results, with a mean aorta-to-aneurysm pressure differential of 51 mm Hg. Two dogs were killed at 1 and 6 days after surgery because of paraplegia produced by graft thrombosis because of kinking but without evidence of aneurysm rupture. Six dogs survived on a long-term basis, and angiography and necropsy performed at 3 and 6 months revealed patent grafts without migration, reduction in aneurysm size, no flow in the excluded lumbar arteries in five of six animals, and complete incorporation of Dacron graft and stents. No evidence of graft infection was found in any animal. The survival rate was significantly better (p < 0.023) in dogs with successfully excluded aneurysms (n = 6) compared with that in dogs without exclusion or with failed aneurysm exclusion (n = 7).

CONCLUSION

This aneurysm model demonstrates that without effective aneurysm exclusion all animals die of rupture and that successfully placed endovascular prostheses can prevent AA rupture with long-term graft patency and stability. Endovascular aortic Dacron grafts in dogs undergo complete incorporation at 3 months from implantation. This aneurysm model is useful for the evaluation of endovascular devices designed for the treatment of AAs.

The first rib as a fluoroscopic marker for subclavian vein access

PURPOSE

To determine whether the anatomic relationship between the subclavian vein (SCV) and the first rib is sufficiently constant to allow safe and reproducible fluoroscopically guided SCV puncture.

MATERIALS AND METHODS

Forty-four subclavian venograms were obtained from 42 consecutive adult patients. Position and width of the SCV crossing over the first rib were recorded by using radial coordinates. Based on this anatomic study, 42 SCV access procedures were performed with use of the first rib as a fluoroscopic marker. Technical success, complications, number of 21-gauge needle passes, physician experience, and patients' body habitus were recorded.

RESULTS

Mean angular position of SCV/first rib crossover was 94.7 degrees (standard deviation [SD], 7.42 degrees). Mean radial width of the SCV was 14.9 degrees (SD, 3.1 degrees). On 25 of the 44 subclavian venograms (60%), the SCV/first rib crossover lay within the 90 degrees-99 degrees segment, and on 36 of 44 (82%) it lay within the 85 degrees-104 degrees segment. Technical success in accessing the SCV was 100% (42 of 42 procedures). Two minor complications involved subclavian artery puncture with the 21-gauge needle without sequelae. The mean number of needle passes required was 2.86 (median, 1.7). There was no correlation between needle passes and patients' body habitus or physician experience.

CONCLUSION

The SCV is reliably constant in its relation to the first rib. The first rib alone provides a reliable fluoroscopic marker for safe SCV access without the need for ultrasound guidance or peripheral contrast material administration.

Transbrachial endovascular exclusion of an axillary artery pseudoaneurysm with PTFE-covered stents

PURPOSE

Endovascular exclusion of arterial injuries associated with arteriovenous fistulas and pseudoaneurysms has only recently been described using various stent-graft prostheses. This report details a transbrachial technique used to exclude an axillary artery pseudoaneurysm developing at the axillary anastomosis of an axillofemoral graft.

METHODS AND RESULTS

Thin-walled polytetrafluoroethylene was expanded with an angioplasty balloon catheter and used to cover standard Palmaz stents. Two covered stents were delivered under fluoroscopic guidance via open brachial artery access to the site, resulting in complete exclusion of the pseudoaneurysm. Follow-up duplex scanning confirmed aneurysm exclusion 3 months postprocedure.

CONCLUSIONS

This technique can be applied in arteries of different sizes and lengths, using currently available materials. However, the long-term behavior of these devices in the arterial tree must be determined before their widespread use can be recommended for most indications.

Proximal venous outflow obstruction in patients with upper extremity arteriovenous dialysis access

To evaluate the impact of central venous obstruction on upper extremity hemodialysis access failure, we retrospectively analyzed our recent experience in managing this problem. We reviewed 158 upper extremity hemodialysis access procedures performed in 122 patients during a 1-year period. Fourteen (11.5%) patients had central vein obstruction as the cause of severe arm swelling, graft thrombosis, or graft malfunction. All 14 patients had had bilateral temporary subclavian vein dialysis catheters and failed upper extremity arteriovenous access. Seventeen lesions were treated in 14 patients including eight subclavian vein occlusions, six subclavian vein stenoses, two internal jugular vein stenoses, and one superior vena cava stenosis. Twenty-one procedures were performed including 17 percutaneous transluminal balloon angioplasties (PTAs) with stent placement in 13, two axillary to innominate vein bypasses, and two axillary to internal jugular vein bypasses. All patients had resolution of symptoms. Thirteen (76%) PTAs were initially successful but in four (24%) cases it was impossible to recanalize the vein. Eight (47%) PTAs provided functional hemodialysis access for 2 to 9 months, two (12%) restenosed at 3 and 10 months and were successfully redilated, two occluded at 2 and 4 months and were unable to be recanalized, and one failed immediately after a successful PTA. Four PTA failures were followed by venous bypass, which remained patent and provided functional access 7 to 13 months after surgery. Of nine stenotic venous lesions six (67%) were successfully dilated without restenosis, whereas of eight occluded veins only two (25%) were successfully treated without recurrence. Temporary central hemodialysis catheters produce a significant number of symptomatic central vein obstructions in patients with upper extremity arteriovenous access.(ABSTRACT TRUNCATED AT 250 WORDS)

Computed tomography interpretations with a low-cost workstation: a timing study

An ergonomically simple prototype workstation with two 900 x 1,100-pixel monitors capable of displaying eight full-resolution computed tomography (CT) images in 0.2 seconds, was compared with film for interpretation of computed tomographic images of the chest and abdomen. The hardware platform for this workstation cost less than $11,500 in 1993. A repeated-measures experiment was used to generate average interpretation times of 6.17 minutes for the workstation and 6.03 minutes for the film, including loading and unloading films, with three of the four subjects averaging about a minute longer for each workstation interpretation. All dictated reports were of clinically acceptable accuracy. All radiologists stated that workstations based on this design would be an acceptable clinical tool. However, observation suggested human working-memory strain among infrequent CT readers that could indicate the need for additional training. These data suggest that low-cost workstations can have practical application in interpretation of digital medical images such as CT, with the possibility of small increases in interpretation time.

Variations in liver-colon anatomic relationship: relevance to interventional radiology

PURPOSE

To determine the prevalence of significant variations in liver-colon anatomy in an unselected patient population and evaluate the potential effect of these variations on liver-related interventional procedures.

PATIENTS AND METHODS

All abdominal computed tomographic (CT) scans were reviewed prospectively over a 4-month period. Cases that revealed variant hepatocolic anatomy were selected and analyzed for the position of the colon, gallbladder, and duodenum; liver morphology; and the anatomic relations of the right portal vein.

RESULTS

Seventeen (3.3%) of 517 abdominal CT scans demonstrated variant hepatocolic anatomic relations. In seven cases, liver lobar morphology was normal, but the colon was interposed between the chest wall and the liver. The remaining 10 cases were characterized by hypoplasia or aplasia of one or both segments of the left lobe. In these cases the right portal vein was anteriorly exposed and was close to the gallbladder and transverse colon. In all 17 cases it was qualitatively judged that technical modifications might be needed in the performance of various interventional procedures, including percutaneous biliary drainage, biopsies, and transjugular intrahepatic portosystemic shunt creation.

CONCLUSION

Variations in liver-colon anatomic relations in isolation or secondary to hepatic developmental anomalies may have a significant potential impact on the performance of various fluoroscopically guided hepatobiliary interventional procedures.

Interpretation of CT studies: single-screen workstation versus film alternator

A prototype single-screen workstation with a 2,048 x 2,560-pixel high-brightness monitor, 0.11-second image display time, and simple ergonomic design was compared to a conventional horizontal film alternator in diagnostic interpretation of chest computed tomography (CT) studies. Four radiologists used either the workstation or film alternator in interpretation of studies obtained in 10 patients. A counterbalanced within-subject repeated measures experimental design was used. Response times were analyzed for both methods of interpretation. Grades of excellent, acceptable, and unacceptable were assigned by a blinded "grader" to reports of the radiologists. The average time needed for an interpretation at the workstation was 5.65 minutes. No interpretations were graded unacceptable. Retrospective power analysis showed that 16 observers rather than four would have been required to show that use of the workstation was faster than the alternator. With this 95% confidence interval, the workstation interpretation time is clinically equivalent to that with the alternator. These data show that this type of workstation has practical application in interpretation of CT, magnetic resonance imaging, and ultrasound studies.

The spleen and its vasculature in pancreatitis: CT findings

The spleen and its vasculature are susceptible to damage from pancreatic inflammatory exudates. Fourteen patients were identified who demonstrated splenic or splenic vascular involvement from pancreatitis on computed tomography. Findings included intra- and perisplenic inflammatory fluid collections (n = 6), acute splenic hematomas (n = 3), splenic infarction (n = 1), splenic artery pseudoaneurysm (n = 1), and splenic vein thrombosis (n = 6). Eight of the 14 patients went on to urgent interventions including percutaneous catheter drainage (n = 2) and transcatheter embolotherapy (n = 6) based on the CT findings.

Radiologic placement of long-term central venous catheters: a review

The need for long-term placement of catheters within the central venous system is continually expanding and follows the increasing use of hemodialysis, total parenteral nutrition, and long-term chemotherapy for neoplastic and infectious diseases. Whereas these catheters have traditionally been placed by surgeons in an operating room, it is now clear that they can be effectively placed by interventional radiologists using percutaneous techniques within an interventional/angiographic suite. This review is based on the radiologic percutaneous placement of nearly 1,500 central venous catheters including approximately 500 tunneled Hickman/Leonard catheters, 350 double-lumen cuffed dialysis catheters, and 150 chest wall subcutaneous ports.

CT diagnosis of paraduodenal hernia

The computed tomographic (CT) findings of a right and left paraduodenal hernia are described. In the right paraduodenal hernia the major findings consist of encapsulation of small bowel loops in the right mid-abdomen with looping of arterial and venous jejunal branches behind the superior mesenteric artery. The findings of the left paraduodenal hernia are less specific and involve encapsulation of bowel loops at or above the level of the ligament of Treitz with intermittent dilatation.

Radiology-assisted placement of implantable subcutaneous infusion ports for long-term venous access

Implantable infusion port devices are generally placed surgically. A technique for radiology-guided placement in adults is described, and the experience with 103 attempted port placements between June 1989 and October 1991 is analyzed. Placements were successful in 102 attempts (99%). Minor procedural difficulties occurred in six patients (5.9%). One major procedural complication (large hematoma) precluded port placement. Two patients were lost to follow-up after uncomplicated placements. There were four (4.0% of 100 patients) minor late complications. Major late complications requiring port removal occurred in 13 (13.0%): five suspected catheter-related infections, four catheter-related venous thromboses refractory to thrombolysis, and one each of wound dehiscence, formation of hematoma near the port, extraluminal migration of the catheter, and poor blood return. With a cumulative follow-up of 15,880 days (43.5 patient-years) available, a rate of major complications of 13.6%, or 0.86% per 1,000 access days, is comparable to the rates of large surgical series. Radiology-guided placement of infusion ports is safe and may offer advantages over surgical implantation.

US guidance for vascular access. Technical note

Real-time ultrasonography (US) is frequently used to access the biliary tree, urinary system, and pleural cavity, as well as abscesses and other fluid collections, but is rarely used to access blood vessels. This article describes the clinically indicated circumstances and technical aspects of US-guided access to veins and arteries. The authors' experience suggests that appropriate use of this modality significantly simplifies vascular access difficulties, reduces procedure time and morbidity, and is cost-effective.

Percutaneous translumbar and transhepatic inferior vena caval catheters for prolonged vascular access in children

Central venous access for children with caval occlusion remains a major challenge to pediatric surgeons. Traditionally, children with superior and inferior vena cava (SVC, IVC) thrombosis have often required a thoracotomy to directly cannulate the azygos system or right atrium (RA). Recently, the possibility of placing tunneled RA catheters (RACs) by a percutaneous translumbar or transhepatic approach has become available. We report our experience of seven children with SVC and IVC obstruction who have received 11 transhepatic and 4 translumbar RACs from 1987 to 1991. All but one child was less than 2.5 years old and all were chronically dependent on parenteral nutrition. All catheters were placed in the angiography suite under general anesthesia using ultrasound guidance and Seldinger technique. This technique was successful in all seven children. Perioperative complications included accidental extubation in one patient and aspiration pneumonia in another. Mechanical complications requiring RAC replacement occurred 5 times in three infants (greater than 2,650 catheter days) and included catheter dislodgement (2) and thrombosis (3). In the patients with catheter thrombosis, the existing tract was successfully wired and the catheter exchanged on three occasions. Thrombolytic therapy was effective in restoring catheter patency on three other occassions. Nine episodes of catheter sepsis occurred in five children. Two late deaths occurred from infection. Of the five remaining children, four are dependent on total parenteral nutrition and have a translumbar or transhepatic catheter in situ and one child has adapted successfully to enteral feedings. Percutaneous translumbar or transhepatic IVC catheters provide excellent alternative routes for prolonged central venous access in those patients whose traditional vascular access sites are no longer available. Complications of the technique itself were minimal and although late catheter complications were not infrequent, they appear to be comparable to the standard approaches reported.

Intrahepatic hepatic artery aneurysm: computed tomography and color-flow Doppler ultrasound findings

An unusual case of intrahepatic hepatic artery aneurysm (IHAA) is presented, in which the diagnosis was initially suspected on computed tomography (CT) and confirmed on color-flow Doppler ultrasound (US). The literature regarding this entity, as well as the utility of color-flow Doppler US in this setting are discussed.

Case report: splenic infarction and acute splenic sequestration in adults with hemoglobin SC disease

While acute splenic sequestration and splenic infarction are commonly observed in infants and young children with sickle cell anemia, they are rarely experienced by adult hemoglobin S homozygotes because the recurrent splenic infarction that takes place during childhood is typically followed by scarring, atrophy, and splenic fibrosis. Both acute splenic sequestration and splenic infarction do remain relatively common in adults with the other sickle hemoglobinopathies. These episodes are almost certainly a consequence of the persistently enlarged and distensible spleens that often remain present in these conditions. In this report, the authors describe two adult patients with hemoglobin SC disease: one who developed acute splenic sequestration and one with splenic infarction. In neither case was there a history of recent air travel or exposure to altitude. The clinical course of these two syndromes is presented, and the hematologic, radiologic, and pathologic manifestations are discussed. Because they can sometimes be difficult to distinguish from one another, and because a failure to identify acute splenic sequestration can be catastrophic, these two entities must be included in the differential diagnosis for any hemoglobin SC patient who present with an unexplained fall in hemoglobin, left upper quadrant pain, unexplained fever, or symptomatic splenomegaly.

Transcatheter management of pseudoaneurysms complicating pancreatitis

Hemorrhage from rupture of an arterial pseudoaneurysm is a potentially fatal complication of pancreatitis. Seventeen patients underwent transcatheter embolization of 23 arteries for the treatment of 20 arterial pseudoaneurysms secondary to pancreatitis. Their records were reviewed retrospectively to evaluate the clinical benefit of transcatheter therapy. At presentation, 15 of the 17 patients had gastrointestinal, intrasplenic, retroperitoneal, intraperitoneal, or postoperative wound bleeding. Transcatheter embolotherapy was the sole treatment for 16 (80%) of the 20 pseudoaneurysms in 13 patients. Four pseudoaneurysms (20%) in four patients were treated prior to splenectomy. Transcatheter therapy was clinically beneficial in all patients. Three patients had procedural complications without significant clinical sequelae. Transcatheter embolotherapy should be the initial treatment of choice in patients with arterial pseudoaneurysms secondary to pancreatitis. Treatment may be definitive or facilitate subsequent surgery.

Evaluation of T1N0M0 lung cancer with CT

Medical records and radiologic studies of 238 patients with non-small cell lung cancer who had preoperative evaluation by chest radiography and CT were reviewed. Thirty-six patients were staged as T1N0M0 by chest radiograph. Of this group, 18 (50%) had abnormalities on CT requiring additional evaluation. Confirmation of abnormalities was by tissue sampling or clinical follow-up. Evidence for unresectable spread of disease was obtained in 12 (33%). We conclude that routine preoperative staging of T1N0M0 lung cancer with CT has a positive impact on patient management.

Amyloidosis: CT appearance of calcified, enlarged periaortic lymph nodes

The radiographic demonstration of lymph node involvement in amyloidosis is rare. We report a case of calcified, enlarged perioartic and mediastinal lymph nodes detected by CT.

Radiologic insertion of Hickman catheters in HIV-positive patients: infectious complications

Ninety-six patients undergoing radiologically guided placement of 104 Hickman catheters were grouped according to their human immunodeficiency virus (HIV) serologic status. Infectious complications were categorized according to their severity (local or systemic) and time of occurrence (periprocedural or late). The number of infectious complications per 100 indwelling catheter days was calculated. Among the 14 catheter placements in 13 HIV-positive patients, two systemic infections occurred, resulting in a 14% overall infection rate and 0.18 infectious complications per 100 indwelling catheter days. The remaining 83 HIV-negative patients underwent 90 Hickman catheter placements. Nine infectious complications (10%) were noted in the 90 catheters, translating into 0.19 infectious complications per 100 indwelling catheters days. These results suggest no significant (relative risk [RR] of 1.4 and .95) difference in infectious complication rates encountered in HIV-positive patients compared with the general population. This supports the clinical usefulness of Hickman catheter placement in HIV-positive patients, although many additional HIV-positive patients must be evaluated to achieve an acceptable level of statistical confidence.

Chronic posttraumatic aortic pseudoaneurysm. Recognition before rupture

Few patients survive transection of the aorta caused by blunt trauma. However, among those who do are a small number who go on to live with an unrecognized pseudoaneurysm that may rupture at any time. Because these aneurysms may be mistaken for more common disease processes, such as hilar adenopathy, atherosclerotic aneurysm, or neoplasia, the authors describe radiographic findings that suggest the correct diagnosis.

Antethoracic colonic esophagoplasty for esophageal atresia: long-term follow-up

We report a case of a 23-year-old woman who underwent antethoracic colonic esophagoplasty at age 3 years 10 months for failed intrathoracic correction of tracheoesophageal fistula and esophageal atresia. The appearance of this rarely performed procedure is shown with barium swallow and computed tomography.

Computed tomography of hepatic venous hypertension: the reticulated-mosaic pattern

A reticulated-mosaic pattern of the liver was identified on contrast-enhanced computed tomography in 4 of 20 patients with constrictive pericarditis or congestive heart failure. Reflux of contrast into a distended inferior vena cava and the hepatic veins was identified in 3 of the 4 patients. This abnormal enhancement pattern combined with hepatic venous or caval reflux of contrast indicates the presence of hepatic venous hypertension, and should not be mistaken for other abnormalities that may result in inhomogeneous hepatic enhancement.