Kathleen Carter

Are we undertreating carotid stenoses diagnosed by ultrasound alone

Clinical management of carotid disease is primarily based on results of national trials (ACAS and NASCET) that used the distal internal carotid artery diameter as a reference. However, commonly accepted ultrasound (US) criteria for carotid stenosis were derived from the correlation of velocity measurements with angiographic bulb diameter reductions (BDR). This study was undertaken to compare the degree of carotid stenosis determined by conventional velocity criteria to the degree of stenosis measured by B-mode (gray scale) diameter at both the carotid bulb and at the distal internal carotid artery, and, second, to evaluate US imaging to derive distal diameter reductions (DDR) noninvasively. During a 3-month period patients referred for carotid US were prospectively analyzed for standard velocity criteria and plaque morphology. Minimum carotid diameter was measured by longitudinal and transverse B-mode measurements and compared to carotid bulb diameter and internal carotid diameter distal to all disease. B-mode diameter reductions were compared to the degree of stenosis determined by velocity criteria and to patient symptoms and the decision for carotid endarterectomy. In total, 131 carotid arteries in 74 patients were evaluated. Based on the University of Washington velocity criteria, lesions were classified as grade I (n= 61, 46%), IIA (n= 58, 44%), IIB (n= 7, 5%), or III (n= 5, 4%). BDR measured by B-mode predicted the grade of disease based on velocity criteria (p<0.001) with an overall accuracy of 95%. With use of the B-mode for DDR (NASCET style), 18 patients exceeded the 60% threshold for surgical intervention. Of these, only 3 patients were symptomatic and were operated on. An additional 3 operated-on patients had an asymptomatic grade III stenosis, our usual threshold for intervention. Twelve additional patients were appropriate for surgical intervention by B-mode but were not treated based on conventional velocity criteria alone. Bulb diameter reduction by B-mode imaging correlates strongly with diameter reduction determined by velocity criteria, and independently predicts the grade of carotid disease. With this in mind, the accuracy of B-mode imaging may be extended to the measurement of carotid stenosis based on DDR. By B-mode criteria, many patients appropriate for intervention were not offered treatment based on conventional velocity criteria. Modern B-mode imaging provides a noninvasive method to obtain “arteriographic equivalent” measurements and should be added as a routine to carotid ultrasound interrogation.

A Technique to Improve the Confidence of Color Duplex Ultrasound assessment of Aortic Endografts: The use of Contrast Agents

Introduction Color duplex ultrasound (CDU) is routinely used in the evaluation of aortic endografts in many centers. CDU compliments computed tomography (CT) and selective angiography in the identification of persistent endoleaks in these grafts. Because of the complexity of these procedures and the subtle nature of endoleaks, CDU can be time-consuming and challenging. Contrast agents can improve the ease of imaging by rapidly detecting low flow endoleaks. The application of ultrasound contrast agents has been studied in other specialties, such as cardiac echocardiography. This article describes our technique and early experience using contrast-enhanced CDU in aortic endograft assessment. Methods Nineteen patients being seen for a routine CDU examination after endovascular aortic aneurysm repair were evaluated according to published protocol. An initial CDU examination was completed, thoroughly assessing for the presence of graft patency, limb dysfunction, and endoleak. After patient consent, a focused ultrasound was performed using a Food and Drug Administration–approved contrast agent (Optison). The residual aneurysm sac was closely inspected after a 0.3-ml intravenous injection. A maximum of three injections were given in 10-min intervals, with careful evaluation in transverse and sagittal views of the residual aortic sac. Contrast was used to confirm endoleaks noted on the baseline study and help clarify subtle perigraft flow, especially on suboptimal examinations. Results Of the 19 patients given the contrast agent, none had side effects, and all tolerated contrast well. In 9 of 19 examinations, contrast-enhanced CDU confirmed the baseline results positive for perigraft endoleak. Six of nine studies had improved ease of identification of endoleak with contrast. Six of 19 studies were negative for endoleak before and after contrast. Three of 19 studies were indeterminate for endoleak by CDU only secondary to bowel gas and body habitus. The contrast agent was given and was negative for endoleak in these three cases. One study was initially negative for endoleak by CDU, and contrast revealed a small lumber artery leaking into the aneurysm sac. The contrast was easily identified within the endograft and leak sites in all patients. Conclusions CDU is a valuable modality in the postoperative evaluation of endovascular aortic aneurysm repairs. These examinations can be challenging and subject to limitations including bowel gas and body habitus, even when performed by experienced technologists. Color artifacts within the residual aneurysm sac can be difficult to differentiate from true endoleak. Contrast-enhanced CDU can improve the technologists confidence in the detection of endoleaks.

Color Duplex Ultrasound Characteristics: Can we Predict Aortic Aneurysm Expansion following Endovascular Repair?

Introduction The goal of aortic endovascular repair (EVAR) is to successfully exclude the aneurysm. Color duplex ultrasonography (CDU) is effective in the identification of endoleak and assessment of abdominal aortic aneurysm (AAA) morphology after EVAR. In a subset of patients with subtle endoleak, there is a characteristic appearance that predicts significant endoleak leading to AAA expansion. These endoleaks are difficult to detect by computed tomography (CT), and CDU and may represent the phenomenon known as endotension when endoleak is not identified. Methods All patients with several EVAR devices were prospectively followed with CDU for evaluation of endoleak at intervals during a 4-year period. All CDU exams were performed using Philips 5000, 3000, and IU22 systems according to protocol. Assessment of the AAA sac with spectral and color Doppler was used to identify endoleak. The B-mode echogenicity of the AAA sac was characterized for echogenicity and sac symmetry. The patients were followed with CT scan and/or angiography for confirmation of endoleaks. Results There were 12 patients with subtle Type II endoleaks and a characteristic texture by CDU identified from 1 month to 16 months after intervention. The endoleaks had low velocities within the sac ranging from 10 to 50 cm/sec with a bidirectional spectral Doppler waveform. An asymmetrical AAA sac with a “spongy” multiechogenic texture was a finding in all 12 patients. The endoleaks were difficult to detect by both CDU and CT scan because of the low velocities despite AAA sac enlargement in all patients. The average AAA sac enlargement was 4.4 mm. CT scan and/or angiography failed to detect endoleak in 6 of 12 patients positive by CDU for endoleak with AAA sac expansion. Conclusion CDU after EVAR can effectively detect the presence of endoleak and assess the B-mode characteristics of the AAA sac. Important clues such as low flow, sac expansion, sac asymmetry, and a “spongy” B-mode appearance are consistent with subtle endoleak that may lead to AAA expansion. When undetected, this type of endoleak may be misdiagnosed as endotension.

The Role of Color Duplex Ultrasound in Patients with Abdominal Aortic Aneurysms and Stent Grafts

Although ultrasound is an inexpensive, effective diagnostic tool in abdominal vascular diagnosis in general, its use in abdominal aortic aneurysm (AAA) diagnosis and endograft follow-up has been the subject of controversy and contradictory reports.1, 2, 3, 4 Endograft replacement for abdominal aortic aneurysms has been used for over 10 years in the United States, but controversy still remains as to the role of ultrasound in postimplant surveillance.5,6 The notable effect of regional variability in the use of ultrasound7 and the marked differences in expertise from center to center have led to the inconsistent application of ultrasound to both general AAA diagnosis as well as to surveillance after endograft treatment. As a result, many divergent opinions exist as to the ultimate role of color duplex ultrasound in aortic aneurysmal disease.

Are there long-term consequences of iliac artery trauma during endograft implantation? Results of serial duplex ultrasound follow-up

Purpose The implantation of abdominal aortic endografts requires the insertion of large devices that have the potential to traumatize the iliac arteries, particularly on the ipsilateral side, where the main body of the endograft is introduced. The consequences of this potential trauma are unknown, but the possibility for significant injury remains. For this reason, a prospective measurement of iliac intimal medial thickness by serial duplex ultrasound was undertaken to determine the effect of endograft placement on iliac arteries. Methods A total of 117 patients had duplex evaluation of their iliac arteries after aortic endograft placement at an average follow-up of 18.8 months (range, 0 to 71 months). Ancure devices were used in 89, AneuRx in 11, Endologix in 12, Vanguard in 1, and unknown devices in 4. All endografts were scanned using Philips/ ATL HDI 5000 or ATL 3000 ultrasound machines with 7–4 MHz transducers and a standard protocol, with additional iliac artery measurements performed for the specifics of this study. Of these 117 patients, bilateral intimal medial thickness (IMT) was measured with a clearly determined ipsilateral (larger diameter sheath) implantation side defined in 66 patients. In these patients the ratio of ipsilateral (main introducer) IMT to contralateral (smaller diameter sheath) IMT was determined. Results Of the 66 patients with complete data available for review, the mean ipsilateral to contralateral IMT ratio was 1.41 (range, 0.3 to 16.4). Nonetheless, when evaluated more closely, only two patients had IMT ratios exceeding 2.0 (12.0 and 16.4). When these two patients are excluded, the IMT ratio averaged 1.01, suggesting an absence of significant intimal trauma secondary to aortic endograft implantation. If we presume that the cause of this increased intimal thickness is iliac trauma secondary to endograft placement, then the maximum incidence is 2/66 (3.0%). Analysis by follow-up intervals suggests no duration effect of significance. Conclusions Iliac artery trauma resulting in intimal hyperplasia or premature atherosclerosis appears to be a rare event after endograft abdominal aortic aneurysm repair. With current devices and current clinical selection, iliac artery pathology after endograft placement is not a significant concern.

Mycotic Pseudoaneurysm following Carotid Intervention

Introduction Pseudoaneurysm formation is a rare complication following carotid artery revascularization with a low estimated occurrence of 0.15 to 0.6%. This may result from percutaneous intervention, trauma, or infection. Patients may present with pain and swelling as well as a pulsatile cervical mass. Case Report A 56-year-old male with a history of multiple carotid endarterectomies and an interposition synthetic graft presented with a recurrent high-grade stenosis. The patient underwent a balloon angioplasty and stent placement in the internal carotid artery. Two months postintervention, the patient presented with swelling and tenderness at the incision site. Color duplex ultrasound (CDU) was performed, demonstrating a 1.7 × 1.8 cm perigraft collection without evidence of flow. The patient returned in 2 weeks with increased swelling and discomfort. This prompted a repeat CDU, demonstrating a 3.7 × 3.9 cm hypoechoic, perigraft collection, now doubled in size from the previous exam. An abscess was confirmed by needle aspiration and positive culture results. He was admitted and underwent 6 weeks of antibiotic therapy. Upon discharge, the patient returned for a follow-up CDU. A perigraft collection with arterial flow was now present that had not previously been noted. Angiography confirmed extraluminal flow at the level of the carotid stent. The patient underwent operative debridement with excision of the infected graft and repair of the pseudoaneurysm. Conclusions Carotid artery interventions have a very low incidence of infection. The occurrence of an infected or mycotic pseudoaneurysm following carotid intervention is extremely rare. CDU is a vital tool in detecting thrombosed versus active pseudoaneurysms, which may help guide appropriate therapeutic decisions.

Femoral Artery Pseudoaneurysm Caused by an Osteochondroma of the Femur: A Case Report

Introduction The osteochondroma is the most common benign tumor of bone. Typically asymptomatic bony protuberances are discovered in childhood or adolescence. Although vascular complications are rare, these bony spikes can course along an artery and cause severe arterial complications. Reported here is a case involving the use of color duplex ultrasonography (CDU) to identify a superficial femoral artery (SFA) pseudoaneurysm as a result of an osteochondroma. Case Report A 12-year-old girl had been experiencing left lower extremity pain for approximately 2 months. The pain became progressively severe, and her parents noticed that she was limping. Magnetic resonance imaging (MRI) demonstrated a mass in the left thigh, suggesting the possibility of a femoral aneurysm. A bony spicule was noted on x-ray at the distal femur, projecting posteriorly. Clinical evaluation revealed an impressive pulsatile mass in the left distal medial thigh. The left thigh was noticeably larger than the right with poor pedal pulses compared with the asymptomatic limb. CDU was performed and identified an aneurysm of the SFA at the adductor canal. There was unusual oscillatory flow in the SFA proximal to the aneurysm with monophasic signals distally. The large aneurysm size displaced the normal anatomic course of the SFA and vein. Ankle-brachial indices (ABI) were 0.72 and monophasic in the affected limb and >1.0 and triphasic in the contralateral limb. Angiography confirmed the CDU and MRA findings, demonstrating a large pseudoaneurysm at the adductor canal caused by an osteochondroma of the femur. At time of surgical repair, the bony spicule was noted to have eroded into the femoral artery. Conclusion Vascular complications as a result of an osteochondroma are rare. Rapid diagnosis is necessary to prevent serious arterial compromise in these young patients. CDU can quickly and accurately confirm the presence of a pseudoaneurysm when an osteochondroma is suspected.