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Biomedical subjects

C R Rees

Publications and source records attributed to C R Rees.

At least 19 recordsLinked to original sources
PubMed2001

Usefulness of catheter-directed thrombolysis using alteplase in peripheral vascular occlusion.

This study evaluated the safety and efficacy of alteplase in catheter-directed treatment for peripheral arterial and venous thrombosis and considered the optimal dosing regimen. Forty-four patients (49 encounters) underwent transcatheter therapy using alteplase between January and November 1999. The most common indications for thrombolysis were peripheral arterial occlusion (PAO) and venous thrombosis (38 patients, 43 encounters). Each encounter was reviewed for indication, dosage of alteplase, duration of infusion, concomitant use of anticoagulation, degree of lysis, and complications. Patients were divided into low-dose (0.5 to 1.0 mg/hr), mid-dose (1.0 to 1.5 mg/hr), and high-dose (>1.5 mg/hr) groups. For PAO, there was no significant difference in the success rate between the 3 dose groups. A lower complication rate was achieved in the low-dose group. For venous thrombosis, there was no difference in the overall success or complication rates for each of the 3 groups. Partial lysis was achieved more readily in the mid and high-dose groups, but the risk of serious complications was greater. Overall, the complete thrombolysis rate was 71% for PAO and 55% for venous thrombosis. Major and minor complication rates were 7% and 19%, respectively. An equivalent success rate with a lower complication rate can be achieved using a low-dose constant catheter-directed infusion of alteplase for cases of PAO. Cases of venous thrombosis had a lower overall success rate compared with PAO. A mid-dose infusion of alteplase can achieve greater complete and partial thrombolysis rates without increasing the complication rate. Major and minor complication rates were similar to the rates given in the published literature.

Journal Article↗
PubMed1999

Balloon rupture during stent implantation: A novel technique of salvage with a new manual power injector.

Pinhole leak or rupture of a stent delivery balloon is a well-recognized technical problem encountered in vascular interventions. This event leads to inadequate stent expansion. These stents cannot be fully deployed with the same balloon and frequently the balloon cannot be retrieved without dislodging the stent. We describe a technique for successful stent deployment in such situations using the Oz Power Syringe, a new manual power injector. Cathet. Cardiovasc. Intervent. 48:74-77, 1999.

Aged↗
PubMed1999

Stents for atherosclerotic renovascular disease.

There is extensive documentation of excellent clinical results with renal stents in patients who have technically failed angioplasty and who would have been expected to otherwise have a high incidence of clinical failure. In addition, the technical success of renal stents is vastly superior to that of conventional angioplasty in atherosclerotic renovascular disease, and stents have been a major factor in making the endovascular treatment of ASRVD both practical and reliable in experienced hands. Restenosis rates appear roughly equivalent or lower for stents versus PTA as far as can be determined without good comparative studies. Restenosis appears to be decreasing to 15%-20% in more recent series, perhaps because of the accumulation of knowledge regarding patient selection and techniques. It is, therefore, clear that the use of stents to treat technical failures of angioplasty will result in overall improved patency in the treated population; however, it remains to be determined whether stents should be routinely placed with the intention of inhibiting restenosis, in the presence of technically successful angioplasty with minimal residual stenosis or pressure gradient. Such a determination may require comparative study that is more complicated than a simple randomized comparison of angioplasty versus stents.

Algorithms↗
PubMed1996

Mesenteric angioplasty in the treatment of chronic intestinal ischemia.

PURPOSE: This study was undertaken to determine the safety and efficacy of percutaneous transluminal angioplasty (PTA) in the treatment of chronic mesenteric ischemia (CMI) in very high-risk surgical patients. METHODS: Twenty-four focal mesenteric stenoses treated from 1984 to 1994 by PTA in 19 patients with CMI were reviewed. All 19 patients were considered poor surgical candidates. Seventeen patients had classic symptoms of CMI, and two patients had atypical abdominal complaints. Vessels dilated included the superior mesenteric artery (18), celiac artery (3), inferior mesenteric artery (1), aorta-superior mesenteric artery vein graft (1), and aorta-splenic artery vein graft (1). Complete follow-up was possible in all patients, with the exception of one patient who had no symptoms when last seen 17 months after the procedure. RESULTS: PTA was technically successful in 18 of 19 patients (95%) and 23 of 24 stenoses (96%). The lone technical failure resulted in superior mesenteric artery dissection with thrombosis and bowel infarction; the patient died despite emergent laparotomy and revascularization (mortality rate, 5%). Complete symptomatic relief was attained in 15 patients (79%), with follow-up showing continued relief of symptoms for a mean of 39 months (range, 4 to 101 months). Partial symptomatic relief was attained in three patients. Recurrent symptoms developed in three patients (20%) at a mean interval of 28 months (range, 9 to 43 months). Repeat PTA performed in two patients provided good technical results and relief from clinical symptoms. One patient had a symptomatic axillary sheath hematoma that required surgical decompression. CONCLUSIONS: Mesenteric PTA is a valuable treatment option in patients who have CMI and are considered very high operative risks. The initial technical success rate is excellent, with the majority of patients having complete symptomatic improvement and continued relief of symptoms at short-term follow-up.

Aged↗
PubMed1995

A comparison of treatment with transjugular intrahepatic portosystemic shunt or distal splenorenal shunt in the management of variceal bleeding prior to liver transplantation.

Recurrent variceal bleeding in liver transplant candidates with end-stage liver disease can complicate or even prohibit a subsequent transplant procedure (OLT). Endoscopic sclerotherapy and medical therapy are considered as first-line management with surgical shunts reserved for refractory situations. Surgical shunts can be associated with a high mortality in this population and may complicate subsequent OLT. The transjugular intrahepatic portosystemic shunt (TIPS) has been recommended in these patients as a bridge to OLT. This is a new modality that has not been compared with previously established therapies such as the distal splenorenal shunt (DSRS). In this study we report our experience with 35 liver transplant recipients who had a previous TIPS (18 patients) or DSRS (17 patients) for variceal bleeding. The TIPS group had a significantly larger proportion of critically ill and Child-Pugh C patients. Mean operating time was more prolonged in the DSRS group (P = 0.014) but transfusion requirements were similar. Intraoperative portal vein blood flow measurements averaged 2132 +/- 725 ml/min in the TIPS group compared with 1120 +/- 351 ml/min in the DSRS group (P < 0.001). Arterial flows were similar. Mean ICU and hospital stays were similar. There were 3 hospital mortalities in the DSRS group and none in the TIPS group (P = 0.1). We conclude that TIPS is a valuable tool in the management of recurrent variceal bleeding prior to liver transplantation. Intraoperative hemodynamic measurements suggest a theoretical advantage with TIPS. In a group of patients with advanced liver disease we report an outcome that is similar to patients treated with DSRS prior to liver transplantation. The role of TIPS in the treatment of nontransplant candidates remains to be clarified.

Adult↗
PubMed1995

Multicenter investigation of the role of transjugular intrahepatic portosystemic shunt in management of portal hypertension.

PURPOSE: To determine the safety and efficacy of transjugular intrahepatic portosystemic shunt (TIPS) placement, a prospective multicenter trial was undertaken. MATERIALS AND METHODS: In eight institutions, 96 patients underwent TIPS placement after failed sclero-therapy (Child-Pugh class A [n = 24], class B [n = 38], and class C [n = 34]), with follow-up for 6 months (with ultrasonography and angiography and clinical and laboratory studies). RESULTS: TIPS placement was successful in all patients (mean initial portosystemic pressure gradient, 22.8 mm Hg + 6.7 [standard deviation]; mean decrease after placement, 12.8 mm Hg + 5.2), with variceal embolization in 25 patients. Complications included liver capsule puncture (n = 12), hepatic artery puncture (n = 3), main portal vein puncture (n = 1), and increased encephalopathy (n = 28). The 30-day mortality rate was 0% for patients with Child class A disease, 18% for class B, and 40% for class C. At 6 months, primary patency was 88% and assisted patency was 94%. CONCLUSION: The risk associated with TIPS placement is reasonable, and it is an effective procedure for the treatment of portal hypertension.

Case-Control Studies↗
PubMed1994

Double-blind study of a new nonionic contrast agent for digital subtraction arteriography.

RATIONALE AND OBJECTIVES: Since the development of the first low-osmolality contrast agent in 1969, a new group of ionic and nonionic compounds have emerged. These new agents have dramatically improved diagnostic imaging by exhibiting significant improvements in safety and technical efficacy over that of high-osmolality agents. This study was designed to compare the safety, tolerance, and technical efficacy of iopromide, a new low-osmolality, nonionic contrast agent, with that of both ioversol and iopamidol for digital subtraction angiography (DSA). METHODS: One hundred fifty patients with conditions requiring intraarterial digital subtraction angiography were randomly assigned to receive 150 mg I/mL iopromide or either 160 mg I/mL ioversol or 128 mg I/mL iopamidol. Cerebral, aortovisceral, and peripheral arteriography was performed. RESULTS: No significant difference was found in safety, tolerance, and technical efficacy between iopromide and ioversol. Iopamidol had significantly less technical efficacy than iopromide, but there were no significant differences in safety or tolerance between these two agents. CONCLUSIONS: All three contrast media (CM) are useful for cerebral DSA. Although these agents were diagnostically adequate for use during aortovisceral and peripheral DSA, none was able to optimally opacify vessels during these studies in the concentrations administered.

Adolescent↗
PubMed1991

Palmaz stent in atherosclerotic stenoses involving the ostia of the renal arteries: preliminary report of a multicenter study.

Palmaz balloon-expandable stents were placed in 28 hypertensive patients with atherosclerosis involving the ostia of the renal arteries. Stents were placed to treat elastic recoil immediately after conventional angioplasty in 20 patients and restenosis after percutaneous transluminal angioplasty in eight patients. Technical success (greater than 30% residual stenosis) was achieved in 27 patients. Complications occurred in five patients. At follow-up (1-25 months), hypertension was cured in three patients and improved in 15 patients, with a cumulative cure or improvement of 64% at 6 months. Of 14 patients with a serum creatinine level of 1.5 mg/dL (132.6 mumol/L) or greater before the placement of stents, five demonstrated improved renal function, five showed stabilization of their condition, and four demonstrated deterioration. Follow-up angiography (2-18 months) was performed in 18 patients. Restenosis was present in seven patients and was accompanied by a relapse of hypertension in only three patients. Of the other four patients with restenosis, two had no initial improvement and two had an initial response without a relapse of hypertension. In this preliminary study, renal stents were beneficial in many patients with poor results from conventional angioplasty for ostial atheroma.

Aged↗
PubMed1990

Placement of balloon-expandable intraluminal stents in iliac arteries: first 171 procedures.

Balloon-expandable intraluminal stents were used to treat iliac artery stenoses or occlusions that failed to respond to conventional balloon angioplasty. One hundred seventy-one procedures were performed in 154 patients, of whom 48 had a limb at risk for amputation. Thirty-six had severe and 70 had moderate intermittent claudication. At the latest follow-up examination (average, 6 months; range, 1-24 months), 137 patients demonstrated clinical benefit, 113 of whom had become asymptomatic. Eleven patients showed no initial benefit, and six improved initially but later developed new vascular symptoms. Complications occurred in 18 patients. In three patients, complications were directly related to the device. Two occlusions were successfully recanalized, and an intramural collection of contrast material secondary to balloon perforation evolved favorably. The remaining patients had groin hematoma (n = 6), distal embolization (n = 4), extravasation (n = 2), transient renal failure (n = 1), pseudoaneurysm at the puncture site (n = 1), or subintimal dissection (n = 1). All stents have remained patent to the latest follow-up examination without evidence of migration or aneurysm formation.

Adult↗
PubMed1990

Angioplasty-induced dissections in human iliac arteries: management with Palmaz balloon-expandable intraluminal stents.

Intravascular stent placement may be an effective treatment for percutaneous transluminal angioplasty (PTA)-induced dissection. Among the first 228 patients treated with Palmaz balloon-expandable intraluminal stents (BEISs) for iliac artery stenosis, stents were used to treat PTA-induced dissection in at least 12 iliac arteries in 11 patients. All 12 vessels were shown by angiography to be severely dissected. Stents were placed at the time of PTA in six vessels and as a separate procedure in the other six. An average of three stents per vessel were employed. All arteries showed marked improvement at angiography. Angiographic follow-up was obtained for eight vessels in seven patients at a mean follow-up time of 12.9 months. All had patent stent lumens with neointima formation, although one stented lumen had narrowed, and another clinical failure occurred despite a patent stented vessel and an ankle-arm index (AAI) of 1.35. With a mean clinical follow-up of 9.5 months, the mean AAI for the stented extremities in the nine remaining patients is 0.91 +/- 0.15. Palmaz BEISs are effective in the management of PTA-induced human iliac artery dissection.

Adult↗
PubMed1989

Nonselective digital subtraction angiography. Compact contrast material bolus for improved image quality.

Digital subtraction angiography (DSA) examinations of major aortic branch vessels traditionally have been performed with aortic injections of dilute contrast material (70-150 mg I/mL) over approximately 2 seconds. This study examines a technique employing rapid boluses of undiluted contrast material (282-300 mg I/mL) in small volumes and compares the quality of the images to those obtained using conventional methods. Twenty intra-aortic DSA angiograms of the renal arteries were performed in 10 patients. In each patient, both compact bolus and conventional injections were performed. Injections of 12 or 15 mL of diatrizoate meglumine-60% at 30 mL/second (duration = 0.4 or 0.5 seconds) were compared with injections of 24 or 30 mL of diatrizoate meglumine-30% at 12 mL/second (duration = 2 seconds). Aside from injection technique and image projection, no other variables were altered, and the iodine loads were the same for the two injections in each patient. The images were paired and rated by four radiologists without knowledge of the technical parameters. The radiologists overwhelmingly preferred the images corresponding to the compact bolus technique (Chi-square analysis P less than .001). Visualization of the main renal arteries and the intrarenal branches was improved (P less than .001 for both). A reduction in misregistration artifact is suggested but not statistically significant. We conclude that image quality in nonselective, intra-arterial DSA can be improved without an increase in iodine dosage by the rapid administration of undiluted contrast material in small volumes.

Adult↗
PubMed1989

Angioplasty and stenting of completely occluded iliac arteries.

Percutaneous angioplasty and placement of balloon-expandable intraluminal stents were performed in 12 iliac occlusions in 12 patients. Indications were limb salvage in seven and claudication in five. After successful stenting, ankle-brachial indexes improved by 0.15 or more in 11 of 12 patients (mean increase, 0.40), transstenotic pressure gradients decreased to less than 5 mm Hg (mean, 0.58 mm Hg) in all patients, and improvement in clinical grade was seen in all patients. At follow-up at 1-14 months (median, 6 months), ankle-brachial indexes were stable (mean, 0.95), and clinical grades were unchanged in all patients. Complications occurred in two patients; both experienced distal embolization, and one, who was receiving corticosteroid therapy, also suffered stent thrombosis. Local surgical embolectomy was successful in both patients, and the thrombosed stent was recanalized with urokinase. This early experience suggests that stenting may play an important role in the management of iliac occlusions, especially in poor surgical candidates.

Adult↗
PubMed1989

Evaluation of polymer-coated balloon-expandable stents in bile ducts.

The long-term patency of and biologic response to the presence of polymer-coated balloon-expandable intraluminal stents in the bile ducts was studied in 18 dogs. Metallic stents coated with two different polymers (silicone rubber and segmented polyether-polyurethane) were placed in 12 dogs and uncoated stents in six, and animals were killed after 4, 12, and 24 weeks of observation. Cholangiograms were obtained at 1, 4, 6, 12, and 24 weeks, depending on length of follow-up. All bile duct segments containing stents remained patent throughout the follow-up periods. Characteristic luminal narrowings due to hyperplastic papillary mucosa occurred with all three stent types. although no difference could be found in the degree of narrowing of the most restrictive segment among the three stent types, mucosal proliferation was most extensive with the uncoated stent. Lack of concretion buildup and benign tissue response encourage the development of a clinically useful expandable biliary endoprosthesis.

Animals↗
PubMed1988

The hemodynamic effects of the administration of ionic and nonionic contrast materials into the pulmonary arteries of a canine model of acute pulmonary hypertension.

Clinical studies have shown pulmonary and right ventricular hypertension to be important factors increasing the risk to patients during pulmonary angiography. This experiment was undertaken to define the hemodynamic changes induced by the administration of contrast material into the pulmonary arteries of dogs with embolic pulmonary hypertension, and to compare the effects of ionic and nonionic agents. Ten closed-chest dogs under light halothan anesthesia were subjected to pulmonary embolization with sephadex microspheres until severe pulmonary hypertension occurred and the cardiac output decreased to 50%-60% of the pre-embolization baseline. Intra-pulmonary injections of contrast material were performed in eight animals while hemodynamic indices were measured. Sodium methylglucamine diatrizoate induced severe, transient, hypotension associated with a large decrease in systemic vascular resistance and little change in the cardiac output. Hypotension is especially undesirable in the presence of pulmonary hypertension because it worsens the preexisting coronary ischemia and compromised right ventricular function. No elevation in mean pulmonary artery pressure was seen, and pulmonary vascular resistance decreased. Iohexol induced milder effects, perhaps because it exerts a less severe systemic vasodilatory effect and is not a negative inotrope. These findings suggest iohexol may be safer in the high risk patient, however, these data may not be directly applied to unanesthetized humans.

Acute Disease↗
PubMed1988

In vitro study of high-pressure catheters and various contrast agents.

The versatility of angiography has been expanded by the introduction of low-osmolality contrast agents; high-pressure, high-flow catheters with small outer diameters; and the use of contrast agents with low iodine concentrations. These changes have resulted in the need for a review of the physical factors that influence the flow of contrast agents through flush catheters. Various contrast agents were injected through several types of high-pressure, high-flow catheters with small outer diameters, and the flow rates were measured. Great differences in the viscosities of contrast agents resulted in proportionately smaller differences in maximum flow rates, and warming the contrast agent from room to body temperature had little effect on the maximum flow rate, except for the most viscous contrast agents. The maximum flow rates of the new low-osmolality contrast agents did not differ significantly from those of conventional ionic contrast agents of similar iodine concentration. With unheated contrast agents, iodine delivery was more rapid for contrast agents with iodine concentrations of 280-300 mg/mL.

Angiography↗
PubMed1988

DSA in acute gastrointestinal hemorrhage: clinical and in vitro studies.

Selective intraarterial digital subtraction angiography (DSA) was used to examine 37 patients with acute gastrointestinal (GI) tract bleeding. Conventional screen-film angiography was used as an adjunct to DSA when a larger field of view was needed (five patients) and when bowel motion prevented the acquisition of adequate image quality with DSA (two patients). Conventional angiography was also performed in all cases in which there were negative DSA examinations. DSA reduced the mean examination time considerably (20% reduction overall), especially for cases involving embolization therapy (35% reduction). DSA was especially valuable in the upper GI tract, where it was used to rapidly locate and/or assist in the embolization of bleeding sites in 19 of 20 patients with positive angiograms. There were 12 true-negative DSA examinations and one false-negative examination due to the limited field of view (9 inches [22.9 cm]). Bowel and respiratory motion were not important problems in the upper GI tract. In the lower GI tract, the usefulness of DSA was severely limited by the small field of view and the misregistration artifact caused by bowel motion. In an in vitro study, DSA and conventional angiography were compared as to their ability to depict several rates of extravasation of contrast material in a model of GI bleeding. DSA tended to be more sensitive for the detection of simulated extravasation (P less than .07).

Acute Disease↗