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Biomedical subjects

G K McLean

Publications and source records attributed to G K McLean.

At least 19 recordsLinked to original sources
PubMed1999

Primary stenting of the superior mesenteric artery for treatment of chronic mesenteric ischemia--a case report.

Percutaneous transluminal angioplasty (PTA) has been well described in the treatment of mesenteric artery stenoses but has met with limited success in ostial lesions. The authors describe a case of a 79-year-old woman diagnosed with chronic mesenteric ischemia associated with a 22-pound weight loss and postprandial pain. The celiac axis and inferior mesenteric artery were occluded. A high-grade, calcified stenosis was present in the proximal superior mesenteric artery. This was treated with primary stent placement using a Palmaz stent deployed from an axillary approach. A brief discussion of mesenteric ischemic and visceral artery PTA is included.

Aged↗
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↗
PubMed1993

Angioplasty, bypass surgery, and amputation for lower extremity peripheral arterial disease in Maryland: a closer look.

Tunis and colleagues attempted to assess the effect of peripheral angioplasty in a large population with descriptive epidemiologic methods. Their study suffered from a vague statement of purpose, inappropriate and inadequate outcome measures, undetermined differences in prevalence of peripheral vascular disease and prevalence of risk factors for bypass/amputation in 1989 versus 1979, no differentiation between levels of amputation or between primary and secondary amputation, lack of a unique ICD-9-CM code indicating angioplasty for peripheral vascular disease of the lower extremities, lack of unique patient identifiers, a mistaken perception of the adoption of angioplasty as "widespread" in Maryland, and the assumption of uniform coding accuracy throughout the period of study. We conclude that the study design of Tunis et al was inadequate to determine the beneficial effects of angioplasty or bypass surgery in the treatment of peripheral vascular disease. Moreover, the conclusion by Coffman (2) that "invasive procedures are indicated only for the severely ischemic limb" is completely unsupported by the study data. Physicians should not attempt to apply the results of the study by Tunis et al to individual case situations. It should be further appreciated that the study findings do not provide an adequate basis for policy-making decisions. It is clear that important clinical questions concerning the roles of angioplasty, bypass, and amputation should be answered with more definitive studies.

Algorithms↗
PubMed1993

Stent placement in a splenic vein stenosis after TIPS creation.

A hemodynamically significant splenic vein stenosis was found during placement of a transjugular intrahepatic portosystemic shunt in a patient with gastric variceal bleeding. A second stent was placed across the splenic vein stenosis, which was obstructing normal hepatopetal flow, causing venous hypertension in the splenic and short gastric veins. This produced a successful hemodynamic and angiographic result and, clinically, controlled the patient's bleeding.

Constriction, Pathologic↗
PubMed1991

Femoropopliteal angioplasty. Factors influencing long-term success.

Prospective data was recorded on 217 percutaneous transluminal angioplasty (PTA) procedures performed in the superficial femoral and popliteal arteries over an 8-year period. After the initial procedure, patients were followed with serial noninvasive studies and, in 71 patients, repeat angiography. The mean follow-up period was 7 years (range, 2-11 years). Standard life-table survival analysis was used to assess the factors potentially affecting long-term outcome. Excluding an initial technical failure rate of 10%, overall patencies at 1, 3, and 5 years were 81%, 61%, and 58%, respectively. After the first year, the prognosis (i.e., failure rate) appears to be linear over the long term (i.e., up to 10 years). Factors negatively influencing long-term patency include the presence of diabetes mellitus, diffuse atherosclerotic cardiovascular disease, or threatened limb loss. Technical factors correlated with failure include lesion length, moderate eccentricity, and a poor post-PTA appearance.

Angioplasty, Balloon↗
PubMed1990

Angiography in poor-risk patients with massive nonvariceal upper gastrointestinal bleeding.

The purpose of this retrospective study was to determine the diagnostic and therapeutic usefulness of gut angiography in patients with massive upper gastrointestinal bleeding from a nonvariceal source. All patients (n = 64) in this category who underwent a gut angiogram between 1980 and 1986 were studied. Pre-angiogram endoscopy was attempted in all patients and was nondiagnostic in 14 (22%). Contrast extravasation at angiography was seen in 25 of 64 patients (39%), and in over half of these patients endoscopy was nondiagnostic (n = 11) or wrong (n = 3). Attempts to control bleeding in this group by selective arterial embolization (n = 14) or intra-arterial vasopressin (n = 11) successfully averted operation in 13 of 25 patients (52%) and was associated with a 50% reduction in mortality (83% versus 38%). Selective embolization of vessels thought to be bleeding on clinical grounds without evidence of contrast extravasation (i.e., "blind" embolization) was not helpful in controlling hemorrhage. Urgent gut angiography in patients with massive upper gastrointestinal bleeding of arteriocapillary source is a useful diagnostic and therapeutic maneuver and warrants continued application in this group of poor-risk patients.

Aged↗
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↗
PubMed1990

Optimizing heparin utilization in angiographic flush solutions.

Various concentrations of heparin in angiographic flush solutions are employed during angiography. In an effort to determine whether differences in outcome are seen when either high or low concentrations of heparin in angiographic flush solutions are utilized, two groups of patients were evaluated. There was no difference in outcome and a small systemic effect from heparin was seen in both groups. Use of a low concentration of heparin is suggested for routine angiography.

Angiography↗
PubMed1989

Obstructions of the hepatic duct confluence: internal drainage of bilateral lesions with a single catheter.

Strictures at the confluence of the right and left hepatic ducts are difficult to treat surgically, endoscopically, or percutaneously. Percutaneous decompression techniques previously described involved separate transhepatic catheterizations of the isolated right and left ducts. In the present study, modifications of existing self-retaining loop drainage catheters allowed bilateral internal biliary drainage of isolated right and left hepatic ductal systems with a single catheter in three patients. The technique can be used for primary palliation and for recurrent strictures after hepaticojejunostomy.

Aged↗
PubMed1989

Shear stress in the performance of esophageal dilation: comparison of balloon dilation and bougienage.

While both the balloon catheter and the bougie are effective for esophageal dilation, each has its proponents. From a biomechanical point of view, the two methods should differ significantly, since bougienage depends on advancing a tapered dilator to generate radial force and balloon catheter dilation depends solely on balloon inflation to generate its radial dilating force. In a series of equivalent esophageal stenoses made by suture plication in swine esophageal segments, the authors measured shear force and radial force generated by dilation with a Maloney bougie, a Savary-Gilliard bougie, and an esophageal balloon. The mean radial forces generated were 6.42, 4.46, and 4.04 N, respectively, which did not differ significantly. However, the mean shear forces measured were 16.92, 6.92, and 1.44 N, respectively. The shear force with the Maloney bougie differed significantly from that with the Savary-Gilliard and the balloon and was on the same order of magnitude as the tensile strength of the esophagus (25-27 N). The shear force with the balloon was significantly lower than that with either bougie. In theory, the reduced shear force associated with balloon dilation might reduce the risk of esophageal perforation, but safety will have to be determined in clinical trials.

Animals↗
PubMed1989

Role of endoprostheses in the management of malignant biliary obstruction.

Therapeutic and palliative procedures for treating biliary obstruction can be surgical, percutaneous, or endoscopic. Incurable malignancies can be palliated by each of these three approaches. None of these has an advantage in terms of longevity over the others. Choosing the procedure which offers the best quality of life for the individual patient is complex. The virulence of the underlying tumor, the anatomic location within the biliary tree, and the availability of expertise in each of the alternative methods must be considered. For the group of patients whose conditions are palliated with transhepatic biliary drainage, the choice between chronic indwelling internal-external catheter versus endoprosthesis placement involves questions of utility, patient acceptance, and the geometry of the obstructed biliary tree. Each of these must be considered before deciding on the approach which offers the best compromise of the technical preferences of the physician, the psychological preferences of the patient, and the limitations imposed by the level and number of obstructions. Research by radiologists and gastroenterologists has resulted in improved endoprosthesis function. Current research aimed at improving stability and patency promises further improvements in endoprosthesis efficacy.

Bile Duct Neoplasms↗
PubMed1988

Interventional radiologic treatment of complications following gastric bypass surgery for morbid obesity.

Complications of gastric bypass surgery include leakage from the gastrojejunal anastomosis with abscess formation and anastomotic stenosis. Using interventional radiologic techniques, we have treated 18 patients with such complications following surgery for morbid obesity, with clinical success in 11. Procedures included 9 abdominal abscess drainages and 7 balloon dilatations of stenotic or occluded gastrojejunal anastomoses. Eight of 9 abscesses resolved completely; 3 of 7 balloon dilatations resulted in long-term clinical improvement. We describe the techniques used as well as problems encountered in these patients.

Abdomen↗
PubMed1988

The midaortic syndrome: diagnosis and treatment.

The midaortic syndrome is an unusual entity seen in children and adolescents. It is characterized by severe narrowing of the abdominal aorta with progressive involvement of the renal and visceral branches. Eleven patients (aged 5 months to 15 years) suspected of having midaortic syndrome were examined preoperatively and postoperatively. All patients had hypertension and were examined with midstream aortography. All aortograms showed a smooth, segmental stenosis of the abdominal aorta and severe bilateral proximal renal artery stenosis. In three patients, percutaneous transluminal angioplasty of the renal artery was attempted, two preoperatively and one for a postoperative stricture. None showed long-term success, presumably due to the progressive nature of the disease. Grafts were surgically placed in ten patients and produced successful results in nine.

Angioplasty, Balloon↗
PubMed1988

Renal and related retroperitoneal abscesses: percutaneous drainage.

Renal and related retroperitoneal abscesses cause significant morbidity and mortality and almost always require drainage. The authors report 18 cases of percutaneous drainage of renal and related retroperitoneal abscesses, all of which were successfully managed. In 11 of these cases (61%), percutaneous drainage constituted the only treatment required. In the remaining seven (39%), the patients' clinical status improved after percutaneous drainage, and they were able to undergo subsequent elective nephrectomy with fewer complications. These results are comparable to those achieved with percutaneous abdominal abscess drainage and justify the use of percutaneous drainage for renal and related retroperitoneal abscesses as the therapeutic procedure of choice.

Abscess↗
PubMed1988

Intraluminal stents in atherosclerotic iliac artery stenosis: preliminary report of a multicenter study.

Fifteen patients with symptomatic iliac artery stenosis were treated with intraluminal placement of balloon-expandable stents. Before treatment, 14 patients had intermittent claudication, and one had a limb at risk for amputation. One patient had diabetes mellitus, nine had hypertension, and all were long-term smokers. Two patients had surgical placement of the stent; in one patient this was part of a combined revascularization procedure. All other stents were placed percutaneously. The transstenotic gradient after injection of vasodilating drugs distal to the lesion decreased from a mean of 32.3 mm Hg +/- 16.7 to 3.1 mm Hg +/- 4.2 after stent placement. Ankle-arm Doppler systolic pressure index increased from a mean of 0.68 +/- 0.22 to 0.96 +/- 0.24 after the procedure. The treatment eliminated intermittent claudication in 14 patients and increased exercise tolerance to 500 m in the patient with a limb at risk for amputation before the procedure. The improved condition persisted in all patients during the follow-up of 6-12 months. Stent placement may be a valuable adjunct in the management of iliac artery disease.

Angiography↗