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Biomedical subjects

G J Becker

Publications and source records attributed to G J Becker.

At least 109 records · Page 6Linked to original sources
PubMed1991

Standards for evaluating and reporting the results of surgical and percutaneous therapy for peripheral arterial disease.

By adopting precise definitions of essential terms, developing objective criteria by which the various measures of success or failure can be judged, and establishing a standardized scheme by which severity of disease, degrees of improvement or deterioration, and risk factors that affect outcome can be graded, the quality of published reports of revascularization procedures for lower extremity ischemia can be greatly improved, allowing comparative evaluation of treatment modalities.

Arterial Occlusive Diseases↗
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↗
PubMed1991

Intravascular stents. General principles and status of lower-extremity arterial applications.

The two major types of intravascular stents are balloon expandable and self-expanding. Many animal and, more recently, clinical studies have begun to delineate the real and potential roles of stents. Although the ideal intravascular stent does not exist, it is possible to identify characteristics of the hypothetical ideal stent. Iliac and femoropopliteal arterial applications of metallic stents are reviewed. Stents have proved useful in postangioplasty elastic recoil, in some cases of postangioplasty restenosis, and in angioplasty-induced dissection. Their role in primary angioplasty procedures is still uncertain, although in iliac angioplasty the immediate hemodynamic effects of angioplasty plus stenting are superior to those of angioplasty alone. It is clear that metallic stents have not solved the problem of postangioplasty restenosis, as restenosis still occurs in a significant number of cases. This problem is particularly evident in the femoropopliteal stent procedures, in which angiographic restenosis (more than 50% single diameter stenosis) at 6 months after treatment has occurred in approximately 30% of cases. The existence of poststenting restenosis, which often involves the stented segment, underscores the need for better drug regimens in angioplasty and for better understanding of the intimal fibrocellular proliferative response of the vessel wall to injury. Although potentially very useful, biodegradable stents are still a dream whose realization will demand the development of better materials.

Animals↗
PubMed1990

Two unusual manifestations of aortic aneurysms.

Pain and pulsation are common presenting features of aortic aneurysms. Massive hematemasis and ureteral obstruction represent rare clinical presentations. This report describes a patient with massive hematemesis in whom a thoracic aneurysm ruptured into the esophagus, and a second patient in whom a large abdominal aortic aneurysm caused bilateral ureteral obstruction.

Aorta, Abdominal↗
PubMed1990

Reflux nephropathy and primary vesicoureteric reflux in adults.

We have studied the clinical features and course of adults with reflex nephropathy and/or primary vesicoureteric reflux, paying particular attention to the differences between males and females, and the presenting features that influence prognosis. In our series of 293 patients, females outnumbered males in the ratio 5:1 and most presented with urinary infection, whereas males most commonly presented with features of renal damage such as proteinuria, hypertension or renal failure. Males more commonly had bilateral scarring and persistent reflux. One hundred and forty-seven patients were followed for two years or more (range 2-19 years); deterioration in renal function occurred in 55 (37 per cent). Risk factors for a rise in plasma creatinine were, in descending order, the presence of proteinuria, an elevated plasma creatinine concentration, bilateral scarring, male sex and the presence of hypertension. Stepwise multiple regression analysis showed that the independent risk factors were proteinuria, elevated plasma creatinine concentration and hypertension; gender and the presence of persistent reflux had no independent influence on the course of renal failure.

Adolescent↗
PubMed1990

Potential of radio-frequency balloon angioplasty: weld strengths, dose-response relationship, and correlative histology.

Previous studies have established the feasibility of combining tissue heat generated by radio-frequency (RF) current and mechanical pressure to manage problems of percutaneous transluminal angioplasty (PTA) that are thought to cause postangioplasty restenosis (PARS). In the current in vitro study of normal and atherosclerotic human aortic layers (intima-media and media-adventitia) separated artificially, the purposes were to identify a dose-response relationship between the total RF energy delivered and the resultant weld strength between vascular tissues and to study the histologic correlates. Twenty-eight control and 100 experimental specimens were evaluated. The mean weld strength for all specimens with no RF current (at 0 J) was 4.1 g +/- 2.0; at 100 J, 5.9 g +/- 2.8; at 200 J, 28.5 g +/- 3.3; at 300 J, 50.0 g +/- 5.5; and at 500 J, 82.0 g +/- 8.2. Inspection of treated specimens revealed vascular molding (depression in the surface corresponding in dimensions to those of the electrode gap in the treatment chamber). Histologic examination revealed necrosis in the region underlying the electrode gap, a hypocellular fusion zone, indistinct boundaries between welded specimen parts, and transition zones to normal histologic characteristics at either end of each specimen. RF energy combined with mechanical pressure produces dose-dependent thermal welds in artificially dissected vascular tissues, molding of vascular tissue, and cellular destruction in the media. These findings may have clinical application in the management or prevention of all forms of PARS in humans and in the treatment of spontaneous aortic dissection.

Angioplasty, Balloon↗
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

The effect of protein restriction on the progression of renal insufficiency.

Dietary protein intake may be an important determinant of the rate of decline in renal function in patients with chronic renal insufficiency. We conducted a prospective, randomized study of the efficacy of protein restriction in slowing the rate of progression of renal impairment. The study lasted 18 months and included 64 patients with serum creatinine concentrations ranging from 350 to 1000 micromol per liter. The patients were randomly assigned to follow either a regular diet or an isocaloric protein-restricted diet (0.4 g of protein per kilogram of the body weight per day). Blood-pressure levels and the balance between calcium and phosphate were similar in the two groups. End-stage renal failure developed in 9 of the 33 patients (27 percent) who followed the regular diet during the study, as compared with 2 of the 31 patients (6 percent) who followed the protein-restricted diet (P less than 0.05). The mean (+/- SE) glomerular filtration rate, as measured by the clearance of 51Cr bound to EDTA, fell from 0.25 +/- 0.03 to 0.10 +/- 0.05 ml per second (P less than 0.01) in the group on the regular diet, whereas it fell from 0.23 +/- 0.04 to 0.20 +/- 0.05 ml per second (P not significant) in the group on the protein-restricted diet. We conclude that dietary protein restriction is effective in slowing the rate of progression of chronic renal failure.

Adult↗
PubMed1989

The effect of radiofrequency-generated thermal energy on the mechanical and histologic characteristics of the arterial wall in vivo: implications for radiofrequency angioplasty.

Abrupt reclosure of atherosclerotic vessels after percutaneous transluminal balloon angioplasty has been blamed on traumatic dissections and elastic recoil of the vessel wall. Thermal energy with compression produces fusion of separated arterial wall layers, and heat appears to alter the elastic recoil of the vessel wall. Radiofrequency (RF) thermal energy has been used to perform vascular anastomoses and thermal angioplasty. A simple in vivo experiment was designed to describe and quantitate vascular tissue weld strength produced by a range of RF thermal energy levels. Canine carotid arteries were compressed between a pair of modified bipolar forceps that applied RF energy, causing occlusive tissue welds between the apposed intimal surfaces. The strength of the welds was evaluated by measuring the perfusion pressure required to reopen the vessel lumen. A dosimetry range of 0 to 205 joules showed a typical dose-response curve for the relationship between energy applied and bond strength, plateauing at approximately 300 mm Hg. Light microscopy showed fusion of the inner surfaces of the vessel with preservation of vessel wall architecture. Additionally inflation of a bipolar RF balloon catheter in the normal canine carotid lumen produced an alteration of vessel profile angiographically and histologically. Results of these preliminary experiments suggest that balloon angioplasty with adjunctive RF thermal energy may have benefits in reducing the factors causing acute failure of conventional percutaneous transluminal balloon angioplasty.

Angiography↗
PubMed1989

Thermal compression and molding of atherosclerotic vascular tissue with use of radiofrequency energy: implications for radiofrequency balloon angioplasty.

The combined delivery of pressure and thermal energy may effectively remodel intraluminal atherosclerotic plaque and fuse intimal tears. To test these hypotheses with use of a non-laser thermal energy source, radiofrequency energy was delivered to postmortem human atherosclerotic vessels from a metal "hot-tip" catheter, block-mounted bipolar electrodes and from a prototype radiofrequency balloon catheter. Sixty-two radiofrequency doses delivered from a metal electrode tip produced dose-dependent ablation of atherosclerotic plaque, ranging from clean and shallow craters with histologic evidence of thermal compression at doses less than 40 J to tissue charring and vaporization at higher (greater than 80 J) doses. Lesion dimensions ranged between 3.14 and 3.79 mm in diameter and 0.20 and 0.47 mm in depth. Tissue perforation was not observed. To test the potential for radiofrequency fusion of intimal tears, 5 atm of pressure and 200 J radiofrequency energy were delivered from block-mounted bipolar electrodes to 48 segments of human atherosclerotic aorta, which had been manually separated into intima-media and media-adventitial layers. Significantly stronger tissue fusion resulted (28.5 +/- 3.3 g) with radiofrequency compared with that with pressure alone (4.8 +/- 0.26 g; p less than 0.0001). A prototype radiofrequency balloon catheter was used to deliver 3 atm of balloon pressure with or without 200 J radiofrequency energy to 20 postmortem human atherosclerotic arterial segments. In 10 of 10 radiofrequency-treated vessels, thermal "molding" of both normal and atherosclerotic vessel wall segments resulted with increased luminal diameter and histologic evidence of medial myocyte damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1989

Ioversol 320: a new nonionic, water-soluble contrast medium for body computed tomography clinical trial.

An open-label noncomparative clinical study was conducted to evaluate the safety, tolerance, and efficacy of ioversol (Optiray 320), a new low-osmolality nonionic contrast medium used in contrast-enhanced computed tomographic (CT) scanning. Forty-two adult patients who required contrast-enhanced body CT scanning participated in the study. Ioversol was administered to patients undergoing CT of the chest, abdomen, and pelvis. Most of the patients received a dose of 150 mL, with smaller doses administered if a patient weighed less than 50 kg or if a patient had only one functioning kidney. The quality of the CT scans was judged to be diagnostic in all 42 patients in the study, with the quality assessed as excellent in 35 patients and good in seven patients. Ioversol was considered well tolerated by patients in the study, with none reporting any pain from the contrast agent. Only mild or moderate sensations of heat were reported. There were no clinically significant changes in vital signs, and only one mild adverse reaction (determined to be procedure-related) was reported. Ioversol was found to be safe, well tolerated, and efficacious for use in body CT scanning.

Adolescent↗
PubMed1989

The neuroradiographic diagnosis of lumbar herniated nucleus pulposus: I. A comparison of computed tomography (CT), myelography, CT-myelography, discography, and CT-discography.

The accuracy of five imaging modalities for the diagnosis of lumbar herniated nucleus pulposus (HNP) is compared prospectively in 124 patients, all of whom underwent surgical exploration. All tests were read independently of each other and the level of confidence in each diagnosis was recorded. The results are based on negative (106) as well as positive (125) findings at the 231 disc sites (level and side) explored. Computed tomography-discography (disco-CT) was the most accurate test (87%) compared to 77% for CT-myelography (myelo-CT), 74% for CT, 70% for myelography, 64% for disc injection pain, and 58% for discography. The false positive rate was lower for disco-CT (19%) than for myelo-CT (24%), CT (24%), and myelography (30%). The false negative rate was also lower for disco-CT (8%) than for myelo-CT (22%), CT (29%), and myelography (30%). Disco-CT was the most accurate test (94%) in patients who had prior disc surgery compared with 81% for myelo-CT, 80% for CT, and 74% for myelography. Disco-CT was also the most accurate test for patients with foraminal HNP (91% compared with 71% for CT, 65% for myelo-CT, and 58% for myelography). Disc injection reproduced the patient's clinical pain pattern in only 36% of herniated discs. This test has high specificity (89%), but low sensitivity (43%). The risks from myelography followed by discography within a 72-hour period are similar to those reported for myelography alone. Disco-CT is the most accurate of these tests (P less than 0.05) for the diagnosis of lumbar HNP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Endoluminal radio-frequency electrocautery for permanent ureteral occlusion in swine.

An animal experiment was undertaken to assess the feasibility of using radio-frequency current-mediated thermal injury of the ureter to produce ureteral occlusion by means of an endoluminal approach. Through open pyelotomies, balloon angioplasty catheters coated with gold bipolar electrodes were introduced into the ureters. Doses (at 650 kHz) were delivered for specific energy totals in 13 of 15 ureters in eight pigs. Two ureters served as controls (balloon inflation without current application). In six experimental animals not killed immediately after the procedure, postoperative ureteral manometric studies and nephrostography were performed and nephrostomy drainage was maintained until death (1-8 weeks). Treatment with 200-400 J produced safe, reliable occlusion by 4 weeks. At histopathologic study at 4 and 8 weeks, necrotic muscularis propria had been replaced by fibrous tissue. Cardiac rhythm was not affected during treatment.

Angioplasty, Balloon↗
PubMed1989

Noncoronary angioplasty.

PTA is an established method of revascularization in a variety of medical conditions. It is performed for specific morphologic and clinical indications. PTA is the procedure of choice in Fontaine stage IIB through IV lower extremity ischemia due to iliac and/or femoropopliteal stenosis or short occlusion. Its role is less certain in infrapopliteal disease, although current studies have begun to establish long-term effectiveness. PTA is the procedure of choice for renal revascularization in renovascular hypertension due to fibromuscular disease or non-ostial atherosclerosis, selected cases of renal artery stenosis associated with renal insufficiency, and transplant renal artery stenosis. It is also useful in treating the renovascular component of complex hypertension and may be indicated in severe renal artery stenosis (75%-99%), even in the absence of clinically demonstrable RVHTN. PTA has limited applications in the venous system and only short-term success in the treatment of stenoses in dialysis access fistulas. PTA often serves as an important adjunct to surgical revascularization by providing improved inflow or outflow. PTA is the procedure of choice when anatomically feasible in subclavian steal syndrome. The role of PTA in carotid artery disease, particularly atheromatous disease of the internal carotid artery, is uncertain. The same may be said of PTA for vertebral artery stenosis, although the overwhelming majority of vertebral artery stenoses are morphologically suitable for PTA. PTA and surgery are both effective in the treatment of abdominal angina. There are more data available to verify the long-term patency of thromboendarterectomy and bypass grafts than PTA for mesenteric ischemia. However, since the technical success for PTA is high and since coronary co-morbidity is the most common cause of perioperative mortality in surgical series, PTA should be seriously considered as the procedure of first choice. Serious complications of PTA occur in approximately 5% of cases. Two to three percent of PTA patients have complications requiring surgery or causing a prolongation or alteration of hospital course. The morbidity, mortality, and cost associated with PTA are low. The discomfort is minor, and postprocedural recovery rapid. The major limitations of PTA include its unsuitability for some lesions (long-segment occlusions and stenoses, orifice lesions, eccentric lesions) and postangioplasty restenosis. These problems are being addressed by ongoing laboratory and clinical research. In the near future, it is likely that endoluminal transmural sonography of the vessel wall will help guide our interventions.

Angioplasty, Balloon↗
PubMed1989

Percutaneous transrenal endoureteral radio-frequency electrocautery for occlusion: case report.

In a patient with advanced cervical carcinoma who had a large vesicovaginal fistula, the authors applied radio-frequency (RF) current endoluminally to the ureter via a percutaneous nephrostomy tract to occlude the ureter. Perineal drainage was initially reduced and then stopped entirely. The procedure was relatively easy to perform and was successful in achieving occlusion until the patient's death 2 1/2 months later.

Adult↗