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TEE-Guided Cardiac Shunt Assessment: Procedural Steps for PFO/ASD Evaluation

Transesophageal Echocardiography (TEE) is the gold standard for detecting and characterizing interatrial communications (patent foramen ovale/PFO, atrial septal defect/ASD). The following outlines a standardized approach for comprehensive shunt assessment using 2D/3D TEE with color Doppler and contrast. This is a technical overview for trained professionals; not a substitute for formal TEE certification.

Pre-Procedure

  • Indications: Cryptogenic stroke, TIA, decompression illness, preoperative screening, unexplained hypoxemia.
  • Consent & Preparation: NPO 6 hrs, IV access, monitoring (ECG, SpO2, BP), topical pharyngeal anesthesia, moderate sedation (midazolam/fentanyl) per protocol.
  • Probe Preparation: Degassed saline flush, test 2D/3D/color/Doppler functions.

Systematic Imaging Protocol

1. Mid-Esophageal (ME) Views (Baseline Anatomy)

  • ME 4-Chamber (0–10°): Assess atrial/ventricular size, function, septal motion.
  • ME 2-Chamber (90°): LA appendage, mitral valve.
  • ME Long Axis (120–140°): Aortic valve, LVOT, mitral valve coaptation.
  • ME AV SAX (45–60°): Aortic valve en face (3D preferred).

2. Interatrial Septum (IAS) Interrogation — The Core Shunt Assessment

ME Bicaval View (90–110°): Rotate from ME 4-chamber counterclockwise. This is the primary view for IAS. Visualizes SVC, IVC, RA, LA, IAS, RA appendage.

  • Identify fossa ovalis (thin, translucent portion of IAS).
  • Assess septal anatomy: flap valve (septum primum), septum secundum rim, tunnel length.
  • Color Flow Doppler (CFD): Nyquist 50–60 cm/s, gain optimized. Scan entire IAS in multiple planes (rotate 0–180°). Look for flow crossing septum.

3. Provocative Maneuvers (Increase RA Pressure → Right-to-Left Shunt)

  1. Valsalva Maneuver (Strain Phase): Patient bears down against closed glottis (or ventilator circuit). Increases RA pressure transiently.
  2. Cough/Sniff: Alternative if Valsalva not feasible.
  3. Leg Raise / Passive Leg Elevation: Increases venous return.
  4. Rapid Saline Flush (Contrast): 10 mL agitated saline via peripheral IV during Valsalva release (or spontaneous contrast echo).

Positive Contrast Study: Microbubbles appear in LA within 3 cardiac cycles (early = PFO; late = pulmonary shunt). Count bubbles: <10 = small; 10–30 = moderate; >30 = large shunt.

4. Pulmonary Vein & LA Assessment

  • ME Pulmonary Vein View (0–30°, withdraw slightly): Assess PV flow (systolic/diastolic dominance), LA size, LA appendage thrombus.
  • 3D Zoom/Full Volume: En face view of IAS from LA side — measures PFO/ASD dimensions, shape, relationship to SVC/IVC, aortic root, coronary sinus.

5. Transgastric & Deep Views (If Needed)

  • TG Basal SAX (0°): Alternative IAS view if ME limited.
  • Deep Transgastric (120–140°): LV apex, apical thrombus.

Key Measurements for Closure Device Sizing

  • Maximal PFO/ASD diameter (2D & 3D, multiple planes).
  • Tunnel length (flap to rim).
  • Rim widths: Aortic, SVC, IVC, coronary sinus, posterior.
  • LA/RA dimensions (volume by 3D or biplane).
  • Eustachian valve / Chiari network prominence (may direct shunt).

Documentation & Reporting

  • Still images + video loops of all views (rest, Valsalva, contrast).
  • Measurements with calipers (leading-edge to leading-edge).
  • Shunt grade (0–3), direction, provocative maneuver used.
  • Device suitability assessment (rim adequacy, anatomy).

Safety & Complications

  • Esophageal perforation (rare, <0.01%), dental injury, arrhythmia, aspiration, sedation complications.
  • Continuous monitoring + dedicated sedation provider recommended.

Mastery of TEE shunt assessment requires structured training (NBE/ASCEeXAM), mentored cases, and ongoing practice. It is a critical skill for structural heart teams.

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