Device selection

Unlike the almost “one‐size‐fits‐all” approach to selecting a TEE probe in an adult, choosing among available TEE devices adds another layer of complexity and sometimes even inconvenience to imaging pediatric patients (Figure 15.2). Two parameters guide the selection of an appropriate probe in the pediatric age group: patient weight and probe size (Table 15.4).

At this time, it is rare to use monoplane and biplane TEE probes, as these may no longer be serviced by their respective manufacturers. However, several centers worldwide, mainly in countries with limited resources, still perform biplane and even monoplane TEE imaging in infants and children.

The pediatric multiplane probe (mini‐multiplane) has allowed safe TEE imaging for many years in infants and small children weighing more than 3 kg. The availability of an even smaller device, a neonatal micro‐multiplane probe, allows the use of this imaging modality in tiny neonates weighing as little as 2.5 kg [42]. These TEE probes incorporate full 2D and Doppler capabilities [43]. In clinical practice, the use of both pediatric and neonatal TEE probes occurs in even smaller patients than recommended by the equipment manufacturers [44, 45]. In older children, the preference is to use multiplane imaging with an adult‐sized TEE probe, if feasible. Current 3D TEE probes have slightly larger dimensions than available adult 2D TEE probes, rendering them unsuitable for use in most young children. Although manufacturers suggest a patient weighing greater than 25 kg to use an adult 2D TEE probe or greater than 30 kg for a 3D TEE probe, in clinical practice, the usage of these devices often occurs in children weighing less than this. In general, these probes have more piezoelectric crystals than equivalent pediatric devices, and their larger size may improve contact with the esophagus; both features enhance the overall image resolution.

Intracardiac echocardiography (ICE) catheters (8–10 F) inserted via the transesophageal approach can provide 2D imaging in a single, longitudinal plane in neonates and small infants [46–48]. Although these catheters are not formally marketed for this specific application, reports indicate that they deliver clinically useful information in some cases, albeit with several limitations.

Probe insertion

In the operating room, TEE probe insertion occurs after induction of general anesthesia, endotracheal intubation, and arterial catheter placement. Although aspirating gastric contents is standard anesthetic practice in many centers, it does not reliably enhance TEE image quality [49]. In pediatric patients, some providers prefer nasal rather than oral endotracheal intubation to better stabilize the endotracheal tube (ETT), which reduces the risk of inadvertent extubation or movement during TEE probe manipulation. This practice, however, is variable. Regardless of the intubation route, securely taping the ETT should minimize the risk of displacement.

Blind positioning of the lubricated probe tip in the oropharynx with gentle advancement into the esophagus should occur with the patient’s head in the midline position. The probe control for transducer tip flexion should remain unlocked at this time to allow free movement.

Slight anterior flexion of the probe tip, forward thrusting of the mandible, and device guidance with a gloved finger can aid advancement of the probe along the contour of the posterior pharynx, thereby minimizing trauma. Alternatively, laryngoscopy can be used initially with direct visualization during probe insertion or after a difficult blind probe insertion [50].

In children, positioning the head to the side may facilitate the probe’s passage, as this position reportedly results in closure of the ipsilateral pyriform sinus, where the probe may encounter obstruction [51]. After placing the transducer behind the heart, repositioning the patient’s head avoids interference with the surgical field during probe manipulation. Independent factors that render probe insertion difficult in infants weighing 4 kg or less include lower weight, abnormal craniofacial anatomy, prematurity, a diagnosis of 22q11 deletion [52], and, possibly, Down syndrome.

Probe placement is an essential skill in the practice of TEE. Distinguishing expected from excessive resistance requires thorough expertise and ongoing experience with the technique [53]. Although esophageal intubation requires some degree of effort, it is important never to force the probe against resistance. Manufacturers recommend insertion of the TEE probe through a bite block (also referred to as bite guard), which is positioned between the patient’s teeth to provide safe passage through the patient’s mouth, prevent damage to the TEE probe, and maintain the probe warranty. In clinical practice, this is more commonly used when imaging is done under sedation than with general anesthesia and more likely to be used in adults versus children.

Probe insertion and manipulation can be significantly stimulating and requires an adequate level of patient sedation or anesthesia and even neuromuscular blockade in most children before placement. These maneuvers can also elicit clinically significant hemodynamic and/or respiratory changes, particularly in patients with specific anomalies with known significant potential risks of TEE (e.g., anomalous pulmonary venous drainage, vascular rings or slings); thus, vigilance is imperative [54]. In the event of acute hemodynamic or airway compromise, the probe should be repositioned or removed immediately.

Outpatient TEE is performed often in adults but rarely in children, because the excellent image quality of TTE in the pediatric population provides adequate information as previously noted. In most cases, TEE is used to address a specific question, such as assessing for a thrombus in the LAA. A combination of oropharyngeal topical anesthesia and intravenous sedation may be sufficient for TEE imaging in the adolescent or adult. In younger patients, some adolescents, and a few adults, deep sedation or general anesthesia with endotracheal intubation may be necessary to overcome lack of cooperation, avoid respiratory compromise, and provide adequate time for a complete study.

The facility where TEE occurs should be equipped with oxygen, suction capabilities, drugs, and equipment for cardiopulmonary resuscitation and other emergency therapies. Standard cardiorespiratory monitoring during the procedure includes intermittent blood pressure measurements, electrocardiography, pulse oximetry, and capnography. Patients with CHD may have significant hemodynamic alterations with marginal compensation, requiring the judicious, titrated administration of pharmacologic agents [55]. Patients with cyanotic heart disease are at additional risk for paradoxical air embolism during the administration of intravenous fluids or drugs. Decreases in systemic vascular resistance associated with a sedative or anesthetic agent can worsen right‐to‐left shunting and exacerbate underlying systemic arterial desaturation, necessitating careful observation of drug responses.

Instrument manipulation and probe controls

Manipulating the TEE probe in several directions aids in imaging cardiovascular structures relative to the sagittal plane (Figure 15.3). The probe shaft can be pushed in (advanced) or pulled back (withdrawn) and can be turned to the right (clockwise) or to the left (counterclockwise). Wheel controls on the probe handle manipulate the probe tip, which can be flexed anteriorly (anteflexed) or posteriorly (retroflexed) and to the right or left (Figure 15.4). Pediatric TEE probes may lack the right‐to‐left flexion control, seldom a limitation, because only minimal adjustments in the probe’s position are needed to navigate from view to view. The imaging plane of a stationary, multiplane transducer can be rotated between angles of 0° and 180°, without the maneuvers required by monoplane and biplane devices to obtain equivalent views [56]. The control to change the multiplane angle in adult devices is electronic, whereas it can be either mechanical or electronic in pediatric devices (Figure 15.5).

View‐based approach

The “view‐based” TEE examination relies on obtaining several specific predefined cross sections by moving the probe to various locations within the esophagus or stomach. Initial guidelines by the ASE and Society of Cardiovascular Anesthesiologists (SCA) suggested a set of 20 TEE views for a comprehensive examination. This widely adopted approach became standard practice for the TEE examination of the adult patient with an anatomically normal heart [57]. Subsequently, updated recommendations incorporated 8 additional cross sections, for a total of 28 TEE views (Figure 15.6) [3]. Recent ASE TEE guidelines specifically addressing children and all patients with CHD recommend 28 views for a comprehensive examination [5]. Most of these views are the same described for imaging of the adult heart, but a few were added in recognition of the need for examination of specific structures or pathologies commonly seen in the pediatric age group or the congenital population (Figure 15.7). Selected adult TEE views were correspondingly excluded to maintain the same overall number of cross sections. A more detailed description of views useful in imaging CHD appears in the subsequent sections. During a complete TEE examination, obtaining most or all these views, regardless of sequence, provides comprehensive anatomic, functional, and hemodynamic information. This approach helps the practitioner learn the basic principles of TEE and represents an excellent foundation on the subject. The reader is referred to the outstanding web‐based educational resources of the Toronto General Hospital (www.pie.med.utoronto.ca/TEE/) for interactive modules on the standard adult TEE examination.

The view‐based TEE examination has substantial benefits, not only as a standardized method of performing the evaluation but also in terms of facilitating teaching, archiving, and reporting of the study, as well as quality assurance. Familiarity with these views, including the nomenclature, where and how to obtain each, the structures displayed by each, and the information derived, enhances one’s ability to perform a detailed examination and to communicate the findings to others.

However, this approach has several limitations. The most recent pediatric and congenital TEE guidelines highlight two of them. First, the suggested TEE views were aimed primarily at the intraoperative interrogation and excluded views that may be necessary in nonoperative settings. Second, the outlined TEE examination was not diagnosis based, potentially excluding important views in the evaluation of specific cardiac conditions. These limitations are particularly relevant to the assessment of CHD, because a strict view‐based approach is inadequate for the detailed evaluation of structural abnormalities in many patients. Standard TEE views may not allow imaging of the complex anatomic relationships that characterize congenital pathology. Of critical relevance is that comprehensively evaluating many structural anomalies requires not only single views but also sweeps between multiple planes, some modified or nonstandard, aimed at building a 3D construct of the anatomic abnormalities.

Structure‐based approach

The “structure‐based” examination focuses on detailed TEE imaging of cardiovascular structures of interest by using complementary views to permit their in‐depth examination. Specific structural imaging in the adult has been described, for example, in the detailed evaluation of cardiac valves, the Ao, and the LAA, among other regions [3, 58–64]. A similar type of approach has been extremely helpful in characterizing specific anatomic and functional abnormalities in the patient with CHD, such as defects that involve the atrial or ventricular septum, pulmonary veins, and other structures [65–67].

This type of image‐acquisition paradigm may be preferable when, for various reasons, a focused TEE examination needs to address only a specific pathology of concern. One potential limitation of this approach in CHD is that by targeting only particular cardiac structures or pathologies, one may overlook relevant coexisting abnormalities or anatomic variants. However, by examining all relevant structures, this is the favored examination approach in CHD [5].

Sequential segmental approach

The “sequential segmental” analysis has been proposed as the foundation of complete anatomic assessment in CHD [68–71]. This approach involves a well‐organized, methodical interrogation of the three major cardiac segments (i.e., atria, ventricles, and great arteries) and their relationships to each other (connections or alignments between the segments), to define a patient’s anatomy and any abnormalities (Figure 15.8; also refer to Chapter 7). The incorporation of this type of analysis into many diagnostic imaging modalities in CHD is key in echocardiographic assessment (TTE and fetal imaging) [72–75].

The fundamental principle of this methodology is the identification of specific cardiac chambers by their characteristic morphologic properties, rather than by their positions within the body. The suggested practice examines the arrangement of the thoracoabdominal organs or situs, atrial structures, ventricles, and great arteries, as well as the connections between the segments, namely, the atrioventricular (AV) and ventriculoarterial (VA) connections [76, 77]. This approach has significant merit as congenital heart lesions can have normal or abnormal relationships among chambers, valves, and vessels (refer to Chapter 7).

The sequential segmental analysis overcomes the limitations of a purely structure‐based approach, as careful interrogation and identification of all cardiovascular structures ensures a thorough TEE assessment. Despite these advantages, for those unfamiliar with segmental anatomy, the methodology involved may be less intuitive and more time‐consuming. However, this approach is very useful, particularly in a preoperative study performed to characterize or confirm the anatomic abnormalities.

The TEE examination

Guidelines and recommendations exist for the application of TTE and TEE imaging in CHD [1, 3, 5–8]. Previous publications have addressed applications of TEE in CHD [10, 78], with the most recent guidelines outlining in detail the comprehensive and systematic examination in these patients [5]. Providing details of the TEE examination in CHD is beyond the scope of this chapter, so we review only selected aspects, and the reader should look to other publications for an exhaustive discussion on the subject [5, 28, 79, 80].

Although there is no predetermined sequence for the order of acquisition of information during a TEE examination in CHD, and one should not be inferred from the following outline, it is valuable for individuals to develop their own organized approach to performing a complete and expeditious interrogation. Unique patient conditions or specific circumstances, such as hemodynamic instability or respiratory impairment by TEE probe manipulation, may shorten the examination.

The sections that follow on imaging windows and planes provide a brief overview of selected TEE views frequently obtained during CHD evaluation. The examination assumes levocardia (heart in the left thoracic cavity with apex pointing to the left) and normal segmental anatomy: in other words, visceroatrial situs solitus (stomach on the left, liver on the right, and normal atrial arrangement), concordant AV and VA connections, normal ventricular topology, and great artery spatial orientation. It may not be possible to obtain all views in all patients, nor will the planes and angles of interrogation necessarily conform to each patient’s unique anatomy. The variety of structural cardiovascular malformations dictates a modified scheme in many cases.

The comprehensive TEE examination in CHD includes detailed 2D imaging and meticulous spectral and color‐flow Doppler interrogation. Contrast echocardiography using an injection of agitated saline or 5% albumin into a peripheral or central vein can detect small intracardiac shunts, further delineate anatomy (e.g., persistent left superior vena cava [SVC]–to–coronary sinus connection), and identify pathology such as atrial baffle leaks [81, 82].

LV systolic function

Normal LV function involves complex 3D movements during the cardiac cycle. Systolic function depends on heart rate, myocardial contractility, and loading conditions. Typically, quantitative echocardiographic assessment of LV function measures changes in LV volume by calculating stroke volume (SV), LV ejection fraction (LVEF), and cardiac output (CO). However, these quantitative measures are time‐consuming, limited by loading conditions, and affected by alterations in geometric shape. Technical concerns when using TEE, such as chamber foreshortening and poor endocardial definition, further complicate the acquisition of quantitative information. Thus, intraoperative ventricular systolic performance is often assessed qualitatively, most commonly by “eyeballing” and at times by using methods such as simple linear (shortening fraction [SF]) and area (fractional area change [FAC]) measurements.

“Eyeballing” of wall motion and thickening in the ME 4‐Ch, TG Mid Pap SAX, and TG LAX views (refer to Figure 15.7 and Table 15.5) can be used to qualitatively assess ventricular systolic function. Although used ubiquitously, this subjective technique lacks standardization, depends on experience, and has significant inter‐ and intra‐observer variability. The TG Mid Pap SAX view is often used but examines only a portion of the LV (six segments) and may not reflect global systolic function in hearts with an abnormal geometric shape or regional wall motion abnormalities.

SF estimates LV systolic function from linear measures of end‐diastolic diameter (LVEDD) and end‐systolic diameter (LVESD) by using M‐mode in a TG Mid Pap SAX view of the LV (Figure 15.10A). The superior temporal resolution of M‐mode echocardiography can capture the movement of structures over time. The SF as a percentage (normal: 26–45%) is determined by the following formula:

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