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Cardiovascular Anesthesiology: Echo Rounds

Embolization of Left Ventricular Apical Thrombus During Cardiac Surgery

Taneja, Rishi, MD; Aguirre, Marco A., MD; Shi, Chen, MD; Greilich, Philip E., MD, FASE

Author Information
doi: 10.1213/ANE.0b013e3181e04fe6

CLINICAL SCENARIO

A 62-year-old man was scheduled for urgent coronary artery bypass graft and aortic valve replacement 24 hours after experiencing an anterior wall myocardial infarction. Preoperative transthoracic echocardiogram revealed aortic sclerosis with moderate regurgitation, severely depressed ejection fraction (approximately 25%), anteroseptal wall akinesis, and a large left ventricular (LV) apical thrombus. Coronary angiography was complicated by severe hypotension necessitating the placement of an intraaortic balloon pump. Postoperative anticoagulation was selected to manage the thrombus in lieu of intraoperative thrombectomy to minimize cardiopulmonary bypass time in an already unstable patient.

After uneventful induction of anesthesia, transesophageal echocardiography (TEE) confirmed the presence of a large (2.3 × 4.3 cm), nonmobile, layered apical thrombus with varying degrees of echodensity (Fig. 1A) (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A140; see Appendix for Video 1 caption). After aortic cross-clamp was applied, dense adhesions were dissected out between the pericardium and apex of the heart to mobilize it. Because of the apical thrombus, an LV vent was not placed. After aortic valve replacement with a bioprosthesis and 4-vessel coronary artery bypass graft, the TEE examination was repeated before cross-clamp removal and revealed a large, freely mobile mass in the left atrium (Fig. 1B) (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A141; see Appendix for Video 2 caption). Cardioplegia was readministered, and the thrombus was removed via a left atriotomy along with remnants noted in the LV apex. Upon visual inspection, it was apparent that the thrombus removed from the left atrium was that seen preoperatively in the LV apex (Fig. 2). The patient was weaned from cardiopulmonary bypass and transferred to the intensive care unit.

Figure 1
Figure 1:
Midesophageal (ME) 4-chamber view of (A) left ventricular apical thrombus, and (B) left ventricular thrombus embolized into the left atrium during rewarming. CPB = cardiopulmonary bypass.
Figure 2
Figure 2:
Embolized thrombus excised from the left atrium.

The patient was tracheally extubated on postoperative day (POD) 3 without evidence of any neurologic injury. On POD 7, the patient had a significant alteration in his neurologic examination, and magnetic resonance imaging of the brain revealed multiple areas of acute infarction caused by emboli. Anticoagulation was initiated and neurologic symptoms were markedly improved by POD 10.

DISCUSSION

Intracardiac thrombectomy is a category 2 indication for intraoperative TEE examination. However, this case demonstrates that even when no intervention is planned, TEE monitoring of apical thrombi and knowledge of the risk factors for embolization can help avoid a catastrophic outcome.

LV apical thrombi occur most frequently in the presence of severe ventricular systolic dysfunction as seen in patients with dilated cardiomyopathy, LV aneurysms, or after myocardial infarction producing a large akinetic segment. The incidence of new-onset LV apical thrombus is greatest in those experiencing large anterior wall myocardial infarction with resultant apical akinesis or dyskinesis. The incidence of systemic embolization has been reported to be as high as 10%.1 Manipulation of the heart during cardiac surgery has the potential to further increase this risk. Avoiding the use of an LV vent is advisable in this setting given the risk of apical trauma.2

Transthoracic echocardiographic imaging of LV apical thrombi is generally considered superior to TEE given the proximity of the probe to the structure of interest. TEE evaluation of an LV thrombus should include multiple views through a complete cardiac cycle to distinguish the presence of a mass from artifact. Vertical scans, such as midesophageal 4-chamber, midesophageal 2-chamber, and deep transgastric views, generally provide the best assessment of the LV apex. Zooming in on the apical region improves image quality by adding resolution. Known apical thrombi not visualized on TEE may be attributable to foreshortening or embolization and efforts to locate it should be attempted.

Echocardiographic features that differentiate LV thrombi from other intraventricular masses include location in an area of abnormally functioning myocardium in multiple imaging planes, movement concordant with the underlying tissue, and an echodensity with well-delineated borders distinct from underlying myocardium.3 The use of contrast agents (Optison, etc.), especially in combination with power Doppler contrast, can significantly improve the detection of intracardiac masses by opacification of cardiac chambers.4 Setting the transducer frequency to >5 MHz can also improve endocardial border delineation when thrombi have a laminated appearance.3 B-color imaging has also been recommended to improve contrast resolution and may provide a more precise delineation between the thrombus and myocardium. Thrombi with the highest risk for embolization are immature, filamentous, and exhibit areas of varying echodensity with central liquefaction and irregular borders. In addition, areas of mobility, chamber protrusion, and location in contiguous zones of akinesis and hyperkinesis also portend higher risk of embolization.3 In contrast, the risk of embolization is less with thrombi that appear layered, echo-dense, immobile, and homogeneous with smooth borders.3 The risk of embolization of the LV thrombus in our patient was increased given its immaturity (age <48 hours, varying echo-density) and location in a large, akinetic apical segment. The need for extensive surgical manipulation of the apex to mobilize the heart further increased the embolic risk.

Although rare, intraoperative embolization of LV thrombi is possible and early detection with TEE can avoid a potentially catastrophic outcome. Schmitz and Hartmann,5 in 2006, highlighted the importance of TEE in diagnosing hemodynamic deterioration due to embolized intracardiac thrombi as well as possible etiologies. Given the relative safety of intraoperative TEE, performing a comprehensive examination in all patients with a known LV thrombus should be considered to monitor for possible catastrophic embolization.

REFERENCES

1. Barbera S, Hillis LD. Echocardiographic recognition of left ventricular mural thrombus. Echocardiography 1999;16:289–95
2. Aintablian A. Unusual complications of coronary bypass surgery. Am Heart J 1978;96:17–23
3. Tan CN, Fraser AG. Transesophageal echocardiography and cardiovascular sources of embolism. Anesthesiology 2007; 107:333–46
4. Bednarz JE, Spencer KT, Weinert LW, Sugeng L, Mor-Avi V, Lang RM. Identification of cardiac masses and abnormal blood flow patterns with harmonic power Doppler contrast echocardiography. J Am Soc Echocardiogr 1999;12:871–5
5. Schmitz A, Hartmann M. Acute intracardiac thrombus formation during thoracoabdominal aortic surgery. Anesth Analg 2006;102:1658–9

Video 1. Midesophageal 4-chamber view before cardiopulmonary bypass.

Video 2. Midesophageal 4-chamber view rewarming.

Teaching Points By Nikolaos J. Skubas, MD, Kent H. Rehfeldt, MD, and Martin J. London, MD
  • Left ventricular thrombi form over an area of myocardium that has severely depressed systolic function due to myocardial infarction, aneurysm formation, or in dilated cardiomyopathy, conditions associated with stasis of blood flow. They are often located in the apex of the ventricle but can occur along a wall in a laminar fashion.
  • Thrombi should be distinguished from underlying myocardium using a combination of midesophageal views (to avoid ventricular foreshortening), the zoom mode (for higher frame rates in a smaller area), higher imaging frequencies (for finer image resolution), and in equivocal cases, administration of ultrasound contrast agents (to better delineate endocardial borders).
  • In this case, transesophageal echocardiography revealed embolization of an apical left ventricular thrombus into the left atrium after cardiopulmonary bypass (despite avoiding use of a left ventricular vent, which is contraindicated in this situation), requiring surgical embolectomy. Although variable echodensity of the thrombus was suggestive of increased embolic potential, other risk factors such as irregular borders, central liquefaction, and filamentous projections, were not present.
  • Intraoperative transesophageal echocardiography is useful in diagnosing thrombus, detecting its embolic characteristics, and altering surgical planning (avoiding instrumentation or maneuvers that could dislodge it).

Supplemental Digital Content

© 2010 International Anesthesia Research Society