Biomedical subjects

K Amplatz

Publications and source records attributed to K Amplatz.

At least 19 recordsLinked to original sources

PubMed1995

Transcatheter occlusion of patent ductus arteriosus using a newly developed self-expanding device. Evaluation in a canine model.

RATIONALE AND OBJECTIVES: A new occlusion device designed for use in a patent ductus arteriosus was tested in an animal model. METHODS: The device consists of a self-expanding conical-shaped stainless steel mesh, with hooks encircling the expanding end acting to secure the device within the ductus. A screw thread at the apex allows attachment to a stylet, and a 6 F delivery system is used. Placement of the device was attempted in 20 canines that previously had a vascular graft surgically inserted between the descending thoracic aorta and main pulmonary artery, creating the patent ductus model. Angiographic follow-up at regular intervals was performed over a 3-month period. RESULTS: Early cases resulted in device misplacement and migration because of inaccurate assessment of ductus position and size. In 15 canines the device was placed within the ductus and regularly assessed over the 3-month placement period. Ductus occlusion occurred within 1 week in 12 of 13 dogs (92%) when device placement was considered ideal. In two dogs where significant protrusion of the device from the ductus was evident (either into the aorta or main pulmonary artery) ductus closure was delayed but present by 3 months, resulting in a 93% overall closure rate at this time. In one dog, the ductus remained partially opened. CONCLUSIONS: This self-expanding patent ductus arteriosus occlusion device is promising. The 6 F delivery system is advantageous over other devices currently available, making it more suited for use in the pediatric population. Accurate assessment of the ductus is imperative, however, to enable correct device sizing. The screw thread system allows the device to be repositioned if desired prior to deployment.

Animals↗

PubMed1994

Relation between changes in severity of coronary artery stenosis and anginal patterns.

Although myocardial ischemia causes angina pectoris, angina and the severity of coronary artery stenosis in individuals do not correlate. However, changes in anginal status over time correlated with changes in the severity of coronary artery stenosis as determined by repeated coronary arteriograms has not been previously studied. Coronary arteriograms, done both at entry into the Program on the Surgical Control of the Hyperlipidemias (POSCH) and 3 years later, were blindly graded for changes in overall severity of coronary artery stenosis according to protocol by the POSCH Arteriography Review Committee. Arteriographic and clinical data from 376 control subjects (347 men, 29 women) were analyzed. There was no statistically significant relation over a long-term (3 year) period between the absence, presence, development, or disappearance of angina pectoris and changes in coronary artery stenosis severity as determined by coronary arteriography.

Analysis of Variance↗

PubMed1994

Alternative design for radiologic guidance in video thoracoscopic surgery.

RATIONALE AND OBJECTIVES: Easy dislodgment and a pneumothorax rate of up to 50% have been reported with the use of mammographic hookwires for radiologic guidance in thoracoscopic surgery. An alternative design is described and preliminary in vitro results are reported. METHODS: The new design is based on the T-fastener used in percutaneous gastrostomies and can be deposited with a 20-Fr guidance needle. In vitro measurements of the anchoring capability of this design were compared with the anchoring capability of the Hawkin's III (Meditech/Boston Scientific, Watertown, MA) mammographic hook wire system. RESULTS: Anchoring capabilities of the alternative anchoring design and the Hawkin's III mammographic hook wire localization system are comparable. Complete dislodgement of both anchors occurs at approximately 350 gm. CONCLUSIONS: Preliminary in vitro investigation demonstrated similar anchoring capabilities of the new design and mammographic hook wires. Potential advantages of this suture-based localization device over hook wires are discussed.

Equipment Design↗

PubMed1994

In vitro metal fatigue testing of inferior vena cava filters.

RATIONALE AND OBJECTIVES: Inferior vena cava filter fractures have been described in vivo on several occasions. No studies have compared the fatigue life of the different filter types. Four different, frequently used filters (Vena-Tech filters [VTF], stainless-steel Greenfield filters [SSGF], Simon nitinol filters [SNF], and titanium Greenfield filters [TGF]) were, therefore, tested with regard to fatigue life. METHODS: Ten filters of each type were tested by compressing the filter legs repeatedly. A travel distance of 1.5 cm was used, setting minimal and maximal filter leg separations of 1.0 cm and 2.5 cm, respectively. The endpoint was filter fracture or 10,000,000 compressions. The test was then repeated on five of the filters from each group, but on a different filter leg pair. RESULTS: Seven of 10 VTFs fractured during the first part of the study, and all five VTFs fractured during the second part of the study. One SSGF fractured in each part of the study. None of the SNFs or the TGFs fractured. Significant difference in fracture frequency was found. CONCLUSION: The VTFs appear to have the shortest fatigue life. The TGF and the SNF have a fatigue life exceeding the test limits. The consequences of filter fracture are unknown.

Alloys↗

PubMed1993

Evaluation of a new vascular occlusion device.

RATIONALE AND OBJECTIVES: A new vascular occlusion device was tested in canine femoral and iliac arteries and in an animal model of a patent ductus arteriosus (PDA). METHODS: Four variations of the vascular plug were placed into 18 iliac or femoral arteries of 17 mongrel dogs. Follow-up angiography was performed 1 hour and, if necessary, 2 hours after placement in all animals, 14 of which were then killed. Three dogs were followed angiographically for 2 weeks to 3 months. The "butterfly" plug was then tested in a canine model of a PDA. RESULTS: All plugs contained thrombi, and 12 of the 18 devices caused complete or nearly complete vascular occlusion within 2 hours. In one dog, one vascular plug had eroded through the vessel wall at 3 months without clinical sequelae. Successful PDA occlusion was achieved in 1 or 2 days in 6 of 8 dogs. Three misplacements occurred, one of which resulted in death. DISCUSSION: The balloon-expandable vascular plug appears to be a promising device for occlusion of blood vessels. Migration has not been observed once the device is placed, thus, sizing of the device appears less critical than with coils. However, modification of the delivery system and considerably more experience with the device are necessary to reduce the risk of misplacement.

Animals↗

PubMed1993

Improved mammography with a reduced radiation dose.

A 2-cm-high focused air-interspaced grid with a 7:1 ratio and eight lamellae per inch was devised. The grid is arc-shaped and pivots on its focal point, the anode-cathode axis. Milliamperage was 35% less for breast phantom radiographs obtained with the new grid versus those obtained with a conventional 5:1 mammographic grid. In a comparison study of five mammograms, each evaluated for five parameters, the images obtained with the new grid were judged to be of equal or better quality than those obtained with a conventional grid in 17 of 20 comparisons.

Female↗

PubMed1993

Mechanical thrombectomy: results of early experience.

PURPOSE: To evaluate the clinical application of a mechanical thrombectomy device in occluded lower extremity arteries and bypass grafts. MATERIALS AND METHODS: A mechanical thrombectomy device was used in five patients with acutely occluded lower extremity bypass grafts (n = 2) or superficial femoral arteries (n = 3). RESULTS: The thrombus was completely removed in three cases (two bypass grafts and one native superficial femoral artery). In two of the patients with occlusions in the native superficial femoral artery, the thrombus was partially removed. In these two patients, the aspirate demonstrated a more fibrous thrombus that was not easily fragmented. In one of these two patients, the coagulum was thought to be embolic from the heart. CONCLUSION: The thrombectomy device works well in recent thromboses, particularly in polytetrafluoroethylene grafts in which organization does not occur. Its efficacy in chronically occluded vessels is not certain.

Aged↗

PubMed1992

Changes in sequential coronary arteriograms and subsequent coronary events. Surgical Control of the Hyperlipidemias (POSCH) Group.

OBJECTIVE: Assessment of the relationship between changes in sequential coronary arteriograms and subsequent clinical coronary events. DESIGN: The Program on the Surgical Control of the Hyperlipidemias, a randomized secondary atherosclerosis intervention trial, obtained coronary arteriograms at baseline, 3, 5, and 7 or 10 years of follow-up. Assessments of changes between pairs of coronary arteriograms were made by two-member panels blinded to the patients' assigned treatment and to the temporal sequence of the films. The relationship of changes between the baseline and the 3-year follow-up arteriograms and subsequent clinical coronary events was examined. SETTING: Three university hospitals and one private primary care facility. PATIENTS: A total of 838 patients, with 417 patients randomized to the control group and 421 to the intervention group. Of all patients, 695 had baseline and 3-year arteriograms. INTERVENTION: The control group received American Heart Association Phase II diet instruction and the intervention group received identical dietary instruction plus a partial ileal bypass operation. MAIN OUTCOME MEASURE: The use of arteriographic changes as a predictor of subsequent clinical coronary events. RESULTS: Changes between the baseline and the 3-year coronary arteriographic overall disease assessment were significantly associated with subsequent overall and atherosclerotic coronary heart disease mortality (P less than .01). For the combined end point of atherosclerotic coronary heart disease mortality or confirmed nonfatal myocardial infarction, a significant relationship between the overall disease assessment and subsequent clinical events was found in the control group (P less than .0001) and in the surgery group (P = .04). For this combined end point, however, the control and the surgery groups were different with respect to clinical coronary events after 3 years, stratified by the baseline to 3-year overall disease assessment (P less than .001, unadjusted; P = .06, adjusted for 3-year clinical covariates). CONCLUSIONS: Coronary arteriographic changes can be used in atherosclerosis intervention trials as a limited surrogate end point for certain clinical coronary events. This relationship is statistically compelling for overall mortality and atherosclerotic coronary heart disease mortality. For an individual patient, changes in the severity of coronary atherosclerosis seen on sequential coronary arteriograms can serve as prognostic indicators for subsequent overall or atherosclerotic coronary heart disease mortality.

Adult↗

PubMed1992

Correlation of coronary with peripheral arterial stenosis. The POSCH Group.

Although it is known that patients with peripheral arterial disease are at high risk for coronary arterial stenosis, it is not known if, conversely, coronary artery disease correlates with peripheral arterial stenosis. In the Program on Surgical Control of the Hyperlipidemias (POSCH) coronary and aortic-iliac-femoral arteriograms were systematically analyzed. POSCH is a randomised, controlled secondary intervention clinical trial of hyperlipidemic subjects, ages 30-64 years with one myocardial infarction and angiographically demonstrable coronary arterial stenosis. Of the 838 subjects enrolled in the study, 436 had diagnostic visualization of both the coronary and aortic-iliac-femoral systems. The aortic-iliac-femoral arteries were normal in 44% (194/436) of the subjects. In contrast, only 9% (37/436) of the subjects had less than 50% stenosis of all 3 coronary arteries. However, there was a positive correlation between the severity of the stenosis, if present, in the aortic-iliac-femoral arteries and that in the coronary arteries (P less than 0.001). The subjects who did exhibit aortic-iliac-femoral arterial disease were significantly older and more frequently were cigarette smokers. We conclude that subjects with coronary arterial stenosis frequently are free of peripheral arterial disease.

Adult↗

PubMed1992

Pneumothorax after lung biopsy: prevention with transpleural placement of compressed collagen foam plugs.

The effectiveness of pleural sealing with a compressed collagen foam plug in preventing the development of pneumothorax was evaluated in a prospective, comparative study of 50 patients undergoing transthoracic needle biopsies. The 4-cm-long plug was deposited through the thin-walled guidance needle at the end of the procedure in a position where it would cross both the visceral and the parietal pleura. The prevalence of postbiopsy pneumothorax was 28% (seven of 25 patients) in the control group and 8% (two of 25 patients) in the plug group. In each study group, two patients with pneumothoraces required chest tubes. Although further experience is necessary, the authors conclude that transpleural collagen foam plug placement may be an effective supplement for transthoracic needle biopsies.

Biopsy, Needle↗

PubMed1991

Positive and negative exercise test results with and without exercise-induced angina in patients with one healed myocardial infarction: analysis of baseline variables and long-term prognosis.

The prognostic implications of exercise test results with and without exercised-induced angina are not completely understood. In the Program On the Surgical Control Of the Hyperlipidemias (POSCH), 838 subjects with hyperlipidemia who had one healed myocardial infarction were studied and followed for 6 to 13 years (mean 8.6). Of the 417 control subjects, 279 had a treadmill exercise test result that was definitely positive or negative. Angina was also induced by exercise in 30% (45/150) and 8% (10/129) of those with a positive and a negative test result, respectively (p less than 0.0001). The data showed no difference between subjects with a positive or a negative test result with or without angina as regards levels of blood lipids, type of myocardial infarction (Q or non-Q wave), left ventricular function, or prognosis as defined by death, atherosclerotic coronary heart disease death, or myocardial infarction.

Angina Pectoris↗

PubMed1991

Incomplete opening of LGM (Vena Tech) filters inserted via the transjugular approach.

Over a 12-month period, 216 LGM vena caval filters were placed in 216 patients at four institutions. The transjugular approach was used in 31 of 216 insertions (14%); 185 of 216 filters (86%) were inserted via the femoral route. Incomplete opening of filters was encountered in 13 of 31 transjugular insertions (41%) and none of 185 transfemoral insertions. Delayed spontaneous filter opening occurred in three of 12 cases (25%) of incomplete opening (in which follow-up was available) at 5 minutes, 4 days, and 2 months after insertion. One filter opened completely after catheter manipulations. Several mechanisms explaining this complication are proposed. In its present form, the LGM filter should not be inserted via the jugular route. Since the filtering capabilities of the incompletely opened LGM device have been shown to be diminished in vitro, it may be advisable to place a second filter cephalad to an incompletely opened LGM filter.

Equipment Failure↗

PubMed1991

Spermatic vein occlusion with hot contrast material: angiographic results.

Spermatic vein occlusion by means of selective injection of boiling contrast material into the spermatic vein was attempted in 175 men with symptomatic varicoceles or infertility. Seventy-six patients (43%) returned for follow-up venography. Of 115 veins injected, 96 (83%) were totally occluded on the follow-up venogram obtained at 6 weeks to 2 years after injection. In the latter portion of the study, the technique was changed slightly, with injection of larger volumes of hot contrast material, resulting in a 91% occlusion rate. Each vein that was found patent on the follow-up venogram (19 of 115 [16%]) was assessed radiographically, and results were categorized as grade 1, a complete failure in which there was no change from the presclerotherapy appearance (nine of 19 [47%]); grade 2, a failure in which the treated vein was smaller but patent (five of 19 [26%]); or grade 3, a failure in which the treated vein was occluded with newly developed collateral vessels (five of 19 [26%]). The pretreatment size of the spermatic vein and the quantity of hot contrast material injected were both statistically significant factors in the treatment outcome.

Adolescent↗

PubMed1991

Thrombectomy with the transluminal endarterectomy catheter (TEC) system: experimental study and case report.

The transluminal endarterectomy catheter (TEC) system was employed as a percutaneous rotational mechanical thrombectomy device in 1-week-old thrombi in five dogs (five thrombosed polytetrafluoroethylene grafts and four thrombosed native superficial femoral arteries). Luminal patency was restored in all vessels with no angiographic evidence of significant distal embolization. The TEC catheter was also successfully used for recanalization of the superior vena cava in a patient with superior vena cava syndrome.

Animals↗

PubMed1991

Urokinase-mediated thrombolysis: a dose-response relationship in cats. Work in progress.

A cat model was developed to study thrombolytic agents. The infrarenal aorta was surgically exposed, all side branches were ligated, and both ends of the segment were occluded. After preformed clot was injected into the segment, proximal flow was restored and a distal stenosis was created. Urokinase was infused at rates varying from 4,000 to 250,000 U/h. Amount of remaining clot was quantified every 15 minutes with cine angiography. Pre- and postinfusion measurements of prothrombin time, partial thromboplastin time, thrombin time, and levels of fibrinogen and fibrin degradation products were obtained. A graph of thrombolysis rate versus infusion rate was obtained yielding maximal thrombolytic activity at 126,000 U/h and 90% of maximal activity at an infusion rate of 70,000 U/h. Levels of fibrin degradation products did not change. Prothrombin, partial thromboplastin, and thrombin times increased with increasing infusion rates, leveling off at 100,000 U/h, while fibrinogen levels decreased, with a plateau at 50,000 U/h.

Animals↗

PubMed1991

Angiogenesis after hepatic arterial occlusion in liver transplant patients.

The authors describe 10 liver transplant recipients who developed occlusion of the hepatic artery or aortic conduit. Since all potential collateral arterial supply to the transplant is severed at hepatectomy, hepatic artery occlusion is usually a catastrophic event that necessitates repeat transplantation. Four patients died within 8 weeks of transplantation. The remaining six developed spontaneous arterial liver revascularization. This phenomenon is believed to be an example of neovascularization through angiogenesis. Radiologic studies, particularly duplex sonography and angiography, were helpful in the evaluation of transplant vascular integrity. The tissues of the omentum and the mesentery have known angiogenic ability. The authors postulate that in transplantation techniques in which these tissues are placed close to the transplanted liver (eg, Roux-en-Y choledochojejunostomy), the omental and mesenteric tissues may be the source of neovascularity.

Adult↗

PubMed1991

Nonselective and semiselective catheters for renal artery evaluation: experimental study.

Abdominal aortography is widely used for evaluation of potential renal donors and for patients with renal failure or hypertension in whom a renal artery ostial or polar branch stenosis is suspected. It would be desirable to use a catheter that consistently enables good bilateral renal artery and polar branch visualization without opacification of overlying mesenteric vessels. Existing and newly designed catheters were compared to determine the optimal design necessary for these studies. An in vitro model of the abdominal aorta and its branches was made, and dye dilution densitometry was employed for quantitative evaluation. Semiselective catheters demonstrated significantly increased renal artery opacification with decreased mesenteric opacification in this in vitro model.

Aorta, Abdominal↗

PubMed1991

Nitinol gooseneck snare for removal of foreign bodies: experimental study and clinical evaluation.

The authors describe their use of a new right-angle snare made of nickel-titanium (nitinol) cable for retrieval of foreign bodies and iatrogenically placed devices. The snare loop is at right angles to the cable and comes in five sizes (5, 10, 15, 25, and 35 mm); its radiographic visualization is enhanced by gold-plated tungsten coils. This snare was used to retrieve wire and catheter fragments introduced into the thoracic vasculature of four dogs. Eleven of 13 attempts were successful. Three attempts to retrieve intravascular foreign bodies were successful in two patients; in one of these patients, a 10-mm snare was used to remove a fractured end of a ventriculoatrial shunt tube from the left pulmonary artery. In three other patients, four ureteral stents were successfully removed under fluoroscopic guidance. All retrievals were performed through a vascular sheath and with standard techniques and angiographic equipment. No complications were seen in any of the patients or dogs.

Alloys↗