Anesthesiology APPLIED Exam › OSCE: echocardiography and POCUS

Atrial septal defect and aortic dissection

OSCE: echocardiography and POCUS·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

Echo station. A 59-year-old man, 88 kg, with tearing chest pain radiating to the back, is anesthetized for emergency repair of an ascending aortic dissection. The ME ascending aortic long-axis loop shows a thin linear echo inside the ascending aorta that flutters independently of the aortic wall. Color flow is brisk and bright on one side of it and dull and swirling on the other. The ME long-axis loop shows a new central regurgitant jet.

Question

Describe what you see, and what else will you look for before the surgeon opens the chest?

Ideal answer

HeadlineA mobile intimal flap separating two lumens in the ascending aorta: Stanford type A dissection. Then I check the four complications that change the operation.

Rule out artifact. It moves independently of the wall, appears in more than one view, and is distinct from reverberation off a calcified wall or a catheter.¹
Identify the lumens. True lumen: systolic expansion, brisk forward systolic flow; false lumen: diastolic expansion, sluggish flow, spontaneous contrast or thrombus.¹
Aortic regurgitation and its mechanism; then the coronaries. Root dilation, cusp prolapse, or the flap prolapsing through the valve;¹ a new regional wall motion abnormality suggests coronary ostial involvement.
Pericardial effusion; then the extent. Effusion points to false-lumen rupture and a poor prognosis;¹ then the flap followed down the descending aorta, short- and long-axis.
Report in that order; keep rate and pressure low. The surgeon plans from each finding.

Breaking down the answer

Aortic dissection and the presence or absence of an ASD are both on the outline's echo list, with 2D and color flow Doppler but no pulsed- or continuous-wave Doppler.²

Finding	Best view	What it identifies
Mobile flap dividing two lumens	ME ascending aortic LAX and SAX; descending aortic SAX (0°) and LAX (~90°)³	Dissection; ascending involvement = type A
Systolic expansion, forward systolic flow	Any aortic view	True lumen¹
Diastolic expansion, smoke, thrombus, absent or reversed flow	Any aortic view	False lumen¹
Flow through a break in the flap	Color over the flap	Entry or re-entry tear¹
Gap in the mid-septum with color flow	ME bicaval, ME four-chamber	Secundum ASD
Dilated RV, diastolic septal flattening	ME four-chamber, TG mid-papillary SAX	Left-to-right shunt volume load⁴

A real acute aortic dissection loop, 2D and color flow side by side:

TEE is a definitive test here — its sensitivity approaches 100% for both type A and type B dissection.¹ Its weakness is the distal ascending aorta and proximal arch, hidden behind the trachea.¹
Reverberation is the trap — artifacts in the ascending aorta cause false positives;¹ a line that moves with the wall, stays at a fixed depth, or crosses the aortic wall is artifact.
The complications set the surgery — aortic regurgitation decides repair or replacement of the valve, and coronary involvement can mean bypass grafting.
Lumen identity matters for cannulation — the perfusion cannula belongs in the true lumen; in the descending aorta the false lumen is usually the larger one.¹

Follow-up question

While surveying the heart, you rotate to the ME bicaval view and see a gap in the middle of the atrial septum with continuous color flow from the left atrium into the right atrium. The RV looks dilated. What is it, and does it change anything today?

Follow-up answer

HeadlineA secundum atrial septal defect, the most common type, with left-to-right flow; I tell the surgeon.

Its mid-septal position makes it secundum, usually from a deficiency of the septum primum;⁴ the dilated RV is the volume load of a chronic left-to-right shunt.⁴ It can be closed on bypass, and it opens a path for paradoxical air or clot whenever right atrial pressure rises above left, as with coughing, Valsalva or positive pressure,⁴ so I de-air every line meticulously. A basic examination identifies it, but an advanced echocardiographer defines it before closure, especially to exclude a sinus venosus or primum defect.³ I reassess the RV after separation from bypass.

Pitfalls that cost points

Calling the bigger lumen false by size alone in the ascending aorta.
Reporting an ASD without commenting on RV size or the risk of paradoxical embolism.
Forgetting the blind spot of the distal ascending aorta and proximal arch.

Rapid-fire

Q: How common is a patent foramen ovale? A: It is present in about 20–25% of adults.⁴

Q: What size is a small secundum ASD? A: Less than 5 mm in maximal diameter.⁴

Q: Stanford classification? A: Type A involves the ascending aorta; dissections of the arch or descending aorta that spare the ascending aorta are type B.¹

Q: Which maneuver provokes right-to-left flow in a bubble study? A: Release of a Valsalva, or a cough, which transiently raises right atrial pressure above left.⁴

Numbers to know

Item	Value
TEE sensitivity, dissection	Approaching 100%¹
Descending aortic SAX / LAX	0° / ~90°³
PFO prevalence	~20–25% of adults⁴
RV basal diameter, dilated	>41 mm⁴
Small ASD	<5 mm⁴

Sources

1.Multimodality Imaging of Diseases of the Thoracic Aorta in Adults: From the ASE and the EACVI · ASE/EACVI, 2015 · asecho.orgGoldstein et al., J Am Soc Echocardiogr 2015;28:119-82; Table 7 and the TEE section on aortic dissection.
2.APPLIED Exam Objective Structured Clinical Examination (OSCE) Content Outline · ABA · theaba.org
3.Basic Perioperative Transesophageal Echocardiography Examination: A Consensus Statement · ASE/SCA, 2013 · asecho.org
4.Guidelines for the Echocardiographic Assessment of Atrial Septal Defect and Patent Foramen Ovale · ASE/SCAI, 2015 · asecho.org

Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.