Makindo Medical Notes

Related Subjects: |Congenital Acyanotic Heart Disease |Congenital Cyanotic Heart Disease |Cardiac Embryology |Cyanosis - Central and Peripheral |Down's syndrome (Trisomy 21) |Tetralogy of Fallot |Patent Foramen Ovale (PFO)

🫀 Introduction

• Patent Foramen Ovale (PFO): An embryological flap-valve between LA ↔ RA that normally closes after birth, but persists in ~25% of adults.
• In utero it is essential for fetal circulation, but persistence allows potential right → left shunting in later life.
• Shunting is usually silent but may become clinically relevant during raised RA pressure (e.g. Valsalva manoeuvre, coughing, straining).

⚖️ Aetiology & Pathophysiology

• Not inherently pathological — most with a PFO never have problems.
• 🧠 Paradoxical embolism: A clot from a DVT bypasses the pulmonary filter via PFO → enters systemic arterial circulation → possible stroke.
• Mechanism: RA pressure > LA pressure (e.g. straining) opens the flap → transient R→L shunt.
• Bubble contrast echo can visualise shunting (≥50 bubbles = significant).

🧠 DVT/PFO/Stroke Hypothesis

• PFOs are found more often in cryptogenic stroke patients than in the general population.
• But ⚠️ association ≠ causation — could be a marker for another risk (e.g. paroxysmal AF).
• Always exclude other causes (especially AF with prolonged monitoring) before attributing stroke to a PFO.

✅ Arguments for Closure

• Younger patient (<55), no other stroke risk factors.
• Multiple embolic strokes in different vascular territories.
• Large or aneurysmal PFO, significant bubble study shunt.
• No evidence of PAF after prolonged monitoring (≥7 days Holter).
• No other indication for anticoagulation.

❌ Arguments against Closure

• Older age (>55) — PFO less likely to be causal.
• Small, non-aneurysmal PFO.
• Clear alternative risk (AF, thrombophilia needing anticoagulation, OCP/HRT-related DVT risk).

🩺 Clinical Clues

• Stroke/TIA preceded by Valsalva (lifting, coughing, straining).
• Multiterritory embolic stroke pattern.
• History of DVT/PE, or procoagulant state.

📊 Trial Evidence (2017)

💬 Key Teaching Point

PFO closure reduces but does not eliminate stroke risk. Absolute risk reduction is small (<1% per year). Trade-off: fewer strokes vs ↑ AF and device risks. Decision = shared discussion, weighing uncertainty, patient values, and stroke pattern.