Pulmonary Veins: Unique Role Carrying Oxygenated Blood to the Heart

Pulmonary veins are the only veins in the adult body that carry oxygen-rich blood. This is a fundamental exception to the "arteries = oxygenated, veins = deoxygenated" rule.

Anatomy & Flow

• Four Pulmonary Veins: Two from each lung (superior/inferior) → drain into left atrium.
• Oxygen Saturation: ~98–100% (post-pulmonary capillary equilibration).
• Pressure: Low (~8–10 mmHg) – thin-walled, no valves.

Contrast: Pulmonary Arteries

• Carry deoxygenated blood from right ventricle → lungs.
• Only arteries with deoxygenated blood in adult circulation.

Clinical Relevance

• Atrial Fibrillation Ablation: Pulmonary vein isolation (PVI) – ectopic foci in PV sleeves trigger AF.
• Pulmonary Venous Hypertension: Left heart failure → ↑ LA pressure → ↑ PV pressure → pulmonary edema.
• Total Anomalous Pulmonary Venous Connection (TAPVC): Congenital – PVs drain to systemic venous system → cyanosis.
• Cor Triatriatum: Membrane partitions LA, obstructing PV drainage.

Fetal Circulation Difference

In fetus, pulmonary veins carry oxygenated blood from placenta → umbilical vein → ductus venosus → IVC → RA → foramen ovale → LA. Postnatal transition switches source to lungs.

Remember: Pulmonary veins → Left Atrium → Left Ventricle → Aorta → Body. They complete the oxygenated circuit.