Jacobs Journal of Anesthesiology and Research

Acute Saddle Pulmonary Embolism: Transesophageal Echocardiography Does Not Predict Clot Burden

*Kristen Jordan
Department Of Cardiothoracic Anesthesiology, University Of Maryland School Of Medicine, Baltimore Maryland, United States

*Corresponding Author:
Kristen Jordan
Department Of Cardiothoracic Anesthesiology, University Of Maryland School Of Medicine, Baltimore Maryland, United States
Email:wbernstein@anes.umm.edu

Published on: 2018-03-28

Abstract

Acute saddle pulmonary embolism (PE) is associated with significant morbidity and mortality. Transesophageal echocardiography (TEE) can be used to directly visualize the clot within the right, left and main pulmonary artery (PA) and determine secondary signs of obstruction, including right ventricular dysfunction, and leftward bowing of interatrial septum. Despite determining the actual existence of clot, TEE is relatively unreliable and grossly underestimates the actual amount of clot burden in the vessel. We present the case of a 60 year old man with a large saddle pulmonary embolus for whom the use of intraoperative TEE was able to diagnose acute PE but did little to evaluate the amount of thrombus.

Keywords

Saddle Pulmonary Embolism; Transesophageal Echocardiography; Pulmonary Artery; Cardiac Surgery Cardiac Anesthesiology; Thromboembolus

Introduction

Acute saddle pulmonary embolism (PE) is associated with significant morbidity and mortality. Successful outcome following a saddle pulmonary embolism depends on prompt diagnosis and treatment. The current gold standard for diagnosis, pulmonary angiography, is difficult to obtain in emergency situations and is relatively inaccessible intraoperative. Tran’s esophageal echocardiography (TEE) can be useful as a diagnostic and therapeutic tool during surgical embolectomy to directly visualize the clot within the right, left and main pulmonary artery (PA). TEE provides valuable information such as homogeneity and mobility of emboli, the relation to the vascular lumen in cross-sectional planes and resultant flow disturbances. TEE can also identify thrombus in extra pulmonary and extracardiac locations, and provide evidence of pulmonary hypertension as demonstrated by global and systolic dysfunction of the right ventricle, dilatation of the right ventricle, tricuspid regurgitation, leftward bowing of nteratrial septum and pulmonary insufficiency.

Despite determining the actual existence of clot, TEE is relatively unreliable and grossly underestimates the actual amount of clot burden in the vessel. We present the case of a 60 year old man with a large saddle pulmonary embolus for whom the use of intraoperative TEE was able to diagnose acute PE but did little to evaluate the amount of thrombus.

Case Presentation

A 60 year old man with a history of squamous cell carcinoma of the lacrimal duct status post chemotherapy and radiotherapy presented to an outside hospital with worsening dyspnea on exertion. Medications included gabapentin, excitalopram and pantoprazole. A chest radiograph showed a right lowers lobe opacity, and a clear left lung field. A computed tomography angiogram (CTA) of the chest demonstrated a saddle pulmonary embolus (PE). Troponins were positive. Patient was transferred to University hospital for further evaluation of suspected PE. On arrival, the patient was mildly tachypneic (101 beats per minute). His vital signs were stable with blood pressure 139/96 mm Hg, and oxygen saturation 91-95% on 2 liters nasal cannula. In the operating room, monitoring lines were placed including a right radial arterial line, and central access. Perioperative antibiotics were administered. A TEE demonstrated an jection fraction of 55%, with moderate RV dilation and an echo density in the right pulmonary artery. A midline sternotomy was performed without incident. Hemostasis was achieved and a standard chest retractor was placed. Weight based dosing of heparin was administered intravenously. Stay sutures were placed to create a pericardial cradle.

                                                Figure 1: Mid-esophageal trans esophageal echocardiogram view at 0° demonstrating thrombus burden in RPA prior to bifurcation

OA: Ascending aorta

RPA: Right Pulmonary artery

SVC: Superior Vena Cava

Purse strings were placed for cannulation of a 20 french plastic tip cannula in the distal ascending aorta and a 24 french single stage cannula in the superior vena cava via the right atrial appendage, and a 28 french single stage cannula in the inferior vena cava via the right atrial body. After achieving a satisfactory activated clotting time (ACT), cardiopulmonary bypass was initiated. A longitudinal arteriotomy was made in the main pulmonary trunk extending into the left pulmonary artery. Suction catheter was placed and a large thrombus was removed. The embolectomy proceeded under direct visualization until all the thrombus was removed. Next, a longitudinal arteriotomy was made in the right main pulmonary artery and thrombus was extracted under direct visualization. When the entire clot had been evacuated safely, the arteriotomies were closed with 5-0 prolene in a running continuous manner. Separation from cardiopulmonary bypass (85 minutes) required low dose epinephrine and vasopressin. He was transfused with 2 unit packed red blood cells, 900 milliliters cell saver, 3600 milliliters crystalloid, and 250 milliliters 5% albumin. The patient was transported to the cardiac surgical intensive care unit  and discharged on postoperative day number nine.

Discussion

Pulmonary embolism is classified by the degree of pulmonary vasculature obstructed by the burden of blood clot. Electrocardiogram can be helpful in adding diagnostic value to determine the extent of clot burden and determining right ventricular dysfunction on echocardiography [7]. A more reliable quantification of clot burden can be achieved with aortography, magnetic resonance imaging or computerized tomography. However, the use of these modalities can involve transport to another location, and delay in diagnosis to complete the study. Cite this article: Wendy K. Bernstein. Acute Saddle Pulmonary Embolism: Trans

                                                            Figure 2: Clot recovered from left and right pulmonary arteries, respectively, during extraction under direct visualization.

esophageal Echocardiography Does Not Pr TEE has gained acceptance in the diagnosis of PE preoperatively. In one intensive care unit study, et al. showed that TEE had a 92% sensitivity and a 100% specificity in detecting massive PE [8]. The high specificity may be due to the fact that TEE can clearly demonstrate the existence of blood clots in the main or lobar pulmonary arteries in patients with suspected PE. The direct visualization of the thrombus rather than relying on indirect signs, such as RV enlargement and strain, can be invaluable to the surgeon in terms of determining surgical accessibility. These findings are important for prompt decision making in patients with hemodynamic compromise for whom thrombolysis or embolectomy is being considered [9].

Transesophageal echocardiography can also identify extra pulmonary thromboembolism in the inferior or superior vena cava, the right atrium, or the right ventricle [10]. Rosenberger et al. demonstrated in a series of 50 consecutive patients undergoing pulmonary embolectomy that TEE reveals extrapulmonary thromboemboli within the previously described locations in 26% of all patients [11]. If not surgically removed, such extra pulmonary thromboemboli can become the source of recurrent PE. While TEE also can be performed easily at the patient’s bedside with minimal risk in experienced hands, it is not without some limitations. Our postinduction TEE clearly demonstrates the presence of thrombus in the main pulmonary artery. However, the actual clot burden in the branches of the pulmonary artery can be difficult to determine. Figure 2 demonstrates the actual amount of thrombus that was retrieved from the surgical procedure in both the right and left pulmonary arteries. Surprisingly, it seems much higher than what was seen in Figure 1 and in a series of 6 other pulmonary emboli patients, we have found similar findings (unpublished data). One of the reasons for the inability to quantitate amount of clot may be due “drop out” or acoustic shadowing in the echo images [12]. Often times, when there is air in the way of the echo images, it can block important structures from being visualized. The use of an A-view catheter is one way to prevent this from happening [13]. By placing a balloon in the trachea, and inflating it with saline solution, an echo window of the aorta with better resolution can be achieved. Such measures are typically used to visualize atherosclerosis in the aorta, however, this method can also be applied to improve visualization of the pulmonary artery branches.

Conclusion

We conclude that while intraoperative TEE may be beneficial in determining whether or not there is thrombus present in the pulmonary artery, TEE does not reliably determine the actual clot burden due to acoustic shadowing. Use of A-view catheters may help to better visualize clot burden during acute saddle pulmonary embolism to improve patient outcome.

Acknowledgements

Financial: No grant funding

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