Getting involved in clinical trials research in the UK: how can Clinical Research Networks help?

The Clinical Research Networks of the National Institute of Health Research have transformed clinical research in the UK, leading to a doubling in the number of patients involved in clinical research studies over the past 3 years. This has been achieved by streamlining the trials approvals process, by providing local infrastructure such as research nurse support for clinical trials recruitment and through recognition of the time and funding necessary for clinicians to contribute to clinical research. Here, we describe the structure and roles of the Comprehensive Clinical Research Networks in gastrointestinal disease and hepatology, particularly in England. We will explain how the networks have already accelerated clinical research in gastrointestinal and liver disease, as well as provide a simple guide about how individual clinicians can contribute to ongoing studies via the networks.

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.

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.

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.

Oral contraceptives and venous thromboembolism: a case-control study designed to minimize detection bias

BACKGROUND

Previous epidemiologic studies of venous thromboembolism and oral contraceptive use are susceptible to bias in the detection of venous thromboembolic events. This case-control study uses a unique design to minimize the influence of detection bias.

METHODS

Nonpredisposed women younger than the age of 40 years who underwent pulmonary angiography, lower extremity venography, or lower extremity duplex Doppler sonography at a large urban hospital were classified into a case group or control group based on results of their diagnostic studies. Medical records were reviewed for a history of current oral contraceptive use.

RESULTS

Fifty-seven women met the study criteria during the 11-year study period. Seven of 9 women in the case group and 17 of 48 women in the control group were currently using oral contraceptives (odds ratio 6.38; 95 percent confidence limits 1.19, 34.2).

CONCLUSIONS

The association previously noted between venous thromboembolism and oral contraceptive use is not due to bias in the detection of venous thromboembolic events.

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.

Metallic stents for the treatment of intrahepatic biliary strictures after liver transplantation

PURPOSE

The authors report their results with use of metallic stents for the treatment of intrahepatic biliary strictures occurring after liver transplantation.

PATIENTS AND METHODS

Twenty-four patients with intrahepatic biliary strictures after liver transplantation were treated with metallic stents. Eleven had undergone prior unsuccessful percutaneous balloon dilation. Successful stent deployment occurred in all subjects. Gianturco, Wallstents, and Palmaz stents were used. Follow-up was obtained in all 24 patients.

RESULTS

Initial technical success was obtained in all 24 patients. In 11 patients, long-term primary, primary assisted, or secondary stent patency was achieved with follow-up ranging from 17 to 58 months. Ten patients died or underwent retransplantation within 14 months for reasons unrelated to their stents. In three patients, stent placements failed because of stent obstructions that were refractory to attempts at secondary patency. By life-table analysis, cumulative primary, primary assisted, and secondary patency rates were 50%, 61%, and 80%, respectively, at 18 months.

CONCLUSION

Metallic biliary stents offer promising results for intrahepatic strictures in the posttransplant patient, particularly in patients with widespread strictures. Stents can become partially or totally obstructed due to sludge and debris, but patency can often be restored with additional interventional techniques.

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.

Effect of a transjugular intrahepatic portosystemic shunt on liver biochemical profiles

PURPOSE

Transjugular intrahepatic portosystemic shunts (TIPS) have markedly simplified the care of patients with refractory variceal bleeding. Follow-up of liver biochemical profiles, however, has not been done in a prospective fashion.

PATIENTS AND METHODS

Twenty-nine patients undergoing TIPS placement for refractory variceal bleeding underwent serial laboratory tests and assessment of encephalopathy to determine the effect of TIPS. Prothrombin time and aspartate aminotransferase, alanine aminotransferase, total bilirubin, alkaline phosphatase, serum albumin, serum creatinine, and venous ammonia levels were checked prior to the procedure, at the time of discharge, and at 3 weeks, 3 months, and 6 months following the procedure.

RESULTS

There was no statistically significant change in any of the obtained laboratory values at up to 6 months of follow-up. The change in aspartate aminotransferase level approached but did not reach statistical significance at the time of discharge and was thought to be secondary to hepatocellular trauma associated with the procedure. New onset of encephalopathy occurred in 18.2% of patients and was easily controlled with medical therapy.

CONCLUSIONS

TIPS does not appear to have a significant effect on the liver biochemical profile with short-term follow-up. Hepatic encephalopathy does occur, however, in a significant number of patients but is easily controlled with medical therapy.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

Recent subsegmental splenic infarction: hypervascular appearance on angiography

The authors describe a case of a focal splenic infarction with a hypervascular appearance on selective splenic arteriography. This appearance of splenic infarction has never before been reported. Angiographers should be aware of this unusual presentation of splenic infarction when they encounter an unexplained focal hypervascular area.

The role of bone scintigraphy in osteogenic sarcoma

Hospital records of 27 children with osteogenic sarcoma were reviewed in an effort to define the usefulness of skeletal scintigraphy in the initial evaluation and follow-up of their disease. Serial bone scans as well as plain radiographs, linear tomograms, and computed tomograms were evaluated for evidence of bone or lung metastases. Eighteen patients developed lung metastases and three developed bone metastases. Seven patients demonstrated uptake of tracer in lung metastases, however, the lesions were all easily identifiable by radiographic means. All bone metastases were detected by scintigraphy, in one instance prior to radiographic abnormality. In no cases were bone metastases known to occur in the absence of lung metastases. None of the bone scans performed for routine follow-up purposes resulted in altered therapy for the patient. We propose that skeletal scintigraphy is useful in the initial metastatic work up of osteogenic sarcoma, and may be helpful in some patients with specific indications during their follow-up, but is less valuable when there is no clinical suspicion for bone metastases.

Percutaneous transluminal angioplasty and valvectomy in a failing in situ saphenous graft

A patient is described who experienced increasing ischemia in the follow-up period of femoral-peroneal artery graft surgery. Transcatheter angiographic management was successful in improving the long-term patency of the graft. The procedure is described, and the applications are discussed.