Fumiya Yoneyama, MD, PhD | WithAScalpel

Left-to-Right vs Right-to-Left Shunting

👉Left-to-right shunts increase pulmonary blood flow and produce pulmonary overcirculation with volume loading of the involved chambers.
👉Right-to-left shunts bypass effective pulmonary oxygenation, causing systemic desaturation and reduced systemic oxygen delivery.
👉Shunt direction and magnitude depend on anatomy, pressure gradients, ventricular compliance, PVR/SVR balance, and pulmonary blood flow.

Fontan Circulation #2: Fundamental Principles

👉Fontan completion directs SVC and IVC flow to the pulmonary arteries without a subpulmonary ventricle.
👉Pulmonary blood flow depends on the CVP–atrial pressure gradient, low PVR, and unobstructed pulmonary pathways.
👉Low PVR supports ventricular preload and output, while elevated CVP predisposes to venous congestion and lymphatic failure.

Subaortic Membrane—Anatomy of LVOT Obstruction🚧

👉The subaortic membrane may involve the aortomitral curtain, anterior mitral leaflet, and adjacent septum, creating fixed LVOT obstruction.

Fontan Circulation #1: Staged Palliation for the Single Ventricle

👉Initial palliation balances Qp/Qs but often exposes the single ventricle to pulmonary flow–related volume overload.
👉The bidirectional Glenn directs SVC flow to the pulmonary arteries, reducing ventricular volume load while preserving IVC return.
👉Fontan completion routes both SVC and IVC flow to the lungs without a subpulmonary ventricle, requiring low PVR and adequate venous pressure.

Tricuspid Valve—Leaflet Anatomy☘️

👉The tricuspid valve consists of anterior, posterior, and septal leaflets, with variable leaflet morphology and chordal attachments, particularly along the septal leaflet.