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drainage

Coronary sinus

Persistent left superior vena cava

Associated anomalies are not mutually exclusive.

Associated anomalies are not mutually exclusive.

Typically, secundum and primum septal defects can be seen with transthoracic imaging. However, multiplane transesophageal echocardiography may be needed to visualize sinus venosus or coronary sinus defects with certainty. Multiplane transesophageal imaging is highly accurate in visualizing the anatomical relationships and associated anomalies sometimes seen with ASDs (Table 1).

The use of color and spectral Doppler can enhance the detection of these defects. Color flow Doppler can confirm the presence and direction of interatrial shunting across visualized aspects of the atrial septum (Fig. 3; please see companion DVD for corresponding video). The color flow signal may also aid in measuring the size and number of defects. For example, should several color flow jets be seen across the area of the septum, a fenestrated defect is implied. Thus, color should be used in different views in order to assess for these flow abnormalities.

Echocardiography Images

Fig. 3. Atrial four-chamber view showing defect or possible drop out in the interatrial septum (arrow, A). Color flow Doppler interrogation showed a typical pattern of predominant left-to-right shunting as seen with secundum atrial septal defects (B). (Please see companion DVD for corresponding video.)

Fig. 3. Atrial four-chamber view showing defect or possible drop out in the interatrial septum (arrow, A). Color flow Doppler interrogation showed a typical pattern of predominant left-to-right shunting as seen with secundum atrial septal defects (B). (Please see companion DVD for corresponding video.)

Should the result of a color and spectral Doppler exam be equivocal, an intravenous agitated contrast saline injection can be used to detect interatrial shunting. This effect is dependent on the fact that the bubbles created from the agitated saline are filtered in the pulmonary vas-culature and do not cross to the left heart. Thus, contrast should only be seen in the right heart chambers in the absence of intracardiac and intrapulmonary shunting. In the typical case of an uncomplicated ASD, left atrial pressures are higher than right atrial pressures and direct predominant left-to-right shunting with occasional early crossing of contrast bubbles to the left heart from right-to-left shunting. Contrast is injected from an upper extremity and enters the right atrium via the superior vena cava (SVC) and tends to be directed more toward the tricuspid valve than the atrial septum, in contrast to blood from the inferior vena cava (IVC), which is usually directed more toward the atrial septum via the eustachian valve. An adequate contrast injection is attained when the bubble contrast is seen to appose the area of the septum. Valsalva maneuver is often used to assess for interatrial shunting with contrast by accentuating right-to-left shunting. The presence of contrast bubbles in the left heart early after injection signifies an interatrial shunt, whereas the appearance of late contrast bubbles (>3-5 cardiac cycles) in the left heart suggests an intrapul-monary shunt (Fig. 4; please see companion DVD for corresponding video).

Typically, ASDs confer a volume load on the right heart. Therefore, a pattern of right ventricular overload is often seen. The right ventricle is often dilated with preserved systolic function. The right atrium is often enlarged. Because of the volume load, ventricular septal motion may be abnormal and display paradoxical motion. The pulmonary pressures will vary depending on the hemodynamic impact of the lesion. In the extreme and rare case, Eisenmenger's physiology may result, with pul-monic pressures equal to or higher than systemic blood pressure.

Quantification of shunt flow can be accomplished with a comparison of pulmonary blood flow to systemic blood flow. The Qp/Qs ratio has been used to measure the hemodynamic impact ASDs. This result is found by calculating flow across the pulmonary valve and dividing this by flow across the aortic valve (Figs. 5 and 6). Flow is calculated by multiplying the cross-sectional area of the outflow tract with the time-velocity integral (TVI). Therefore,

, _n (radius of RVOT)2 x TVIrvot Qp'Qs _ n (radius of LVOT)2 x TVIrVOT

Accurate Qp/Qs calculations necessitate precise measurements, particularly pertaining to the size of the valvular annuli, and are valid in the absence of significant regurgitant or stenotic lesions of the semilunar valves.

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