Secundum ASDs, in general, are adequately visualized in this view with slight clockwise probe shaft rotation (Fig. 7.2, Video 7.2). Color flow Doppler interrogation in this plane demonstrates the presence and direction of shunting across the interatrial septum that can be verified by pulsedwave Doppler. This assessment also assists in the characterization of the flow across an interatrial communication in terms of the presence or absence of restriction (Fig. 7.3, Video 7.3). Slight probe withdrawal may be required to visualize small superior secundum defects, or probe advancement for small inferior secundum defects. Minimal probe shaft movements enhance the 2D evaluation allowing for examination of the defect in relation to adjacent structures as well as interrogation of the rims of the defect (Fig. 7.4). At times, smaller and/or more eccentric atrial defects will be detected in a standard TEE view (e.g. ME 4 Ch) only when a thorough sweep is performed of the septum. This emphasizes the importance of full sweeps when assessing communications at the atrial septum, as well as many other defects (Video 7.4).

Progressive withdrawal of the probe in the ME 4 Ch view to above the level of the fossa ovalis demonstrates the superior aspect of the interatrial septum—the location of superior sinus venosus defects (Fig. 7.5, Video 7.5)—as well as the superior vena cava in cross-section. Anomalous drainage of the pulmonary veins as they enter the vena cavae can be seen from these views and attempts to visualize all veins should be made. The ME 4 Ch view also allows for 2D assessment of primum ASDs and Doppler interrogation of the atrioventricular valves (Fig. 7.6, Video 7.6; discussed in detail in Chap.​ 8).

Clockwise turning of the probe in the ME 4 Ch view visualizes the remainder of the RA. The proximal aspect of the right atrial appendage (RAA) can be seen with slight probe withdrawal (Fig. 7.7, Video 7.7), in addition to portions of the tricuspid valve and right ventricular inflow (Fig. 7.8, Video 7.8) with clockwise probe shaft rotation. Tricuspid valve inflow and the degree of tricuspid regurgitation can be assessed from this window as well as in the mid esophageal right ventricular inflow-outflow (ME RV In-Out) and transgastric right ventricular inflow (TG RV In) views. Determination of the Doppler peak velocity of tricuspid regurgitation can be used to estimate right ventricular and pulmonary artery systolic pressures. Pulmonary artery diastolic pressure may be predicted by measurement of theend-diastolic velocity of pulmonary regurgitation from the ME RV In-Out, mid esophageal aortic valve short axis (ME AV SAX), or deep transgastric sagittal (DTG Sagittal) views. Increased tricuspid valve inflow and pulmonary outflow Doppler velocities may be seen within the context of large ASDs with significantly increased pulmonary to systemic blood flow (Qp:Qs) ratios. Increased flow across these structures does not necessarily represent valvar stenosis and in most cases are regarded as ‘flow-related gradients’. Pulmonary hypertension is quite rare, but may occur in patients with isolated ASDs over a period of many years.

Returning to the ME 4 Ch view, sometimes requiring slight further clockwise turning, as well as advancement or withdrawal of the probe, connection of the right pulmonary veins to the LA posteriorly can be demonstrated (Figs. 7.9 and 7.10, Videos 7.9 and 7.10; also refer to Chap.​ 6).

The sweep continues from the ME 4 Ch view with counterclockwise turning of the probe shaft to better visualize the LA (Fig. 7.11, Video 7.11). Probe advancement and retroflexion will enhance visualization of the coronary sinus and identify areas of unroofing, if present. Continued further counterclockwise rotation of the probe in conjunction with advancement or withdrawal demonstrates the left pulmonary venous connections to the left atrial posterior-lateral wall (Fig. 7.12, Video 7.12). Color and pulsed wave Doppler can be applied to facilitate this assessment (Fig. 7.13, Video 7.13). Pulmonary vein stenosis, although rare in most uncomplicated ASDs, may be suggested by aliasing/turbulence by color Doppler (Fig. 7.14, Video 7.14). This finding should be confirmed by spectral Doppler interrogation. This view may demonstrate a dilated coronary sinus in cross section if a persistent left superior vena cava to coronary sinus connection is present (Fig. 7.15, Video 7.15). Anterior to the entry of the left pulmonary veins with slight probe withdrawal to nearly a ME AV SAX plane, the proximal portion of the left atrial appendage (LAA) can be seen from this window (Fig. 7.16, Video 7.16). Forward axial rotation of the multiplane angle from the ME 4 Ch to the mid esophageal two chamber (ME 2 Ch) view (angle ~90°) displays the LA in an orthogonal plane and the LAA in long axis (Fig. 7.17, Video 7.17). Further counterclockwise turning of the TEE probe may visualize a left superior vena cava in long axis if one is present. From the ME 2 Ch plane forward transducer rotation displays a mid esophageal long axis (ME LAX) view (angle ~110°) and demonstrates the LA, mitral valve, and left ventricular outflow (Fig. 7.18, Video 7.18).

Slight advancement of the probe in the ME 4 Ch will allow for visualization successively of the coronary sinus as it courses longitudinally along the posterior atrioventricular groove (Fig. 7.19, Video 7.19), along with the coronary sinus orifice as it normally drains into the RA, and the lower portion of the interatrial septum. This is also the area where deficiency of atrial septal tissue surrounding the coronary sinus orifice on the RA may be identified in patients with a coronary sinus-type ASD. A dilated coronary sinus should not be confused for a primum ASD. Agitated saline injection into a left arm vein or left jugular vein will demonstrate contrast in the coronary sinus and drainage into the RA if a persistent left superior vena cava to coronary sinus connection is present (Fig. 7.20, Video 7.20) (Chap.​ 6).

From the ME 4 Ch view, clockwise turning of the probe and forward angle rotation displays the mid esophageal bicaval (ME Bicaval) view, angle ~90°–110°. This provides an excellent cross-section of the entire atrial septum (superior to inferior) (Figs. 7.21 and 7.22, Videos 7.21 and 7.22). The majority of the interatrial septum will be oriented optimally with respect to 2D and Doppler imaging from this view. This window is ideal for confirming the presence of superior (Fig. 7.23, Video 7.23) and inferior sinus venosus defects, secundum defects (Figs. 7.24, 7.25, and 7.26, Videos 7.24, 7.25, and 7.26), and a PFO [42–44]. As mentioned, contrast echocardiography with a Valsalva (or simulated Valsalva maneuver during mechanical ventilation) may be required for the detection of shunting across a PFO.

Slight clockwise/counterclockwise probe turning from the ME Bicaval view may be necessary to optimally visualize an ASD depending upon its size and location. Withdrawal of the probe while in this view displays the superior vena cava in long axis. Probe advancement provides long axis imaging of the inferior vena cava (Fig. 7.22, Video 7.22). Anomalous pulmonary veins entering either vena cavae may be seen from these views with appropriate probe withdrawal and/or advancement (Fig. 7.27, Video 7.27)

While in the ME 4 Ch view, advancement of the probe displays the lower esophageal situs short axis (LE Situs SAX) view. The junction of the inferior vena cava into the RA and upper portion of the vena cava can be seen in this cross-section. Further clockwise turning of the probe may be necessary during this sweep. This view can also be useful in the assessment of inferior vena cava-type of sinus venosus defects and anomalous pulmonary veins entering the vena cava.

Forward axial rotation of the imaging probe through the ME RV In-Out view (angle ~60°), allows more complete anatomic assessment of the tricuspid valve, right atrial, and ventricular size, and right ventricular outflow tract and pulmonary valve. This view is particularly helpful to demonstrate right ventricular volume overload and systolic function (Fig. 7.28, Video 7.28) in the setting of communications at the atrial level. The transgastric mid short axis (TG Mid SAX) view also provides information regarding right ventricular size and magnitude of atrial level shunting in these lesions (Fig. 7.29, Video 7.29).

Further views of the interatrial septum can also be obtained from the deep transgastric window. Once the DTG Sagittal view is obtained (angle ~90°–100°) clockwise probe rotation as necessary allows for the entire interatrial septum to be displayed; the multiplane angle can be adjusted for optimal visualization of the atrial septum (Figs. 7.30, 7.31, and 7.32, Videos 7.30, 7.31, and 7.32). The deep transgastric windows complement the assessments of ASDs (Fig. 7.33, Video 7.33) and in some cases allow for details of the anatomy not visualized in other views to be demonstrated.

Evaluation of right atrial and right ventricular size, which generally reflect the relative volume of left-to-right shunting through an ASD, provides a qualitative assessment of the clinical significance of the defect. Pertinent TEE windows include: at the mid esophageal level the 4 Ch, RV In-Out and Bicaval views (Fig. 7.34, Video 7.34); at the transgastric level the RV In, Basal SAX, and Mid SAX views; and at the deep transgastric window the DTG Sagittal view and modified cross-sections. Qualitative assessment of right and left ventricular systolic function and color and spectral Doppler evaluation of associated lesions, as appropriate, are also indicated. Normal biventricular systolic function with flattening of the interventricular septum in diastole is a common finding in defects resulting in right ventricular volume overload.

The considerations in the echocardiographic assessment of atrial level communications are summarized in Table 7.1.