Renal transplant evaluation with MR angiography and MR imaging.

Magnetic resonance (MR) angiography is a widely used, noninvasive tool for evaluating the aorta and its branches. It is particularly useful in renal transplant recipients because it provides anatomic detail of the transplant artery without nephrotoxic effects. Volume rendering is underutilized in MR angiography, but this technique affords high-quality three-dimensional MR angiograms, especially in cases of tortuous or complex vascular anatomy. An imaging protocol was developed that includes gadolinium-enhanced MR angiography of the transplant renal artery with volume rendering and multiplanar reformation postprocessing techniques. Axial T2-weighted and contrast material-enhanced T1-weighted MR images are also obtained to examine the renal parenchyma itself and to evaluate for hydronephrosis or peritransplant fluid collections. This imaging protocol allows rapid global assessment of the renal transplant arterial system, renal parenchyma, and peritransplant region. It can also help detect or exclude many of the various causes of renal transplant dysfunction (eg, stenosis or occlusion of a transplant vessel, peritransplant fluid collections, ureteral obstruction). Conventional angiography can thus be avoided in patients with normal findings and reserved for those with MR angiographic evidence of stenosis.

Lessons learned in adopting endovascular techniques for treating abdominal aortic aneurysm.

HYPOTHESIS: Endovascular exclusion of abdominal aortic and common iliac aneurysms can be performed safely, and in the short term represents a feasible alternative to traditional, open aneurysm repair. PATIENTS AND METHODS: Forty-one patients were treated with endovascular grafts for 39 abdominal aortic and 2 common iliac artery aneurysms. RESULTS: All devices were successfully deployed. The size of the abdominal aortic aneurysms varied from 4.9 to 11.9 cm (average, 6.13 cm). The median procedure time was 195 minutes. There was one iliac artery rupture, which required celiotomy for repair. The hospital stay varied from 2 to 39 days (average, 6.7 days). The perioperative mortality rate was 2.4%. Sixteen patients (39%) had groin wound complications. Ten patients (24%) had evidence of contrast (endoleak) within the aneurysm sac on completion of the procedure. There were no obvious direct leaks from either the point of proximal or distal fixation. Seven of these endoleaks have resolved spontaneously. Two patients required additional procedures in the postoperative period to treat endoleak. The final patient has evidence of persistent endoleak on 3-month surveillance computed tomography scan. Major late problems occurred in 3 patients. CONCLUSION: Patients with large abdominal aortic aneurysms and considerable cardiac comorbidity can safely undergo endovascular aneurysm repair. Femoral groin wound complications resulting in prolonged hospitalization remain the major cause of perioperative morbidity. In contradistinction to open aneurysm repair, long-term surveillance is essential to detect migration of the device and identify flow within the residual aneurysm sac-complications that could lead to aneurysm rupture following endovascular repair.

Endovascular therapy of iliac arteries: routine application of intraluminal stents does not improve clinical patency.

Our objective in this study was to review our experience with endovascular therapy of iliac artery occlusive disease over the past decade, and to compare the results of angioplasty alone with the addition of endovascular stents to these procedures. This report details a retrospective analysis of clinical data on 141 consecutive patients with iliac artery occlusive disease, treated by balloon angioplasty alone, or with the addition of intraluminal stents. The procedures analyzed included 58 common iliac artery interventions (26 angioplasties and 32 stent insertions) and 83 external iliac artery procedures (43 angioplasties and 40 stent insertions). Early and continued success, and their components, are reported and compared according to published standards. While endovascular therapy of iliac artery occlusive disease is effective in relieving symptoms, clinical patency rates are lower than those reported for direct reconstruction. Primary stent placement has not enhanced clinical patency in the iliac arteries, and the selective insertion of these devices for more complicated angioplasty procedures seems warranted.

Impact of peripherally inserted central catheters on phlebitic complications of peripheral intravenous therapy in spinal cord injury patients.

We investigated the impact of peripherally inserted central catheter (PICC) placement in spinal cord injury patients at high risk for infusion phlebitis. The rate and etiology of phlebitis was investigated in two phases. During Phase I, peripheral IV cannulae and conventional central venous catheters (CVC) were used. During Phase II, patients identified to be at risk for phlebitis received PICCs. The number of peripheral IVs, CVCs and PICCs was tabulated for both phases of the study. Technical, infectious and thrombotic complications were studied prospectively for PICCs and retrospectively for CVCs. We found the rate of phlebitis was 16.5 percent and 2.4 percent for Phases I and II, respectively (p = 0.0002). Three infections occurred in 38 PICCs and one infection was documented in 13 conventional CVCs. The number of peripheral IVs and conventional CVCs was reduced significantly from Phase I to Phase II. No procedural complications, catheter sepsis or clinically apparent venous thrombosis occurred. In conclusion, PICCs reduced the rate of phlebitis thresholds with a low complication rate and reduced the use of peripheral IVs and conventional CVCs.

Interventional procedures in the intensive care unit patient.

Image-guided interventional techniques have markedly altered the management of many cardiothoracic problems in the intensive care unit. These techniques are less invasive, more patient friendly, and cost-effective. This article covers venous line placement and management, transpleural and transpulmonary biopsy and drainage procedures and interventions for variceal bleeding, massive hemoptysis, massive pulmonary embolism, and veno-occlusive disease.

Fibrin sleeve stripping for salvage of failing hemodialysis catheters: technique and initial results.

PURPOSE: To evaluate percutaneous fibrin sleeve stripping (PFSS) to prolong functional patency in failing hemodialysis catheters. MATERIALS AND METHODS: Forty PFSS procedures were performed in 24 catheters in 23 consecutive patients with an inadequate blood flow rate (< 200 mL/min) during hemodialysis. The fibrin sleeve was mechanically stripped off the shaft of the catheter with a snare introduced via the common femoral vein. Durability of PFSS was determined with life-table analysis. RESULTS: Median time from catheter placement to initial failure was 3.5 months (range, 5 days to 22 months). The technical success rate for PFSS was 100%; initial patency was restored in 39 of 40 procedures (98%), and no symptomatic pulmonary embolism occurred. Primary patency after single PFSS was 45% at 3 months and 28% at 6 months (median added patency, 2.8 months). Postprocedure secondary patency with multiple PFSS procedures was 83% at 3 months and 72% at 6 months (P = .01) (overall catheter patency, 90% at 6 months and 81% at 1 year [P < .001]). CONCLUSION: Multiple PFSS procedures can prolong patency in hemodialysis catheters with a fibrin sleeve.

Detection of pulmonary embolism in patients with unresolved clinical and scintigraphic diagnosis: helical CT versus angiography.

OBJECTIVE: This study was designed to prospectively compare helical CT with pulmonary angiography in the detection of pulmonary embolism in patients with an unresolved clinical and scintigraphic diagnosis. SUBJECTS AND METHODS: Twenty patients with an unresolved suspicion of pulmonary embolism were evaluated with contrast-enhanced helical CT and with selective pulmonary angiography. An average of 11 hr separated the two studies. The CT scans were obtained during one 24-sec or two 12-sec breath-holds. CT scans were interpreted without knowledge of the results of scintigraphy or angiography. Selective pulmonary angiograms were obtained with knowledge of the findings on the ventilation/perfusion scan only. The sensitivity and specificity of CT were compared with those of angiography for central vessels (segmental and larger) only and for all vessels. RESULTS: Eleven of the 20 patients had proved pulmonary embolism (seven in central vessels and four in subsegmental vessels only). When only central vessels were analyzed, CT sensitivity was 86%, specificity was 92%, and the likelihood ratio was 10.7. However, when subsegmental vessels were included, CT results were 63%, 89%, and 5.7, respectively. CONCLUSION: In our subset of patients, helical CT was only 63% sensitive. Subsegmental emboli are difficult to diagnose. Pulmonary angiography remains the study of choice. CT has a limited role in the evaluation of acute pulmonary embolism.

Postcontrast CT in the diagnosis and assessment of response to thrombolysis in massive pulmonary embolism.

We present a case of massive acute pulmonary embolism where contrast enhanced helical CT was compared with standard angiography for diagnosis and for monitoring subsequent response to thrombolytic therapy. There was very close concordance of the findings on these modalities suggesting that contrast enhanced helical CT may be an easy and reliable alternative to standard angiography.

Placement of the Palmaz stent with use of an 8-F introducer sheath and Olbert balloons.

PURPOSE: The authors describe a modified technique for delivering Palmaz 30-mm stents. MATERIALS AND METHODS: The modification is based on the use of an 8-mm Olbert balloon mounted on a 5.8-F shaft. The Palmaz stent is crimped onto the balloon by using finger pressure only. An 8-F introducer sheath can be used instead of a 10-F sheath. The surface material of the balloon prevents the stent from moving as it is introduced through the sheath and lesion. The balloon has a very small profile after deflation, which means it can be easily removed without dislodging the stent. The balloon can be used for placement of more than one stent. RESULTS: Nineteen Palmaz 30-mm stents have been placed with this method, and there have been no complications or difficulties related to this method. In one case, four stents were delivered by using the same balloon. CONCLUSION: This modification should reduce the complications of stent delivery, especially in small iliofemoral systems.

Arterial enhancement in acute cerebral ischemia: clinical and angiographic correlation.

PURPOSE: To investigate the cause and clinical significance of arterial enhancement (AE) in contrast-enhanced T1-weighted MR examinations after acute cerebral ischemia. METHODS: Contrast MR examinations and conventional angiograms of 17 patients studied following an acute ischemic event or an internal carotid occlusion were retrospectively reviewed. MR and angiographic studies were performed within 1 day of each other. The presence of AE was correlated with both angiographic findings and patient clinical status. RESULTS: AE was not confined to patients with angiographic evidence of complete arterial occlusion. Only 64% of patients demonstrating AE had complete occlusion angiographically. Complete arterial occlusion did not always correlate with AE. In two of nine patients with complete occlusion, no AE was identified. In five of 10 patients with AE, angiographic slow flow was identified. In patients without AE, no angiographic slow flow was identified. In the 64% of patients with AE, significant symptoms were identified. Patients without AE were either asymptomatic or had mild symptoms at the time of the MR study. CONCLUSIONS: Our data support the hypothesis that arterial slowing is the cause of AE, which appears to be an indicator of decreased brain perfusion. Such MR findings may add important supplemental information to those provided by conventional angiography.

MR evaluation of CNS tumors: dose comparison study with gadopentetate dimeglumine and gadoteridol.

In phase II and III trials of gadoteridol (Gd-HP-D03A), a new nonionic, low-osmolar contrast agent, 40 patients with intracranial neoplasms underwent magnetic resonance (MR) imaging with experimental doses of 0.05-0.3 mmol/kg. Fifteen patients also underwent contrast studies with the standard dose (0.1 mmol/kg) of gadopentetate dimeglumine. Both gadopentetate dimeglumine and gadoteridol appear to have a similar effect when given in equal doses (0.1 mmol/kg, n = 5). Lesion enhancement and delineation were better at higher experimental doses (0.2 or 0.3 mmol/kg, n = 7) and worse at a lower experimental dose (0.05 mmol/kg, n = 3). Quantitative analysis of 10 lesions examined with identical imaging protocols revealed a directly proportional relationship (r = .975) between lesion contrast ratio and dose over a range of 0.05-0.3 mmol/kg. Phantom experiments support the clinical results. Improved enhancement, detection, and delineation of central nervous system (CNS) neoplasms resulting from increased injected doses of gadoteridol have the potential to be clinically significant and may justify the possibly higher cost of increased contrast material dosage. Lower doses may not be adequate for the evaluation of most CNS tumors.

MR imaging of cerebral ischemia: findings in the first 24 hours.

MR changes of cerebral ischemia have been shown to occur as early as 1-2 hr after vessel occlusion in experimental models of stroke. However, the MR findings in the early stages of ischemic stroke in the clinical population have not been well established. We studied 41 lesions in 39 patients in whom MR was performed within the first 24 hr after onset of ischemic symptoms. Twenty-five lesions were studied with gadopentetate dimeglumine. Vascular flow-related abnormalities, including absence of normal flow void and presence of arterial enhancement, were the earliest MR findings, detected within minutes of onset. Morphologic changes (brain swelling) on T1-weighted images without signal changes on T2-weighted images could be detected within the first few hours. Signal changes were not usually found before 8 hr on T2-weighted images or before 16 hr on T1-weighted images. In contrast to the absence of parenchymal enhancement typically found in cortical infarctions in the first 24 hr, a few lesions (including transient occlusions, partial occlusions, and isolated watershed infarctions) exhibited early, exaggerated parenchymal enhancement. We conclude that signal changes may not be reliable in detecting ischemic stroke within the first 8 hr after onset. Vascular abnormalities, when present, are the most reliable and earliest findings. Other MR findings of early ischemic stroke, including morphologic changes and early, exaggerated parenchymal enhancement, may also precede signal changes. Paramagnetic contrast administration often provides valuable information in the detection and evaluation of acute ischemia.

Cerebral ischemia: evaluation with contrast-enhanced MR imaging.

Eighty patients with a total of 82 ischemic lesions were examined with contrast-enhanced MR imaging 1 hr to 1 month after onset of symptoms. The studies were reviewed retrospectively to determine the presence of arterial enhancement and the patterns of parenchymal enhancement. Arterial enhancement was often detected on the initial MR examination (45%), was frequently demonstrated in cortical infarction (86%), in some cases preceded the development of signal changes on T2-weighted images, and resolved by 11 days. The presence of arterial enhancement appeared to be a better indicator of clinical severity than was the presence of proximal vessel occlusion on MR or angiographic studies. Two patterns of parenchymal enhancement were seen: progressive enhancement and early and/or intense enhancement. In patients with the progressive pattern, parenchymal enhancement on postcontrast T1-weighted images was rarely seen before 7 days, while signal abnormalities on T2-weighted images were intense during the first few days. The early and/or intense enhancement pattern was usually present within the first 3 days, approximated or exceeded the area and intensity of signal changes on T2-weighted images, and was usually associated with minimal or reversible neurologic sequelae (except when located in or near a watershed zone), suggesting a lesser degree of ischemic insult than was associated with the progressive pattern.(ABSTRACT TRUNCATED AT 250 WORDS)