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Incidental Detection of an Intracardial Floating Thrombus by Echocardiography During Coronary Artery Bypass Surgery

Liang, Yafen MD*; Chaichana, Khan MD; Pretorius, Mias MB, ChB, MSCI*; Eagle, Susan MD*; Jiang, Yandong MD, PhD*

doi: 10.1213/ANE.0000000000001739
Perioperative Echocardiography and Cardiovascular Education
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SDC

Published ahead of print January 19, 2017.

From the *Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee; and Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.

Published ahead of print January 19, 2017.

Accepted for publication September 29, 2016.

Funding: None.

The authors declare no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website.

Reprints will not be available from the authors.

Address correspondence to Yafen Liang, MD, Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232. Address e-mail to yafen.liang@vanderbilt.edu.

A 54-year-old man presented for coronary artery bypass graft (CABG) surgery as a result of 3-vessel coronary  artery disease. He had an inferior ST elevation myocardial infarction 9 days before surgery. Transthoracic echocardiography (TTE) 5 days before revealed a dilated left ventricle (LV) with an estimated ejection fraction of 30% and no LV thrombus was identified. Delayed enhancement cardiac magnetic resonance imaging on the same day as TTE, to assess myocardial viability before surgical revascularization, did not reveal any LV thrombus either. Given the late presentation of myocardial infarction (Q wave on electrocardiogram), heparin was not given for treatment of acute coronary syndrome before the surgery.

Intraoperative transesophageal echocardiogram (TEE) before cardiopulmonary bypass (CPB) demonstrated severely depressed LV function with spontaneous echo contrast (SEC) in the left ventricle (Supplemental Digital Content, Video 1, http://links.lww.com/AA/B581). The basal to midventricular inferior and inferolateral walls were akinetic and showed increased reflectivity suggesting an old infarct. The LV apex was dilated and dyskinetic. Multiple echocardiographic views including midesophageal 4-chamber, 2-chamber, and long-axis view did not reveal any LV thrombus. The left atrial appendage (LAA) was free of thrombus with no filling defect by color flow Doppler at orthogonal views (Supplemental Digital Content, Video 2, http://links.lww.com/AA/B582). A linear structure parallel to the apical anteroseptal wall was viewed at different planes. It was thought to be a prominent LV false tendon (Supplemental Digital Content, Video 1, http://links.lww.com/AA/B581). Given the negative result on the preoperative study, and good visualization of the LV wall including the apex on the intraoperative TEE, LV thrombus was thought to be unlikely. The patient underwent triple-vessel bypass on CPB.

Figure 1.

Figure 1.

Shortly after removal of the aortic cross-clamp when the patient remained on CPB, a large cylindrical mass was visualized freely floating in the left atrium (Supplemental Digital Content, Video 3, http://links.lww.com/AA/B583). This mass transited through the mitral valve orifice into the left ventricle (Figure 1A) and then back into the left atrium. Given the rapid transition of the thrombus between the left atrium and left ventricle, an aortic cross-clamp was reapplied emergently to prevent transit of the thrombus into the systemic circulation. A left atriotomy was performed, and the thrombus was evacuated successfully. Pathology confirmed a 3.2 × 1.8 × 1.0-cm red–brown blood clot with a gray–white, smooth aspect indicating endocardial denting (Figure 1B), suggesting a well-organized LV mural thrombus. A follow-up TTE on postoperative day 2 revealed no residual LV thrombus. The patient was discharged home on postoperative day 7 without any embolic events.

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DISCUSSION

This case demonstrates that despite multiple preoperative diagnostic modalities and a comprehensive intraoperative TEE examination, a LV thrombus could still be missed. Knowledge of the risk factors of LV thrombus formation, timing of the diagnostic examination, and application of different echocardiographic techniques to improve imaging quality might have aided in detecting this thrombus. It also highlights the importance of continuous TEE monitoring in diagnosing a potentially life-threatening hemodynamic emergency in a patient undergoing CABG surgery.

Thromboembolic events secondary to LV thrombus formation represent 1 of the most serious complications after acute myocardial infarction (MI). In patients with acute anterior MI with LV ejection fraction <45%, LV thrombus can occur up to 26%.1 Approximately 10% of patients with a post-MI LV thrombus develop systemic embolization.2 The risk factors for LV thrombus include anterior MI, large infarct size, severe apical asynergy (ie, akinesis or dyskinesis), LV aneurysm, LV dilation, and low LV ejection fraction <40%.2,3 This patient had multiple risk factors: (1) severely depressed LV function; (2) LV dilation with left ventricular end-diastolic diameter >6 cm; and (3) a large inferior and inferolateral infarct with apical dyskinesis.

There is no general consensus on whether patients with risk factors for LV thrombus formation but no imaging evidence of thrombus should receive pre-emptive thrombolytic therapy or anticoagulation. Data from the GISSI-3 database, including more than 8000 patients, showed no reduced incidence of thrombus formation in patients who received either thrombolytic therapy or heparin.2 If thrombus is identified by imaging studies, however, American College of Cardiology/American Heart Association guidelines recommend vitamin K antagonist therapy for 6 months to decrease risk of systemic embolization. Therefore, the presence of LV thrombus should guide the perioperative anticoagulation strategy, surgical approach, and monitoring technique.

Among the imaging techniques, delayed enhancement cardiac magnetic resonance imaging allows for rapid assessment of thrombus presence, size, and location and is considered the reference standard with a sensitivity up to 88%.4 The LV apex, the most common site for thrombus formation, is usually foreshortened with TEE, but it is easier to visualize with TTE. The sensitivity of TTE ranges widely from 23% to 95%, mainly dependent on the patient’s anatomy and visualization of the heart.4 The sensitivity of TEE is approximately 40%; however, it offers real-time monitoring of the thrombus, especially those dislodged during surgical manipulation. In contrast, for diagnosing LAA thrombus, TEE showed superior sensitivity compared with TTE because the TEE transducer is closer to the left atrium.5

In addition to the diagnostic techniques, timing of LV thrombus assessment is crucial, because assessment too soon after the onset of MI will miss LV thrombus. Visser et al6 performed serial echocardiographic studies that showed approximately 90% of thrombi are formed at a peak of 2 weeks after MI. Because preoperative TTE and cardiac magnetic resonance imaging in this patient were done earlier than the expected peak for thrombus formation, both studies did not reveal any thrombus.

LV thrombus on echocardiography usually presents as a discrete echo-dense mass with defined margins that are distinct from the endocardium and seen throughout a complete cardiac cycle.7 It is usually located adjacent to an LV wall with regional motion abnormalities from multiple views. The differential diagnoses include normal LV structures such as false tendons, trabeculations, and a tangentially cut LV wall as well as artifacts (reverberations, side lobe, or near field artifacts). Imaging adjustments such as narrowing the sector size to increase frame rate, varying gain settings, and focus are helpful to differentiate true structures from artifacts. Even with these techniques, the echocardiograms can be still inconclusive. Additional techniques to improve the blood–endocardial interface definition (eg, harmonic imaging and echo contrast) may improve overall quality of diagnostic image. B-color imaging has also been shown to improve visual perception of images and may provide a better delineation between the thrombus and myocardium compared with gray-scale imaging. Epicardial echocardiography can also facilitate the identification of thrombus when TEE images are equivocal. Three-dimensional echocardiography has shown superiority to 2-dimensional techniques because it acquires a pyramidal volume of information that can be visualized from different angles.8 The LV could also be cropped in different planes so that thrombus could be easily identified and differentiated from other structures. However, lower frame rate, lower spatial resolution, or artifacts (eg, blooming) may potentially impair the detection of the thrombus.

In our case, the thrombus was missed despite a comprehensive prebypass examination for a variety of reasons: (1) the LV apex appears to be well visualized but the focus was set at the midventricular level at some views resulting in low spatial resolution in the far field; (2) the transgastric long-axis and deep transgastric views were suboptimal; and (3) an additional technique such as contrast echocardiography was not performed because of low suspicion for LV thrombus. In retrospect, a linear structure parallel to the apical anteroseptal wall raised the suspicion for LV thrombus. This structure could be viewed at different planes; however, it did not move concordantly with the underlying myocardium. It was still visualized after thrombus evacuation (Supplemental Digital Content, Video 1, http://links.lww.com/AA/B581) and was thought to be a prominent false tendon. A LAA thrombus was unlikely for a few reasons: (1) the LAA was noted to be free of thrombus in the prebypass examination by 2-dimensionals and color flow Doppler; (2) the size of the evacuated thrombus (3.2 × 1.8 × 1.0 cm by pathology report) was much larger than the size of LAA (approximately 1.5 × 1.0 × 1.0 cm by TEE); and (3) sinus rhythm reduced risk for thrombus formation.

This case demonstrates the utility of intraoperative TEE for the early diagnosis and rapid intervention of a dislodged LV thrombus to prevent a potentially catastrophic systemic embolism. The identification of the location of the thrombus also helped determine the surgical approach (aortotomy for LV thrombus versus atriotomy for LA thrombus). A thorough intraoperative TEE should be considered in patients undergoing CABG surgery who are at high risk for developing LV thrombus.

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PATIENT CONSENT STATEMENT

The patient has given written consent for publication of this case.

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Clinician’s Key Teaching Points

By Alina Nicoara, MD, FASE, Kent H. Rehfeldt, MD, and Nikolaos J. Skubas, MD

  • Left ventricular (LV) thrombus can form after myocardial infarction (MI). The most common risk factors are large size, anterior MI, apical akinesis or dyskinesis, LV aneurysm, or LV ejection fraction <40%. An LV thrombus most commonly develops at the apex.
  • Transesophageal echocardiography (TEE) has a lower sensitivity for LV thrombus detection compared with transthoracic echocardiography or magnetic resonance imaging because the LV apex is located away from the TEE probe and is subjected to foreshortening. However, the sensitivity of a comprehensive, multiplane examination TEE can be improved by adjusting the gain and imaging focus as well as the use of harmonic imaging, B-color with different tissue colors, or IV contrast agent.
  • In this case, a patient presented for coronary artery surgery 9 days after MI. Intraoperative TEE identified a dilated LV with an ejection fraction of 30% along with apical dyskinesis, but no intracardiac thrombus was detected. Before separation from cardiopulmonary bypass, a mobile mass with tissue-like echogenicity was identified moving between the left atrium and LV. The mass, which proved to be thrombus, had not been detected by preoperative magnetic resonance imaging or transthoracic echocardiography.
  • LV thrombus formation peaks 2 weeks after MI and may be missed if imaging is performed earlier, underscoring the need for repeat examination in patients at increased risk of this complication. Normal LV structures such as false tendons and prominent trabeculations as well as imaging artifacts need to be differentiated from thrombus. Epicardial echocardiography and 3-dimensional imaging may be useful adjuncts in equivocal examinations.
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DISCLOSURES

Name: Yafen Liang, MD.

Contribution: This author helped design the study and prepare the manuscript.

Name: Khan Chaichana, MD.

Contribution: This author helped design the study and prepare the manuscript.

Name: Mias Pretorius, MB, ChB, MSCI.

Contribution: This author helped prepare the manuscript.

Name: Susan Eagle, MD.

Contribution: This author helped prepare the manuscript.

Name: Yandong Jiang, MD, PhD.

Contribution: This author helped prepare the manuscript.

This manuscript was handled by: Nikolaos J. Skubas, MD, DSc.

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REFERENCES

1. Meurin P, Brandao Carreira V, Dumaine R, et al.; College National des Cardiologues Français; Collège National des Cardiologues des Hôpitaux Français, Paris, FranceIncidence, diagnostic methods, and evolution of left ventricular thrombus in patients with anterior myocardial infarction and low left ventricular ejection fraction: a prospective multicenter study. Am Heart J. 2015;170:256–262.
2. Chiarella F, Santoro E, Domenicucci S, Maggioni A, Vecchio C. Predischarge two-dimensional echocardiographic evaluation of left ventricular thrombosis after acute myocardial infarction in the GISSI-3 study. Am J Cardiol. 1998;81:822–827.
3. Bakalli A, Georgievska-Ismail L, Koçinaj D, et al. Left ventricular and left atrial thrombi in sinus rhythm patients with dilated ischemic cardiomyopathy. Med Arch. 2012;66:155–158.
4. Srichai MB, Junor C, Rodriguez LL, et al. Clinical, imaging, and pathological characteristics of left ventricular thrombus: a comparison of contrast-enhanced magnetic resonance imaging, transthoracic echocardiography, and transesophageal echocardiography with surgical or pathological validation. Am Heart J. 2006;152:75–84.
5. Acar J, Cormier B, Grimberg D, et al. Diagnosis of left atrial thrombi in mitral stenosis—usefulness of ultrasound techniques compared with other methods. Eur Heart J. 1991;12(suppl B):70–76.
6. Visser CA, Kan G, Lie KI, Durrer D. Left ventricular thrombus following acute myocardial infarction: a prospective serial echocardiographic study of 96 patients. Eur Heart J. 1983;4:333–337.
7. Taneja R, Aguirre MA, Shi C, Greilich PE. Embolization of left ventricular apical thrombus during cardiac surgery. Anesth Analg. 2010;111:74–75.
8. Vaggar JN, Gadhinglajkar S, Pillai V, Sreedhar R, Cahndran R, Roy S. Echocardiographic detection of free-floating thrombus in left ventricle during coronary artery bypass grafting. Ann Card Anaesth. 2015;18:579–583.

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