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Biomedical subjects

K Amplatz

Publications and source records attributed to K Amplatz.

At least 145 records · Page 8Linked to original sources
PubMed1984

Percutaneous transluminal angioplasty of the aorta. Light and electron microscopic observations in normal and atherosclerotic rabbits.

Histological changes which developed after percutaneous transluminal angioplasty in normal and atherosclerotic rabbit aortas were correlated with balloon size and inflation time. In normal rabbits, progressive changes were observed in the intima and media with increasing balloon size and inflation time. The atherosclerotic aortas exhibited unpredictable fragility, with limited correlation between histological changes, balloon size, and inflation time, attributable mainly to the distribution and thickness of plaques. In atherosclerotic vessels, the mechanism of angioplasty consisted of plaque dehiscence and fracture, followed by overstretching of the plaque-free wall segments. No plaque compression was observed.

Angioplasty, Balloon↗
PubMed1984

Balloon dilatation of benign biliary strictures.

Percutaneous transhepatic balloon dilatation of benign postoperative biliary strictures was performed in 6 patients. The procedure was curative in 1 patient. These findings indicate the need for repeated long-term, high-pressure dilatation of these strictures, using an inflation device and pressure gauge. Large catheters should be left in place as stents. Early non-surgical management may improve the salvage rate of this surgical complication.

Adult↗
PubMed1984

Carbon dioxide as a lighter-than-urine contrast medium for percutaneous nephrostomy.

Carbon dioxide was used either alone or in combination with standard triiodinated contrast media in 32 patients who underwent percutaneous nephrostomy. Carbon dioxide was used to opacify the posterior calyces, which are the uppermost structures in the kidney of the prone or prone-oblique patient. Carbon dioxide is usually injected in small amounts (20-40 cm3), although clinical and laboratory data indicate that it can be used as the only medium in large amounts with complete safety. There were no complications.

Adult↗
PubMed1984

Dual stiffness Malecot (Stamey) catheter.

A new catheter with a soft plastic shaft and a stiff mushroom has been developed for drainage of various fluid-filled cavities. It can be introduced with a flexible guidewire system. Its dual stiffness provides greater comfort for and acceptance by the patient.

Catheterization↗
PubMed1984

A new vena caval filter for percutaneous placement and retrieval: experimental study.

A new vena caval filter that can be inserted percutaneously through an angiographic catheter is described. The filter is secured by controlled penetration of the caval wall and is designed for percutaneous retrieval. The filter was easily and safely placed and removed in 11 mongrel dogs, and in an in vitro study, the filter was shown to be highly effective and less dependent than the Greenfield filter on positioning. The authors believe that the filter will be suitable for prophylactic placement in patients at high risk for pulmonary thromboembolic disease.

Animals↗
PubMed1984

Failing arteriovenous dialysis fistulas: evaluation and treatment.

A total of 31 patients with 45 episodes of failing arteriovenous dialysis fistulas was studied. Fistula failure was usually due to venous and/or anastomotic stenosis, often in conjunction with thrombosis. Abnormalities were treated by percutaneous dilation and occasionally streptokinase infusion. Most complications and failures occurred either in patients with recently created fistulas or in those with multiple or long segment stenosis associated with thrombosis. Patients with a single nonobstructing stenosis were very successfully treated with percutaneous techniques, which are the treatment of choice for this condition.

Adult↗
PubMed1984

Nephrotoxicity of contrast media assessed by occlusion arteriography.

The authors describe an experimental model for the study of nephrotoxicity induced by contrast media, based on a standardized injection combined with occlusion of the renal artery so as to expose the kidney to a high concentration of contrast medium for ten minutes. Iopamidol, ioxaglate, and both isosmolar and hyperosmolar saline were well tolerated, but diatrizoate caused marked radiological and pathological changes. This model may be helpful in studies of the mechanisms underlying contrast medium nephrotoxicity and evaluating differences in toxicity between contrast agents.

Animals↗
PubMed1984

Transluminal angioplasty evaluated by electron microscopy.

To gain more understanding about the changes that follow balloon angioplasty, an electron and light microscopic study was carried out in normal canine arteries. Thirty-five arterial segments were dilated with balloon catheters. Early changes consisted of denudation of the intima with widespread necrosis of myocytes and dehiscence of collagen fibers. After three days, myocytes had disappeared leaving empty spaces and edematous ground substance. After two weeks, reendothelization occurred and there was evidence of intimal hyperplasia persisting up to two months. Repair of the dilated arterial segments occurred by proliferation of myocytes, formation of intima, and proliferation of collagen. In two to three months, repair of the intima and media was completed. After six months, dilated segments were characterized by persistent intimal hyperplasia and increased collagen content in the media.

Angioplasty, Balloon↗
PubMed1984

Renal vein renin sampling in essential hypertension using hydralazine and the tourniquet test.

The results of renal vein renin sampling were assessed in 40 patients who had uncomplicated essential hypertension. All had normal creatinine clearance, intravenous pyelography, and arteriography. During sampling, renin release was stimulated in 29 patients with intravenous hydralazine and in 11 with the tourniquet blood trapping test. Simultaneous sequential renal vein samples were drawn over a 30-minute period. Positive renal vein renin ratios (greater than or equal to 1.5) were seen in 52% of the hydralazine group at 0 minutes and in 69% post-hydralazine. In the tourniquet group, 27% had a positive ratio at 0 minutes as compared with 64% post-tourniquets. A significant difference was found in renal vein plasma renin activity between the two kidneys (p greater than or equal to .0001). The asymmetry of renal vein renin activity and the large renal vein renin ratios in these two groups suggest the presence of true differences in renin secretion. These differences may be due to focal nephrosclerosis. The therapeutic significance of a positive renal vein renin ratio in the hypertensive patient should be determined in conjunction with arteriography.

Blood Volume↗
PubMed1984

Long-term patency of the ductus arteriosus after balloon dilatation: an experimental study.

Balloon dilatation of the ductus arteriosus was carried out in vivo in eight piglets that were 12 to 16 days old. The ductus was functionally closed in all animals before dilatation. Long-term patency for periods of up to 6 months after the procedure was demonstrated in six animals by angiography, Doppler ultrasound examination, and at autopsy. The presence of hemodynamically significant shunts was indicated by clinical development of heart failure, pulmonary infections, and left ventricular hypertrophy. These results confirm the value of this laboratory preparation to create left-to-right shunts at the ductus level.

Angioplasty, Balloon↗
PubMed1984

Role of ischemia in contrast-induced renal damage: an experimental study.

Total and regional cortical blood flow was measured in dogs by the radioactive microsphere technique after renal damage of varying severity had been induced by combining selective injection of diatrizoate, iopamidol, or normal saline with a 10 min occlusion of the renal artery. There was extensive tubular and glomerular damage in the kidneys exposed to diatrizoate, but not in the kidneys exposed to saline. Iopamidol caused intermediate changes. Average cortical blood flow was reduced from baseline levels in all groups 5 min after perfusion was restored. After 1 hr the flow had returned to the baseline level. Analysis of variance did not show a statistically significant difference among the groups. A tendency for redistribution of flow from outer to inner cortical layers was seen, but this was present in all groups. The flow changes detected in this study cannot explain the varying severity of renal damage.

Animals↗
PubMed1984

Coil embolization of congenital thoracic vascular anomalies in infants and children.

When significant thoracic vascular anomalies occur in children, they may present surgical difficulties making operative management undesirable. The recent development of a new, accurate coil-delivery system has enabled us to embolize 17 vessels in five children by passing Gianturco steel coils coated with thrombogenic Dacron strands through No. 5 or 6F end-hole catheters suitable for infants. Coils of 0.038 inch packed diameter were fed through the catheter lumen by a flexible guidewire emerging as 3, 5, or 8 mm diameter loose coils. Fifteen of 17 vessels were successfully occluded. No complications or errors in placement of coils occurred. Four of five children clearly benefitted from the procedure. One died in spite of partial occlusion. Coil embolization can be performed accurately and safely even in small infants with a high rate of successful occlusion and may prove to be a valuable adjunct to operative management.

Aorta↗
PubMed1984

The pathologic basis of angioplasty.

Traditionally it has been said that transluminal angioplasty increases lumen diameter by compression and remodeling of atheromatous material. Recently, a new concept explaining the mechanics of angioplasty was described which challenges the classic concept of Dotter. It was argued that arterial balloon dilatation is achieved by intimal disruption and overstretching of the arterial wall, not by remodeling of atheromatous material.

Angioplasty, Balloon↗
PubMed1984

Effect of prostaglandin inhibition on the renal vascular response to ionic and non-ionic contrast media in the dog.

In an attempt to study the role of prostaglandins in the renal vascular response to contrast media in mongrel dogs, renal arterial injections of 6 ml of either the non-ionic contrast medium Iopamidol or the ionic medium diatrizoate meglumine/Na+ were performed, before and after intravenous injection of a buffered solution of acetylsalicylic acid (10 mg/kg) (ASA). Renal blood flow was recorded using non-occluding electromagnetic flow probes. The resting renal blood flow was significantly reduced after ASA. The usual biphasic response to contrast injection was observed both before and after ASA, and using either contrast medium. Analysis of the results failed to show any difference in degree of vasodilation or vasoconstriction after ASA. We conclude that prostaglandins may affect the resting level of renal blood flow but are not mediators of the instantaneous changes in response to contrast injection.

Animals↗