Intraoperative evaluation currently represents the most common indication for TEE in patients with CHD and children with acquired cardiovascular disorders. Indications for intraoperative TEE include settings where there exists potential for significant residual pathology and/or myocardial dysfunction related to cardiovascular interventions.

It is recommended that all patients undergo a complete preoperative TTE prior to TEE. The study should be reviewed by the echocardiographer prior to initiating the intraoperative TEE assessment. TEE should be considered a complementary imaging modality, rather than a substitute for a comprehensive TTE. This is in recognition of the inherent limitations associated with transesophageal imaging such as the inability to evaluate certain cardiovascular structures, suboptimal conditions for imaging, and other challenges.

The benefits of the preoperative TEE study are many, including:

The exam provides a baseline evaluation of the underlying cardiac abnormalities and serves as a framework for later comparison in the postsurgical assessment. Also, the study can be used to address any important remaining preoperative concerns regarding intracardiac anatomy and physiology, questions in which TEE has a reasonable expectation of providing accurate and useful information. Important goals of the examination include the confirmation and/or exclusion of preoperative diagnoses, assessment of cardiac pathology, and the immediate preoperative evaluation of hemodynamics and ventricular function. TEE demonstrates in real-time the cardiac abnormalities to the perioperative providers prior to the intervention. The examination allows for refinements or modifications in the surgical plan and facilitates anesthetic care. Several reports have documented the many contributions of preoperative TEE including, for example, guidance during placement of intravascular and intracardiac catheters [22]. Performing a complete study (Chap.​ 4) should be an objective during the preoperative period; however, a focused examination might be necessary due to patient-related issues or unanticipated intraoperative problems/complications that could limit this assessment.

The benefits of the postsurgical TEE examination are also well recognized and include:

Numerous publications have documented the impact of this imaging approach in patients with congenital cardiovascular defects and in children with acquired cardiovascular pathology [23–35]. While weaning from cardiopulmonary bypass, TEE ensures the adequacy of cardiac de-airing [36] and allows for assessment of ventricular function and loading conditions [37, 38]. Changes in inotropic strategy and volume replacement have also been reported as a direct result of intraoperative TEE [39, 40]. The postoperative study encompasses a complete analysis of the surgical results, hemodynamics, and functional status. The clinical condition, in conjunction with the TEE findings and other available hemodynamic information, are considered in the determination of whether the surgical repair is acceptable or if there is a need for reinstitution of cardiopulmonary bypass to revise the repair or address unsatisfactory results. In some cases, an “acceptable” result must be distinguished from a “perfect” result. The main goal of intraoperative TEE is the assessment of hemodynamically significant residual defects that may need reintervention prior to leaving the operating room, in order to improve overall clinical outcomes.

Additional settings where TEE has been shown to be useful in these patient groups include: during minimally invasive surgery when adequate visualization of structures may be limited [41–44], in the postoperative patient with suboptimal transthoracic windows or an open sternum [45, 46], in the critical care setting, and in the management of patients undergoing mechanical circulatory support [47]. These applications are discussed in further detail later in this chapter.

Over the past several decades, the contributions of TEE have accounted for improved perioperative care, by limiting morbidity and likely reducing mortality in many patients. The experience has been so compelling that the technology has been incorporated into standard clinical practice by many centers that care for patients with CHD and children with acquired cardiovascular pathology, despite the lack of rigorous scientific scrutiny of the impact of TEE on patient outcome.

Several practice guidelines have addressed the applications of TEE during noncardiac surgery in the adult. These indicate that TEE should be used during noncardiac procedures when the patient has known or suspected cardiovascular pathology that might result in hemodynamic, pulmonary, or neurologic compromise [48]. This indication, also applicable to the adult with CHD, has been emphasized in more recent recommendations.

Although the role of TEE during noncardiac surgery has not been extensively documented in children, nor adults with CHD, the limited experience suggests that this approach may facilitate perioperative management in selected patient groups [49–51]. High-risk individuals that may benefit from TEE during noncardiac surgery include those with untreated or palliated CHD, single ventricle physiology, or other complex structural abnormalities. In addition, TEE is likely to assist in the care of patients with residual hemodynamic abnormalities, myocardial dysfunction, cardiomyopathies, or pulmonary hypertension undergoing noncardiac operative procedures where significant fluid shifts are anticipated, or perturbations may result in hemodynamic compromise.

An executive summary regarding perioperative cardiovascular evaluation and care for noncardiac surgery was published as a joint effort of the American College of Cardiology and American Heart Association in 2007. In reference to CHD this indicated that certain postoperative patients may be at higher risk during noncardiac surgery [52]. As limited information is available for perioperative risk assessment in these patients, specific recommendations for intraoperative management, including monitoring, were not made. It was pointed out at the time the guidelines were developed that there was insufficient evidence to support the routine use of TEE during noncardiac surgery.

Interventional procedures have become increasingly employed in the non-surgical management of CHD. TEE allows for safer and more effective application of catheter-based approaches and may reduce radiation exposure, amount of contrast material administered, and duration of the interventional procedure. Major contributions during catheter-based interventions include: (1) acquisition of detailed anatomic and hemodynamic data prior to and during the procedure, (2) real-time evaluation of catheter placement across valves, vessels, and cardiac structures, (3) immediate assessment of the results, and (4) monitoring and detection of complications associated with the interventions [53–59]. The refinements in interventional cardiac catheterization techniques coupled with advances in TEE now allow for a high success rate of these procedures along with a low incidence of complications.

In the cardiac catheterization laboratory TEE has been applied to the closure of atrial septal defects [60–68], ventricular septal defects [69, 70], and occlusion of patent ductus arteriosus [71, 72], as well as communications such as Fontan baffle leaks and fenestrations [73, 74]. Additional procedures suitable for TEE monitoring/guidance include: balloon/blade atrial septostomy [75–77], stenting of restrictive atrial communications or other cardiovascular structures [78], balloon valvuloplasty [79, 80], radio frequency perforation of atretic valve or atrial septum, endomyocardial biopsy [81], pericardiocentesis [82, 83], and retrieval of devices/foreign bodies [84] (Chap.​ 17). TEE is also used to facilitate guidance of percutaneous ventricular septal defect closure and other interventions performed by combining catheter techniques and operative procedures, otherwise known as hybrid approaches [85, 86].

In adults, TEE is routinely and regularly utilized in the ambulatory setting. This is due in large part to the more difficult transthoracic windows and marginal imaging quality encountered in many adults, which limits the amount of information obtainable by TTE. However it also reflects the fact that ambulatory TEE is easier to perform in adult patients, because in most cases it can be done with moderate sedation.

In contrast, ambulatory TEE is less likely to be used in the pediatric setting. As indicated previously, transthoracic imaging generally provides high-quality diagnostic images in pediatric patients, particularly neonates, infants, and young children. Rarely does TEE provide any significant advantage compared to transthoracic imaging in the younger age-group; in addition, the greater availability of transthoracic windows means that a more comprehensive evaluation of the heart and adjacent cardiovascular structures can be performed, including those areas not consistently imaged by TEE (e.g. the branch pulmonary arteries, aortic arch). The other important deterrent is that ambulatory TEE is generally more involved in younger patients from the practical aspects. Even with sedation, children and adolescents are rarely able to cooperate and lie still. This not only can compromise patient safety but adds the potential for damage to the TEE probe. Thus, deep sedation or general anesthesia is necessary in most patients particularly in those with significant cyanosis, myocardial dysfunction, or potential ventilatory abnormalities [87].

When standard TTE imaging is unsatisfactory, the need for ambulatory TEE must be ascertained after a risk versus benefit analysis. This involves consideration of the type of information required and alternative diagnostic imaging modalities along with their attendant risk and benefits. Despite a good safety profile, TEE is a semi-invasive procedure with important potential risks and relative/absolute contraindications. Cardiac catheterization, cardiac magnetic resonance imaging, and chest tomography each provide certain types information (i.e., hemodynamic measurements, aortic arch imaging) that cannot be obtained by TEE. Nonetheless, there are a number of instances in which ambulatory TEE can provide superior diagnostic information in the patient with CHD, even compared to other imaging modalities. Abnormal atrioventricular valves, for example, are much better evaluated by TEE than other diagnostic approaches, as are prosthetic valves (Chap.​ 16). Subaortic membranes and subaortic stenosis are clearly shown by TEE, as are atrial septal defects, particularly those of the superior sinus venosus type. Other examples (by no means inclusive) include ventricular septal defect morphology, aortic valve pathology, proximal coronary artery anatomy, and relationship of ventricular defects to the semilunar valves (e.g. in complex malpositions of the heart). There are certain types of postoperative cardiac defects in which TEE is extremely useful, i.e. in patients who have undergone atrial baffles (Mustard/Senning procedures), Fontan, or Rastelli procedures. It is also well documented that TEE plays an important role in the evaluation of endocarditis and other infectious pathologies.

The critical care setting is one area in which TEE can provide significant benefit. While TTE remains the first modality of choice for noninvasive cardiac assessment, a number of factors associated with the nature of the intensive care unit (ICU) can significantly limit the effectiveness of TTE. These factors include mechanical ventilation, tenuous hemodynamic and respiratory status, inability to alter patient positioning, and in some cases, recent cardiac and/or thoracic surgery. Such factors often contribute to poor or nonexistent conditions for TTE imaging. Indeed, in the adult experience the percentage of successful diagnostic TTE examinations approximates only about 50 % [88, 89], whereas TEE examination yields adequate results in >90 % of cases [90]. Thus, TEE now plays an increasing role in the diagnostic evaluation of adult patients in the critical care unit, particularly for indications unique to that setting including unexplained hypotension, suspected pulmonary embolism, unexplained hypoxemia, suspected endocarditis, prosthetic valve assessment, central line placement, and complications of cardiothoracic surgery [91, 92]. For pediatric patients in the ICU, indications for TEE are similar to those in adults but there are additional considerations pertinent to the child and young adult with CHD [93]. First, since patients are younger and tend to have better echocardiographic windows, TTE tends to provide more satisfactory imaging in general as previously mentioned, although image quality can vary significantly. Second, the semi-invasive nature of the TEE procedure necessitates careful consideration, particularly in the younger or more unstable patient. As in the ambulatory setting, TEE in the younger patient is optimally performed under conditions of deep sedation/endotracheal intubation. In the unintubated patient, a determination must be made as to whether the potential additional information gleaned from TEE warrants the small additional risk associated with the examination, particularly as compared to alternate diagnostic modalities. Third, the examiner must have a thorough understanding of the patient’s previous history and underlying cardiac anatomy, as well as the specific indications for the TEE study. Common indications for TEE in the critical care setting include:

The American Society of Echocardiography Committee for Physician Training in Echocardiography published guidelines for training in TEE in 1992 [3]. The recommendations were aimed at physicians in general wishing to provide TEE services either in the operating room environment or other nonoperative settings. The report suggested that individuals using TEE should have:

Initial practice guidelines specifically addressing the use of perioperative TEE were published in 1996 [5]. Subsequently, task forces by the American Society of Echocardiography and Society of Cardiovascular Anesthesiologists have documented guidelines for physician training on the subject [10, 93, 94]. In these reports, different levels of expertise in echocardiography are recognized and level-specific recommendations for training outlined. In addition to the training objectives suggested for basic level perioperative TEE practice, the advances level assumes comprehensive cognitive and technical skills to allow for the full potential applications of the TEE technology. TEE practice in pediatric patients and those with CHD is considered within the advanced pathway. Training requirements with respect to this application include detailed knowledge of the techniques, advantages, disadvantages, and potential complications of commonly used cardiac surgical procedures for the treatment of acquired and CHD.

In regards to training elements for the practice of advanced perioperative echocardiography, guidelines focusing mostly on adult applications suggest the following [10]:

A task force by the American College of Cardiology/American Heart Association/American College of Physicians-American Society of Internal Medicine in collaboration with other professional societies focused on clinical competence in echocardiography and published a statement on the subject in 2003 [7]. The document distinguished between training requirements and documentation of competence.

Regarding competence with respect to CHD, cognitive skills required for TEE included knowledge of alterations in cardiovascular anatomy that result from congenital pathology and their specific appearance on TEE.

Skills necessary to perform perioperative echocardiography in patients with CHD were listed under the category of advanced level and specified:

The guidelines underscored the requirement for additional training in CHD. In regards to training requirements for performance and interpretation of TEE, for individuals in a formal cardiology fellowship training program the guidelines indicated the following:

The task force emphasized that in certain specialized clinical settings even this training may be not be adequate for independent TEE practice and cited the assessment of complex CHD as one of these situations.

It is acknowledged that physicians from different specialties must attain comparable expertise in perioperative echocardiography while requiring different training to reach this goal. It is also recognized that trainees from different disciplines would use their time in training somewhat differently, depending on their varying backgrounds.

Although several publications delineate guidelines for perioperative echocardiography in general, it is well known that competent performance of TEE in pediatric patients with congenital or acquired heart disease, or adult patients with CHD, requires specialized knowledge, skills, and training. The guidelines for performance of TEE in these patient groups differ in many respects from those for TEE in the general adult population.

In recognition of the unique aspects and evolving applications of TEE, the statement of the Pediatric Council of the American Society of Echocardiography issued in 2005 outlined guidelines for performance of TEE in these particular patient groups [9]. Regarding knowledge base and skills the recommendations can be summarized as follows:

Specific recommendations regarding guidelines for training and maintenance of proficiency in the performance of TEE in this patient population were made as indicated in Table 3.2. In addition to prerequisite experience in TTE, a minimum number (25 cases) of esophageal intubations were suggested, as well as performance and interpretation of examinations under supervision. For physicians without formal training in pediatric cardiology or without a focus on TEE, acquisition of medical/echocardiographic knowledge base and practical skills equivalent to those acquired during pediatric cardiology specialty training were recommended in order to perform TEE independently. Required cognitive skills included knowledge of cardiac anatomy, congenital and acquired cardiac pathology, pathophysiology, differential diagnosis, and alternative diagnostic modalities.

The issue of who should be responsible for the intraoperative TEE interpretation in patients undergoing interventions for CHD and the respective roles of the specialized perioperative providers has been the subject of raging controversy [96–101]. To ensure quality of the evaluation, interpretation of findings, and to promote patient safety, expertise is required. The availability of a second appropriately trained individual in echocardiography or cardiovascular anesthesiology has been suggested when intraoperative echocardiography is being performed by a cardiovascular anesthesiologist. In their statement the Pediatric Council of the American Society of Echocardiography indicated that there was no intent in their guidelines of excluding physicians from performing TEE in pediatric patients. Ideally, intraoperative imaging should be collaboration between pediatric cardiologists, anesthesiologists, and cardiothoracic surgeons.

The safety of TEE has been the focus of various reports. A number of studies comprising large numbers of patients, and following an extensive clinical experience in the adult population (including relatively high-risk patient groups), have documented an overall extremely favorable safety profile for this modality [102–106].

Data in the pediatric age group likewise demonstrates a high margin of safety and low incidence of TEE-related complications in the range of 1–3 %. The use of TEE has been successfully reported in very small infants under 3.0 kg in weight, however extreme caution must be exercised in view of potential procedure-related respiratory or hemodynamic compromise [107].

Stevenson prospectively examined the incidence and severity of complications during TEE in 1650 pediatric cases (mean age of 3.6 years, mean weight of 17.2 kg) [108]. The complication rate was reported to be low, occurring in 2.4 % of the patient group (failure of probe placement excluded). Problems, when encountered, were mostly related to the respiratory system or vascular compression. No significant bleeding, arrhythmias, esophageal injuries, or deaths occurred.

Other studies addressing the use of TEE in children and/or during surgery for CHD have reported upon safety and the low incidence of complications. Randolph and associates did not identify major complications among 1,002 patients that comprised both children and adults with CHD [109]. Minor complications were noted in 1 % of the cases, most often observed in infants less than 4 kg in weight. A 10-year experience that examined 580 TEE studies during pediatric cardiac surgery observed a 2.7 % incidence of complications and the absence of any prolonged problems or morbidity secondary to TEE [110]. Others have reported similar results [111].

Andropoulos and colleagues evaluated the impact of TEE on ventilation and hemodynamic variables in small infants undergoing cardiac surgery [112, 113]. No significant changes in several measured parameters of gas exchange and pulmonary mechanics were observed in relation to probe insertion. The investigation noted that hemodynamic complications from TEE, although possible, were rare in this patient group. These data provided reassurance to those involved in intraoperative TEE imaging of very young infants.

Evidence linking anticoagulation with a significant risk for bleeding during a TEE examination is lacking. However, since minor trauma to oropharyngeal structures may occur at the time of probe placement and/or removal, it may be prudent for these maneuvers to be performed during times when patients are not expected to be fully heparinized for cardiopulmonary bypass.

Although rarely observed, the most frequently encountered complications relate to trauma to the oropharynx and/or esophagus, resulting in symptomatology such as pharyngeal discomfort, odynophagia, and dysphagia. The use of direct laryngoscopic guidance during TEE probe placement has been examined in adult patients in an effort to minimize potential oropharyngeal mucosal injury [114]. Whether this may also be the case in children remains to be determined. An interesting investigation proposed that head positioning to the side rather than the midline facilitated esophageal intubation with the TEE probe in children under 10 kg of body weight. The study theorized that anatomic changes in the hypopharynx associated with head turning would favor probe passage, which in their experience was confirmed by turning the head to the left [115].

Less likely problems related to TEE are respiratory difficulties or hemodynamic changes. Reported complications include: accidental tracheal extubation, ventilatory compromise related to impingement of the esophageal probe on the tracheobronchial tree, and alterations of cardiac rhythm [116–122]. Compression of adjacent cardiovascular structures by the probe has been reported resulting in circulatory derangement [123]. Compression of an aberrant subclavian artery may lead to a dampened radial artery blood pressure tracing [124]. Descending aortic compression may manifest as a change in the contour of a lower extremity arterial tracing or pulse oximeter signal. Serious complications such as esophageal perforation, inadvertent gastric incision during sternotomy, and subglottic stenosis have been described although, fortunately, these have been extremely rare [108, 125, 126].