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Biomedical subjects

T C McCowan

Publications and source records attributed to T C McCowan.

At least 19 recordsLinked to original sources
PubMed1992

Complications of the nitinol vena caval filter.

Simon nitinol vena caval filters were placed percutaneously in 20 patients. Follow-up (average, 14 months) data were available for 16 patients, and four patients were lost to follow-up. There were no proved or suspected cases of pulmonary embolism after filter insertion. Complications encountered included caval penetration (n = 5, one acute and four at follow-up), caval thrombus (n = 4, two determined radiologically and two clinically), postplacement deep venous thrombosis (n = 2, one radiologic and one clinical), filter migration (n = 1), and delayed fracture of a filter leg (n = 2). Although no deaths or significant morbidity resulted from any complication, the relatively high complication rate, especially of significant caval penetration (documented in 25% of filter insertions), merits continued short- and long-term assessment of patient status after filter placement.

Adult↗
PubMed1992

Vena caval filter use in orthopaedic trauma patients with recognized preoperative venous thromboembolic disease.

This study comprises a series of 35 patients with pelvic or lower extremity fractures requiring surgery who also had a documented significant acute deep venous thrombosis (DVT). The authors treated these with low-dose Coumadin and 36 vena caval filters, which were used prophylactically prior to surgery. The patients received low-dose warfarin after placement of the vena caval filters and were maintained at 1.3-1.5 times the prothrombin control value for 6 weeks to 3 months. In this group of patients, there were no fatal pulmonary emboli and no clinically significant complications from filter placement. There were nine asymptomatic filter complications demonstrated radiographically in eight patients. Additionally, one patient with a tilted vena caval filter required placement of another filter. The combination of vena caval filters and low-dose warfarin appears to be a successful and relatively safe method of managing those patients who have acute DVT and require surgery for their pelvic or lower extremity fractures.

Combined Modality Therapy↗
PubMed1991

LGM vena cava filter: objective evaluation of early results.

One hundred one LG-Medical (LGM) vena cava filters were placed in 97 patients at four institutions. Placement was a complete technical success in 90% (91 of 101). In 6% of attempts, LGM filter insertion was complicated by incomplete opening of the filter. Pulmonary embolism after filter placement was not definitely demonstrated in any patient. The probability of inferior vena cava patency was 92% at 6 months after filter insertion. Thrombosis at the insertion site was seen in eight of 35 patients (23%) evaluated with duplex ultrasound or venography. Thrombus was observed in 37% of filters at follow-up examination, with cephalic extension of thrombus above the filter in 20% of all patients examined. Filter migration (greater than 1 cm) was seen in 12%; significant angulation was observed in only one patient (2%). In vitro experimentation demonstrated that incomplete opening of the LGM filter during placement can be avoided, in part, by brisk retraction of the insertion cannula. The low-profile introducer system of the LGM filter allows increased alternatives in selecting the site for filter insertion. The low-profile system also makes outpatient filter placement a possibility. No significant difference in the prevalence of thrombosis at the insertion site following LGM filter insertion was noted compared with previous results reported for percutaneous transfemoral placement of the Greenfield filter. The nonopaque sheath does not permit careful localization prior to filter deposition. Modification of the LGM filter to include a radiopaque sheath is suggested.

Equipment Design↗
PubMed1991

External iliac artery rupture during angioplasty: control by balloon tamponade.

Transluminal angioplasty, particularly of stenoses of the iliofemoral arteries, is an excellent technique with a success rate greater than 90%, an overall complication rate of less than 5%, and a low incidence of major complications. Of these major complications, arterial rupture is one of the most urgent. We have presented a case of external iliac artery rupture during angioplasty that graphically demonstrates the value of balloon tamponade in managing this potentially catastrophic event. The angiographer's sensitivity to the possibility of arterial rupture and prompt management, combined with close collaboration with the vascular surgeon, can lead to a good clinical outcome.

Angioplasty, Balloon, Coronary↗
PubMed1991

Duplex scanning versus venography as a screening examination in total hip arthroplasty patients.

Combined B-mode/Doppler (duplex) scanning and venography were compared in routine perioperative screening for proximal deep vein thrombosis (DVT) in 158 total hip arthroplasty (THA) patients. Preoperative scans were performed in the first 60 patients; the low preoperative prevalence of 2% for proximal DVT was thought not to warrant routine preoperative scanning. Postoperatively, duplex scanning had a sensitivity of 79%, a specificity of 98%, and an accuracy of 97% when venography was considered as the gold standard. The postoperative incidence of proximal DVT was 12% in this group of THA patients treated with mechanical and pharmacologic prophylaxis. Including calf vein thrombosis, 30% had DVT postoperatively. This study demonstrates the efficacy of duplex scanning for diagnosing proximal DVT and describes an effective noninvasive method of screening THA patients for the presence of proximal DVT.

False Negative Reactions↗
PubMed1991

Preoperative venography. A risk factor for postoperative deep venous thrombosis in hip arthroplasty patients?

The incidence of postoperative deep venous thrombosis was compared between patients who had or had not received a preoperative screening venogram. No statistically significant difference in the deep venous thrombosis rate was noted postoperatively. Thirty percent of patients who received a preoperative venogram developed postoperative deep venous thrombosis, and 28% of those who did not have a preoperative venogram developed postoperative deep venous thrombosis. These results suggest that an orthopaedic surgeon may order a preoperative venogram for a patient at potential high risk of thromboembolic complications without predisposing the patient to an increased risk of postoperative deep venous thrombosis.

Causality↗
PubMed1991

Recurrent intracaval renal cell carcinoma: the role of intravascular ultrasonography.

The presence of extension into the vena cava does not preclude curative resection for extensive renal cell carcinomas. However, preoperative assessment of (1) the proximal extent of the tumor and (2) the degree of adherence within the vena cava is necessary to plan operative strategies. The following report describes the successful use of intravascular ultrasonography in the preoperative evaluation of a patient with recurrent renal cell carcinoma with vena caval extension.

Carcinoma, Renal Cell↗
PubMed1990

Use of external jugular vein as a route for percutaneous inferior vena caval filter placement.

Vena caval filter placement via the right external jugular vein was attempted in 13 cases. Eleven percutaneous vena caval filters of four types were successfully placed in the inferior vena cava. Two of the attempts were unsuccessful. The indications for the external jugular vein approach were obstructive lower-extremity deep venous thrombosis in eight cases and hip or pelvic fractures in three cases; the approach was simply the radiologist's preference in the remaining two cases. There were five minor complications in four patients. None of the complications necessitated operative intervention or changed the clinical course of the patient. The external jugular vein is an excellent alternative route for caval filter placement. The external jugular vein approach does not necessitate surgical cutdown in the operating room for venous access, avoids deep vascular punctures in the neck and groin, and is safe in patients receiving systemic anticoagulation therapy.

Female↗
PubMed1990

Inferior vena caval filter thrombi: evaluation with intravascular US.

A 20-MHz intravascular ultrasound (US) transducer inside a percutaneously inserted catheter was used to evaluate inferior vena caval (IVC) filters for thrombi in vitro and in vivo. Six different IVC filters were studied with intravascular US in a saline-filled model. Each filter had a characteristic, recognizable US pattern. Experimental thrombi as small as 0.5 cm3 were easily detected. Intravascular US was used clinically 25 times to evaluate the IVC in 23 patients with 24 IVC filters. Positive-contrast cavograms were available for comparison in all 25 cases. In 13 cases, no thrombi were identified in the filter or IVC with either intravascular US or cavography; in five of 12 cases with thrombi, intravascular US and cavography demonstrated the thrombi equally well. In six cases, intravascular US was superior to cavography in detection or delineation of thrombus in the IVC or filter. Intravascular US was considered superior to external duplex US in evaluation of caval thrombi in all 21 cases available for comparison. No complications from intravascular US were noted.

Adult↗
PubMed1990

Amplatz vena caval filter: clinical experience in 30 patients.

Amplatz vena caval filters were inserted percutaneously in 30 patients. Radiologic and clinical follow-up was available in 24 patients (cavogram, CT, or sonography in 20 patients, plain abdominal radiographs in two, and lower extremity venograms in two). Clinical follow-up only was available in four patients, and autopsy reports were available in two patients without radiologic follow-up. The filter was inserted without difficulty in 29 (97%) of the patients. Complications after insertion included recurrent pulmonary embolism in two (7%) of 30, caval thrombosis in seven (23%) of 30, ipsilateral lower extremity deep venous thrombosis after placement of the filter in one (3%) of 30, caval penetration in two (10%) of 20, and caval stenosis in one (5%) of 20. No migration of the filter was noted. Our experience suggests that the Amplatz vena caval filter is easy to insert and adequately prevents recurrent pulmonary embolism but is associated with a relatively high rate of caval thrombosis.

Aged↗
PubMed1989

Peripheral laser-assisted balloon angioplasty. Initial multicenter experience in 219 peripheral arteries.

In this multicenter clinical series of peripheral laser-assisted balloon angioplasty with an argon laser-heated, metallic-capped fiberoptic, angiographic and clinical success was achieved in a total of 155 (71%) of 219 attempted lesions. When the anatomy of the lesion was subjectively categorized by the angiographer into those considered possible or impossible to treat by conventional balloon angioplasty, clinical success was achieved in 116 (78%) of 149 lesions considered possible to treat with balloon angioplasty (39 [95%] of 41 stenoses and 77 [71%] of 108 occlusions). More importantly, clinical success was achieved in 39 (56%) of 70 lesions considered impossible to treat by conventional means. The incidence of complications, including vessel perforation (4.1%), with this new technique was equal to that reported for conventional balloon angioplasty, decreased with operator experience, and was less than that reported for argon laser angioplasty with bare fiberoptics. Thus, laser thermal angioplasty with a laser-heated, metallic-capped fiberoptic is a safe procedure that is easily learned by physicians skilled in interventional techniques. It allows for nonsurgical treatment of lesions considered difficult or impossible to treat by conventional balloon angioplasty.

Angioplasty, Balloon↗
PubMed1989

Interventions in pulmonary embolism.

Various interventions are available to assist in the management of patients with pulmonary embolism. Most are reserved for patients who either fail standard systemic anticoagulation therapy or are not candidates for anticoagulant therapy. The most common intervention is placement of a vena caval filter. Several different filter devices are available, most of which may be placed percutaneously. Pulmonary thrombolysis with urokinase or streptokinase may be appropriate in some patients with severe, symptomatic pulmonary embolism. Finally, pulmonary embolectomy by means of either a transvenous catheter or surgical technique may be necessary in cases of refractory cardiovascular collapse.

Humans↗
PubMed1989

Duplex pulsed Doppler US versus intracranial pressure in the neonate: clinical and experimental studies.

This study was conducted to determine if the resistive index (RI) could be used for the examination and follow-up of neonates with increased intracranial pressure. First, in a laboratory model with four mongrel dogs, RI was found to correlate linearly with cerebral perfusion pressure. Second, RI was studied in 57 healthy neonates and 285 neonates with abnormal clinical or head ultrasound findings. Average RI for healthy newborns was 75 +/- 10 and was inversely related to gestational age. RI in newborns with abnormal findings was uniformly elevated, but these values varied considerably and were not statistically different from normal values. Third, the RI was found to decrease significantly after patent ductus arteriosus ligation, tapping of subdural effusions, ventricular tapping (later cerebrospinal fluid shunting led to a further drop in RI), and ventriculoperitoneal shunting. Elevated RI indicates possible intra- or extracranial abnormality affecting cerebral blood flow. Doppler RI is valuable in following up neonates with abnormal or unstable conditions and in assessing the effectiveness of therapies to improve cerebral perfusion.

Animals↗
PubMed1988

Effect of a 1.5 Tesla magnetic field on Greenfield filters in vitro and in dogs.

The authors have tested four Greenfield filters for deflection in a 1.5 Tesla magnetic field and found large variations in the amount of deflection among filters. They also placed two filters in dogs and checked the filter for migration by taking radiographs before and after magnetic resonance imaging (MRI) scans. They found no evidence of migration. They conclude that, while most Greenfield filters respond to a magnetic field, the chance of migration of a filter because of an MRI scan is small. Therefore, MRI scanning of patients with Greenfield filters has little risk.

Animals↗