Endovascular surgery based solely on noninvasive preprocedural imaging

PURPOSE

Conventional pre-endovascular procedural evaluation uses both noninvasive testing and diagnostic arteriography. Diagnostic and therapeutic procedures often must be performed separately because of concerns about excessive contrast administration or inappropriate location of vascular access for the interventional procedure. We wanted to determine if patients could successfully undergo endovascular procedures based on noninvasive modalities alone.

METHODS

One hundred nineteen consecutive patients requiring intervention for lower-extremity ischemia were evaluated by means of physical examinations and segmental pressure measurements. Patients then underwent magnetic resonance angiography (MRA) to image native vessels or duplex scanning for failing bypass grafts. Suitable patients underwent endovascular procedures with "road map" arteriography, which was compared with preoperative duplex scanning or MRA findings. Costs of the conventional and noninvasive approaches were compared, on the basis of estimated hospital cost schedule.

RESULTS

Sixty consecutive endovascular procedures were performed in 56 patients (105 lesions angioplastied), either alone (30, 50%) or in combination (30, 50%) with another vascular reconstruction. Completely noninvasive evaluation was accomplished in 43 procedures (72%), either by means of duplex scanning (11, 18%) or MRA (32, 53%). Conventional arteriography (CA) was required in 2 patients (3%) because of MRA contraindications and in 1 patient because of complex previous arterial reconstruction. Fourteen patients had earlier CAs. The findings of the noninvasive modalities were confirmed in every case by means of intraoperative arteriography, and no additional lesions were revealed (no false positive or negative studies). After endovascular interventions, the mean patient ankle-brachial index (ABI) improved from 0.64 +/- 0.03 to 0.81 +/- 0.03 (P <.001) and the mean limb-status category improved from 3.4 +/- 0.2 to 0.8 +/- 0.2 (P <.001). There were 4 initial technical failures (7%), 1 morbidity (1%), and no mortalities. The noninvasive approach was less costly than if preprocedural diagnostic CA had been used, allowing $551 saved for each duplex scanning case and $235 saved for each MRA case. If the cost of a short-stay unit after a diagnostic arteriogram was included, the savings were greater: $695 saved for each duplex scanning case and $379 saved for each MRA case.

CONCLUSION

Endovascular procedures can be performed based on preprocedural noninvasive modalities alone. For patients requiring endovascular procedures, knowledge of the arterial anatomy before obtaining arterial access avoids the need for additional punctures or sessions (eg, antegrade puncture for femoral angioplasty after retrograde puncture for the diagnostic arteriogram). This approach is less costly than performing preprocedural diagnostic arteriography and avoids the hazards of arterial puncture and nephrotoxic contrast agents.

Direct percutaneous jejunostomy: techniques and applications--ten years experience

PURPOSE

To present 10 years experience with direct fluoroscopically guided percutaneous jejunostomy.

MATERIALS AND METHODS

Percutaneous jejunostomy was performed in 62 patients, most of whom had undergone major abdominal surgery. A new or replacement jejunostomy was created for alimentation in 20 and 21 patients, respectively. Jejunostomy was performed for interventional procedures of the bile ducts or intestine in 13 patients and for retrograde gastroesophageal drainage in eight. The distended jejunum was accessed with a 21-gauge needle, immobilized with a gastric anchor, and catheterized with a 10-14-F locking loop drain.

RESULTS

The technical success rate was 19 of 20 (95%) for new feeding jejunostomy and 17 of 21 (81%) for replacement feeding jejunostomy. Jejunostomy facilitated drainage, dilation, stone extraction, and recanalization in the bile ducts or intestine in all 13 patients. Retrograde jejunoesophagogastrostomy suction effectively replaced painful nasogastric suction in all eight patients. Two patients who underwent replacement jejunostomy required laparotomy for possible leakage; there was no important procedure-related morbidity and no procedure-related mortality.

CONCLUSION

The technical success and complication rates of feeding percutaneous jejunostomy compare favorably with those of surgery or endoscopy. Percutaneous jejunostomy is a useful and underused approach to managing bowel and biliary obstruction.

Magnetic resonance angiography of lower-extremity arterial disease

Improvements in vascular technique have expanded the treatment options for patients with severe occlusive peripheral vascular disease. The decision to perform a major revascularization procedure in patients who are often at high risk for cardiovascular morbidity and mortality depends on the risk-benefit ratio. Detailed and accurate vascular imaging is essential and evaluating the likelihood of a successful revascularization with subsequent limb salvage. Although contrast angiography has been the time-honored reference standard imaging technique, the method is an invasive procedure with limitations and risks. MRA is a new, noninvasive vascular imaging technique that may now be added to the imaging options with the potential for improved sensitivity for finding patent runoff vessels, avoidance of morbidity, and cost equivalent to that of conventional contrast angiography. Magnetic resonance angiography is a rapidly developing and exciting new vascular imaging technique. As with any new technique, it is imperative that individual centers validate their MRA results and interpretations against the time-honored standard, which continues to be contrast arteriography. Several studies now indicate that MRA can be a cost-effective outpatient imaging technique sufficient for planning and successfully performing peripheral bypass procedures. As developments in hardware, software, and non-nephrotoxic contrast agents continue to increase, applicability of MRA in vascular surgery will continue to expand. Predictably, MRA will have a major role in the future of vascular imaging, and it is likely to supplant the need for conventional contrast angiography in the majority of patients.

Replacement of failing tunneled hemodialysis catheters through pre-existing subcutaneous tunnels: a comparison of catheter function and infection rates for de novo placements and over-the-wire exchanges

PURPOSE

Tunneled hemodialysis catheter dysfunction often occurs from fibrin sheath formation. As a way to preserve existing catheter venous access sites, the authors evaluated over-the-wire exchange of catheters through pre-existing subcutaneous tunnels as an alternative to catheter removal and de novo catheter replacement.

PATIENTS AND METHODS

One hundred nineteen catheters were placed in 68 patients. Seventy-seven catheters were placed de novo and 42 catheters were placed through the pre-existing subcutaneous tunnels of failing catheters. Technical success, short-term complications, infection rates, and functional catheter longevity were evaluated.

RESULTS

Technical success for catheter exchange was 93%. Infection rates were comparable to those of de novo catheter placement: 0.15 and 0.11 infections per 100 catheter days for de novo and exchanged catheters, respectively. Catheter duration of function was not significantly different for de novo versus exchanged catheters: 63% and 51% at 3 months, 51% and 37% at 6 months, and 35% and 30% at 12 months, respectively.

CONCLUSIONS

Over-the-wire exchange of tunneled hemodialysis catheters is safe and easily performed. It causes no increase in infectious complications and provides similar catheter longevity to de novo catheter placement. The procedure is an important option for prolonging tunneled hemodialysis catheter access sites.

Percutaneous varicocele embolization versus surgical ligation for the treatment of infertility: changes in seminal parameters and pregnancy outcomes

PURPOSE

To compare the success of percutaneous varicocele embolization to surgical ligation with regard to changes in semen characteristics and pregnancy outcome.

MATERIALS AND METHODS

Infertility records from 346 men who underwent correction of their varicocele for infertility (surgical ligation 149; embolization 197) were reviewed retrospectively. Preprocedural and postprocedural semen analyses and pregnancy outcomes were obtained with use of chart and telephone follow-up.

RESULTS

In men who successfully impregnated their partners, there were significant improvements in sperm density, percent total improvement, motility, and progression. Postprocedural (embolization vs surgery) percentage increases in seminal parameters were density, 156.8% versus 138.5%; total, 168.8% versus 157.91%; and motility, 2.7% versus 3.2%. The percent of individuals who had a change in sperm progression was 31% versus 41%. There was no statistical difference between the techniques based on t tests. The pregnancy rates were similar for the two groups, 39% and 34% for embolization and surgery, respectively.

CONCLUSION

There is no significant statistical difference in seminal values or pregnancy outcome between the two techniques.

Mechanical declotting of thrombosed dialysis grafts: experience in 86 cases

PURPOSE

To evaluate the efficacy, safety, and primary patency of percutaneous mechanical declotting of thrombosed dialysis grafts using latex balloons.

MATERIALS AND METHODS

Fifty-nine patients with 86 episodes of dialysis graft thrombosis underwent percutaneous mechanical declotting with balloons using crossing catheter or transjugular technique. Vital signs, peripheral oxygenation, technical success, procedure time, and complications were recorded prospectively. Technical success was defined as a patent graft at the completion of the procedure. Clinical success, defined as successful dialysis for 1 week, and primary patency were obtained retrospectively from review of the dialysis records.

RESULTS

Technical success was achieved in 74 of 86 procedures (86%). Median procedure time was 115 minutes, including failed cases. Ten of the 12 technical failures were due to resistant vascular stenoses precluding graft patency, despite removal of thrombus. There were no immediate complications. One patient died of sepsis 4 days after declotting. Clinical success was achieved after 65 of 86 procedures (76%); nine grafts thrombosed within 1 week of a technically successful declotting procedure. Primary patency (including technical failures) was 37% at 3 months, 31% at 6 months, and 17% at 12 months.

CONCLUSION

Mechanical declotting is an effective means of restoring patency to thrombosed dialysis grafts.

Safety of decreasing bedrest after coronary angiography

This study was designed to assess the safety of allowing patients to ambulate after 2 hr of bedrest following coronary angiography. A total of 205 patients were randomized to either 2 or 4 hr of bedrest following hemostasis after angiography utilizing five, six, or seven French catheters. The primary endpoint was defined as bleeding requiring recompression and additional bedrest. No significant difference was demonstrated overall between the two groups with respect to rebleeding or hematoma formation when the angiogram was performed using five or six French catheters. However, the use of seven French catheters resulted in a significantly higher rebleeding rate in the 2-hr group compared to the 4-hr population. The findings of this study suggest that 2 hr of bedrest following angiography utilizing five or six French catheters is adequate to obtain hemostasis safely in the majority of patients, whereas 4 hr is suggested when seven French catheters are utilized.

Balloon occlusion portography to diagnose new-onset left hepatic vein thrombosis and widening of an existing Wallstent TIPS by Palmaz stents for recurrent portal hypertension and variceal bleeding

A 31-year-old man with Child's class A micronodular cirrhosis, left lobe hypertrophy, and a transjugular intrahepatic portosystemic shunt (TIPS) which had been placed 6 months earlier, was admitted for recurrent esophageal bleeding and a portosystemic gradient of 42 mmHg. Balloon occlusion portography documented unsuspected ostial thrombosis of the previously patent left hepatic vein. This was considered the cause of the pressure rise. As it was not possible to insert a second TIPS in parallel, the shunt, stented originally with 10-mm Wallstents, was overdilated to 12 mm, and two 12-mm Palmaz stents were placed coaxially, reducing the portosystemic pressure gradient to 13 mmHg.

Transvenous removal of fibrin sheaths from tunneled hemodialysis catheters

PURPOSE

Long-term hemodialysis catheters are prone to significant dysfunction due to fibrin accumulation around their tips. The authors assessed the efficacy of transvenous snare removal of fibrin to prolong function of these catheters.

PATIENTS AND METHODS

Twenty-four procedures were performed in 20 patients with tunneled hemodialysis central venous catheters. Technical success was gauged by venography and the ability to infuse and aspirate catheters. Durable efficacy was assessed by improvement in hemodialysis.

RESULTS

Twenty-two of 24 procedures were performed successfully. In two cases residual material remained despite repeated stripping. Mean preprocedure hemodialysis blood-liters processed per hour increased from 15.1 to 19.1 L/h in the first dialysis session after stripping, and blood flow rates of 300 mL/min or greater were restored. By the fifth dialysis session after stripping, the blood-liters processed per hour dropped to 15.9 L/h as catheter flow rates returned to unacceptable levels.

CONCLUSIONS

Percutaneous fibrin removal with a loop snare provides no durable benefit in improving function of failing hemodialysis catheters.

The fate of bypass grafts to angiographically occult runoff vessels detected by magnetic resonance angiography

PURPOSE

Magnetic resonance angiography (MRA) is a noninvasive vascular imaging technique that is more sensitive than contrast arteriography (CA) for the detection of patent distal runoff vessels. This technique has facilitated performance of MRA-directed bypass procedures for patients who were believed not to be bypass candidates because of the absence of a suitable target vessel on the preoperative CA. The fate of bypasses to these angiographically occult runoff vessels is unknown, however, and it has been proposed that patients with angiographically occult runoff may have aggressive occlusive disease, rendering bypass procedures ultimately futile.

METHODS

Between April 1992 and February 1995, 212 autogenous vein infrageniculate bypasses were performed for limb-salvage indications, 22 (12%) to angiographically occult runoff vessels. Results of bypasses performed to angiographically occult vessels were compared with those of bypasses to CA-detected runoff vessels. Life-table analysis of graft-patency and limb-salvage rates was performed.

RESULTS

The accuracy of the MRA-predicted patency of angiographically occult vessels was confirmed in every case by the operative findings. Life-table analysis revealed no significant difference in primary graft patency (p > 0.05) or limb-salvage (p > 0.05) rates between patients with bypasses to runoff vessels seen by MRA alone. At 35 months after surgery, the primary graft patency rate was 68% for bypasses to CA-detected vessel bypass and 67% for MRA-detected vessels. The limb salvage rate was 83% for CA-detected vessel bypass patients and 78% for patients with angiographically occult runoff.

CONCLUSIONS

MRA can accurately identify patent runoff vessels not visualized by CA. Results of bypasses performed to angiographically occult runoff vessels are similar to those of bypasses performed to vessels detected by CA. MRA should be performed in patients in whom CA fails to reveal runoff vessels suitable for use in a limb-salvage procedure. The greater sensitivity of MRA may facilitate successful bypass surgery and improve the overall limb-salvage rate.

Temporary use of a Bird's Nest filter during iliocaval thrombolysis

A jugular Bird's Nest filter (Cook, Bloomington, Ind) was partially deployed in the suprarenal cava for prophylaxis to prevent pulmonary embolism in a young woman with phlegmasia cerulea dolens. It was effective in capturing large emboli during thrombolysis of a loose iliocaval thrombus. It was safely removed 6 1/2 hours later, after lysis of most retained filter clots.

Transjugular intrahepatic portosystemic shunt-related arterial injuries: prospective comparison of large- and small-gauge needle systems

PURPOSE

The authors prospectively compared the nature and incidence of hepatic arterial injuries resulting from creation of a transjugular intrahepatic portosystemic shunt (TIPS) with large- and small-gauge needle systems.

PATIENTS AND METHODS

Fifty patients underwent hepatic and superior mesenteric angiography immediately before and after shunt creation. A sheathed 16-gauge needle system was used to locate and puncture the portal vein in 24 patients. A 21-gauge needle system was used in 26 patients.

RESULTS

Shunts were successfully created in all patients. Three inadvertent hepatic arterial punctures were recognized during shunt placement, two with the small needle and one with the large needle system. No hepatic arterial lesions were detected in any patient. Two incidental hepatomas were identified at angiography.

CONCLUSION

TIPS-related hepatic arterial injuries are rare. In this series, large and small needle systems were indistinguishable with respect to this complication.

Magnetic resonance angiography of the distal lower extremity

OBJECTIVE

To assess magnetic resonance angiography (MRA) for demonstration of arterial patency in the ankle and foot of patients with peripheral vascular disease.

METHODS

Peripheral MRA of the ankle and foot was performed on 34 limbs of 31 insulin-dependent diabetics. 2-D time-of-flight MRA (TR 33 ms/TE 7.7 ms/inferior saturation band) was performed with 16 cm field of view. Pre- or intra-operative angiographic correlation was available in all cases.

RESULTS

In 24 limbs MRA was compared to conventional angiography. MRA showed more patient run-off vessel segments (120) than angiography (100). In 10 limbs MRA was compared to intraoperative angiography and for the detection of patent vessel segments showed a sensitivity of 87.5% (42/48) with a 95% confidence interval of 75% to 95% and a specificity of 95% (38/40) with a 95% confidence interval of 83% to 99%. Pitfalls included difficulty in visualizing flow at the bifurcation of the peroneal artery, in the plantar arch and retrograde flow in the lateral plantar artery.

CONCLUSIONS

MRA is sensitive for the detection of patent arteries in the ankle and foot but artefacts may cause overdiagnosis of focal stenoses or occlusions.

Multicenter trial to evaluate vascular magnetic resonance angiography of the lower extremity. American College of Radiology Rapid Technology Assessment Group

OBJECTIVES

To assess the value of magnetic resonance angiography (MRA) in presurgical evaluation of patients with severe lower limb atherosclerotic occlusive disease and to assess the feasibility of rapidly conducting rigorous technology assessment.

DESIGN

Blinded, prospective study of consecutive patients with signs or symptoms of severe infrainguinal peripheral vascular disease who were candidates for percutaneous or surgical intervention. Using both descriptive statistics and multivariate logistic analyses, MRA was compared with contrast arteriography (CA) (the current technique) for imaging 15 arterial segments of the leg and foot. Intraoperative contrast angiography was the "gold" standard. Also studied was the effect of adding MRA to the information used in planning treatment.

SETTING

Six US hospitals, one a community hospital.

PATIENTS

A total of 155; 84% with either rest pain or tissue loss.

RESULTS

Sensitivity in distinguishing patent segments from completely occluded segments was 83% for CA and 85% for MRA; both had 81% specificity. For distinguishing near-normal segments (suitable as bypass graft termini), CA was less sensitive than MRA (77% vs 82%), but more specific (92% vs 84%). After adjusting for same-reader effects, odds of correctly distinguishing patent segments were 1.6 times as great for MRA as for CA (P < .01); for distinguishing near-normal segments, the odds for CA were 1.5 times as great as for MRA (P < .05). The addition of MRA changed the treatment plan in 13% of patients; in 86% of these cases, the surgery actually performed indicated that the MRA-inclusive plan was superior.

CONCLUSIONS

Individually, MRA and CA are approximately equivalent in diagnostic accuracy. The addition of MRA to treatment plans based only on CA and other diagnostic information clearly improves the plans. Completed in 15 months (as planned), our study demonstrates the feasibility of conducting rigorous technology assessment rapidly enough to be timely even in fields in which diagnostic and treatment techniques are rapidly changing.

Intentional reversible thrombosis of transjugular intrahepatic portosystemic shunts

PURPOSE

To assess whether balloon occlusion of a transjugular intrahepatic portosystemic shunt (TIPS) will allow permanent yet reversible shunt thrombosis.

MATERIALS AND METHODS

A balloon catheter was inflated in the midportion of the TIPS in two women with severe, uncontrollable encephalopathy or liver failure (aged 42 and 65 years, respectively) to allow occlusive thrombus to develop below the balloon.

RESULTS

Balloon occlusion led to rapid TIPS thrombosis, which was readily reversible.

CONCLUSION

Balloon thrombosis is a simple technique for complete occlusion of a TIPS. This technique may also be useful for occlusion of surgical mesocaval H-graft shunts or dialysis access shunts.

Cost-effectiveness of MR angiography in cases of limb-threatening peripheral vascular disease

PURPOSE

To evaluate the cost-effectiveness of magnetic resonance (MR) angiography in the preoperative planning of treatment in patients with limb-threatening peripheral vascular disease (PVD).

MATERIALS AND METHODS

A decision model was developed to study the effects of MR angiography on the outcome and cost of treatment. The authors calculated the incremental cost per quality-adjusted life-years gained (ie, cost-effectiveness ratio) when conventional angiography was replaced or supplemented with MR angiography. Previously reported data regarding the accuracies of MR and conventional angiography were used in the analysis.

RESULTS

The cost-effectiveness ratio of MR angiography ranged from negative (cost-reducing) values to $78,000. For the base case in which the sensitivity and specificity of MR angiography for the evaluation of inflow vessels were 92% and 88% and those of conventional angiography were 97% and 97%, respectively, the cost-effectiveness ratio was $25,895.

CONCLUSION

MR angiography may be a cost-effective alternative to conventional angiography in patients with limb-threatening PVD if its accuracy for the inflow evaluation reaches certain thresholds. Further prospective investigation is warranted.

Peripheral vascular surgery with magnetic resonance angiography as the sole preoperative imaging modality

PURPOSE

Magnetic resonance angiography (MRA) is a developing technique that provides arteriograms without the risks associated with iodinated contrast and arterial puncture or the expense of hospitalization. Prior reports have demonstrated the accuracy of peripheral vessel MRA for evaluation of the aorta through pedal vessels. This study sought to determine whether vascular reconstructions could be planned and accomplished on the basis of MRA alone.

METHODS

Eighty consecutive candidates for bypass with ischemic rest pain or tissue loss were studied with preoperative outpatient MRA of the juxtarenal aorta through the foot. Confirmation of MRA findings was provided by intraoperative intraarterial pressure measurements for proximal vessels and postbypass arteriography for the runoff. Life-table analysis of graft patency and limb salvage was performed.

RESULTS

Two patients could not tolerate MRA and required contrast arteriography, but all others underwent reconstructive procedures on the basis of MRA alone (11 aortobifemoral, 67 infrainguinal). Intraoperative findings regarding suitability of inflow and outflow vessels confirmed the accuracy of the MRAs in every case. MRA indicated that none of the patients undergoing infrainguinal bypass had significant inflow occlusive disease, and this was confirmed at operation with pressure measurements of inflow vessels that were always within 10 mm Hg (peak systolic) of systemic pressure. The results of intraoperative completion arteriography and preoperative MRAs were identical for all but two patients who had minor discrepancies. All aortobifemoral reconstructions remained patent, and all limbs remained intact. The infrainguinal reconstructions had an 84% limb salvage rate and 78% primary graft patency rate at 21 months. Comparison of charges for patients undergoing preoperative MRA versus contrast angiography showed a cost savings of $1288 for each patient treated with preoperative MRA alone.

CONCLUSIONS

MRA is a noninvasive, cost-effective outpatient imaging technique that, if properly performed and interpreted, is sufficient for planning peripheral bypass procedures. Its use may supplant contrast arteriography in many patients.

Intracardiac thrombosis and antiphospholipid antibodies: a case report and review of the literature

A case report and review of the literature are reported concerning the relationship of intracardiac thrombosis and antiphospholipid antibody syndromes. Nine cases are identified, divided into three categories: three patients had antiphospholipid syndrome associated with systemic lupus erythematosus, three had primary antiphospholipid syndrome, and three had probable secondary antiphospholipid syndrome. All had intracardiac thrombosis. All patients were women, and the average age was 36 years. Although intracardiac thrombosis appears to be an unusual association with antiphospholipid antibody syndromes, young women with embolic events should be evaluated for antiphospholipid antibodies and intracardiac source of embolus.

Preliminary experience with magnetic resonance venography: comparison with findings at surgical exploration

While conventional magnetic resonance imaging has been described for the evaluation of the venous system, we have recently developed the technique of magnetic resonance venography (MRV), which generates three-dimensional projection venograms. Our purpose was to determine if MRV reliably images the venous system by comparison with findings at surgical exploration. Thirteen of fourteen consecutive patients undergoing bypass surgery (26 limbs) were studied by 2D time-of-flight MRV preoperatively from the inguinal ligament to the ankle bilaterally. The average examination time was 50 min. The size and quality of each saphenous vein were recorded at the saphenofemoral junction, mid-thigh, knee, mid-calf, and malleolus. Intraoperatively the quality and size of each vein were measured in situ and when distended by saline. Twelve veins were of good quality. MRV predicted this in every case. One vein, found to be recanalized, had an abnormally thick wall noted on MRV. MRV measurements of average vein size were intermediate between that of the in situ and distended vein and correlated most closely with the distended vein (R = 0.74, P < 0.001). The superficial and deep femoral veins and lesser saphenous veins were routinely visualized by MRV; thus a complete map of all available vein was obtained by a single study. It is concluded that MRV is an accurate method of venous imaging as confirmed by findings at operative exploration. This new technique holds promise as a noninvasive method for evaluation of the venous system and warrants further investigation.

Transjugular intrahepatic portosystemic shunt stenosis and revision: early and midterm results

OBJECTIVE

The purpose of this study was to define the pattern, rate, and interval during which stenosis develops in transjugular intrahepatic portosystemic shunts (TIPS) and to assess the effect of revision in prolonging shunt patency.

MATERIALS AND METHODS

TIPS were created in 100 patients during a 34-month period. Sixty-one shunt venograms were obtained in 38 consecutive patients between 1 and 24 months after TIPS placement. Eighteen patients were examined because of recurrent symptoms, and all 38 had routine follow-up.

RESULTS

Stenoses attributed to neointimal hyperplasia developed within both the TIPS stent and the outflow hepatic veins. Stenoses of greater than 50% developed in 12 patients within 6 months of TIPS placement. In addition to focal stenoses, the outflow hepatic veins diffusely shrank an average of 51% in diameter. Thirty-six shunt interventions were required: eleven balloon dilatations and 25 placements of an additional stent. Life-table analysis showed that patency of the primary shunt was 75% at 6 months, 50% at 1 year, and 32% at 2 years. The primary-assisted patency of the shunt was 85% at 12 months after shunt creation.

CONCLUSION

The results indicate that TIPS are prone to significant and frequent early stenosis, warranting follow-up within 3-6 months in all cases. Stenosis of the outflow hepatic vein is the most common cause of shunt malfunction. Revision of a shunt significantly prolongs shunt patency.

Evaluation of renal artery stenosis by magnetic resonance angiography

BACKGROUND

Accurate identification of patients with surgically correctable renovascular hypertension has been difficult by noninvasive means. Advances in the technique of magnetic resonance angiography (MRA) have begun to provide detailed, accurate imaging of the vascular system. This study reports our recent experience in the evaluation of the renal arteries by this technique.

METHODS

MRA and contrast arteriography were performed in 32 arteries (16 adult patients) for evaluation of hypertension, abdominal aortic aneurysm, mesenteric vascular disease, and aorto-iliac occlusive disease. Luminal diameter reduction (%) was determined from two-dimensional time-of-flight (TOF) axial images. Contrast arteriography served as the gold standard for comparison.

RESULTS

Contrast arteriography revealed a 50% or greater stenosis in 11 of 32 vessels studied (34%). As a screening test for detection of greater than 50% diameter reduction, MRA had a sensitivity of 91%, a negative predictive value of 94%, and an overall accuracy of 81%. Linear regression analysis demonstrated significant correlation between MRA and arteriographic measurements (r = 0.8; P < 0.001).

CONCLUSIONS

This study demonstrates the ability of MRA to accurately assess the main renal arteries for the presence of critical stenosis. This noninvasive evaluation compares well with conventional angiography and may have increasing application in the screening of patients with suspected renovascular disease.

Magnetic resonance angiography of the aorta, iliac, and femoral arteries

BACKGROUND

Successful management of patients with peripheral vascular disease requires detailed vascular imaging, usually performed by contrast arteriography. Recently, magnetic resonance angiography (MRA) has been shown to be a noninvasive technique with greater sensitivity than contrast arteriography for detecting distal runoff vessels in patients with peripheral arterial occlusive disease. However, to supplant the need for contrast arteriography and provide a completely noninvasive evaluation of patients with occlusive disease, accurate imaging of the inflow vessels and the runoff vessels is necessary.

METHODS

We used both conventional arteriography and MRA in preoperative studies of the aorta, iliac, and femoral vessels of 47 patients. Conventional arteriography and MRA studies were compared for their ability to detect vessel patency and the presence of hemodynamically significant stenoses. Independent interventional plans were developed based on the information provided by each technique. The findings of conventional and MRA studies were verified by intraoperative arteriography or direct operative exploration.

RESULTS

Results of the two studies were identical in 41 (87%) of 47 patients or 600 (98%) of 614 segments imaged. MRA accurately detected patent and occluded arterial segments (sensitivity 99.6%, specificity 100%, positive predictive value 100%, negative predictive value 98.6%) and hemodynamically significant stenoses. Therapeutic plans based on either MRA or conventional arteriography were identical for each patient.

CONCLUSIONS

MRA provides comparable results to contrast arteriography in the proximal arterial system and superior results for imaging the distal vasculature. This noninvasive technique may replace contrast arteriography in a large number of patients in the future.

Magnetic resonance angiographic imaging of angioplasty and atherectomy sites

Magnetic resonance angiography (MRA) provides detailed morphologic and flow information that demonstrates complex changes at sites of percutaneous transluminal angioplasty (PTA) and atherectomy. The purpose of this study is to examine the appearance of the vessel by MRA in the initial post-procedural and early follow-up periods.

METHODS

MRA was performed to evaluate 35 infrainguinal endovascular procedures (20 patients), including PTA (20), atherectomy (4), and combination PTA/atherectomy (11). MRA imaging was performed within 24 hours of the procedure and at a mean follow-up interval of 3.5 months (range 1-8).

RESULTS

Abnormalities in the immediate post-procedural MRA were seen in 55% of the PTA group and 93% of the atherectomy group (p = 0.04). Importantly, three of 35 lesions (9%) were shown by MRA to harbor > 50% stenoses despite angiographically "successful" procedures. Follow-up MRA showed abnormalities in 25% of those undergoing PTA, and in 67% of those with atherectomy (p = 0.01). At the time of follow-up MRA, four areas showed > 50% stenosis and four areas showed occlusion, revealing unfavorable outcomes in 22%.

CONCLUSIONS

MRA provides a detailed noninvasive image of the sites of endovascular interventions and reveals vessel wall abnormalities not appreciated by conventional arteriography. Continued observation may allow prediction of segments at increased risk for restenosis.