Characterization of Restenosis following Carotid Endarterectomy Using Contrast-Enhanced Vessel Wall MR Imaging.

BACKGROUND AND PURPOSE: Restenosis is an important determinant of the long-term efficacy of carotid endarterectomy. Our aim was to assess the role of high-resolution vessel wall MR imaging for characterizing restenosis after carotid endarterectomy. MATERIALS AND METHODS: Patients who underwent vessel wall MR imaging after carotid endarterectomy were included in this study. Restenotic lesions were classified as myointimal hyperplasia or recurrent atherosclerotic plaques based on MR imaging features of lesion compositions. Imaging characteristics of myointimal hyperplasia were compared with those of normal post-carotid endarterectomy and recurrent plaque groups. Recurrent plaques were matched with primary plaques by categories of stenosis, and differences in plaque features were compared between the 2 groups. RESULTS: Twenty-two recurrent lesions from 18 patients (14 unilateral and 4 bilateral) were classified as myointimal hyperplasia or recurrent plaque. Myointimal hyperplasia showed no difference in enhancement compared with normal post-carotid endarterectomy vessels (5 unilateral) but showed stronger enhancement than recurrent plaques (80.10% [SD, 42.42%] versus 56.74% [SD, 46.54%], P = .042). A multivariate logistic regression model of plaque-feature detection in recurrent plaques compared with primary plaques adjusted for maximum wall thickness revealed that recurrent plaques were longer (OR, 4.27; 95% CI, 1.32-13.85; P = .015) and more likely to involve a flow divider and side walls (OR, 6.96; 95% CI, 1.37-35.28; P = .019). Recurrent plaques had a higher prevalence of intraplaque hemorrhage (61.5% versus 30.8%, P = .048) by a χ2 test, but compositional differences were not significant in the multivariate model. CONCLUSIONS: Vessel wall MR imaging can distinguish recurrent plaques from myointimal hyperplasia and reveal features that may differ between primary and recurrent plaques, highlighting its value for evaluating patients with carotid restenosis.

Carotid plaque neovascularization and hemorrhage detected by MR imaging are associated with recent cerebrovascular ischemic events.

BACKGROUND AND PURPOSE: Pathologic studies suggest that neovascularization and hemorrhage are important features of plaque vulnerability for disruption. Our aim was to determine the associations of these features in carotid plaques with previous cerebrovascular ischemic events by using high-resolution CE-MRI. MATERIALS AND METHODS: Forty-seven patients (36 men; mean age 72.5 ± 10 years) underwent CE-MRI and MRA examinations for carotid plaque at 3T. IPH presence was recorded. Neovascularity was categorized by the degree of adventitial enhancement (0, absent; 1, <50%; 2, ≥50%). Reader variability was assessed by using weighted κ. Associations with events were determined by using multivariable logistic regression. RESULTS: Intra- and inter-reader agreement for grading adventitial enhancement were good to excellent. IPH was present in 49% of patients and was associated with events (P = .03). Patients grouped by categories 0, 1, and 2 adventitial enhancement had increasing frequencies of events (14% category 0, 48% category 1, 65% category 2; P = .02). Events were associated with IPH (OR, 10.18; 95% CI, 1.42-72.21) and adventitial enhancement (compared with category 0: OR, 14.90, 95% CI, 0.98-225.93 for category 1; OR, 51.17, 95% CI, 3.4-469.8 for category 2) after controlling for age, sex, cardiovascular risk factors, wall thickness, and stenosis. Stenosis was not associated with events. CONCLUSIONS: Adventitial enhancement and IPH are independently associated with previous events and may provide important insight into stroke risk not achievable by stenosis.

Identification of intraplaque hemorrhage on MR angiography images: a comparison of contrast-enhanced mask and time-of-flight techniques.

BACKGROUND AND PURPOSE: MRA is widely used to measure carotid narrowing. Standard CE- and TOF-MRA techniques use highly T1-weighted gradient-echo sequences that can detect T1 short blood products, so they have the potential to identify IPH, an indicator of plaque rupture. We sought to determine the accuracy and reliability of these MRA sequences to detect IPH. MATERIALS AND METHODS: 3D TOF and CE carotid MRA scans were obtained at 3T on 15 patients (age range, 58-86 years; 13 men) scheduled for CEA. The source images from the precontrast (mask) CE-MRA and the TOF sequences were reviewed by 2 independent readers for IPH presence (identified as hyperintense signal intensity compared with adjacent muscle). CEA specimens were stained with antibody against glycophorin A and Mallory stain to detect IPH and were correlated with MR images. RESULTS: Nine of 15 CEA specimens (61 of 144 MR images) contained IPH confirmed by histology. Compared with TOF, CE-MRA mask demonstrated greater sensitivity, specificity, PPV, and NPV for IPH detection. The accuracy for correctly identifying IPH by using CE-MRA mask images and TOF images was 94% and 84%, respectively. Inter- and intraobserver agreement for IPH detection was excellent by mask images (κ = 0.91 and κ = 0.94, respectively) and TOF images (κ = 0.77 and κ = 0.84, respectively). CONCLUSIONS: CE-MRA mask images are highly accurate and reliable for identifying IPH, more so than the TOF sequence, and can potentially provide valuable information about risk for rupture.

A new vascular Endostaple: a technical description.

OBJECTIVE: The purpose of this report is to describe a new vascular Endostapling system. METHODS: The vascular Endostapling system can be passed through a 13F insertion sheath that is inserted through the femoral artery. An optical fiber and overlying Endostaple will penetrate a previously inserted endoprosthesis and the aortic wall at whatever points are desired. Once the optical fiber is withdrawn, the Endostaple assumes its preformed shape and acts like a through-and-through wire suture. As tissue ingrowth proceeds, the long-term security and stabilization of the coiled coil mechanism are likely to increase. CONCLUSIONS: We think Endostaples can be useful in preventing endograft migration and in treating endoleak at the site of the aortic neck-proximal endograft interface.

Vascular surgery and the Resource-based Relative Value Scale five-year review.

PURPOSE: The first 5-year review of the Medicare Resource-based Relative Value Scale (RBRVS) work values (RVUs) began in 1995, and adjustments became effective January 1, 1997. This report summarizes the methods used by The Society for Vascular Surgery (SVS) and the International Society for Cardiovascular Surgery, North American Chapter, (ISCVS-NA) Joint Council Government Relations Committee (GRC) to evaluate vascular surgery work RVUs and the results that were achieved. METHODS: The GRC performed a work study to determine accurate skin-to-skin operative times for typical vascular and nonvascular operations. These were compared with the original Harvard/Hsiao time estimates and intraservice work per unit time (IWPUT) values that had been used to determine work RVUs. For most vascular procedures the current operative times were longer than the original Harvard estimates, resulting in calculated IWPUTs substantially less than the Harvard values. This lack of correspondence was not identified in the nonvascular procedures, where operating room times and IWPUT values were more consistent with Harvard data. These study results were then used to support compelling evidence arguments in a petition to the Health Care Financing Administration (HCFA) that identified vascular surgery as being undervalued in the RBRVS. Nine commonly performed vascular procedures were cited for review in the 5-year update, and five distinct work analysis methods were used to justify each recommended RVU increase. These techniques included a standardized survey from the American Medical Association (AMA)/Specialty Society Relative Value Update Committee (RUC), a work calculation using accurate intraservice times and appropriate IWPUT values, and an evaluation and management (E&M) building-block approach. RESULTS: The RUC met throughout 1995 to assess codes submitted for review, and recommendations were forwarded to HCFA. The Notice of Proposed Rule Making (NPRM), which contained HCFA's preliminary RVU determinations, was released in May 1996. RVU increases from 11.5% to 44.6% were proposed for the nine vascular services cited by the SVS/ISCVS-NA. Also included were two increases and two reductions in less-common vascular operations. Of far greater overall fiscal import, HCFA proposed substantial increases in the work RVU for all E&M except that performed within global surgical packages. The SVS/ISCVS and most other surgical societies appealed HCFA's proposal regarding E&M. The Final Rule for the 1997 Medicare Fee Schedule was published late in 1996. CONCLUSIONS: The Final Rule upheld the 11 vascular work value improvements and the E&M increases that excluded global service packages. Because most surgical E&M is performed within 10- or 90-day global periods, the E&M ruling will produce an estimated annual $2.5 billion shift from surgical to nonsurgical specialties. Because the overall fiscal impact of the 5-year review was mandated to be budget-neutral, HCFA imposed an 8.3% reduction in the work payment of every service in Part B of the Medicare program, primarily to compensate for the increased nonsurgical E&M payments. The net fiscal impact of the 5-year review for vascular surgery has been estimated at +0.5%.

Arteriovenous fistula simulating arteriovenous malformation.

A 36-year-old man was thought (for 20 years) to have an arteriovenous malformation that could not be excised. Repeated ligations of proximal arterial supply to the vascular lesion were only transiently beneficial and may have caused a delay in correct diagnosis because of impaired angioaccess. Once it was discovered that he had an arteriovenous fistula--probably caused by a tonsillectomy at age 6--it was possible to occlude the fistula with detachable balloons. The mass and his headaches subsequently resolved. AV fistulas are caused by trauma. Growth of AVMs is often stimulated by trauma. Both lesions have pulsatile masses associated with overlying bruits. The differential diagnosis can usually be made by arteriography, since AV fistulas are acquired lesions with a single communication between an artery and a vein, whereas AVMs are congenital lesions with multiple, large arterial feeding vessels and numerous arteriovenous communications. Proper diagnosis is important, since AVMs are aggressive lesions that tend to regrow if not completely excised. AV fistulas will be cured if the single arteriovenous communication can be obliterated. Proper treatment for AV fistula is obliteration of the single arteriovenous communication, operatively or with occlusive balloons; treatment of AVMs--when possible--is excision of the entire mass, combined (on occasion) with preoperative embolization of the tumor mass. This case report emphasizes the importance of accuracy in the differential diagnosis between arteriovenous malformations and arteriovenous fistulas; moreover, it demonstrates both the ineffectiveness and deleterious consequences of proximal arterial ligation, since collateral development is enhanced and angiographic access is compromised.

Regional nerve block for femoropopliteal and tibial arterial reconstructions.

Thirteen high-risk patients underwent lower extremity revascularization anesthetized with a regional nerve block technique. The sciatic, femoral, and obturator nerves were infiltrated with 1% lidocaine and 0.25% bupivacaine. Eight femoropopliteal and five femorotibial bypasses were performed for limb salvage (11 patients), disabling claudication (one patient), and popliteal artery aneurysm (one patient). Analgesia was adequate with only one patient who needed supplemental nitrous oxide. One patient died on the sixth postoperative day of a myocardial infarction. Regional nerve block is an effective anesthetic technique that should be considered if general or spinal anesthesia is inappropriate.

Transperitoneal approach and right retroperitoneal dissection for abdominal aortic aneurysm.

Most abdominal aortic aneurysms can be resected through a standard transperitoneal approach. In patients with large aneurysms, supra-renal extension of the aneurysm, those requiring renal reconstructive procedures and in patients who have had previous extensive intra-abdominal operations, alternative approaches have been recommended. We exposed the abdominal aorta in ten of these difficult patients using a midline transperitoneal incision and right retroperitoneal dissection that provided excellent exposure of the suprarenal aorta. We recommend this technique for performance of complicated abdominal aortic aneurysm resections.

Anomalies of the inferior vena cava.

The inferior vena cava is formed by a complex process of embryogenesis during the sixth to tenth week of gestation. Improper completion of the process may result in four anatomic anomalies: duplication of the inferior vena cava, transposition or left-sided inferior vena cava, retroaortic left renal vein, and circumaortic left renal vein. The first two anomalies can be diagnosed by sonography and all four anomalies can be seen on CT scan of the abdomen. Duplication and transposition of the inferior vena cava should be further delineated by preoperative phlebography. Preoperative diagnosis of the anomalies should reduce the complication rate of abdominal aortic operations.

Management of patients with hemangiomas and arteriovenous malformations.

Hemangiomas and AVMs are distinct congenital, benign, vascular lesions. Differentiation between the two is important because AVMs are amenable to embolization techniques and because patients with hemangiomas can be told they have a better prognosis than those with AVMs. A major error of management is to ligate the arterial blood supply to an AVM proximally, as the lesion will continue to grow, more collateral vessels will develop, and future angioaccess for purposes of evaluation or embolization will be denied. With care and prudence, many of these lesions can be successfully excised, or at least managed, so that the effect of these sometimes devastating lesions can be ameliorated.

Lytic therapy in the treatment of axillary and subclavian vein thrombosis.

The importance of individualized treatment of patients with primary and secondary axillary-subclavian vein thrombosis is described with special emphasis on the use of thrombolytic therapy. Nine patients were treated with streptokinase or urokinase. Balloon dilation of the axillary or subclavian vein and first rib resection were also selectively used. Of the five patients with primary axillary-subclavian thrombosis, three did not have symptoms after the thrombus was lysed. Two had successful lysis of the thrombus but later suffered a rethrombosis, one of which most likely resulted from an untreated stenosis. All four of the patients with secondary thrombosis had successful thrombolysis. Patients with primary axillary-subclavian thrombosis are usually young and as many as 40% continue to have intermittent upper extremity edema or pain. For this reason we believe aggressive attempts to reestablish normal venous return through the axillary and subclavian veins are warranted. Patients with secondary axillary-subclavian thrombosis usually require prolonged venous catheterization for chemotherapy or total parenteral nutrition. Since patency of major upper extremity veins is extremely important in these patients with secondary thrombosis, we believe that vigorous attempts to restore these venous access routes are indicated and appropriate.

Timing of carotid artery endarterectomy after stroke.

Carotid endarterectomy has been advocated to prevent further neurologic deterioration in patients who have had a stroke. Previous reports have shown that endarterectomy within 2 weeks of a stroke is associated with high morbidity and mortality rates presumably from hemorrhagic complications in the brain. Some recommend a 2- to 6-week waiting period after a stroke, but the safety of operation in the interval of time beyond 2 weeks has not been documented in the literature. The present study investigated the morbidity and mortality rates of 352 consecutive carotid endarterectomies. Three hundred three endarterectomies were performed on patients with symptoms other than stroke. Forty-nine endarterectomies were performed on patients with a deficit lasting more than 24 hours. Of these, 27 carotid endarterectomies were performed in an interval less than 5 weeks after initial stroke (early interval) and 22 operations were performed in a 5- to 20-week interval after stroke (late interval). Five strokes occurred in the 27 patients operated on within 5 weeks, an incidence of 18.5%; none of the patients operated on after 5 weeks exhibited worsening of their preoperative neurologic status. With the use of Fisher's exact test to compare these two intervals, the results were found to be significant (p less than 0.05). The cause of stroke in those operated on in the early interval was investigated by postoperative CT scans; in only one instance was there a hemorrhagic infarct of the ipsilateral hemisphere. The literature suggests that a variety of intracerebral vascular changes render the brain more susceptible to reinfarction soon after stroke. This study suggests an unstable situation in the 5-week interval following stroke that contraindicates carotid endarterectomy.

Stimulation of gastric acid secretion in the rhesus monkey.

Similar maximal rates of gastric acid secretion are achieved with histamine and gastrin stimulation in human, dog, or cat, but gastrin produces higher rates than histamine in the rat. Gastric acid secretion was measured in seven nonsedated, alert, chaired rhesus monkeys (Macaca mulatta). Dose-response studies were performed using intravenous histamine or tetragastrin. These studies showed histamine to be a much more efficacious and more potent stimulant of gastric acid secretion than tetragastrin in the monkey. Both histamine and tetragastrin had similar potency and efficacy in the dog, while tetragastrin, pentagastrin, and hog heptadecapeptide were similarly less active than histamine in the monkey. Background carbachol (4 micrograms/kg/hr) did not affect the histamine or tetragastrin dose-response curves. Histamine stimulation with background tetragastrin (64 micrograms/kg/hr) did not produce a dose-response curve statistically different from histamine alone. Tetragastrin stimulation with background histamine (60 micrograms/kg/hr) increased the tetragastrin dose-response curve, with a probable additive effect. We conclude that the rhesus monkey differs from cat, dog, and man in that gastrin and its analogs are not able to stimulate maximal acid secretion to the level achieved by histamine.

Vascular malformations.

Fourteen patients with hemangiomas or arteriovenous malformations treated with operative management are described. Particular emphasis is placed on the definition of terms and the methods of differentiating arteriovenous fistulas, hemangiomas, and arteriovenous malformations. Arteriovenous fistulas are acquired lesions consisting of a single communication. Hemangiomas are congential lesions that rarely pulsate or have an associated bruit; moreover by angiography they have multiple small feeding arterial vessels and histologically are composed of numerous thin-walled, but normal-appearing, blood vessels. Arteriovenous malformations are also congenital but they pulsate and have associated bruits; furthermore on angiography they have a number of larger arterial feeding vessels and histologically are composed of abnormal dysplastic vessels. Operative management of all lesions should be carefully planned and executed. Arteriovenous malformations and skeletal muscle hemangiomas will have a tendency to recur if not completely excised.

Priority of revascularization in patients with graft enteric fistulas, infected arteries, or infected arterial prostheses.

Patients with arterial infections, infected arterial prostheses, or graft enteric erosions or fistulas have high amputation and mortality rates after treatment. An unresolved therapeutic question is whether remote ("extra-anatomic") bypass should precede or follow removal of the infected artery or prosthesis. None of the ten patients reported here who had a remote bypass inserted first developed distal limb ischemia or infection of the remote bypass. Literature review of patients with aortic prosthetic infections revealed a mortality of 71% (10/14) if infected graft removal preceded remote bypass and 26% (6/23) if remote bypass was first. Patients with graft enteric erosions or fistulas had a mortality of 53% (40/75) if graft removal was first and 17% (5/29) if remote bypass was first. Subsequent infection of the remote bypass was rare. Therefore, when possible, remote bypass with a prosthetic graft should precede removal of an infected artery, an infected arterial prosthesis, a graft enteric erosion, or a graft enteric fistula.

The use of fluoroscopy with the C arm for femoral arterial embolectomy and cannulation of the popliteal trifurcation vessels.

Fluoroscopy with the C arm allows for the immediate assessment of distal arterial circulation following embolectomy. With the use of two embolectomy catheters, each one of the trifurcation vessels can be separately cannulated to remove additional thrombus. The technique described is not difficult and adds little time to the operative procedure.