Biomedical subjects

K Amplatz

Publications and source records attributed to K Amplatz.

At least 19 recordsLinked to original sources

PubMed2001

Renal artery embolization with diluted hot contrast medium: an experimental study.

PURPOSE: To evaluate the safety and efficacy of diluted hot contrast medium to embolize the renal arteries in a canine model. MATERIALS AND METHODS: Transcatheter embolization was performed in 15 dogs (five dogs in each phase: I, II, and control). The diluted hot contrast medium was heated to 90 degrees C--100 degrees C and 30--60 mL were injected into a renal artery of each dog in phase I (optimization studies) and II (efficacy studies). In the control group, balloon inflation was performed without injection of diluted hot contrast medium. The temperature measurement was performed on one dog in phase I by temperature probe. Follow-up angiography was performed immediately (n = 15), at 1 week (n = 9), at 1 month (n = 9), and after 3 months (n = 5). All dogs were killed and kidneys were removed for histologic examination. RESULTS: The procedure was performed successfully in all dogs. Follow-up angiography showed complete obstruction of the injected renal arteries in phases I and II. The microscopic findings showed acute full-thickness necrosis of the renal cortex and renal artery in phase I, and complete coagulative necrosis of the cortex, medulla, and intrarenal blood vessels in phase II. There were no histologic changes of renal veins, inferior vena cava (IVC), and aorta. There were nonspecific findings in the control group. CONCLUSION: This preliminary experimental study suggests that diluted hot contrast medium may be a safe agent for renal ablation without thrombus formation in the renal vein or IVC.

Animals↗

PubMed1999

New device for closure of muscular ventricular septal defects in a canine model.

BACKGROUND: Repair of muscular ventricular septal defects (MVSDs) has always been challenging to the surgeon. Long-term morbidity and mortality are significantly increased if the defects are closed via left ventriculotomy or if they are associated with other complex congenital anomalies. The purpose of this study was to close MVSDs with the Amplatz ventricular septal defect device. This device is constructed from 0.004-in nitinol wire mesh filled with polyester fibers. It is retrievable, repositionable, self-centering, and of low profile. METHODS AND RESULTS: MVSDs were created with the help of a sharp punch in 10 dogs. The location of the defects was anterior muscular (n=3), midmuscular (n=3), apical (n=3), and inlet muscular (n=1). The diameter of the defects ranged from 6 to 14 mm. All defects were closed in the catheterization laboratory. The device was placed with the help of transesophageal echocardiography and fluoroscopy. A 7F sheath was used to deploy the device from the right ventricular side in 8 and the left ventricular side in 2 dogs. Placement was successful in all animals. The complete closure rate was 30% (3/10) immediately after placement and 100% at 1-week follow-up. Pathological examination of the heart revealed complete endothelialization of the device in dogs killed after 3 months. CONCLUSIONS: The Amplatz ventricular septal defect device appears highly efficacious in closing MVSDs. The advantages include a small delivery sheath, complete retrievability before release, and the fact that it is self-centering and self-expanding, thereby making it an attractive option in smaller children.

Alloys↗

PubMed1999

A new technique for sizing of atrial septal defects.

This article evaluates a new compliant balloon catheter for sizing of Atrial Septal Defects (ASDs) in vitro and in vivo using X-ray and echo measurements. A phantom consisting of a plastic plate with 17 circular holes varying from 8 to 30 mm was used to determine the accuracy of the measurements. The catheter has a 7 Fr shaft with a double lumen. The balloon is made from a 0.002" plastic membrane. Four platinum marker bands on the shaft of the catheter allow radiographic measurements. The balloon catheter was placed through various holes of the phantom and inflated with 38% contrast medium. X-ray measurement by video and cine recording were performed and compared with the true measurement of the model. The study was carried out in a double blind fashion. For echo measurements, the plastic model was immersed in a water bath. The balloon was inflated with water and measured in a long-axis view. The actual diameters were compared with the measurements obtained by video, cine, and echo recordings. One young pig with a surgically created ASD was used for in vivo measurement. The balloon catheter was passed through the ASD over an exchange wire, inflated with diluted contrast medium until a waist was observed, which was measured by video and cine techniques. The animal was euthanized, and the defect was measured by a tapered measuring probe. The difference between the actual size and measurements obtained by video recordings was 0.54 +/- 0.30 mm, by cine 0.62 +/- 0.20 mm, and by echo measurements 0.60 +/- 0.43 mm. All measurements were less than 1 mm in error except for four measurements (<1.5 mm). A strong correlation was present between each two groups (r = 0.99, P < 0.0001). In the in vivo study, the size of the video and cine recordings (14.2 and 13.9 mm, respectively) were very closer to the actual size (14 mm) as measured by a probe in the postmortem specimen. The new balloon catheter provides a more rapid and precise determination of the stretched diameter of atrial septal defects. It eliminates the error of pulling a catheter through the communication. This new technique should be of benefit to all investigators using septal occlusion devices and will facilitate the selection of the properly sized Amplatzer septal occluder.

Animals↗

PubMed1999

New self-expanding patent foramen ovale occlusion device.

Our purpose was to evaluate a new self-expanding device for closure of the patent foramen ovale (PFO). A transeptal catheter passage through the flap of the fossa ovalis was performed with a transeptal needle inside a catheter, creating a PFO in two minipigs. In an additional five animals, a naturally occurring PFO was found. The device is made from 0.005 inch nitinol wire mesh with polyester fabric inside, similar in construction to the Amplatzer atrial septal occluder. However, the left atrial disc is smaller (18 mm) than the right atrial disc (26 mm). Both discs are connected by a very short flexible waist (3 mm) that allows free movement of both retention discs. Pulmonary and right atrial angiography were performed after placement, at 1 month, and at 3 months follow-up. Placement of the device was technically successful in six animals. One animal died from ventricular fibrillation during placement. Pulmonary angiography and echocardiography showed complete occlusion of the PFO in six animals. Two animals were sacrificed after 1 month and four animals after 3 months. In the animals sacrificed at 1 month, histopathological examination showed partial (n = 2) endothelialization, and in the 3 months follow-up group (n = 4) endothelialization was complete. The device appears to be highly effective for occlusion of PFOs. This procedure may be performed as an outpatient procedure due to the small 7 Fr delivery system sheath. Cathet. Cardiovasc. Intervent. 47:370-376, 1999.

Alloys↗

PubMed1999

The nitinol vascular occlusion plug: preliminary experimental evaluation in peripheral veins.

PURPOSE: To compare the nitinol occlusion plug with standard stainless steel coils for the occlusion of moderate-size peripheral veins. MATERIALS AND METHODS: The nitinol plug is a braided multilayered vascular occlusion device filled with thrombogenic polyester fibers. It is self-expanding and can be recaptured into its 6-F introducing sheath for repositioning prior to detachment. Ten occlusion procedures were performed in five dogs from a retrograde transjugular venous approach. Five nitinol plugs (diameter: 7.4 mm +/- 0.5) were deployed in five femoropopliteal veins (diameter: 6.5 mm +/- 0.7; mean oversizing 14.6%). Two sequential Gianturco coils (diameter: 7.4 mm +/- 0.9) were deployed in the corresponding contralateral veins (diameter: 6.2 mm +/- 0.8; mean oversizing 19.6%). Follow-up venography was performed at 1 month, following which the animals were killed and the vessels were explanted. RESULTS: Time-to-occlusion was significantly shorter with the nitinol plug as compared to two Gianturco coils (4.2 minutes +/- 3.4 vs 25.6 minutes +/- 14.1, respectively [P < .03]). At 1 month all but one coil-doublet (80%) had recanalized or migrated, compared to only one nitinol occluder (20%, P < .04). Histopathologic examination of plug-occluded veins showed a uniform organized matrix and underlying intimal proliferative response. CONCLUSION: A single nitinol occluder resulted in significantly faster occlusion time and significantly lower recanalization or migration rate than two Gianturco coils, in moderate-size peripheral veins.

Alloys↗

PubMed1999

Injury potential to venous valves from the Amplatz thrombectomy device.

PURPOSE: To evaluate the acute effects of the Amplatz thrombectomy device (ATD) on peripheral venous valves in a canine model. MATERIALS AND METHODS: ATD thrombectomy was performed in 17 veins, and control experiments with use of an 8-F sheath-dilator were performed in four veins. Prethrombectomy ascending venography was performed, followed by device passage across the vein segment. Post-thrombectomy ascending venography was then performed, followed by heparinization and euthanasia. The treated veins were carefully explanted and stored in formaldehyde for histopathologic examination. Severity of valve injury was graded on a scale of 0 to 4. RESULTS: In ATD-treated veins: 10 veins sustained no injury [grade 0] (diameter, 6.7 mm +/- 1.7; antegrade/retrograde approach, 5/5), five veins sustained mild injury [grade 1-2] (diameter, 5.2 mm +/- 0.8; antegrade/retrograde, 3/2), while the remaining two veins sustained moderate-to-severe injury [grade 3-4] (diameter, 5 and 6 mm; antegrade/retrograde, 1/1). In sheath-dilator treated veins: no injury [grade 0] in any of the four treated veins (mean diameter, 5.5 mm +/- 0.6; all retrograde). In ATD-treated veins, valve injury (of any grade) was significantly more frequent in veins 6 mm or less in diameter than in veins at least 7 mm in diameter (seven of 12 vs zero of five; P < .03). There was no significant association between thrombectomy approach and injury grade. CONCLUSION: Veins 7 mm or greater in diameter were associated with no significant valve injury during ATD thrombectomy. However, long-term and short-term effects on valvular function will need to be assessed.

Animals↗

PubMed1997

Transvenous closure of secundum atrial septal defects: preliminary results with a new self-expanding nitinol prosthesis in a swine model.

BACKGROUND: Our purpose was to evaluate a new prosthesis for percutaneous closure of secundum atrial septal defects (ASDs). METHODS AND RESULTS: Percutaneous closure of surgically created fossa ovalis ASD was attempted in 15 minipigs. The mean balloon-stretched ASD diameter was 12.3+/-2.3 mm (range, 10 to 16 mm). The self-expanding prosthesis was braided from 0.005-in Nitinol wires in the shape of two flat buttons with a short connecting waist with a diameter corresponding to that of the defect to be closed. Polyester filling was added to enhance thrombogenicity. Pulmonary arteriography with levo-phase was obtained before placement; immediately after placement; and at 1-week, 1-month, and 3-month follow-ups. Four animals were killed at 1 week, 1 month, and 3 months for histopathological correlation. Three deaths resulted from ventricular fibrillation (one during anesthesia and two during the placement procedure). Successful placement of the prosthesis was achieved in the remaining 12 animals. Overall immediate ASD closure on angiography occurred in 7 of 12 animals (all polyester-filled prostheses). Absent or trace shunt by angiography was present in 11 of 12 devices at 1 week, with the remaining one demonstrating a small shunt. All septal defects were completely closed at 1 month with the exception of one case in which delayed partial dislodgment of an undersized prosthesis into the right atrium had developed. Closure rate at 3 months was 100%. Neoendothelialization and fibrous incorporation of the prosthesis were completed within 1 to 3 months. CONCLUSIONS: Effective and permanent occlusion of secundum ASDs is feasible with a device that offers the advantages of easy placement, self-centering, and repositionability.

Alloys↗

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↗