Anesth Analg 2007;104:1037-1039
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000263269.68845.83
CARDIOVASCULAR ANESTHESIA
Spontaneous Echocardiographic Contrast Indicating Successful Endoleak Management
Madhav Swaminathan, MD, FASE*,
Georg B. Mackensen, MD, FASE*,
Mihai V. Podgoreanu, MD, FASE*,
Richard L. McCann, MD*,
Joseph P. Mathew, MD, FASE*, and
George C. Hughes, MD*
From the *Division of Cardiothoracic Anesthesiology and Critical Care Medicine, Department of Anesthesiology, and 
Division of Thoracic Surgery, Department of Surgery, Duke University Medical Center, Durham, North Carolina.
Address correspondence to Madhav Swaminathan, MD, FASE, Department of Anesthesiology, Box 3094, DUMC, Duke University Medical Center, Durham, NC 27710. Address E-mail to swami001{at}mc.duke.edu.
A 75-yr-old woman was admitted with an enlarging descending thoracic aortic aneurysm (TAA). The patient had undergone open repair 12 yr before this admission. Tomographic scanning revealed a 9.9 x 9.6 cm2 proximal TAA with dilation of the ascending aorta and thrombus within the aneurysm. It extended from the proximal descending aorta at the level of the pulmonary bifurcation to the distal descending thoracic aorta. Given her risk profile, she was scheduled for endovascular repair.
A transesophageal echo (TEE) examination performed after induction of anesthesia confirmed the preoperative findings along with mild aortic insufficiency. A "TAG" thoracic endoprosthesis (WL Gore, Newark, DE) was deployed with the distal end within the previous graft. A second TAG endoprosthesis was deployed proximal to the first, covering the left subclavian artery. Subsequently, both TEE and cine-angiography revealed a large Type IA endoleak (Table 1). The TEE images showed spontaneous echocardiographic contrast (SEC or "smoke") within the aneurysm, indicating entry of blood into the aneurysm sac (Fig. 1; please see video clip available at www.anesthesia-analgesia.org). Color flow Doppler (CFD) imaging with a reduced velocity scale confirmed these findings (online video clip) and failed to show evidence of patent collateral vessels. A third TAG endoprothesis was then deployed 15 mm proximal to the second device and secured to the aortic walls with a trilobed endoaortic balloon. Subsequently, no further movement of the smoke, which had now acquired echodensity similar or brighter than surrounding tissue, was observed (Fig. 2, and online video clip). Initially, the origin of the flow within the sac could not be determined. However, using different imaging planes, the inflow channel was identified in the proximal stent region. This was confirmed with CFD (online video clip) and angiography. Retrograde flow from a collateral artery (type II endoleak) was considered unlikely, since flow initially was brisk, no flow in the collateral branches could be detected, and flow ceased with further endograft deployment. The primary decision regarding endoleakage and deployment of additional stents was based on angiography, with TEE providing supporting evidence. Her postoperative course was complicated by delayed onset paraparesis. She was discharged on the 16th postoperative day with some improvement.
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Figure 1. Midesophageal short axis view of the aorta at the level of the proximal descending thoracic aorta showing the position of the aneurysmal sac (A) and the endovascular device (B).
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Figure 2. Mid-esophageal short axis view of the aorta at the same level as Figure 1 after deployment of the third device, showing increased opacification of the echo contrast in the aneurysmal sac (arrow) indicating successful closure of the endoleak.
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The goal of an endovascular aortic repair is to deploy a graft that seals tightly above and below the aneurysm, excluding the aneurysmal sac from systemic bloodflow to decrease risk of rupture. Although general or regional anesthesia have been used successfully, if TEE is to be used, general anesthesia is required. Small clinical studies have suggested that TEE is more sensitive and specific than angiography in detecting endoleaks (2,3). The disadvantage of angiography is that it relies on a fixed volume of contrast to circulate within the endoleak. Small leaks may be missed, as the volume of contrast may not be detectable by fluoroscopy, or the imaging plane may not encompass the leak. TEE is limited by the echodensity of the endograft material, which creates a "dropout" shadow precluding imaging of distal structures. If the aneurysmal sac is in the far field relative to the endograft, TEE assessment of endoleaks is problematic. While TEE cannot be used as a sole imaging modality for endovascular repair, it can assist in confirming the presence or absence of an endoleak should angiography prove inconclusive. TEE is limited in evaluation of the proximal aortic arch due to poor acoustic windows and can therefore not be used in endografts that extend to this region.
Care must be exercised while inserting a TEE probe in patients with TAA, particularly where resistance to insertion is encountered, in which case it may be prudent to forego use. This is especially relevant with a preoperative complaint of dysphagia, hoarseness (recurrent nerve palsy), or stridor. The TEE probe may have to be withdrawn into the proximal esophagus to allow imaging during graft deployment. It can later be readvanced to assess for endoleaks. Six standardized views of the thoracic aorta provide a comprehensive assessment of most aortic pathology. Some of the endografts currently used are strong echo reflectors, complicating TEE use.
Echo contrast has been described as a useful adjunct to identification of an endoleak (4). Pharmacologic contrast agents have also been used to detect persistent endoleaks (5). However, the change in character of SEC within the aneurysm can also indicate successful closure of an endoleak. Smoke, or SEC, is caused by slow moving blood through the imaging plane. The echodensity of blood increases as flow decreases, approaching that of surrounding tissue when it becomes a thrombus. Increasing ultrasound backscatter from blood at low shear rates is a major factor in visualization of SEC. Compression and compensation (gain) settings on the machine can influence the character of SEC. Therefore, it is important to maintain constant settings to compare changes in character of SEC. Between Figure 1/online video clip and Figure 2/online video clip, compression has been decreased from 49 to 35. Despite this, the SEC appears more echodense, indicating significant backscatter from stagnant blood.
After deployment of the first two devices, an endoleak was clearly identified with both CFD and the appearance of SEC (online video clips). There was movement of SEC within the sac indicating persistent bloodflow. However, with successful deployment of the third device, the character of the SEC immediately changed to increased echodensity and no movement (online video clip). The pulsations within the aneurysmal sac are most likely transmitted from pulsatile flow within the aorta. This makes the SEC shake with each pulse. However, the character of the SEC does not change, indicating absence of an endoleak.
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Footnotes
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This article has supplementary material on the Web site: www.anesthesia-analgesia.org.
Supported by Intramural Departmental funds.
Reprints will not be available from the author.
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REFERENCES
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- Veith FJ, Baum RA, Ohki T, et al. Nature and significance of endoleaks and endotension: summary of opinions expressed at an international conference. J Vasc Surg 2002;35:1029–35.[ISI][Medline]
- Gonzalez-Fajardo JA, Gutierrez V, San Roman JA, et al. Utility of intraoperative transesophageal echocardiography during endovascular stent-graft repair of acute thoracic aortic dissection. Ann Vasc Surg 2002;16:297–303.[ISI][Medline]
- Swaminathan M, Lineberger CK, McCann RL, Mathew JP. The importance of intraoperative transesophageal echocardiography in endovascular repair of thoracic aortic aneurysms. Anesth Analg 2003;97:1566–72.[Abstract/Free Full Text]
- Dobson G, Maher N, Ball M, Kryski A, Moore R. Images in anesthesia: echo contrast as an adjunct to intraoperative angiography in the detection of endoleaks. Can J Anaesth 2006;53:516–7.[Free Full Text]
- Napoli V, Bargellini I, Sardella SG, et al. Abdominal aortic aneurysm: contrast-enhanced US for missed endoleaks after endoluminal repair. Radiology 2004;233:217–25.[Abstract/Free Full Text]
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