**3.1 Atrial septal defect**

Atrial septal defects (ASD) can be classified into four types: ostium secundum, ostium primum, sinus venosus, and coronary sinus defects (Joffe et al., 2008). The pathophysiological effects of ASD are determined by the defect size and degree of left-toright shunting. A large defect or unrepaired defect for a long time may lead to right heart volume overload, and subsequent right atrium (RA), RV, and PA dilation.

Ostium secundum ASD is the most commonly encountered ASD. It is located in the central portion of the interatrial septum. Mitral valve prolapse and regurgitation sometimes accompany this defect. With the advancement in treatment, many people now have transcatheter occluder placement instead of surgical patch repair. Mid-esophageal fourchamber and bicaval views delineate the interatrial septum clearly and are used in the evaluation of ASD repair surgery (Figure 1).

Fig. 1. Secundum atrial septal defect. (A) Preoperative mid-esophageal four-chamber view shows a defect (D) in interatrial septum. (B) The defect is repaired with a patch (P). RA, right atrium; RV, right ventricle; LA, left atrium.

poor airway control should consider transthoracic echocardiography or epicardial echocardiography instead. Besides, patients with history of esophageal surgery, esophageal varices or diverticulum, gastric or esophageal bleeding, oropharyngeal pathology, severe coagulopathy, cervical spine injury or anomaly require extra attention for TEE probe insertion. Although TEE examination is semi-invasive, some people do suffer from complications related to TEE probe insertion (Huang et al., 2007). These include bradycardia due to vagal stimulation, oropharyngeal injury, and esophageal perforation (Kamra et al., 2011). Besides, airway compromise, vascular compression, and dysphagia may be seen after TEE probe insertion. Physicians should respect individual differences and be vigilant to

Atrial septal defects (ASD) can be classified into four types: ostium secundum, ostium primum, sinus venosus, and coronary sinus defects (Joffe et al., 2008). The pathophysiological effects of ASD are determined by the defect size and degree of left-toright shunting. A large defect or unrepaired defect for a long time may lead to right heart

Ostium secundum ASD is the most commonly encountered ASD. It is located in the central portion of the interatrial septum. Mitral valve prolapse and regurgitation sometimes accompany this defect. With the advancement in treatment, many people now have transcatheter occluder placement instead of surgical patch repair. Mid-esophageal fourchamber and bicaval views delineate the interatrial septum clearly and are used in the

Fig. 1. Secundum atrial septal defect. (A) Preoperative mid-esophageal four-chamber view shows a defect (D) in interatrial septum. (B) The defect is repaired with a patch (P). RA, right

volume overload, and subsequent right atrium (RA), RV, and PA dilation.

evaluation of ASD repair surgery (Figure 1).

atrium; RV, right ventricle; LA, left atrium.

possible complications.

**3. Specific defects 3.1 Atrial septal defect**  Ostium primum ASD is also known as partial atrioventricular canal defects (see below). It is located in the inferior portion of the interatrial septum. It can be visualized in midesophageal four- chamber view (Figure 2). Incomplete formation of the septum primum is sometimes associated with anterior mitral leaflet cleft and regurgitation.

Sinus venosus ASD occurs near the superior vena cava (SVC) or inferior vena cava (IVC) entrance. This kind of defect is often associated with partial anomalous pulmonary venous drainage. After surgical repair, we should look not only for the residual shunt, but also the unobstructed flow in SVC, IVC, and pulmonary veins (Figure 3).

Coronary sinus defects are rare, and result from a communication between the left atrium and coronary sinus. They are commonly associated with a persistent left side SVC.

Preoperative TEE exam should confirm the location, size, shunt magnitude and direction, atrioventricular(AV) valve competence, RA and RV size, associated anomalies, and ventricular function. Post-bypass TEE exam should evaluate the adequacy of surgical repair, valvular competence, and ventricular function.

Fig. 2. Mid-esophageal four-chamber view demonstrates a primum atrial septal defect (arrow). RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle.

Intraoperative Transesophageal Echocardiography for Congenital Heart Disease 119

Fig. 4. Perimembranous ventricular septal defect. The right ventricle (RV) inflow-outflow view demonstrates the septal defect (D) and mid-right ventricular obstruction (arrow). RA,

Doubly committed, subarterial, or supracristal defects (Type I) are roofed by the arterial valves in fibrous continuity. The defects account for approximately 5% and 30% of VSDs in western and oriental population, respectively. The defects may associate with aortic valve

Muscular defects (Type IV) are completely surrounded by a muscular rim. The defects account for about 5-15% of VSDs. Multiple muscular defects can occur (Figure 6). The muscular outlet defects can also associate with aortic cusp prolapse and aortic insufficiency. Atrioventricular canal or inlet defects (Type III) occur close to the atrioventricular valves in the posterior portion of the ventricular septum. The defects account for approximately 5% of

Preoperative TEE exam should confirm the defect location, size, and numbers. Besides, the shunt direction and magnitude, the cardiac chamber size and PA dimension, competence of AV valve, presence of septal malalignment, LVOT or RVOT obstruction, evidence of pulmonary hypertension, and associated cardiac anomalies should be evaluated thoroughly. The velocity of TR jet can be used to calculate PA pressure in the absence of RVOT obstruction. The post-bypass TEE can offer information about the presence of residual shunts or outflow tract obstruction, changes in severity of valvular regurgitation, and

right atrium;, TV, tricuspid valve.

VSDs.

ventricular function.

prolapse and aortic insufficiency (Figure 5).

Fig. 3. Modified bicaval view shows a superior sinus venosus atrial septal defect near the superior vena cava and right atrial junction. RA, right atrium; LA, left atrium.

#### **3.2 Ventricular septal defect**

Ventricular septal defect (VSD) can be classified by its location to four groups: type I, doubly-committed defects; type II, perimembranous defects; type III, atrioventricular defects; and type IV, muscular defects. Perimembranous and muscular defects can be further subdivided to inlet type, trabecular type, and outlet type according to the extension of the defects (Penny & Vick, 2011). The pathophysiological effects are affected by the size of defect, the systemic and pulmonary vascular resistance, and associated defects such as ASD and patent ductus arteriosus (PDA). The left-to-right shunt can lead to increased left ventricle (LV) volume load, excessive pulmonary blood flow, and decreased systemic cardiac output. A long-standing pulmonary overcirculation may lead to pulmonary hypertension and Eisenmenger's syndrome eventually.

Perimembranous VSDs (Type 2) are confluent with and involve the membranous septum. The defects account for approximately 60-80% of VSDs. Aneurysmal transformation of tricuspid valve may occur and limit the shunt flow. Tricuspid regurgitation (TR) may occur because the tricuspid valve is deformed. Perimembranous outlet defects can associate with aortic cusp prolapse and even aortic insufficiency. Patients with perimembranous defects may develop RV hypertrophy and right ventricular outflow tract (RVOT) narrowing. When the hypertrophied muscular band divides the RV cavity into two chambers, the condition is called double-chambered RV (DCRV) (Figure 4). The outlet septum may be malaligned anteriorly or posteriorly which can possibly result in RVOT or left ventricular outflow tract (LVOT) obstruction respectively.

Fig. 3. Modified bicaval view shows a superior sinus venosus atrial septal defect near the

Ventricular septal defect (VSD) can be classified by its location to four groups: type I, doubly-committed defects; type II, perimembranous defects; type III, atrioventricular defects; and type IV, muscular defects. Perimembranous and muscular defects can be further subdivided to inlet type, trabecular type, and outlet type according to the extension of the defects (Penny & Vick, 2011). The pathophysiological effects are affected by the size of defect, the systemic and pulmonary vascular resistance, and associated defects such as ASD and patent ductus arteriosus (PDA). The left-to-right shunt can lead to increased left ventricle (LV) volume load, excessive pulmonary blood flow, and decreased systemic cardiac output. A long-standing pulmonary overcirculation may lead to pulmonary

Perimembranous VSDs (Type 2) are confluent with and involve the membranous septum. The defects account for approximately 60-80% of VSDs. Aneurysmal transformation of tricuspid valve may occur and limit the shunt flow. Tricuspid regurgitation (TR) may occur because the tricuspid valve is deformed. Perimembranous outlet defects can associate with aortic cusp prolapse and even aortic insufficiency. Patients with perimembranous defects may develop RV hypertrophy and right ventricular outflow tract (RVOT) narrowing. When the hypertrophied muscular band divides the RV cavity into two chambers, the condition is called double-chambered RV (DCRV) (Figure 4). The outlet septum may be malaligned anteriorly or posteriorly which can possibly result in RVOT or left ventricular outflow tract

superior vena cava and right atrial junction. RA, right atrium; LA, left atrium.

hypertension and Eisenmenger's syndrome eventually.

**3.2 Ventricular septal defect** 

(LVOT) obstruction respectively.

Fig. 4. Perimembranous ventricular septal defect. The right ventricle (RV) inflow-outflow view demonstrates the septal defect (D) and mid-right ventricular obstruction (arrow). RA, right atrium;, TV, tricuspid valve.

Doubly committed, subarterial, or supracristal defects (Type I) are roofed by the arterial valves in fibrous continuity. The defects account for approximately 5% and 30% of VSDs in western and oriental population, respectively. The defects may associate with aortic valve prolapse and aortic insufficiency (Figure 5).

Muscular defects (Type IV) are completely surrounded by a muscular rim. The defects account for about 5-15% of VSDs. Multiple muscular defects can occur (Figure 6). The muscular outlet defects can also associate with aortic cusp prolapse and aortic insufficiency.

Atrioventricular canal or inlet defects (Type III) occur close to the atrioventricular valves in the posterior portion of the ventricular septum. The defects account for approximately 5% of VSDs.

Preoperative TEE exam should confirm the defect location, size, and numbers. Besides, the shunt direction and magnitude, the cardiac chamber size and PA dimension, competence of AV valve, presence of septal malalignment, LVOT or RVOT obstruction, evidence of pulmonary hypertension, and associated cardiac anomalies should be evaluated thoroughly. The velocity of TR jet can be used to calculate PA pressure in the absence of RVOT obstruction. The post-bypass TEE can offer information about the presence of residual shunts or outflow tract obstruction, changes in severity of valvular regurgitation, and ventricular function.

Intraoperative Transesophageal Echocardiography for Congenital Heart Disease 121

Atrioventricular septal defects (AVSD), also called endocardial cushion defects, are defects involving atrioventricular septum. Normally, mitral valve is attached to a more cephalad position than tricuspid valve. However, in patients with AVSD, their mitral valve and tricuspid valve attach to the same level. There are two types of AVSD, partial AVSD and complete AVSD. In patients with partial AVSD, there is a primum type ASD and anterior mitral leaflet cleft. Though there are usually two orifices for the AV valve, their mitral valve attachment to ventricular septum is not normal, and the leaflet can be thickened, irregular, and dysplasic. Their mitral valve is actually part of the common AV valve and the mitral cleft is a commissure between anterior and posterior bridging leaflets. The attachment of mitral leaflet in the LVOT can cause LVOT obstruction, and poor apposition of the valve can cause mitral regurgitation (MR). Complete AVSD composes single orifice AV valve with deficiency of both atrial and ventricular septum (Figure 7). Rastelli classified this complex into three types according to their different degrees of bridging of superior bridging leaflet, its chordal attachment pattern, and the degree of associative of hypoplasia of the tricuspid anterorsuperior leaflet. The function of common AV valve can be quite variable, ranging from nearly normal function with minimal regurgitation to severely limited dysplastic valve

Fig. 7. Complete atrioventricular septal defect. The mid-esophageal four-chamber view shows deficiency of both interatrial (arrow) and interventricular (double arrow) septum.

The pathophysiology of partial AVSD is similar to simple primum ASD. The magnitude of left-to-right shunt is determined by the size of defect and relative ratio of systemic and pulmonary vascular resistance. Mitral cleft can cause significant MR and LV volume

**3.3 Atrioventricular septal defect** 

with marked incompetence.

Fig. 5. Doubly-committed ventricular septal defect. Mid-esophageal long-axis view shows the prolapse of aortic cusp (arrow) and the septal defect (double arrow). LA, left atrium; LV, left ventricle; Ao, aorta.

Fig. 6. Mid-esophageal four-chamber view demonstrates multiple muscular ventricular septal defects (arrow). RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle.

#### **3.3 Atrioventricular septal defect**

120 Echocardiography – In Specific Diseases

Fig. 5. Doubly-committed ventricular septal defect. Mid-esophageal long-axis view shows the prolapse of aortic cusp (arrow) and the septal defect (double arrow). LA, left atrium; LV,

Fig. 6. Mid-esophageal four-chamber view demonstrates multiple muscular ventricular septal defects (arrow). RA, right atrium; RV, right ventricle; LA, left atrium; LV, left

left ventricle; Ao, aorta.

ventricle.

Atrioventricular septal defects (AVSD), also called endocardial cushion defects, are defects involving atrioventricular septum. Normally, mitral valve is attached to a more cephalad position than tricuspid valve. However, in patients with AVSD, their mitral valve and tricuspid valve attach to the same level. There are two types of AVSD, partial AVSD and complete AVSD. In patients with partial AVSD, there is a primum type ASD and anterior mitral leaflet cleft. Though there are usually two orifices for the AV valve, their mitral valve attachment to ventricular septum is not normal, and the leaflet can be thickened, irregular, and dysplasic. Their mitral valve is actually part of the common AV valve and the mitral cleft is a commissure between anterior and posterior bridging leaflets. The attachment of mitral leaflet in the LVOT can cause LVOT obstruction, and poor apposition of the valve can cause mitral regurgitation (MR). Complete AVSD composes single orifice AV valve with deficiency of both atrial and ventricular septum (Figure 7). Rastelli classified this complex into three types according to their different degrees of bridging of superior bridging leaflet, its chordal attachment pattern, and the degree of associative of hypoplasia of the tricuspid anterorsuperior leaflet. The function of common AV valve can be quite variable, ranging from nearly normal function with minimal regurgitation to severely limited dysplastic valve with marked incompetence.

Fig. 7. Complete atrioventricular septal defect. The mid-esophageal four-chamber view shows deficiency of both interatrial (arrow) and interventricular (double arrow) septum.

The pathophysiology of partial AVSD is similar to simple primum ASD. The magnitude of left-to-right shunt is determined by the size of defect and relative ratio of systemic and pulmonary vascular resistance. Mitral cleft can cause significant MR and LV volume

Intraoperative Transesophageal Echocardiography for Congenital Heart Disease 123

PDA is a postnatal communication between the main pulmonary trunk and descending thoracic aorta due to persistent patency of fetal ductus arteriosus (Schneider & Moore, 2006). Shunt flow is determined by diameter of PDA and the pressure gradient. The preoperative TEE can demonstrate the shunt flow in the ascending aorta short-axis view (Figure 9). The size of left-side chambers, ventricular function, valvular regurgitation, degree of pulmonary hypertension, and associated cardiac anomalies must also be evaluated. The postoperative TEE exam can be used to detect the presence of residual

Aortopulmonary defect, also known as aortopulmonary (AP) window, is a defect between ascending aorta and pulmonary artery. Without treatment, pulmonary system will be overloaded due to left to right shunt, and eventually develop pulmonary vascular occlusive disease. A significant portion of the patients have other associated cardiac anomalies. Preoperative TEE can detect a shunt between ascending aorta and PA (Figure 10). Evidence of pulmonary hypertension, ventricular function and size, defect size and shunt pressure gradient can be measured by intraoperative TEE. Surgical treatment usually involves aorta incision, defect visualization, and a patch is sutured to close the defect over the aortic side. The post-repair TEE exam should detect the presence of residual shunt, valvular

Fig. 9. The upper esophageal aortic arch long-axis view demonstrates the patent ductus

arteriosus (arrow) connecting aortic arch and left pulmonary artery. Ao, aorta.

**3.4 Patent ductus arteriosus and aortopulmonary window** 

ductal flow.

competence, and ventricular function.

overload. The MR can pass the primum ASD and results in LV to RA shunt, RA volume overload, and pulmonary overcirculation. In patients with complete AVSD, the presence of concomitant atrial and ventricular shunting can cause increased shunt flow. Pulmonary hypertension, secondary pulmonary vascular change, and increased pulmonary vascular resistance (PVR) can occur thereafter. The hemodynamic changes are affected by the magnitude and direction of shunt flow. There may be different directions of AV valve regurgitation: LV-to-left atrium (LA), RV-to-RA, LV-to RA, or RV-to-LA.

The mid-esophageal four-chamber view of intraoperative TEE can demonstrate the defect of inferior part of atrial septum. Secundum ASD or patent foramen ovale (PFO) can be present in some patients. The broad-base MR jet not originating from the coaptation may suggest the presence of a cleft mitral valve (Figure 8). Cleft mitral valve may be demonstrated in transgastric basal short-axis view. Besides, the presence of ventricular shunting, sizes of both ventricle, ventricular function, magnitude and direction of AV valve incompetence, degree of AV valve straddling, presence of LVOT obstruction, degree of pulmonary hypertension, and associated cardiac anomalies must be evaluated preoperatively. The postoperative TEE exam should include the evaluation of ventricular function, AV valve competence, and the presence of residual shunt (Cohen et al., 2007). Because valvular regurgitation is quite pressure and load dependent, it is important that we take patient's volume status and cardiac contractility into consideration when comparing preoperative and postoperative regurgitation severity. If prosthetic valve is replaced, it is important to check the function of prosthetic valve and the presence of paravalvular leak.

Fig. 8. Partial atrioventricular septal defect. The mid-esophageal four-chamber view demonstrates a primum atrial septal defect (atrial) and mitral cleft (double arrow) with severe mitral regurgitation.
