What is the recommended diagnostic work‑up to evaluate a patent foramen ovale (PFO) or atrial septal defect (ASD) in a patient with right‑ventricle (RV) dilatation?

Diagnostic Work-up for PFO/ASD with RV Dilatation

When RV dilatation is present in the context of suspected PFO or ASD, proceed directly to transesophageal echocardiography (TEE) with saline contrast and Valsalva maneuver to definitively characterize the defect, assess shunt size and direction, evaluate for associated anomalies, and determine suitability for percutaneous closure.

Initial Diagnostic Approach

The presence of RV dilatation fundamentally changes your diagnostic strategy—this suggests a hemodynamically significant left-to-right shunt (more consistent with ASD than simple PFO) and requires comprehensive anatomic characterization beyond basic detection.

Why TEE is Essential

Transesophageal echocardiography has superior sensitivity compared to transthoracic imaging for detecting interatrial communications and is specifically recommended for detailed visualization when intervention is being considered 1. The 2014 EACVI guidelines explicitly state that TEE is indicated for evaluation of atrial septal defect morphology 2.

Critical TEE Assessment Components

When performing TEE in this context, you must systematically evaluate:

1. Defect Classification

• Distinguish ASD from PFO: ASDs appear as a membrane with a hole and show perpendicular contrast jet flow across the septum, while PFOs show a channel-like appearance with contrast flowing toward the inferior vena cava 3, 4
• ASD subtypes: Identify secundum (most common), primum, sinus venosus (superior or inferior vena cava type), or coronary sinus defects 2

2. Shunt Characterization

• Direction: Use color Doppler and saline contrast injection to confirm shunt direction—RV dilatation suggests predominant left-to-right shunting 1
• Size assessment: Measure largest defect diameter, though estimating PFO size based on contrast amount may be unreliable 1
• Valsalva maneuver: Increases right atrial pressure and enhances sensitivity for detecting right-to-left shunting 1

3. Anatomic Details for Potential Closure

• Rim assessment: Measure tissue rims at all segments (superior vena cava, aortic, anterosuperior, anteroinferior, inferior, posterior/inferolateral)—rim width <5mm (except aortic side) generally precludes device closure 2
• Associated findings: Look for atrial septal aneurysm (≥10mm protrusion, marker of increased embolic risk), Eustachian valve, Chiari network, tissue strands crossing defect 1, 2, 4

4. Exclude Other Pathology

The work-up must rule out alternative embolic sources that could coexist 1:

• Cardiac tumors (myxoma, papillary fibroelastoma)
• Valve vegetations (bacterial or non-bacterial)
• Atrial thrombi
• Aortic atherothrombosis

5. Pulmonary Venous Anatomy

Critical pitfall: Sinus venosus ASDs invariably have partial anomalous pulmonary venous drainage—TEE must demonstrate whether right upper or lower pulmonary veins drain into superior or inferior vena cava 2

Complementary Imaging

3D Echocardiography

Offers improved spatial orientation and en-face views of the septum, particularly valuable for complex defects and fenestrations 2, 5. Useful for defining multiple defects that might be missed on 2D imaging.

Cardiac CT Angiography

While not first-line, CT can differentiate PFO from ASD based on contrast jet direction and septal appearance if echocardiography is non-diagnostic 3, 4. However, TEE remains the gold standard.

Cardiac MRI

Provides additional information on RV size/function quantification and can assess for other structural abnormalities 6, though not mentioned in primary guidelines for this indication.

Clinical Context Matters

The significance of your findings depends heavily on presentation:

• If cryptogenic stroke: The combination of interatrial shunt with RV dilatation suggests a large ASD rather than simple PFO, requiring different risk stratification 7
• If RV enlargement without stroke: ASD closure is indicated for hemodynamically significant shunts causing RV dilatation 8
• Age and risk factors: ASD patients with stroke tend to be older with more cardiovascular risk factors compared to high-likelihood PFO-related strokes 7

Key Pitfalls to Avoid

1. Don't assume PFO: RV dilatation strongly suggests ASD with significant left-to-right shunt, not simple PFO
2. Don't miss sinus venosus defects: These are easily overlooked but always have anomalous pulmonary venous drainage 2
3. Don't rely on transthoracic echo alone: TEE is mandatory for adequate anatomic characterization when intervention is considered 1, 2
4. Don't forget to assess for pulmonary hypertension: Monitor oxygen saturation during TEE in patients with suspected pulmonary hypertension 2