Coandă Effect in Cardiology

🔹 The Coandă Effect – General Concept

The Coandă effect is a fluid dynamics principle where a jet of fluid tends to be attracted to and follow a nearby surface, rather than traveling in a straight line.

In aviation, this explains how airflow attaches to curved wings.
In medicine (cardiology & echocardiography), this same principle applies to blood flow jets inside the heart.

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🔹 Coandă Effect in Cardiology

In echocardiography, the Coandă effect is particularly important in valvular regurgitation:

1. Mitral Regurgitation (MR)
   • A regurgitant jet from the mitral valve may not project centrally into the left atrium.
   • Instead, it can adhere to the atrial wall (posterior or lateral) and spread along it, appearing smaller or narrower on color Doppler than the actual severity.
   • This can underestimate MR severity if only jet area is measured.
2. Tricuspid Regurgitation (TR)
   • Similar wall-hugging eccentric jets may occur.
3. Aortic Regurgitation (AR)
   • The regurgitant jet may hug the LV wall instead of appearing centrally.

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🔹 Echocardiographic Importance

• Eccentric wall-hugging jets due to the Coandă effect often look deceptively small, despite being hemodynamically severe.
• Therefore, jet area alone is unreliable for grading regurgitation.
• Guidelines recommend using multiple parameters:
  • Vena contracta width
  • PISA (proximal isovelocity surface area)
  • Pulmonary vein flow reversal (for MR)
  • Regurgitant volume and effective regurgitant orifice area (EROA)

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🔹 Clinical Pearl

👉 If a jet is eccentric and hugs the wall (Coandă effect), always suspect that regurgitation severity may be worse than it looks.

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🔹 Summary Table

Aspect	Explanation
Definition	Fluid jet adheres to a nearby surface instead of flowing straight
In cardiology	Regurgitant valve jets hug atrial/ventricular walls on Doppler
Common valves	Mitral (most common), Tricuspid, Aortic
Appearance	Small, narrow jet area despite severe regurgitation
Problem	Leads to underestimation of severity if only jet area is used
Solution	Use multiparametric assessment (vena contracta, PISA, pulmonary vein flow, regurgitant volume)

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#	Key Point	Explanation
1	Definition	Fluid jet tends to attach to a nearby surface instead of flowing centrally.
2	Origin	Named after Henri Coandă (aerodynamics principle).
3	In cardiology	Seen in valvular regurgitant jets on echocardiography.
4	Most common valve	Mitral regurgitation (MR).
5	Other valves	Tricuspid regurgitation (TR), Aortic regurgitation (AR).
6	Jet appearance	Eccentric, wall-hugging jet on color Doppler.
7	Problem caused	Underestimation of regurgitation severity.
8	Jet area	Appears smaller than actual due to wall adherence.
9	Vena contracta	More reliable than jet area in presence of Coandă effect.
10	PISA method	Useful for quantification as it is less affected by eccentric jets.
11	Supporting signs	Pulmonary vein systolic flow reversal (in MR) indicates severity.
12	Left atrium	Enlarged in chronic severe MR despite small jet area.
13	Right atrium	Wall-hugging jets may be seen in TR.
14	Echocardiographic pitfall	Mistaking small jet for mild MR/TR.
15	Severity assessment	Must be multiparametric (not just jet area).
16	TEE utility	Transesophageal echo provides better visualization of eccentric jets.
17	Clinical risk	Missing diagnosis of severe regurgitation.
18	Eccentric vs central	Coandă effect mainly affects eccentric jets, not central ones.
19	Physical basis	Jet entrainment by nearby surface reduces visible spread.
20	Key message	If a jet hugs the wall → suspect more severe regurgitation than it looks.

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Short Questions & Answers – Coandă Effect in Cardiology

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Q1. What is the Coandă effect?
👉 The tendency of a fluid jet to attach to and follow a nearby surface instead of flowing centrally.

Q2. Which valvular lesion most commonly demonstrates it?
👉 Mitral regurgitation (eccentric MR jet hugging LA wall).

Q3. What is the main echocardiographic pitfall caused by the Coandă effect?
👉 Underestimation of regurgitation severity by jet area measurement.

Q4. How does an eccentric MR jet appear on color Doppler due to Coandă effect?
👉 Small, wall-hugging, and deceptively less severe.

Q5. Which parameter is more reliable than jet area in Coandă effect?
👉 Vena contracta width.

Q6. What Doppler method helps quantify severity despite Coandă effect?
👉 PISA (proximal isovelocity surface area) method.

Q7. What additional clue suggests severe MR with Coandă effect?
👉 Pulmonary vein systolic flow reversal.

Q8. Which chamber is involved in TR with Coandă effect?
👉 Right atrium (RA wall-hugging jet).

Q9. Which imaging modality is superior for eccentric MR assessment?
👉 Transesophageal echocardiography (TEE).

Q10. What is the key clinical pearl about Coandă effect?
👉 If the jet hugs the wall, severity is usually worse than it appears.

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Short Q&A Block – Coandă Effect in Cardiology

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Q1. Define the Coandă effect.
👉 The tendency of a fluid jet to adhere to a nearby surface instead of flowing centrally.

Q2. In cardiology, where is it most often observed?
👉 In eccentric mitral regurgitation jets hugging the left atrial wall.

Q3. What diagnostic error does the Coandă effect cause?
👉 Underestimation of regurgitation severity.

Q4. Which measurement is unreliable when Coandă effect is present?
👉 Jet area on color Doppler.

Q5. Which measurement is more reliable in this setting?
👉 Vena contracta width.

Q6. Which Doppler method helps quantify regurgitation despite Coandă effect?
👉 PISA (proximal isovelocity surface area).

Q7. What supportive finding indicates severe MR with Coandă effect?
👉 Pulmonary vein systolic flow reversal.

Q8. Besides MR, which other lesion can show Coandă effect?
👉 Tricuspid regurgitation (eccentric RA wall-hugging jet).

Q9. Which imaging modality improves visualization of eccentric jets?
👉 Transesophageal echocardiography (TEE).

Q10. What is the key clinical pearl about the Coandă effect?
👉 If the jet hugs the wall, severity is worse than it appears.

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