Intraoperative rescue transesophageal echocardiography (TEE)

INTRODUCTION — Rescue transesophageal echocardiography (TEE) is an unplanned TEE examination performed on an urgent or emergent basis to diagnose causes of unexpected hemodynamic instability or cardiopulmonary arrest. This topic will discuss use of rescue TEE in the perioperative setting. Urgent and emergent uses of TEE (and other ultrasonographic diagnostic methods) in other settings (eg, the intensive care unit and emergency department) are discussed in other topics. (See "Indications for bedside ultrasonography in the critically ill adult patient" and "Emergency ultrasound in adults with abdominal and thoracic trauma".)

TEE is also used by anesthesiologists during elective cardiac and noncardiac surgical procedures, as discussed in separate topics:

●(See "Anesthesia for cardiac valve surgery".)

●(See "Intraoperative transesophageal echocardiography for noncardiac surgery".)

Other ultrasound modalities used by anesthesiologists in the perioperative setting (eg, transthoracic echocardiography [TTE], thoracic lung ultrasonography, and ultrasound for vascular cannulation or regional nerve block placement) are discussed elsewhere. (See "Overview of perioperative uses of ultrasound".)

RESCUE TEE EXAMINATION

General indications — Urgent and emergent transesophageal echocardiography (TEE), also termed rescue TEE, has been effectively used for determining the cause of unexpected hemodynamic instability or shock, cardiopulmonary arrest during cardiac and noncardiac surgical procedures, and to facilitate ongoing management including guidance during procedures (algorithm 1) [1]. Intraoperative causes of hemodynamic instability diagnosed with TEE can be categorized as types of hypovolemic, distributive, cardiogenic (eg, right or left ventricular dysfunction), or obstructive shock, as noted below [2-12]. (See "Intraoperative management of shock in adults".)

A focused TEE examination can often rapidly diagnose the cause of hemodynamic instability, exclude other common abnormalities, and facilitate rapid institution of appropriate therapies [1]. Notably, TEE probe placement may be challenging in the intraoperative setting due to the position of the patient (eg, prone or lateral body position), or the presence of surgical drapes or equipment [13].

Key views — The three most valuable views during rescue TEE are the transgastric left ventricular (LV) midpapillary short-axis (TG LV SAX) view, the midesophageal four-chamber (ME 4C) view, and the midesophageal long-axis (ME LAX) view (http://anesthesiaeducation.net/aba_key_tee_views). Thus, most of the examination can be completed in the transgastric and midesophageal windows. These TEE views are similar to those recommended for the basic TEE examination [14]. Although no absolute standards exist for the TEE examination sequence in an unstable patient, there is general agreement that these are the views with the greatest utility [7,8].

Technical details for obtaining these views are available in an interactive video grid (click on the line drawing of each view to see a video example of the view accompanied by an audio clip discussing how to obtain the view [http://anesthesiaeducation.net/aba_key_tee_views]), and in a separate UpToDate topic. (See "Transesophageal echocardiography: Indications, complications, and normal views".)

Transgastric left ventricular midpapillary short-axis view — The TG LV SAX view is obtained with a multiplane TEE probe with imaging angle of zero degrees by advancing the probe into the stomach at a depth of approximately 50 cm from the incisors, then gently anteflexing the probe. A short-axis view of the left and right ventricles generally displays the LV with a circular cavity on the right of the TEE image (on the patient's left), and the right ventricle (RV) with a crescent-shaped cavity on the left side of the image (on the patient's right) (movie 1) (http://anesthesiaeducation.net/aba_key_tee_views).

The TG LV SAX is used to rapidly assess global LV and RV size, biventricular global function, biventricular volume status, and the presence or absence of pericardial effusion. Since this view shows myocardial walls supplied by each of the coronary arteries (ie, left anterior descending [LAD], left circumflex [LCX], and right coronary [RCA] arteries) in a single scan plane (figure 1 and figure 2), it is also used to assess LV regional wall motion abnormalities (RWMAs) which may be caused by myocardial ischemia or infarction or other processes.

Midesophageal four-chamber view — The ME 4C view of the LV is obtained with a multiplane angle of 0 to 10 degrees at a depth of 30 to 40 cm. The left atrium (LA) is visualized at the upper right of the imaging sector separated by the mitral valve from the foreshortened view of the LV located immediately anterior to it with the near apical LV positioned at the bottom (anterior edge) of the image (http://anesthesiaeducation.net/aba_key_tee_views). The true LV apex is generally located inferiorly to the ME 4C imaging plane and is thus rarely seen in this view, so LV apical thrombus cannot be excluded. From the ME 4C view of the LV, rotating the TEE probe slightly to the right (counter-clockwise) centers the right atrium (RA) and RV in the image, separated by the tricuspid valve (the ME 4C view of the RV) (movie 2). From this position, slight anteflexion of the TEE probe at a multiplane angle of zero degrees will bring the LV outflow tract (LVOT) and part of the aortic valve into view. This ME 5C view (4C with LVOT view, also known as the ME five-chamber view (image 1)), enables assessment for LVOT obstruction (movie 3).

These ME 4C views are used to assess biatrial and biventricular filling status, LV and RV size and global function, and RWMAs in the septal, lateral, and near apical segments of the LV (figure 1 and figure 2). Also, the mitral and tricuspid valves can be visualized for evidence of thickening or restricted mobility consistent with stenosis. If color-flow Doppler flow is added to these views, the presence and degree of mitral or tricuspid regurgitation or stenosis can be assessed (image 2 and image 3 and movie 4).

Midesophageal long-axis view — The ME LAX view is obtained by rotating the multiplane angle of the probe to 120 to 160 degrees (at a depth of approximately 30 to 40 cm) (http://anesthesiaeducation.net/aba_key_tee_views). This view allows two-dimensional (2D) and color Doppler assessment of the aortic and mitral valves for evidence of stenosis or regurgitation. This view is also used to assess RWMAs of the anteroseptal and inferolateral walls of the LV (figure 1 and figure 2). Furthermore, the mitral valve is assessed for systolic anterior motion (SAM), and the LVOT can be visualized, as well as the RV outflow tract (on the right of the screen, which is to the anterior right of the LV) (image 4 and movie 3).

HYPOVOLEMIC SHOCK — Hemodynamic instability with hemorrhagic or other causes of hypovolemic shock is due to reduced intravascular volume with consequent reduced preload and cardiac output (CO). Causes and management of intraoperative hypovolemic shock are discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Hypovolemic shock management'.)

Incidence of hypovolemia — Hypovolemia is a common cause of hemodynamic instability prompting perioperative rescue transesophageal echocardiography (TEE) as illustrated by case series in which 5 to 42 percent of patients undergoing rescue TEE had findings consistent with hypovolemia [3,8,9,15-17].

Key views and findings — During a rescue TEE examination, we typically start with a transgastric left ventricular (LV) midpapillary short-axis (TG LV SAX) view, as described above (see 'Transgastric left ventricular midpapillary short-axis view' above). In this view, hypovolemia manifests as a small LV cavity size associated with normal or hyperdynamic global LV systolic function, which is easily identified by visual qualitative assessment and is often accompanied by tachycardia (movie 5 and movie 6) [8,18,19]. However, in patients with concentric LV hypertrophy (image 5) or hypertrophic cardiomyopathy (HCM), a small LV cavity may be present in the absence of hypovolemia. Conversely, in patients with dilated cardiomyopathy or other cause of ventricular dilation at baseline (image 6), hypovolemia may not manifest as a small LV cavity.

Rapid qualitative assessment of LV chamber size is typically adequate during a rescue TEE examination because an abnormally small LV end-diastolic area (EDA) or end-diastolic diameter is easily distinguished from normal ventricular size. If time allows, quantitative measurements may be made in the TG LV SAX view at end-diastole (image 7 and image 8 and table 1) [20]. Acute changes in LV end-diastolic diameter and LV EDA measured using the TEE TG LV SAX view correlate well with acute changes in intravascular volume [19]. In some cases, measurements made at both end-diastole and end-systole may be helpful to distinguish hypovolemia from a low systemic vascular resistance (SVR) state (see 'Distributive shock (low systemic vascular resistance)' below).

Another finding seen in some hypovolemic patients is rightward deviation of the interatrial septum (ie, towards the right atrium [RA]), as seen in the midesophageal four-chamber (ME 4C) view. Conversely, a small LV cavity size associated with leftward deviation of the interatrial septum typically indicates right ventricular (RV) failure or markedly elevated RV systolic pressure (eg, due to severe pulmonary hypertension) (see 'Key views and findings' below).

Notably, hypovolemia can cause regional wall motion abnormalities (RWMAs); thus, both hypovolemia and myocardial ischemia should be considered when RWMAs are present (see 'Myocardial ischemia' below) [21].

DISTRIBUTIVE SHOCK (LOW SYSTEMIC VASCULAR RESISTANCE) — Hemodynamic instability with distributive shock is due to severe peripheral vasodilation with reduced systemic vascular resistance (SVR). Causes and management of intraoperative distributive shock are discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Distributive shock management'.)

Incidence of low systemic vascular resistance — While evidence for distributive shock is not a common finding on rescue transesophageal echocardiography (TEE), this diagnosis should be considered, particularly when other causes of hemodynamic instability are not found. As an example, in one retrospective case series describing perioperative use of rescue TEE in 364 patients, findings consistent with low SVR states were present in 4.4 percent (3.9 percent in the intraoperative period and 4.9 percent in the postoperative period) [7].

Key views and findings — During a rescue TEE examination, low SVR manifests as a very small left ventricular (LV) cavity at end-systole, but with normal end-diastolic values, on both the transgastric LV midpapillary short-axis (TG LV SAX) view and the midesophageal four-chamber (ME 4C) view (movie 7) (see 'Transgastric left ventricular midpapillary short-axis view' above and 'Midesophageal four-chamber view' above). It is relatively easy to mistake low SVR for hypovolemia during initial qualitative assessment because a small LV systolic cavity size may be associated with severe hypotension in either type of shock. Thus, it is useful to obtain LV area and internal diameter measurements at both end-diastole and end-systole (table 1). Further details regarding TEE assessment of low SVR in the intraoperative setting are available in a separate topic. (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Systemic vascular resistance'.)

CARDIOGENIC SHOCK — Hemodynamic instability with cardiogenic shock is due to reduced cardiac output (CO) caused by left and/or right ventricular systolic dysfunction. Causes and management of intraoperative cardiogenic shock are discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Cardiogenic shock management'.)

Left ventricular failure — Causes and management of intraoperative left ventricular (LV) failure are discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Cardiomyopathic shock'.)

Incidence of LV failure — Findings consistent with LV failure were present in 12 to 50 percent of patients included in case series describing intraoperative use of rescue TEE [2,3,9].

Key views and findings — During a rescue TEE examination that starts with a transgastric LV midpapillary short-axis (TG LV SAX) view, qualitative estimates of LV systolic function and LV ejection fraction (LVEF) can be rapidly obtained (movie 1 and movie 8) (see 'Transgastric left ventricular midpapillary short-axis view' above) [22-26]. Reduced or absent LV systolic wall motion and systolic wall thickening indicates LV failure.

The midesophageal four-chamber (ME 4C) view is also useful to diagnose global LV failure because it allows assessment of LV size, shape, ejection fraction, and segmental wall motion (see 'Midesophageal four-chamber view' above). In this view, the LV cavity is normally shaped like a bullet or truncated ellipsoid, being widest at the base at the level of the mitral valve annulus and tapering toward the left ventricular apex (movie 9). Cardiomyopathy, eccentric hypertrophy, or LV failure can distort the shape of the LV to make it more spherical. The ME 4C view also provides images of the near apex (the true apex is generally not visualized) and the septal and lateral walls, allowing assessment of regional wall motion abnormalities (RWMAs) (movie 9). Further details regarding TEE evaluation of global LV function in the intraoperative setting are available in a separate topic. (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Global LV systolic function'.)

Generally, if the patient is hypotensive and the LV walls are not contracting inward and thickening during systole, then LV systolic dysfunction is the likely cause, and immediate management should include inotropic support and cardiopulmonary resuscitation as necessary. In such patients, a dilated, spherical LV suggests underlying cardiomyopathy or eccentric hypertrophy, while a normal LV cavity size with RWMAs suggests acute myocardial ischemia. If an intra-aortic balloon pump (IABP), ventricular assist device (VAD), or extracorporeal membrane oxygenation (ECMO) is required during resuscitation, the TEE probe should be left in place to guide placement of these devices and to assess their efficacy [27,28]. (See "Short-term mechanical circulatory assist devices".)

Right ventricular failure — Causes and management of intraoperative right ventricular (RV) failure are discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Cardiomyopathic shock'.)

Incidence of RV failure — Findings consistent with moderate or severe RV failure were present in 18 to 29 percent of patients included in case series describing intraoperative use of rescue TEE [3,8]. Pulmonary embolus is a major cause of intraoperative acute RV failure in some surgical populations (eg, patients undergoing orthopedic surgery) (see 'Pulmonary embolus' below). Other causes of RV dysfunction include myocardial ischemia or infarction, pulmonary arterial hypertension, or primary respiratory failure. Also, cardiac contusion in a trauma patient can manifest as acute RV dysfunction [5]. (See "Anesthesia for thoracic trauma in adults", section on 'Blunt cardiac injury'.)

Key views and findings — During a rescue TEE examination, global RV failure is qualitatively assessed on the ME 4C view, with the TEE probe rotated slightly counter clockwise to center the right ventricle in the imaging plane (movie 10 and movie 11 and movie 12 and table 2) (see 'Midesophageal four-chamber view' above) [22,23]. In particular, reduced or absent tricuspid valve annular plane systolic excursion towards the RV apex (with mobility of less than 16 mm throughout the cardiac cycle) or severe TR indicates RV dysfunction. Other TEE evidence of RV failure includes RV dilation (eg, RV cross sectional area ≥LV cross-sectional area or RV width >50 percent of RV length), severely decreased or absent RV free wall endocardial excursion and wall thickening, and leftward deviation of the interatrial septum into the left atrial cavity (movie 10 and movie 11). Further details regarding TEE evaluation of global RV function are available in a separate topic. (See "Echocardiographic assessment of the right heart".)

Myocardial ischemia — Causes and management of intraoperative myocardial ischemia are discussed in separate topics. (See "Anesthesia for noncardiac surgery in patients with ischemic heart disease" and "Intraoperative management of shock in adults", section on 'Cardiomyopathic shock'.)

Incidence of myocardial ischemia — Findings consistent with RWMAs indicating myocardial ischemia were present in 12 to 27 percent of patients included in case series describing intraoperative use of rescue TEE [3,8,9,16]. This percentage is probably higher (approximately half) in survivors of cardiac arrest [2]. A rare cause of myocardial ischemia that can be diagnosed with TEE is coronary air embolism (movie 13) [29]. While it can be variable, air embolism most commonly impacts the right coronary artery distribution and manifests as acute right ventricular dysfunction and enlargement with tricuspid regurgitation. Air bubbles of varying degrees may be visualized in the cardiac chambers.

Key views and findings — During a rescue TEE examination, myocardial ischemia is qualitatively assessed by detecting RWMAs on the TEE short and long-axis views of the LV. In particular, the TG LV SAX view shows representative regions of the myocardial walls supplied by each of the coronary arteries (ie, left anterior descending [LAD], left circumflex [LCX], and right coronary [RCA] arteries) (movie 1 and figure 1 and figure 2) (see 'Transgastric left ventricular midpapillary short-axis view' above). Normal ventricular systolic function includes both endocardial excursion toward the center of the LV cavity and systolic thickening of the LV wall (movie 1).

The LV long-axis views provide supplemental information to detect and characterize the extent of the RWMAs. For example, the ME 4C view images the inferoseptal and anterolateral walls of the LV from base to apex (see 'Midesophageal four-chamber view' above), the midesophageal long-axis (ME LAX) view images the anteroseptal and inferolateral walls of the LV from base to apex (see 'Midesophageal long-axis view' above), and the midesophageal two-chamber view (ME 2CV) images the inferior and anterior walls of the LV from base to apex (http://anesthesiaeducation.net/aba_key_tee_views) (figure 1 and figure 2). Myocardial ischemia or infarction may also manifest as severe LV or RV dysfunction (see 'Left ventricular failure' above and 'Right ventricular failure' above).

Further details regarding TEE evaluation of myocardial ischemia in the intraoperative setting are available in a separate topic. (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Regional LV systolic function'.)

Cardiac valve abnormalities — Although valvular heart disease is typically chronic with slow progression, previously unrecognized severe aortic stenosis or acute aortic or mitral regurgitation may cause hemodynamic instability. Severity of these abnormalities is rapidly assessed with TEE. Management of intraoperative cardiogenic shock caused by acute cardiac valve abnormalities is discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Mechanical shock'.)

Incidence of cardiac valve abnormalities — Although findings consistent with valvular heart disease were noted in some patients included in intraoperative rescue TEE case series, these abnormalities were not the primary cause of any episodes of hemodynamic instability in most studies [3,8]. In one case series that included 32 patients undergoing cardiopulmonary resuscitation in the emergency department (ED) or intensive care unit (ICU), severe aortic regurgitation (AR) (n = 2), severe aortic stenosis (AS) (n = 1), or severe mitral regurgitation (MR) due to papillary muscle rupture (n = 1) were the causes of arrest [30].

Mitral regurgitation — MR is qualitatively estimated in the ME 4C view (see 'Midesophageal four-chamber view' above), using color-flow Doppler to assess regurgitant jet size (ie, length, area, and eccentricity of the regurgitant jet in the left atrium [LA]), as well as the size of the vena contracta (image 2 and movie 14 and table 3). (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Assessment of mitral regurgitation'.)

The preceding criteria apply to chronic MR. In acute MR, the jet area may not be large and the jet is often markedly eccentric; thus acute MR may be underestimated or not appreciated [31]. Identification of a flail leaflet or ruptured papillary muscle, pulmonary vein flow reversal, and/or a hyperdynamic LV with low systemic output by Doppler suggest acute MR, even in the absence of a large MR jet. (See "Acute mitral regurgitation in adults", section on 'Echocardiography'.)

Causes of acute severe MR include chordal rupture in a patient with myxomatous mitral disease or endocarditis, papillary muscle rupture due to myocardial infarction, or as a consequence of myocardial ischemia (ischemic mitral regurgitation), decompensated heart failure (functional mitral regurgitation), or dynamic LV outflow tract (LVOT) obstruction with systolic anterior motion (SAM) of the mitral valve (movie 3). (See 'Left ventricular outflow tract obstruction' below and "Acute mitral regurgitation in adults".)

Aortic regurgitation — Severity of AR is best qualitatively estimated in the ME LAX view (movie 15), but may also be assessed in the ME five-chamber view (which includes the LVOT) (image 9) (see 'Midesophageal long-axis view' above and 'Midesophageal four-chamber view' above). Color-flow Doppler is used to measure the largest jet width in the LVOT within 1 cm of the aortic valve. For central AR jets, this jet width is expressed as a percentage of the width of the LVOT (mild regurgitation is a jet width <25 percent of the LVOT; severe regurgitation is a jet width ≥65 percent of the LVOT) (table 4 and movie 15 and image 9). Additional parameters including vena contracta width, pressure half-time, and diastolic flow reversal in the descending aorta are described in the table (table 4). (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Assessment of aortic regurgitation'.)

With acute aortic regurgitation, there is early closure of the mitral valve (before the R wave) and flow reversal in the proximal descending aorta may not be holodiastolic [31]. Causes of acute aortic regurgitation include acute aortic dissection involving the aortic root or endocarditis. (See "Acute aortic regurgitation in adults".)

Aortic stenosis — Severe AS is suggested by heavily calcified or poorly mobile aortic valve leaflets. This is best observed in the midesophageal aortic valve short-axis (ME AV SAX) view (movie 16) (http://anesthesiaeducation.net/aba_key_tee_views), and the ME LAX view (image 10) (see 'Midesophageal long-axis view' above). Continuous-wave Doppler measurement of the transvalvular gradient can usually be obtained from the deep transgastric or transgastric long-axis views, and sometime from the ME LAX view, to confirm the diagnosis; a mean aortic valve gradient >40 mmHg suggests severe AS (image 10 and table 5). Since TEE sometimes underestimates aortic valve gradients due to inadequate alignment of the Doppler beam with the blood flow through the aortic valve, severe AS is not excluded if the valve appearance is suggestive of AS but the TEE-measured mean aortic valve gradient is <40 mm Hg. (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Assessment of aortic stenosis'.)

Previously undiagnosed severe aortic stenosis is an established risk factor for cardiovascular complications in patients undergoing anesthesia for noncardiac operations. (See "Evaluation of cardiac risk prior to noncardiac surgery".)

Mitral stenosis — Severe mitral stenosis (MS) is best identified with TEE using the ME 4C view by noting a thickened mitral valve with reduced leaflet opening, as well as a high-velocity aliased LV inflow on color-flow Doppler imaging (image 11 and image 3) (see 'Midesophageal four-chamber view' above). Continuous-wave Doppler interrogation of the mitral inflow can be used to measure the transvalvular gradient (image 11); the mean mitral valve gradient is usually >5 to 10 mmHg with severe MS but is variable depending upon heart rate and forward flow (table 6). (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Assessment of mitral stenosis'.)

Severe MS may be seen on rescue TEE in patients with evidence of severe RV dysfunction, and is often associated with pulmonary hypertension (see 'Right ventricular failure' above).

Left ventricular outflow tract obstruction — Causes and management of LVOT obstruction that may cause cardiogenic shock are discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Mechanical shock'.)

Incidence of LVOT obstruction — Findings consistent with dynamic LVOT obstruction and/or mitral valve SAM as a cause of hemodynamic instability have been noted in approximately 4 percent of patients undergoing intraoperative rescue TEE [7].

Key views and findings — During a rescue TEE examination, virtually complete obstruction of the LVOT may be observed in the ME LAX view or the ME five-chamber view with anteflexion of the TEE probe at a multiplane angle of 0 degrees to bring the LVOT and part of the aortic valve into view. (See 'Midesophageal long-axis view' above and 'Midesophageal four-chamber view' above.) This occurs when the LVOT is narrowed by LV septal hypertrophy and/or abnormal length and positioning of the mitral valve leaflets, resulting in SAM and LVOT obstruction due to contact of the anterior mitral valve leaflet with the LV septal wall (image 4 and movie 3) [32-34]. Severe MR may also be a consequence of SAM of the mitral valve (movie 3) [35]. The degree of obstruction of the LVOT and the severity of MR are dynamic processes that are influenced by cardiac loading conditions and inotropic state [36,37]. Further details regarding diagnosis and management of MR due to dynamic LVOT obstruction in the intraoperative setting are available in a separate topic. (See "Anesthesia for patients with hypertrophic cardiomyopathy undergoing noncardiac surgery".)

Aortic dissection or injury

Incidence of aortic dissection or injury — Rescue TEE findings consistent with aortic injury are uncommon in most surgical populations. For example, only 1 of 32 patients suffered an aortic injury in one case series involving noncardiac surgical patients [8]. However, interventional procedures that involve instrumentation of the thoracic aorta (eg, cardiac catheterization, percutaneous coronary interventions, endovascular procedures, arterial angiography, transcatheter aortic valve replacement) may cause acute iatrogenic aortic dissection. Also, aortic dissection or other injury is more commonly diagnosed by TEE in certain patients presenting to the emergency department [2,30,38]. For example, aortic rupture and mediastinal hematoma are readily diagnosed with TEE when thoracic aortic injury occurs after blunt thoracic trauma (image 12 and image 13 and image 14). Further details regarding TEE evaluation of traumatic aortic injuries are available in a separate topic. (See "Clinical features and diagnosis of blunt thoracic aortic injury".)

Key views and findings — Rescue TEE can be used to diagnose thoracic aortic dissection in the ME LAX view or the ME ascending aortic SAX or LAX views (http://anesthesiaeducation.net/aba_key_tee_views) (image 15 and image 16 and movie 17 and movie 18). However, only limited visualization of the distal ascending aorta and proximal aortic arch is possible with TEE examination, due to the interposition of the distal trachea and left mainstem bronchus between the esophagus and the aorta [39-43]. TEE can also be used to diagnose abdominal aortic dissection, although only the proximal segment of the abdominal aorta below the diaphragm can be imaged on the descending aortic SAX or LAX views (http://anesthesiaeducation.net/aba_key_tee_views) (movie 19). Further details regarding TEE evaluation of aortic dissection are available in separate topics (See "Clinical features and diagnosis of acute aortic dissection", section on 'Cardiovascular imaging' and "Anesthesia for aortic surgery with hypothermia and elective circulatory arrest in adult patients", section on 'Transesophageal echocardiography'.)

Furthermore, critically important complications of aortic dissection may be detected during a rescue TEE examination (eg, presence and quantification of the severity of AR due to dissection that involves the aortic root (image 16 and image 15), detection of cardiac tamponade (image 17), and detection of left ventricular RWMAs indicating myocardial ischemia or infarction due to dissection involving the coronary arteries (figure 1)) [44].

OBSTRUCTIVE SHOCK — Hemodynamic instability with obstructive shock is due to reduced cardiac output caused by an extracardiac cause of cardiac pump failure. (See "Intraoperative management of shock in adults", section on 'Cardiogenic shock management'.)

Cardiac tamponade — Since the aortic root and first 10 cm of the ascending aorta are within the pericardium, perforation or rupture of the aortic root or proximal ascending aorta can cause cardiac tamponade. Causes and management of cardiac tamponade causing obstructive shock are discussed in separate topics. (See "Anesthesia for thoracic trauma in adults", section on 'Cardiac tamponade' and "Anesthesia for thoracic trauma in adults", section on 'Anesthetic considerations for specific procedures'.)

Incidence of cardiac tamponade — Findings of cardiac tamponade as a cause of hemodynamic instability were present in 7 to 9 percent of patients included in case series describing intraoperative use of rescue transesophageal echocardiography (TEE) [3,9]. The incidence is higher in trauma patients [38], and in patients who require cardiopulmonary resuscitation during interventions to extract a pacemaker or defibrillator lead [15].

Key views and findings — TEE findings in cardiac tamponade typically include a pericardial effusion on the transgastric left ventricular (LV) midpapillary short-axis (TG LV SAX) view (image 17), or the midesophageal four-chamber view (ME 4C) view (see 'Transgastric left ventricular midpapillary short-axis view' above and 'Midesophageal four-chamber view' above). Since pericardial pressure is affected by the rate of fluid accumulation, cardiac tamponade can occur with small, moderate, or large pericardial effusions. Examples of small or loculated effusions that may cause tamponade include loculated effusions or hemopericardium due to mediastinal bleeding after cardiac surgery, or a pericardial effusion or hematoma adjacent to the right ventricular (RV) free wall due to RV perforation during pacemaker implantation or right heart catheterization [45]. Notably, a hemodynamically significant loculated pericardial effusion or hematoma may be identified in one TEE view but not identified in other views (image 18).

TEE signs of cardiac tamponade include collapse of the right atrium (RA) (movie 20), especially if this persists for more than one-third of the cardiac cycle, collapse of the RV (movie 21), which is less sensitive than RA collapse but very specific for tamponade, left atrial collapse, and dilation of the inferior vena cava (IVC). While the specificity for tamponade is highest for combined right atrial and right ventricular collapse with abnormal venous flow, collapse or compression of any cardiac chamber is suggestive of tamponade. Echocardiographic findings consistent with tamponade can also be quickly obtained with transthoracic echocardiography (TTE) which is particularly helpful when TEE views are suboptimal or incomplete [46]. (See "Echocardiographic evaluation of the pericardium" and "Pericardial effusion: Approach to diagnosis", section on 'Echocardiography'.)

Pulmonary embolus — Causes and management of thromboembolic pulmonary embolus (PE) causing obstructive shock are discussed in a separate topic. (See "Intraoperative management of shock in adults", section on 'Pulmonary embolism'.) Causes and management of embolization of other material (eg, air [47], fat, cement, amniotic fluid [48], tumor) that may cause obstructive shock are discussed in separate topics:

●(See "Intraoperative management of shock in adults", section on 'Air embolism'.)

●(See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Orthopedic surgery'.)

●(See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Renal cell tumor resection'.)

●(See "Sudden cardiac arrest and death in pregnancy", section on 'Massive pulmonary embolism and ischemic stroke'.)

Incidence of pulmonary embolus — Rescue echo diagnosed thromboembolic PE in 16 percent of noncardiac surgical patients examined in one small case series [8]. Most of the patients in this series were undergoing orthopedic procedures. Other case reports have noted PE during liver transplantation [49-51], or resection of renal cell carcinoma [52]. In one study, TEE sensitivity and specificity for detection of a proximal PE were both 84 percent [53]. However, the overall sensitivity of TEE for PE detection was only 58 percent in this study because thrombus is rarely visualized in distal locations, particularly the left pulmonary artery (PA).

Case reports confirm that rescue TEE or TTE has also been used to diagnose air, fat, cement, tumor, or amniotic fluid embolic phenomena [9,16,17,54-58].

Key views and findings — The most useful TEE views to identify echogenic masses indicating PE in the proximal pulmonary arterial tree include the ME ascending aortic SAX view (which provides images of the main PA and the proximal left and right PA in their long axis) and the ME ascending aortic LAX view (which provides an image of the right PA in its short-axis) (http://anesthesiaeducation.net/aba_key_tee_views). Also, the RV outflow track and proximal segment of the main PA may be interrogated for echogenic masses in the ME 4C view of the RV (movie 2) (see 'Midesophageal four-chamber view' above) or the midesophageal RV inflow outflow view (http://anesthesiaeducation.net/aba_key_tee_views). In some patients, residual thrombus or tumor is seen in the RA, RV, or within the intrahepatic IVC after a PE has occurred (movie 2 and image 19).

Secondary findings on the rescue TEE examination that are consistent with hemodynamically significant PE include RV dilation and RV systolic dysfunction (eg, in 96 percent of patients with PE in one study) (movie 2) [59]. In addition to RV dysfunction, leftward shift of the interatrial septum was found in 98 percent of patients with PE, and moderate to severe tricuspid regurgitation was found in 50 percent [59]. (See 'Right ventricular failure' above.) The IVC may also appear to be dilated and engorged in the midesophageal bicaval view if the PE is hemodynamically significant (http://anesthesiaeducation.net/aba_key_tee_views).

Pneumothorax or hemothorax — In rare cases, hemothorax or pneumothorax causing severe intraoperative hemodynamic instability has been diagnosed with rescue TEE [60,61].

Hemothorax is occasionally noted adjacent to the RA and liver in various TEE views, particularly if this possibility is suspected after chest trauma, pacemaker lead extraction, or thoracic or cardiac surgical procedures [15]. The pleural cavities can be imaged to detect pleural effusions or hemothorax in the descending aortic SAX view, or by turning the TEE probe to the right (ie, clockwise) past the RV in the TG LV SAX view or the ME 4C view of the RV (movie 22) (http://anesthesiaeducation.net/aba_key_tee_views).

Although pneumothorax is most commonly diagnosed by chest wall ultrasound lung examination, secondary signs of tension pneumothorax detectable with TEE include compression of atrial or ventricular chambers or atrial or ventricular septal shift [62,63]. Other secondary TEE findings in patients with either tension pneumothorax or hemothorax may be similar to the appearance of hypovolemia, except that the IVC will appear dilated and engorged.

EFFICACY OF RESCUE TEE — Intraoperative rescue transesophageal echocardiography (TEE) is most effectively used in patients with hemodynamic instability with the goal of preventing progression to cardiopulmonary arrest. TEE may be particularly useful if the immediate cause of instability is uncertain or to ensure appropriate treatment of persistent instability. In a 2019 single-institution review of use of a rescue echocardiography protocol in 48 patients undergoing various types of surgical procedures during a 22 month period, clinical management was changed in 73 percent of the cases [64]. A 2015 case series noted that TEE findings changed management in 60 percent of 364 patients who developed hemodynamic instability and/or cardiopulmonary arrest [7]. Other case series confirm that use of rescue TEE in unstable noncardiac surgical patients provided a diagnosis to explain the cause of instability in most cases, and that management changes based on the diagnosis resulted in a good outcome [8,9,65].

Even during cardiac arrest, intraoperative TEE may occasionally be useful to demonstrate the presence or absence of cardiac activity during cardiac arrest. Notably, in some cases, TEE has demonstrated that cardiac activity is present with an identifiable cardiac rhythm (eg, ventricular fibrillation) even in the absence of detectable activity on the electrocardiogram (ECG), thereby altering the treatment approach [38]. As expected, complete absence of cardiac activity is predictive of death [66,67], as is the appearance of spontaneous echo contrast (commonly termed "smoke") in the ventricular chambers [6].

Also, TEE has been employed to complement transthoracic echocardiography (TTE) during resuscitation efforts, particularly in intensive care unit and emergency department settings [6,8]. TEE is typically able to identify more findings and alter diagnoses in more patients compared with TTE, although both technologies are useful [10,11].

Evidence from other case series supports utility of rescue TEE even after cardiopulmonary arrest has occurred [2-6]. In a case series of 22 patients suffering cardiac arrest during noncardiac surgery, rescue TEE produced a working diagnosis that led to additional therapies in >80 percent [3]. Similar results after intraoperative cardiopulmonary arrest have been noted in other case series [4-6]. In one study that included 49 patients who did not survive intraoperative cardiopulmonary arrest, diagnoses made with rescue TEE were correlated with autopsy results (with a sensitivity of 93 percent, specificity of 50 percent, and positive predictive value of 87 percent) [2].

IMPLEMENTATION OF RESCUE TEE SERVICES — Some anesthesiology departments have established programs to ensure that appropriate skilled personnel are available for urgent or emergent perioperative transesophageal echocardiography (TEE) services [68,69]. Such rescue TEE teams may include a cardiac anesthesia attending and/or fellow and/or a cardiologist, as well as other personnel (eg, a sonographer or anesthesia technician) [70].

Visual cognitive aids that focus on key views may be used to facilitate rapid diagnosis in emergent situations (figure 3 and figure 4 and algorithm 1) [64] (see 'Rescue TEE examination' above). Also, operating room crisis checklists are employed to facilitate immediate appropriate management once a diagnosis is made by the rescue TEE team [71]. (See "Cognitive aids for perioperative emergencies".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Use of point-of-care echocardiography and ultrasonography as a monitor for therapeutic intervention in critically ill patients".)

SUMMARY AND RECOMMENDATIONS

●Indications for rescue TEE – Urgent and emergent transesophageal echocardiography (TEE), also termed rescue TEE, allows effective diagnosis of the immediate cause of unexpected hemodynamic instability, shock, or cardiopulmonary arrest during cardiac and noncardiac surgical procedures, and facilitates ongoing management including guidance during procedures (figure 3 and figure 4 and algorithm 1). (See 'General indications' above.)

●Key TEE views – The key TEE views used to facilitate rapid diagnosis in a rescue TEE examination are shown in an interactive video grid (http://anesthesiaeducation.net/aba_key_tee_views) (see 'Key views' above):

•Transgastric left ventricular (LV) midpapillary short-axis (TG LV SAX) view

•Midesophageal four-chamber (ME 4C) view; a modification of the ME 4C view includes the left ventricular outflow track that is known as the five-chamber view (ME 5C).

•Midesophageal long-axis (ME LAX) view

Other views should be used to develop a more complete picture of the situation.

●Intraoperative causes of shock – Intraoperative causes can be categorized as types of hypovolemic, distributive, cardiogenic, or obstructive shock.

•Hypovolemic shock – Hypovolemic shock manifests as a very small left ventricular (LV) cavity size throughout the cardiac cycle, associated with normal global LV systolic function, in the TG LV SAX view (movie 5 and movie 6). (See 'Hypovolemic shock' above.)

•Distributive shock – Distributive shock due to low systemic vascular resistance (SVR) manifests in the TG LV SAX view and the ME 4C view as a very small LV cavity at end-systole, but with normal end-diastolic values (movie 7 and table 1). (See 'Distributive shock (low systemic vascular resistance)' above.)

•Cardiogenic shock – Cardiogenic shock occurs due to an intracardiac cause of cardiac pump failure including (see 'Cardiogenic shock' above):

-Left ventricular failure – Global LV failure is diagnosed by noting reduced or absent LV systolic wall motion and thickening on the TG LV SAX view (movie 1 and movie 8), as well as LV dilation on this view and the ME 4C view (movie 9). (See 'Left ventricular failure' above.)

-Right ventricular failure – Global right ventricular (RV) failure is typically assessed qualitatively on the ME 4C view with the TEE probe turned slightly to the right to center the right ventricle in the imaging plane (movie 10 and movie 11 and movie 12), with particular attention to reduced or absent tricuspid valve annular plane systolic excursion. Other TEE evidence of RV failure includes RV dilation, severely decreased or absent RV free wall endocardial excursion and wall thickening, deviation of the interatrial septum to the left, a dilated inferior vena cava, and tricuspid regurgitation. (See 'Right ventricular failure' above.)

-Myocardial ischemia – Myocardial ischemia is qualitatively assessed by noting regional wall motion abnormalities (RWMAs) on the TG LV SAX view, which shows representative myocardial walls supplied by each of the coronary arteries (figure 1). Combining the ME 4C, ME LAX, and midesophageal two-chamber views enables all left ventricular wall segments to be assessed (figure 2). (See 'Myocardial ischemia' above.)

-Cardiac valve abnormalities – Although valvular heart disease is typically chronic with slow progression, previously unrecognized severe aortic stenosis or acute severe aortic regurgitation or mitral regurgitation (MR) may cause hemodynamic instability. (See 'Cardiac valve abnormalities' above.)

-Left ventricular outflow tract (LVOT) obstruction – Virtually complete obstruction of the LVOT may be observed in the ME LAX view when the LVOT is narrowed by LV septal hypertrophy and/or abnormal length and positioning of the mitral valve leaflets with resultant systolic anterior motion (SAM) of the mitral valve causing mitral leaflet-septal contact, as well as severe MR (image 4 and movie 3). However, severity of both LVOT obstruction and MR are typically dynamic. (See 'Left ventricular outflow tract obstruction' above.)

-Aortic dissection or injury – Rescue TEE can be used to diagnose thoracic aortic dissection (although only limited visualization of the distal ascending aorta and proximal aortic arch is possible with TEE) (image 15 and image 16 and movie 17 and movie 18), or abdominal aortic dissection (although only the proximal segment of the abdominal aorta below the diaphragm can be imaged) (movie 19). Rescue TEE may also be used to diagnose associated complications such as aortic regurgitation, coronary malperfusion, and cardiac tamponade. (See 'Aortic dissection or injury' above.)

•Obstructive shock – Obstructive shock occurs due to an extracardiac cause of cardiac pump failure including (see 'Obstructive shock' above):

-Cardiac tamponade – TEE findings in cardiac tamponade typically include a pericardial effusion on the TG LV SAX view (image 17), or the ME 4-CV view (see 'Transgastric left ventricular midpapillary short-axis view' above and 'Midesophageal four-chamber view' above). Since pericardial pressure is affected by the rate of fluid accumulation, cardiac tamponade can occur with small, moderate, or large pericardial effusions. A hemodynamically significant loculated pericardial effusion may be identified in one TEE view but not identified in other views. TEE signs of cardiac tamponade include right atrial (RA) collapse (especially if this persists for more than one-third of the cardiac cycle) (movie 20), RV collapse (movie 21), and dilation of the inferior vena cava (IVC). (See 'Cardiac tamponade' above.)

-Pulmonary embolus – A proximal pulmonary embolus (PE) (eg, thrombus, air, fat, cement, tumor, amniotic fluid) may be detected by TEE within the main and proximal right or left pulmonary arteries. Secondary findings associated with a hemodynamically significant PE include RV failure with moderate to severe tricuspid regurgitation and leftward shift of the interatrial septum (movie 2). (See 'Pulmonary embolus' above.)

-Pneumothorax or hemothorax – In rare cases, hemothorax or pneumothorax is diagnosed (movie 22). (See 'Pneumothorax or hemothorax' above.)

●Efficacy of rescue TEE – Intraoperative rescue TEE is most effectively used in patients with hemodynamic instability with the goal of preventing progression to cardiopulmonary arrest. TEE may be particularly useful if the immediate cause of instability is uncertain or to ensure appropriate treatment of persistent instability. (See 'General indications' above.)