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Biomedical subjects

W R Castañeda-Zúñiga

Publications and source records attributed to W R Castañeda-Zúñiga.

At least 19 recordsLinked to original sources
PubMed1999

A simplified arteriovenous malformation model in sheep: feasibility study.

BACKGROUND AND PURPOSE: Recently, a swine model of a cerebral arteriovenous malformation (AVM) has been developed that closely resembles a human AVM of the brain. The creation of such a model requires sophisticated neurointerventional techniques. The purpose of this study was to develop a simple and cost-effective AVM animal model that does not require additional endovascular techniques. METHODS: A surgical anastomosis was created in seven sheep between the common carotid artery and the ipsilateral jugular vein, followed by ligation of the jugular vein above the anastomosis and of the proximal common carotid artery below the anastomosis. The anastomosis was created on the left side in four animals and on the right side in three. Cerebral angiography from the contralateral carotid artery was performed before and immediately after surgery to delineate the relevant cerebral vascular anatomy and to determine the direction of blood flow. RESULTS: An angiographic appearance simulating an AVM was found in all the animals. The ramus anastomoticus and arteria anastomotica functioned as the feeding vessels to the rete mirabile, which represented the nidus in our model, and to the jugular vein, which represented the draining vein from the malformation. Extensive collateral flow through the rete mirabile into the distal segment of the external carotid artery above the ligature was observed angiographically, with retrograde flow through the surgical anastomosis into the jugular vein. CONCLUSION: A simple surgically created experimental model for cerebral AVMs was developed in sheep without the need for additional complex endovascular catheter manipulations of intracranial branches. Such an animal model can substantially reduce the cost of research and training in the neurointerventional or radiosurgical management of AVMs.

Anastomosis, Surgical↗
PubMed1996

Effect of transjugular intrahepatic portosystemic shunt on quality of life.

OBJECTIVE: The objective of this study was to determine the effect of the transjugular intrahepatic portosystemic shunt (TIPS) procedure on the quality of life. SUBJECTS AND METHODS: Data were collected on 99 patients who underwent the TIPS procedure between September 1991 and September 1995. Quality of life was assessed by the Karnofsky scale before and at intervals after the procedure. Procedure-related complications and other aspects of the patients' overall well-being, as reflected in liver and kidney function and nutritional status, were reviewed immediately before and after TIPS creation. Finally, mortality and TIPS patency rates were tabulated. RESULTS: We observed significantly improved quality of life. The quality of life remained significantly improved throughout the 24-month follow-up period. During the 1- to 3-month interval after the TIPS procedure, we observed in patients a significant decrease in blood urea nitrogen and an increase in albumin and bilirubin. During this period, patients had no significant change in liver enzymes, prothrombin time, ammonia, or creatinine. Complications of the TIPS procedure included a 30% incidence of new or worsened encephalopathy and a 15% incidence of other severe complications (intraperitoneal hemorrhage, severe accelerated liver failure). The procedure-related death rate was 5%. Longer term follow-up showed an overall sustained decrease in blood urea nitrogen, an increase in albumin, and a return of bilirubin to the pre-TIPS levels or below. CONCLUSION: For patients who survive longer than 1 month, TIPS results in an overall, sustained improvement in the quality of life. Improved quality of life may result from a low incidence of repeat variceal bleeding, decreased ascites, and improved nutritional status.

Adolescent↗
PubMed1995

Duplex sonography after transjugular intrahepatic portosystemic shunts (TIPS): normal hemodynamic findings and efficacy in predicting shunt patency and stenosis.

OBJECTIVE: Portal hemodynamics are altered by placement of a transjugular intrahepatic portosystemic shunt (TIPS). Normal duplex sonographic findings after TIPS placement and hemodynamic alterations indicating shunt failure have not yet been well described. The purposes of this study were to determine normal hemodynamic changes on duplex sonography after TIPS placement and to assess the efficacy of duplex sonography in detecting shunt dysfunction. SUBJECTS AND METHODS: Forty patients underwent TIPS placement and were entered into a study that included routine sonographic evaluation and portal venography at regular intervals. Portal venography was also performed if shunt velocities on duplex sonography changed from the baseline, which raised the question of shunt stenosis or occlusion. The pre-TIPS duplex sonographic study included determination of patency, velocity, and flow direction in the main, right, and left portal veins and in the hepatic artery. Follow-up sonography included the pre-TIPS examination in addition to velocity determinations in three segments of the shunt. Correlation was made between 82 concurrent sonographic and portal venographic studies. RESULTS: High-velocity blood flow (mean peak velocity, 135-200 cm/sec) was consistently seen within patent, well-functioning shunts. Hepatic artery peak systolic velocities increased from 79 cm/sec before TIPS placement to 131 cm/sec after TIPS placement (p < .001). Main portal vein velocities increased from 21.8 cm/sec before TIPS placement to 41.5 cm/sec after TIPS placement (p < .001). When compared with portal venography, duplex sonography was 98% sensitive and 100% specific in predicting the presence of blood flow within the stent. Sonography was highly sensitive and specific for detecting stent stenosis. Final sonographic criteria for shunt stenosis in angiographically documented cases were low-velocity shunt flow (< or = 60 cm/sec) in the entire stent, or low-velocity shunt flow with an associated focal velocity elevation. CONCLUSION: Consistent changes in portal venous and hepatic arterial hemodynamics are normally seen on duplex sonography after placement of a TIPS. Duplex sonography accurately predicts shunt patency and dysfunction when compared with portal venography. Duplex sonography is an effective, noninvasive method of evaluating shunt function and should be considered for use as the primary imaging technique in routine follow-up after TIPS placement.

Adolescent↗
PubMed1995

The forgotten indwelling ureteral stent: a urological dilemma.

Ureteral stents are an integral part of urological practice. However, stents that migrate, fragment or are forgotten pose a management and legal dilemma. Our series consists of 31 patients, 22 with forgotten stents that were left indwelling for more than 6 months (mean 22.7) and 9 migrated stents. Of the forgotten stents 15 (68%) were calcified, 10 (45%) were fragmented, and 3 (14%) were calcified and fragmented. Procedures to render the patient stent-free were ureteroscopy in 16 (52%), percutaneous nephroscopy in 8 (26%), cystoscopic electrohydraulic lithotripsy in 6 (19%), extracorporeal shock wave lithotripsy in 10 (32%), open cysto-litholapaxy in 1 (3%) and simple nephrectomy in 1 (3%). Multiple procedures were required in 6 patients (19%). Management of such complicated ureteral stents requires a multimodal therapeutic approach incorporating the latest in extracorporeal shock wave lithotripsy and endourological techniques. These patients are at increased risk for loss of renal function. A computerized tracking registry of ureteral stents may help prevent this urological travesty.

Adult↗
PubMed1994

Development of stenoses in transjugular intrahepatic portosystemic shunts.

PURPOSE: To evaluate the frequency and significance of stenoses or occlusions developing within transjugular intrahepatic portosystemic shunts (TIPS) and identify predictive factors. MATERIALS AND METHODS: Medical records of 52 patients who underwent TIPS placement between September 1991 and October 1993 were reviewed. Various shunt parameters were correlated with the development of shunt abnormalities. Findings at follow-up portography and frequency of variceal bleeding and paracentesis were also noted. RESULTS: Twenty-four patients were followed up for at least 6 months. In eight patients, stenoses developed within 6 months; one shunt occluded. No clear correlations were found between shunt parameters and development of shunt abnormalities. Two of four patients with recurrent variceal bleeding had associated shunt abnormalities. The frequency of stenosis of TIPS was high. CONCLUSION: Early detection and prompt revision of stenotic shunts may decrease the frequency of recurrent variceal bleeding and ascites.

Adolescent↗
PubMed1994

Color Doppler sonography of transjugular intrahepatic portosystemic shunts (TIPS).

Transjugular intrahepatic portosystemic shunts (TIPS) have largely replaced surgically created shunts in the treatment of life-threatening sequelae of portal venous hypertension [1-5]. Conventional duplex and color Doppler sonography are proving to be useful tools in the assessment of the stents and their associated hemodynamic changes [2-5]. A thorough Doppler survey before and immediately after TIPS placement provides a baseline for evaluation of shunt function and procedure-related complications. Routine follow-up studies at regular intervals after the procedure provide noninvasive assessment of shunt patency and late complications. This pictorial essay illustrates the anatomic and hemodynamic abnormalities present with portal hypertension before TIPS and discusses the expected duplex and color Doppler findings after TIPS. The sonographic characteristics of immediate and delayed complications, as well as potential diagnostic pitfalls, are discussed.

Follow-Up Studies↗
PubMed1993

Evaluation of a new vascular occlusion device.

RATIONALE AND OBJECTIVES: A new vascular occlusion device was tested in canine femoral and iliac arteries and in an animal model of a patent ductus arteriosus (PDA). METHODS: Four variations of the vascular plug were placed into 18 iliac or femoral arteries of 17 mongrel dogs. Follow-up angiography was performed 1 hour and, if necessary, 2 hours after placement in all animals, 14 of which were then killed. Three dogs were followed angiographically for 2 weeks to 3 months. The "butterfly" plug was then tested in a canine model of a PDA. RESULTS: All plugs contained thrombi, and 12 of the 18 devices caused complete or nearly complete vascular occlusion within 2 hours. In one dog, one vascular plug had eroded through the vessel wall at 3 months without clinical sequelae. Successful PDA occlusion was achieved in 1 or 2 days in 6 of 8 dogs. Three misplacements occurred, one of which resulted in death. DISCUSSION: The balloon-expandable vascular plug appears to be a promising device for occlusion of blood vessels. Migration has not been observed once the device is placed, thus, sizing of the device appears less critical than with coils. However, modification of the delivery system and considerably more experience with the device are necessary to reduce the risk of misplacement.

Animals↗
PubMed1993

Transjugular intrahepatic portosystemic shunt: early experience with a flexible trocar/catheter system.

OBJECTIVE: The purpose of this study was to determine the feasibility of using a flexible trocar/catheter system to create a transjugular intrahepatic portosystemic shunt (TIPS). SUBJECTS AND METHODS: A flexible needle/trocar was used to connect the hepatic vein to the portal vein in 23 patients with portal hypertension and a history of bleeding gastroesophageal varices. Five patients had signs and symptoms of encephalopathy before shunting; in four, the disease was classified as Child's class C and in one, as Child's class B. Nine-millimeter self-expandable metallic stents were used in all patients. RESULTS: The procedure was technically successful in all patients. The mean portosystemic pressure gradient decreased from 26 to 16 mm Hg (range, 7-23 mm Hg). Eight patients have died. One patient in a hepatic coma with hepatorenal failure survived percutaneous portosystemic shunting, but died 2 days after the TIPS procedure was done. After creation of the shunt, three other patients died of unrelated disease without recurrence of bleeding from gastroesophageal varices. Two patients died of massive bleeding from esophageal varices, one 24 hr after shunting and one of disseminated intravascular coagulation after a second attempt to establish a shunt. One patient died of sepsis associated with infected ascitic fluid 2 months after the TIPS procedure was done, and one died of unknown causes 4 months after the procedure was done. The mean follow-up time in the surviving 15 patients was 12 months. Seven patients had recurrence of gastrointestinal bleeding; the recurrence was due to a thrombosed shunt in two, to hepatic vein stenosis in four, and to a high portosystemic pressure gradient (22 mm Hg) after creation of the shunt in one. Hepatic vein stenosis was noted on portal venograms in another three otherwise asymptomatic patients. In four of five patients, encephalopathy was adequately controlled after shunting. The fifth patient with encephalopathy (Child's class C) and an additional patient in whom encephalopathy (Child's class C) developed after the TIPS procedure have had two additional hospital admissions because of difficulty in controlling the encephalopathy. The amount of ascitic fluid decreased or totally disappeared after treatment in all cases. No severe complications associated with creation of a TIPS were observed. CONCLUSION: Use of a flexible trocar/catheter system to create a TIPS is a simple, safe, and moderately reliable means of decompressing the portal vein in patients with portal hypertension.

Adult↗
PubMed1992

Portal vein reflectors: duplex sonographic appearance.

Duplex sonography has established utility in the noninvasive evaluation of the portal venous system. Recently, the duplex sonographic features of suspected portal venous air have been described. We report on an experimental study in dogs undertaken to establish if the same sonographic features could be reproduced in a laboratory setting and to determine if small fragments of clot emboli could produce similar gray-scale and Doppler findings. Injections of microbubbles of air and clot fragments into the portal venous system were monitored using duplex ultrasound. The gray-scale and Doppler features of flow in the main portal vein were indistinguishable in both microbubble and clot injections. Superimposition of high-amplitude spikes on the normal portal venous waveform was seen in 19 of 24 (79%) microbubble and 13 of 23 (56%) clot fragment injections. We conclude that the appearance of rapidly moving, bright intraluminal echoes coupled with spike-like aberrations of the portal venous waveform can be associated with portal venous air bubbles or small blood clot emboli.

Animals↗
PubMed1991

Nitinol gooseneck snare for removal of foreign bodies: experimental study and clinical evaluation.

The authors describe their use of a new right-angle snare made of nickel-titanium (nitinol) cable for retrieval of foreign bodies and iatrogenically placed devices. The snare loop is at right angles to the cable and comes in five sizes (5, 10, 15, 25, and 35 mm); its radiographic visualization is enhanced by gold-plated tungsten coils. This snare was used to retrieve wire and catheter fragments introduced into the thoracic vasculature of four dogs. Eleven of 13 attempts were successful. Three attempts to retrieve intravascular foreign bodies were successful in two patients; in one of these patients, a 10-mm snare was used to remove a fractured end of a ventriculoatrial shunt tube from the left pulmonary artery. In three other patients, four ureteral stents were successfully removed under fluoroscopic guidance. All retrievals were performed through a vascular sheath and with standard techniques and angiographic equipment. No complications were seen in any of the patients or dogs.

Alloys↗
PubMed1991

1990 ARRS Executive Council Award. Intravascular sonography in the detection of arteriosclerosis and evaluation of vascular interventional procedures.

The purpose of this study was to evaluate the use of intravascular sonography for the detection of arteriosclerosis and to determine the effects of vascular interventional procedures on the arterial wall. A catheter-based 20-MHz transducer was used. Forty patients were studied. Twelve had clinical evidence of peripheral vascular disease, 13 were healthy renal donors, and 15 underwent vascular interventional procedures. The aorta and the ipsilateral iliac artery were examined in real time under fluoroscopic guidance and the results were compared with angiography. Sonography in eight of the 13 renal donors showed arterial wall abnormalities in the absence of angiographic evidence of disease. Sonography of the 15 patients after angioplasty or atherectomy demonstrated plaque fractures, intramural dissections, or atherectomy grooves. Our experience suggests that intravascular sonography is of value in reducing the use of angiography to monitor progress or complications of vascular interventional procedures.

Adult↗
PubMed1990

Prostatic urethroplasty with balloon catheter as a nonsurgical alternative for prostatic hyperplasia.

Prostatic urethroplasty with balloon catheter is a new interventional uroradiological procedure that appears promising in treating benign prostatic hyperplasia in selected patients. As with many of the interventional radiographic procedures, it reduces the cost of therapy, it is associated with very low morbidity in an outpatient setting, and it can be performed in almost any patient, regardless of their medical condition. The recovery period is minimal. The procedure is easy to perform, but certain guidelines have to be followed to avoid complications. The workup of these patients is relatively the same as a patient undergoing surgical intervention. The patient needs to be thoroughly assessed to exclude the possibility of prostatic malignancy.

Catheterization↗
PubMed1990

Use of Gianturco self-expandable stents in the tracheobronchial tree.

Gianturco self-expandable stents were used successfully in the management of 5 patients with tracheobronchial pathology. Placement was performed under endoscopic and fluoroscopic guidance. None of the patients has experienced complications secondary to the stent placement, and in all of them the clinical problems resolved satisfactorily. Longer follow-up is required to determine the place of tracheobronchial stenting in patients with respiratory compromise.

Aged↗
PubMed1990

The Simpson atherectomy catheter in the management of complete obstructions.

The Simpson atherectomy catheter has been used successfully to recanalise eleven complete occlusions of the iliac and femoropopliteal arteries. Atherectomy and angioplasty were used in combination in 8 cases. Following atherectomy, all patients showed clinical improvement. Distal pulses returned in 7; rest pain and/or claudication disappeared in the other 4. Ischaemic ulcers healed in the 2 affected patients. Overall, ankle-arm indices (AAI) improved by an average of 0.43, with the improvement being greatest (0.55) in patients in whom the lumen was recanalised to within 91-100% of the native luminal diameter. Seven patients have remained with stable AAI values and without change in their clinical status at 18 months follow-up.

Adult↗
PubMed1990

The inferior vena cava clip. The percutaneous approach.

Pulmonary embolism in high-risk patients may be minimized by surgical inferior vena cava (IVC) clipping or by the insertion of caval filters. A percutaneous clipping technique was developed that narrows the cava while allowing caval patency. The caval clip is inserted through a percutaneous translumbar approach under fluoroscopic control. Nine dogs underwent percutaneous translumbar caval clip placement without complications. Three of four dogs, followed-up for 5 to 19 weeks by angiography and caval pressure measurements, showed caval patency. This technique eliminates the risks of surgical IVC clip placement and risks from the insertion of intravascular foreign bodies such as filters.

Angiography↗
PubMed1989

Mortalities associated with use of a commercial suspension of polyvinyl alcohol.

Two cases of symptomatic neonatal hepatic arteriovenous malformation (AVM) are presented. Both were treated with percutaneous transcatheter embolization and a commercially available polyvinyl alcohol suspension. Both infants died soon after AVM embolization. The results of laboratory examination of particle-size homogeneity of this commercial suspension demonstrate marked inhomogeneity of particle size very probably contributed to the death of these patients. A protocol has been developed to help determine appropriate particle size in individual cases; this may help prevent such catastrophic results during transcatheter embolization.

Arteriovenous Malformations↗