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Biomedical subjects

M D Dake

Publications and source records attributed to M D Dake.

At least 73 records · Page 4Linked to original sources
PubMed1995

Endovascular stent-grafting after arch aneurysm repair using the "elephant trunk".

A 68-year-old woman with severe chronic obstructive pulmonary disease, aortic valvular insufficiency, and diffuse thoracic aortic aneurysm underwent aortic valve replacement and separate Dacron graft replacement of the ascending aortic and arch aneurysms using the elephant trunk technique. She was discharged on the tenth postoperative day. Five months later, she underwent endovascular stent-graft repair of the descending thoracic aortic aneurysm. She recovered uneventfully, and was discharged on the third postoperative day. Follow-up computed tomography at 6 months demonstrated exclusion of all flow into the descending thoracic aortic aneurysm. The elephant trunk technique followed by endovascular stent-grafting of the descending thoracic component is a potential therapeutic option in selected high-risk patients with diffuse aortic aneurysmal disease.

Aged↗
PubMed1995

Assessment of living renal donors with spiral CT.

PURPOSE: To determine whether spiral computed tomography (CT) can be used to evaluate potential living renal donors. MATERIALS AND METHODS: Twelve potential living renal donors underwent spiral CT and conventional arteriography. CT angiography was performed with 30-second spiral acquisition during injection of 150 mL of nonionic iodinated contrast material into an antecubital vein at 5 mL/sec. Five minutes after injection, a frontal abdominal scout projection was obtained to assess the renal collecting system. Results of blinded interpretations of axial CT angiograms, three-dimensional CT angiograms, and conventional arteriograms were correlated with intraoperative findings in 11 cases. RESULTS: Axial and three-dimensional CT angiography were 100% sensitive for identifying seven accessory renal arteries and 14% and 93% sensitive for identifying five prehilar renal artery branches. Renal venous anomalies were confirmed in three patients at surgery. Operative management changed in four of 11 patients who underwent donor nephrectomy. CONCLUSION: Spiral CT holds promise as a single examination for anatomic assessment of living renal donors.

Adult↗
PubMed1995

Percutaneous endoluminal placement of stent-grafts for the treatment of isolated iliac artery aneurysms.

PURPOSE: To evaluate the feasibility of stent-grafts for treatment of isolated iliac artery aneurysms (IAAs). MATERIALS AND METHODS: Nine IAAs in eight patients were treated with transluminally placed endovascular stent-grafts. All patients were men (median age, 72 years). In three, the aneurysm involved both the common and internal iliac arteries. In one, common and external iliac arteries were involved. The other aneurysms involved only the common iliac artery. Two aneurysms were treated with balloon-expandable stents covered with polytetrafluoroethylene (PTFE) graft material, three were treated with self-expanding Z-stents covered with a woven polyester graft, and four were treated with self-expanding Z-stents covered with PTFE. RESULTS: Transluminal placement of the stents was successful in all patients with thrombosis of the aneurysms. There were no distal thromboembolic events, deaths, or infections. The median follow-up period was 8.5 months. CONCLUSION: Initial results suggest that transluminal stent-graft placement for treating isolated IAAs is a safe and effective alternative to surgery in selected patients. Long-term follow-up data are needed before this approach can be recommended for the primary treatment of IAAs.

Aged↗
PubMed1995

Current status of three-dimensional spiral CT scanning for imaging the vasculature.

Three-dimensional CT angiography is a new modality for minimally invasive vascular imaging. Meticulous attention to technique is critical to optimizing image quality and achieving diagnostic images. In this article, the properties of spiral CT acquisitions, intravenous contrast delivery, and three-dimensional rendering techniques, as they pertain to the optimization of CT angiograms, are discussed. Next, a review of initial investigations into the clinical applicability of CT angiography in the cranium, neck, chest, abdomen, and pelvis is provided. Finally, CT angiography is compared with MR angiography and conventional angiography.

Angiography↗
PubMed1994

Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms.

BACKGROUND: The usual treatment for thoracic aortic aneurysms is surgical replacement with a prosthetic graft, but the associated morbidity and mortality are considerable. We studied the use of transluminally placed endovascular stent-graft devices as an alternative to surgical repair. METHODS: We evaluated the feasibility, safety, and effectiveness of transluminally placed stent-graft to treat descending thoracic aortic aneurysms in 13 patients over a 24-month period. Atherosclerotic, anastomotic, and post-traumatic true or false aneurysms and aortic dissections were treated. The mean diameter of the aneurysms was 6.1 cm (range, 5 to 8). The endovascular stent-grafts were custom-designed for each patient and were constructed of self-expanding stainless-steel stents covered with woven Dacron grafts. RESULTS: Endovascular placement of the stent-graft prosthesis was successful in all patients. There was complete thrombosis of the thoracic aortic aneurysm surrounding the stent-graft in 12 patients, and partial thrombosis in 1. Two patients initially had small, residual patent proximal tracts into the aneurysm sac, but both tracts thrombosed within two months after the procedure. In four patients, two prostheses were required to bridge the aneurysm adequately. There have been no deaths or instances of paraplegia, stroke, distal embolization, or infection during an average follow-up of 11.6 months. One patient with an extensive chronic aortic dissection required open surgical graft replacement four months later because of progressive dilatation of the arch. CONCLUSIONS: These preliminary results demonstrate that endovascular stent-graft repair is safe in highly selected patients with descending thoracic aortic aneurysms. This new method of treatment will, however, require careful long-term evaluation.

Adult↗
PubMed1994

Three-dimensional spiral CT angiography of the abdomen.

Spiral CT angiography is a technical innovation in vascular imaging that can produce spectacular three-dimensional reconstructions of the abdominal vessels and organs using modified CT scanning techniques. Rapid volume data acquisition allows contrast material to be imaged in the arterial or venous phase. CT reconstruction in cross-sections avoids superimposition of overlying structures. The combination of these features allows spiral CT angiography to produce extraordinary images of the abdominal vasculature and organs. This review outlines fundamental techniques in spiral CT angiography and summarizes our initial clinical experience at Stanford University Medical Center.

Abdomen↗
PubMed1994

Aortic cobwebs: an anatomic marker identifying the false lumen in aortic dissection--imaging and pathologic correlation.

PURPOSE: To describe and estimate the frequency of fibroelastic cords or bands projecting from the false lumen wall ("aortic cobwebs") in acute and chronic dissections. MATERIALS AND METHODS: Pathologic specimens (n = 23), routine magnetic resonance (MR) images (n = 27), and intravascular (n = 5) and transesophageal (n = 3) ultrasound (US) images from 43 patients with aortic dissection were reviewed, and the presence and configuration of cobwebs were noted. RESULTS: Aortic cobwebs usually bridge the junction of the dissection flap with the outer wall of the false lumen (the line of dissection) but occasionally project like small tendrils from the false lumen wall remote from the line of dissection. Cobwebs were found in 17 of 23 pathologic specimens and on six of 27 MR images, two of five intravascular US scans, and one of three transesophageal US scans. CONCLUSION: Aortic cobwebs most likely represent residual ribbons of media that have been incompletely sheared from the aortic wall during the dissection process. As such, they can serve as an anatomic marker of the false lumen. They are occasionally seen on routine aortic images and may, therefore, prove useful for orientation during percutaneous or surgical interventional procedures to relieve ischemic complications of aortic dissection.

Aortic Dissection↗
PubMed1994

Spiral CT of renal artery stenosis: comparison of three-dimensional rendering techniques.

PURPOSE: To evaluate the accuracy of computed tomographic (CT) angiography in the detection of renal artery stenosis (RAS). MATERIALS AND METHODS: CT angiography was performed in 31 patients undergoing conventional renal arteriography. CT angiographic data were reconstructed with shaded surface display (SSD) and maximum-intensity projection (MIP). Stenosis was graded with a four-point scale (grades 0-3). The presence of mural calcification, poststenotic dilatation, and nephrographic abnormalities was also noted. RESULTS: CT angiography depicted all main (n = 62) and accessory (n = 11) renal arteries that were seen at conventional arteriography. MIP CT angiography was 92% sensitive and 83% specific for the detection of grade 2-3 stenoses (> or = 70% stenosis). SSD CT angiography was 59% sensitive and 82% specific for the detection of grade 2-3 stenoses. The accuracy of stenosis grading was 80% with MIP and 55% with SSD CT angiography. Poststenotic dilatation and the presence of an abnormal nephrogram were 85% and 98% specific, respectively. CONCLUSION: CT angiography shows promise in the diagnosis of RAS. The accuracy of CT angiography varies with the three-dimensional rendering technique employed.

Adult↗
PubMed1994

Stent placement for arterial and venous cerebrovascular disease: preliminary experience.

PURPOSE: To report initial clinical experience with stent placement in the cerebrovascular circulation. MATERIALS AND METHODS: Four patients underwent arterial or venous stent placement. Two patients had cervical internal carotid artery dissections, with aneurysms and stenoses of the distal cervical carotid artery. Two patients had venous occlusive disease involving the major dural sinuses, with substantial pressure gradients across the stenoses. RESULTS: Immediately after stent placement, the true arterial lumina returned to normal diameter and both carotid aneurysms were more than 90% occluded. Follow-up angiography demonstrated continued improvement in the arterial aneurysms. Both patients with dural sinus venous occlusive disease showed substantial improvement of the sinus stenoses and substantial reversal of the pressure gradients after venous stent placement. At follow-up, these patients have done well. CONCLUSION: This preliminary experience suggests there may be a role for stents in the management of arterial and venous cerebrovascular disease, including carotid artery dissection and venous occlusive disease.

Adult↗
PubMed1994

Iliofemoral deep venous thrombosis: aggressive therapy with catheter-directed thrombolysis.

PURPOSE: To evaluate the efficacy of catheter-directed thrombolysis with urokinase in treating symptomatic iliofemoral deep venous thrombosis (DVT). MATERIALS AND METHODS: Twenty-one consecutive patients with iliofemoral DVT underwent treatment for 27 affected limbs (acute DVT, n = 20; chronic DVT, n = 7). The average urokinase dose was 4.9 million IU (range, 1.4 million to 16.0 million IU) infused over an average of 30 hours (range, 15-74 hours). RESULTS: Lysis was complete in 18 (72%), partial in five (20%), and not achieved in two (8%) of 25 treated limbs. Two chronically occluded iliac veins could not be crossed with a guide wire and did not receive urokinase. Sixteen limbs had underlying venous stenoses (> 50%) that were treated with angioplasty (n = 2) or angioplasty and stent placement (n = 14). There were no major complications or clinically detectable pulmonary emboli. The technical and clinical success rates were 85%. CONCLUSION: This initial experience suggests that catheter-directed thrombolysis with urokinase for treatment of symptomatic iliofemoral DVT is safe and effective.

Catheterization, Peripheral↗
PubMed1993

Intravascular stenting of acute experimental type B dissections.

To evaluate the efficacy of intravascular stenting for acute aortic dissection, 12 dogs underwent surgical creation of an acute type B dissection. Intravascular ultrasound evaluated luminal diameter, distal propagation, and branch involvement. Three animals underwent no further treatment (control). In 9 dogs, balloon-expandable intravascular stents (15-20 mm) were placed proximally to compress the intimal flap. One dog with a small dissection had complete obliteration of the false lumen after initial stent placement. Six dogs with extension below the diaphragm were initially stented proximally to restore flow; 3 were left with a residual distal false lumen, while 3 had additional stents placed to obliterate their entire false lumen. In the final 2 dogs, proximal stenting resulted only in partial compression of the false lumen. Two animals died within 24 hr due to prolonged hemodynamic instability and aortic rupture at the intimal flap, respectively. Six weeks later, radiologic and histologic evaluation was performed on the 10 surviving animals. All stented true lumens were patent without thrombus formation, and stents were covered by neointima. In dogs with stenting of the entire dissection, the aortic wall had healed and no false lumen was present. However, in all dogs with only proximal obliteration, 1/2 with partial compression, and 2/3 controls, a patent false channel was present indicative of a chronic dissection. Thus, we found that intravascular stents can restore true lumen flow and obliterate the false lumen in experimental dissections; however, stenting limited to the proximal dissection does not prevent formation of a chronic residual patent false lumen.

Acute Disease↗
PubMed1993

The role of intravascular ultrasound in acute traumatic aortic rupture.

Acute traumatic aortic rupture is a lethal injury and requires immediate diagnosis and surgical repair. The standard of diagnosis for aortic rupture is aortography. In patients in whom the angiographic findings of rupture are subtle or uncertain, intravascular ultrasound (IVUS) imaging of the descending aorta has been useful in confirming or excluding mural injury. However, because IVUS is unable to provide a complete and expeditious survey of the aorta and brachiocephalic arteries, the diagnosis of rupture will continue to rely on aortography or current generation computed tomography.

Acute Disease↗
PubMed1993

Three-dimensional spiral CT angiography of the abdomen: initial clinical experience.

Spiral computed tomography (CT) is a new technology that couples continuous tube rotation with continuous table feed. This allows compilation of a data set that has continuous anatomic information without the establishment of arbitrary boundaries at section interfaces as in conventional CT. The unique method of data collection of the spiral scanner has been combined with a dynamic intravenous contrast material bolus to image abdominal vasculature, specifically, the aorta, renal arteries, and splanchnic circulation. Through various techniques of image processing, including surface renderings and maximum-intensity projections, it is possible to obtain excellent anatomic detail of the aorta and its major branches. The authors applied this technique in 15 patients and reliably saw third-order aortic branches as well as third-order splenic-portal venous anatomic detail with remarkable clarity. Pathologic conditions detected include stenotic renal arteries, abdominal aortic dissection, abdominal aortic aneurysm, and celiac bypass graft occlusion.

Abdomen↗
PubMed1993

Percutaneous femoropopliteal graft placement.

Femoropopliteal bypass surgery is now recommended for the treatment of long-segment or diffuse superficial femoral artery disease. The authors describe a technique for percutaneous placement of a prosthetic femoropopliteal graft. The technique has been accomplished with conventional polytetrafluoroethylene graft material and a variety of implantation techniques. Technical success was achieved in eight patients who underwent graft placement. Grafts up to 28 cm in length were placed, and graft patency was demonstrated up to 6 months after implantation. Six of the eight patients were asymptomatic during the follow-up period; one patient who had symptoms during this time underwent thrombolysis and redilation of the distal stent, and the symptoms resolved. This study demonstrates the feasibility of percutaneous graft placement in the femoral artery, but durability must be established in relation to traditional bypass surgery before it can be recommended on a wider scale.

Aged↗
PubMed1993

The use of endovascular techniques for the treatment of complications of aortic dissection.

Intravascular ultrasonography, balloon angioplasty, stent placement, and endovascular septal fenestration have been used in the evaluation and treatment of vascular complications of acute and chronic aortic dissection in five patients. There were three men and two women with an average age of 52 years (range 39 to 64 years). There were three chronic type A dissections, one acute type B, and one subacute type B dissection. Intravascular ultrasonography was used in all five cases. The three patients with chronic type A dissections underwent unilateral renal artery angioplasty (RA PTA) and stent placement; one patient with an acute type B dissection and associated fibromuscular dysplasia underwent bilateral RA PTA without stent placement. These procedures were performed to ameliorate severe hypertension. The final patient, with a subacute type B dissection, underwent iliac artery stenting to correct severe lower extremity ischemia. During a second intervention, this patient, who also had bowel ischemia and nonresolving acute renal failure, underwent balloon dilatation of a preexisting septal fenestration to augment visceral blood supply and bilateral RA PTA and stent placement in an effort to improve renal function. This patient eventually died of gut ischemia. After RA PTA and stent placement, one patient had a major intrarenal hemorrhage that required coil embolization and transfusion. In the four survivors, RA PTA and stent placement resulted in immediate improvement in blood pressure control. This response has been sustained during follow-up intervals ranging from 8 to 18 months (average 10 months). Intravascular ultrasonography can clearly demonstrate the pathologic anatomy associated with aortic dissection (even when angiography is ambiguous) and is essential for guiding therapeutic endovascular interventions. Further exploration of the efficacy of these endovascular techniques is warranted in this high-risk group of patients with aortic dissection who have appropriate clinical indications.

Acute Disease↗