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| Transesophageal Echocardiographic Examination |
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Transesophageal echocardiography is an important intraoperative monitor not only for diagnosis and or confirmation of atrial septal communications, but also for estimating pulmonary artery pressures, and quantifying the degree of shunting. Furthermore, functional consequences of the shunting can be evaluated by assessing degree of chamber enlargement . Following the procedure TEE has added utility in assessing adequacy of the surgical repair. |
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2D and Examination Doppler |
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A thorough 2-D examination can characterize the specific defect and associated anomalies. The entire interatrial septum should be carefully scanned from multiple imaging planes to characterize the location and size of the ASD. The various subtypes are classified according to the location of defect and the TEE examination should be specifically focused on the imaging planes in region of the specific defect. |
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| Ostium secundum defects involve an absence of tissue in region of the fossa ovalis. The mid-esophageal bicaval, right ventricular inflow-outflow and 4-chamber views with particular focus on the region of the fossa ovalis will enable the echocardiographer to delineate the size of the defect and the direction of shunting. False positive results (detected as echocardiographic drop out in the area of the fossa ovalis) can be avoided with the use of color flow Doppler and a contrast study. Color flow Doppler will demonstrate flow across the region of the defect and a contrast injection may display contrast in the left atrium. |
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| Ostium Secundum Defect |
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| Ostium Secundum Defect Video |
Ostium Secundum Defect Video |
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| Ostium primum defects involve a lack of tissue in the lower portion of the interatrial septum to the level of the atrioventricular valves. Mid-esophageal 4-chamber view will typically delineate the defect in the lower portion of the septum. Color flow Doppler will display shunt flow in the region of the defect. |
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| Ostium Primum Defect |
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| Ostium Primum Defect Image |
Ostium Primum Defect Video |
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| Since these defects are often associated with a cleft in the anterior mitral valve leaflet a through evaluation for detection, mechanism and quantification of mitral regurgitation should be elucidated. |
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| Cleft Mitral Valve Image |
Cleft Mitral Valve Video |
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| Sinus venosus defects are located in the upper portion of the interatrial septum near the entrance to where the superior vena cava enters the right atrium. A careful TEE evaluation of the interatrial septum from multiple imaging planes is necessary to avoid making an incorrect diagnosis. A mid-esophageal bicaval imaging plane best delineates this defect. As mentioned, this ASD is associated with partial anomalous pulmonary venous connections. |
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| Sinus Venosus Defect |
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| Sinus Venosus Defect Image |
Sinus Venosus Defect Video |
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| Indirect 2-D findings associated with ASD include a dilated right atrium and ventricle, paradoxical motion of the interventricular septum and abnormal ventricular septal geometry characterized by diastolic flattening of the septum due to right ventricular volume overload. |
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| Paradoxical Interventricular Septal Motion Video |
Diastolic Septal Flattening Video |
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| Agitated saline contrast injection or 'bubble study' is a technique used to detect intracardiac shunting through an ASD. Demonstration of contrast within the left atrium suggests right to left shunting and a negative contrast effect is suggestive left to right shunting. |
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| Positive Agitated Saline Contrast |
Negative Agitated Saline Contrast |
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| Transesophageal echocardiography is also useful in the assessment of shunt flow with the use of Doppler techniques. Magnitude of an intracardiac shunt can be determined by flow ratios between the pulmonary (Qp) and systemic circulation (Qs). Stroke volume of the pulmonic valve and aortic valve or left ventricular outflow tract can be calculated and the magnitude of the Qp/Qs ratio determined from the following: |
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(Qp) Pulmonic valve = .785 x d 2 x TVI (PV)
(Qs) Aortic valve = .785 x d 2 x TVI (AV)
(SV, stroke volume; d, diameter; TVI, time velocity integral) |
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Estimates of pulmonary artery systolic pressure can be derived from the peak velocity of the tricuspid regurgitant jet (if present) with the use of the modified Bernoulli equation along with an estimate of right atrial pressure. The modified Bernoulli equation may also aide in calculating pulmonary artery diastolic pressure from the end-diastolic velocity profile of the pulmonary regurgitation velocity profile. |
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