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Biomedical subjects

A C Waltman

Publications and source records attributed to A C Waltman.

At least 37 records · Page 2Linked to original sources
PubMed1996

Guide-wire entrapment by inferior vena caval filters: in vitro evaluation.

PURPOSE: To study guide-wire engagement and entrapment by inferior vena caval (IVC) filters. MATERIALS AND METHODS: Patterns of engagement were determined in six IVC filters with four commonly used guide wires in a simulated IVC. Force required to disengage guide wires from filters was measured. RESULTS: Eleven engagement patterns were identified with J-tipped guide wires; straight guide wires never engaged. The Simon-Nitinol filter engaged guide wires with the highest frequency (P < .05). The 15-J wire was engaged most frequently overall (P < .0005) but disengaged with forces not significantly different (P > .05) from those required to open the J. Entrapment occurred with only the Vena-Tech (VT) and 12-F stainless steel Greenfield (12SSG) filters and the 1.5-J and 3-J guide wires. The former guide wire became entrapped regardless of engagement pattern; the latter became entrapped only when engaged in the hole in the apex of the 12SSG and VT filters. CONCLUSION: Guide wires with a J tip 3 mm or less in radius are at risk for entrapment by the 12SSG and VT filters.

Catheterization, Central Venous↗
PubMed1996

Renal insufficiency: gadopentetate dimeglumine as a radiographic contrast agent during peripheral vascular interventional procedures.

Gadopentetate dimeglumine diluted 1:1 with 0.9% normal saline was used as the radiographic contrast agent in two patients with azotemia who underwent peripheral vascular interventional procedures. The patients had no evidence of contrast material-induced renal failure after the procedures. The radiographic attenuation of the diluted gadopentetate dimeglumine was equivalent to diatrizoate meglumine diluted to 40 mg iodine per milliliter. Gadopentetate dimeglumine is an alternative radiographic contrast material for azotemic patients.

Aged↗
PubMed1996

Long-term outcomes of radiologically placed arm ports.

PURPOSE: To evaluate long-term outcomes of an initial experience with radiologic placement of arm ports. MATERIALS AND METHODS: The follow-up of 46 consecutive arm port placements (44 patients) was reviewed by means of chart review (hospital, office, and clinic) in 41 patients, telephone interview in 20, physical, examination in 15, and venous ultrasound in 14. Data on port complications and function were recorded. Statistical methods were the Fisher Exact Test and Cochran-Mantel-Haenszel Test. RESULTS: Technical success for placement was 100%. Follow-up was obtained in 41 (93%) of the 44 patients (43 ports); mean days of catheter use was 344 days (total, 14,797 days; range, 10-1,104 days; median, 278 days). Rate (per 100 catheter days) of symptomatic central venous thrombosis was 0.054; arm phlebitis, 0.007; confirmed infection, 0.034; and catheter dysfunction, 0.095. Prophylactic anti-coagulants did not affect symptomatic central venous thrombosis (P > .05, Fisher Exact Test). Catheter tip high in the right atrium was marginally associated with better catheter function (P = .041, Fischer Exact Test). CONCLUSION: Good long-term results can be anticipated with radiologic placement of arm ports.

Adult↗
PubMed1996

Embolization of pulmonary catheter-induced pulmonary artery pseudoaneurysms.

STUDY OBJECTIVES: To determine the outcome of patients with pulmonary catheter-induced pulmonary artery pseudoansurysms (PSAs) treated with embolization. DESIGN: Retrospective outcomes review. SETTING: Large urban tertiary-care hospital. PATIENTS: All patients who presented to diagnostic angiography for ruptured pulmonary artery PSA caused by pulmonary artery catheters (PACs) from November 1990 to September 1995. A total of six patients were examined. INTERVENTIONS: Transcatheter embolotherapy with coils, absorbable gelatin sponges (Gelfoam), and suture material. RESULTS: These procedures were technically successful in all patients, and none had recurrent hemoptysis. Four of the six patients were discharged from the hospital. CONCLUSION: Embolotherapy is a useful alternative to surgery for some patients with PAC-induced pulmonary PSA.

Aged↗
PubMed1996

Preoperative staging of cancer of the pancreas: value of MR angiography versus conventional angiography in detecting portal venous invasion.

OBJECTIVE: The purpose of this study was to compare contrast-enhanced MR angiography with conventional catheter angiography for detecting portal venous invasion in the preoperative staging of pancreatic cancer, using the surgical confirmation of vascular involvement as the standard of truth. SUBJECTS AND METHODS: MR and conventional angiography were performed in 20 patients with pancreatic carcinoma, with surgical confirmation in all cases. MR angiography was performed at 1.5 T, with coronal (2.9 mm) and axial (6.0 mm) contrast-enhanced breath-hold two-dimensional time-of-flight imaging. Data from each imaging technique were collected prospectively and analyzed in a blinded fashion by expert vascular radiologists. Vascular involvement in each patient and in each vessel (main portal vein, confluence, splenic vein, and superior mesenteric vein) determined whether the tumor was resectable (normal, abutment) or nonresectable (encased, occluded). Surgical confirmation of the vascular involvement of the portal venous structures was used as the standard of truth in all patients. RESULTS: Among the 20 patients, 11 tumors were surgically resectable and seven were nonresectable with performance of a palliative bypass. MR angiography and conventional angiography had an overall concordance in 65% of patients (13/20; seven resectable, four nonresectable, two false-negatives) on the basis of the vascular status in each patient of the portal venous structures and in 84% (47/56) of the individual vessels surgically confirmed. MR angiography correctly identified 11 of 11 resectable patients and five of nine nonresectable patients, with four false-negative cases. Conventional angiography correctly identified seven of 11 resectable patients and six of nine nonresectable patients, with three false-negative cases and four false-positive cases. CONCLUSION: The lack of false-positives by MR angiography suggests that MR imaging may provide a noninvasive screen for nonresectability on the basis of vascular involvement, with no patients with potentially resectable tumors being denied surgery by MR angiography in this cohort. However, the presence of false-negatives using MR angiography indicates the procedure would still not fully eliminate unnecessary laparotomies.

Aged↗
PubMed1996

MR angiography of tibial runoff vessels: imaging with the head coil compared with conventional arteriography.

OBJECTIVE: We compared peripheral vascular MR angiography done with a standard transmit-receive head coil with conventional arteriography for identifying and evaluating runoff vessels below the knee. MATERIALS AND METHODS: We examined 55 legs in 31 symptomatic patients with both conventional contrast angiography and gradient-echo two-dimensional time-of-flight MR angiography. Both legs of patients were placed in a standard transmit-receive head coil for MR angiography and were imaged simultaneously. For evaluation of stenoses, images of vessels were divided into 10 segments, and each segment was graded on a four-point scale. RESULTS: In the 393 native vascular segments evaluated, the sensitivity of MR angiography in identifying normal vessels was 95% and the specificity was 98%. In detecting segmental occlusion, MR angiography was 98% sensitive and 97% specific. Sensitivity and specificity for stenoses greater than 75% were 98% and 96%, respectively, and for stenoses greater than 50%, they were 98% and 95%, respectively. Interpretative discrepancies were found in 35 vessel segments in 18 legs; none was of clinical relevance. Of all vessel segments shown as occluded by conventional angiography, 1% appeared patent on MR angiograms. No vessel segments shown as normal on MR angiograms were found to be occluded on conventional angiograms. CONCLUSION: When performed simultaneously on both legs of symptomatic patients, 2D time-of-flight MR angiography with a standard transmit-receive head coil provides a time-efficient and highly sensitive and specific means of evaluating below-knee runoff.

Adult↗
PubMed1995

Complications of peripheral arteriography: a new system to identify patients at increased risk.

PURPOSE: The most quoted literature on arteriographic complications is based on self-reports collected during the mid 1970s. We sought to determine whether those results remain valid despite changes in arteriographic practice and whether patient subgroups at increased risk could be identified. METHODS: Five hundred forty-nine consecutive patients were examined after arteriography and twice over 72 hours. Patients were telephoned at least 2 weeks later to identify delayed complications. The sample was divided into two groups to allow independent validation of suspected prognostic factors. RESULTS: The rate of major complications was 2.9% (16/549), but varied from 0.7% to 9.1% among three strata of relative risk. Rates were highest in patients studied for suspected aortic dissection, mesenteric ischemia, gastrointestinal bleeding, or symptomatic carotid artery stenosis and lowest in patients with trauma or aneurysmal disease. Patients studied for claudication or limb-threatening ischemia had intermediate risk (2.0%). Within these strata, congestive heart failure and furosemide use were the only variables independently associated with a significantly increased complication rate. CONCLUSIONS: Previous reports have overestimated the risk of arteriography for trauma or aneurysm but substantially underestimate the risk for patients with other common conditions. Such stratified complication rates are essential to understand relative costs and benefits of arteriography and other vascular imaging modalities in specific clinical situations.

Acute Kidney Injury↗
PubMed1995

Magnetic resonance angiography in the preoperative evaluation of abdominal aortic aneurysms.

PURPOSE: Contrast arteriography (CA) is a useful but invasive technique for the preoperative evaluation of patients with abdominal aortic aneurysms (AAA). To evaluate the use of magnetic resonance arteriography (MRA) as a preoperative study we prospectively studied 38 patients undergoing AAA repair. METHODS: All patients underwent biplane CA and MRA with use of a gadolinium-enhanced technique. Radiographic studies were then independently evaluated by blinded radiologists for anatomic findings with CA used as the standard. Studies were then independently evaluated by blinded vascular surgeons, and a surgical plan was made. RESULTS: With CA and intraoperative findings as the standards, MRA proved highly accurate in the determination of multiple key anatomic elements. The proximal extent of aneurysmal disease was correctly predicted in 87% (33/38) patients. Significant iliofemoral occlusive disease was identified with a sensitivity of 83% (5/6). Iliac or femoral aneurysms were detected with a sensitivity of 79% (22/28) and specificity of 86% (41/48). Significant renal artery stenosis was detected with a sensitivity of 71% (12/17) and a specificity of 99% (72/73). Accessory renal arteries were correctly identified in 71% (12/17). Surgeon evaluators correctly predicted the proximal cross-clamp site in 87% (33/38) of patients with use of MRA as compared with the actual operative conduct. Proximal anastomotic sites were correctly predicted in 95% (36/38) with MRA and 97% (37/38) with CA. Renal revascularization was predicted by MRA with a sensitivity of 91% (10/11) and specificity of 100% (65/65). The use of bifurcated aortic prostheses was correctly predicted by MRA in 75% (12/16), which was similar to that predicted by CA (81%, 13/16). CONCLUSIONS: MRA can provide preoperative anatomic information that is equivalent to CA for surgical planning. Because of favorable cost and patient safety considerations MRA will assume increasing importance in the preoperative evaluation of AAA.

Aged↗
PubMed1995

A theoretical model using mechanical principles to quantify the physical principles of balloon dilatation.

RATIONALE AND OBJECTIVES: Balloon dilatation is a mechanical form of controlled injury used to alleviate vascular stenoses. Several factors influence successful angioplasty. Few mechanical models exist to illustrate the physical principles of balloon dilatation. METHODS: We used mechanical analysis of membrane stresses, along with Laplace's law, to determine a relation between balloon inflation and dilating pressures exerted by balloons in stenoses of varying severity, length, and eccentricity. The balloons were assumed to be perfectly inelastic and flexible. We also examined the resultant stresses in the lesion wall of concentric and eccentric stenoses from exertion of dilating pressures. RESULTS: Dilating pressures depend directly on maximal balloon inflation pressure and balloon diameter. Short, focal stenoses experience greater dilating pressures, which often are several multiples of the inflation pressure, than similarly narrowed longer lesions. CONCLUSION: Dilating pressures depend on inflation pressure, balloon diameter, and lesion severity.

Angioplasty, Balloon↗
PubMed1995

Operator errors during percutaneous placement of vena cava filters.

Operator errors during percutaneous insertion of inferior vena cava (IVC) filters are procedural complications specific to filter placement that cannot be attributed to defects in the device itself. These errors can occur during preplacement imaging of the IVC, selection of the filter, or deployment of the filter. Although technical problems are reported to occur in 5-20% [1] of filter insertions, the precise frequency of operator errors is not known. This pictorial essay reviews the different types of operator errors that can occur during percutaneous insertion of IVC filters.

Humans↗
PubMed1994

MR imaging (including MR angiography) of abdominal aortic aneurysms: comparison with conventional angiography.

OBJECTIVE: The purpose of this report is to compare the results of MR imaging, including MR angiography, with the results of conventional angiography in the imaging of abdominal aortic aneurysms (AAA). SUBJECTS AND METHODS: Twenty seven nonconsecutive patients with known AAA underwent both MR imaging (including MR angiography) and conventional angiography preoperatively. MR imaging was done before angiography according to the following protocol in all patients: sagittal and coronal T1-weighted images of the abdomen, followed by axial MR angiograms obtained with a multiple overlapping thin-slab acquisition (MOTSA) three-dimensional time-of-flight (3D TOF) volume centered on the renal arteries. Last, coronal MR angiograms were obtained with a dynamic contrast-enhanced 3D TOF volume centered on the aorta. Conventional angiography was subsequently performed in all patients. Data from each study were collected prospectively and analyzed in a blinded manner. For the MR studies, all sequences were used to determine the extent of the AAA and the presence of iliac aneurysms; stenotic disease of the celiac, superior mesenteric, renal, and iliac arteries and the number and location of renal arteries were determined from the MR angiograms. For evaluation of the extent of the aneurysm, results from both techniques were compared with surgical results; otherwise MR angiography was compared with conventional angiography. Confidence intervals for sensitivity and specificity were calculated at the 95% level. The McNemar test was used for comparison of proportions. RESULTS: MR angiography had a sensitivity of 100% (4/4) and a specificity of 91% (21/23) for the four stenoses of the celiac artery that were greater than 50%. For detection of renal artery stenoses of greater than 50%, present in nine arteries, the sensitivity was 89% (8/9) and specificity was 98% (49/50). MR angiography showed 100% (54/54) of all main renal arteries and 78% (7/9) of all accessory renal arteries seen on conventional angiograms. The proximal extent of the aneurysm was correctly predicted on the basis of MR findings in 100% (26/26) of patients with surgical correlation, compared with 92% (24/26) when conventional angiograms were used. This difference was not statistically significant (p > .1). MR imaging had a sensitivity of 100% (19/19) for detection of isolated aneurysms of the common iliac artery, and MR angiography had a 100% sensitivity (5/5) and specificity (103/103) for detection of stenosis greater than 50% in the common and external iliac arteries. One circumaortic left renal vein was visualized on MR images. CONCLUSION: These results suggest that MR angiography may be a useful noninvasive method for determining the presence of coexistent celiac, superior mesenteric, renal, and iliac atherosclerotic disease in patients with AAA.

Aged↗
PubMed1993

Time of flight renal MR angiography: utility in patients with renal insufficiency.

We studied the renal arteries prospectively in 16 patients with renal insufficiency using a combination of two-dimensional and three-dimensional time of flight magnetic resonance angiography (MRA). Results were compared with conventional angiography. All renal arteries were identified by MRA. Accuracy for classifying renal arteries into patent, moderately (30-70%) stenotic, severely (> 70%) stenotic, or occluded was 91%. With regard to the presence or absence of severe occlusive disease (> 70% stenosis or occlusion) the sensitivity was 100%, with a specificity of 93%.

Aged↗
PubMed1993

The potential for lower extremity revascularization without contrast arteriography: experience with magnetic resonance angiography.

PURPOSE: We report an initial experience with 24 patients studied between March 1990 and April 1992 with magnetic resonance angiography (MRA) for lower extremity occlusive disease. METHODS: All patients underwent vascular intervention with either balloon angioplasty or bypass grafting, and in six patients this intervention was based on MRA findings alone. Eighteen patients were studied with both MRA and contrast arteriography, and there was observed agreement between the two studies in 98% of all arterial segments examined. RESULTS: Agreement between MRA and contrast arteriography was uniform for arterial segments below the inguinal ligament. Intraoperative findings and favorable early results of seven bypass grafts performed in six patients after MRA alone suggested this was a valid approach for patients at prohibitive risk of complications from contrast arteriography. CONCLUSIONS: Magnetic resonance angiography is accurate in demonstrating relevant anatomy in peripheral arterial occlusive disease and in selected patients may eliminate the need for contrast arteriography before lower extremity revascularization.

Angiography↗
PubMed1993

Renal function in patients at risk of contrast material-induced acute renal failure: noninvasive, real-time monitoring.

Real-time changes in renal function were studied in a group of 20 patients at risk of contrast-material-induced acute renal failure during different angiographic procedures. Renal function was evaluated with an ambulatory renal monitor (ARM) after a single injection of the glomerular filtration agent technetium-99m diethylenetriaminepentaacetic acid (DTPA). The ARM was used to continuously monitor the clearance of Tc-99m DTPA activity from the extracellular space in the arm of the patient during angiography. A one-compartment model was used to calculate on-line the rate constant for clearance of Tc-99m DTPA from the extracellular space. Changes in the rate constant were compared with changes in plasma creatinine level measured 1-4 days after angiography. The results showed that the ARM measured rapid changes in renal function during angiography with a resolution time of 5-10 minutes in patients with normal to moderately decreased renal function and 15-20 minutes in patients with severe renal dysfunction. The sensitivity of this technique was superior to that of plasma creatinine level analysis.

Acute Kidney Injury↗
PubMed1993

Atherosclerotic occlusive disease of the lower extremity: prospective evaluation with two-dimensional time-of-flight MR angiography.

A prospective, blinded comparison of two-dimensional time-of-flight (TOF) magnetic resonance (MR) angiography and conventional arteriography was performed in 25 patients who underwent routine arteriography for symptomatic atherosclerotic occlusive disease of the lower extremity. MR angiography was performed from the distal abdominal aorta through the popliteal trifurcation. The native arterial tree was divided into nine segments; each segment was assessed for patency (defined as stenosis < 50% of arterial diameter), moderate stenosis (50%-69%), severe stenosis (70%-99%), or occlusion (100%). In all 206 segments examined, the sensitivity of MR angiography in diagnosis of occlusion was 100%; the specificity, 98%. All long occlusions were correctly classified. In specific categories of occlusive disease, the sensitivity and specificity were as follows: in all segments with 70% or greater stenosis, including occlusions, 90% and 97%; in all segments with 50% or greater stenosis, including occlusions, 92% and 88%; in femoropopliteal segments with 50% or greater stenosis, 92% and 93%; and in iliac segments, 93% and 83%. Long occlusions were distinguished from short occlusions and stenoses; hence, MR angiography enabled identification of patients with lesions suitable for angioplasty.

Adult↗
PubMed1992

Color Doppler flow imaging appearance of a popliteal venous aneurysm.

Popliteal venous aneurysms are rare lesions that usually become evident when thrombus from within the aneurysm embolizes to the lungs. The authors report an unusual case in which the patient presented without thromboembolic complications. The appearance of a popliteal venous aneurysm at color Doppler flow imaging is described.

Adult↗