During EP studies, which anatomical structure can complicate access to the coronary sinus ostium?

During EP studies, which anatomical structure can complicate access to the coronary sinus ostium?

• A. Thebesian Valve
• B. Eustachian Valve
• C. Chiari Network
• D. Thebesian Vein

Answer: (A)

A prominent Thebesian valve at the coronary sinus ostium can directly obstruct access during EP studies. This small flap in the right atrium sits right at the opening of the coronary sinus; when it is enlarged or mobile, it can cover or narrow the ostium, making catheter entry difficult. In practice, this may require adjusting the catheter shape or deflection, or using a different approach to achieve cannulation. The other structures described can affect catheter navigation in the right atrium in their own ways, but they do not typically block the coronary sinus ostium itself: the Eustachian valve is at the IVC entrance and can misdirect catheters, the Chiari network is a net-like RA structure that can entangle wires, and the Thebesian vein is a small intramural drainage vessel not involved in obstructing the CS ostium.

A prominent Thebesian valve at the coronary sinus ostium can directly obstruct access during EP studies. This small flap in the right atrium sits right at the opening of the coronary sinus; when it is enlarged or mobile, it can cover or narrow the ostium, making catheter entry difficult. In practice, this may require adjusting the catheter shape or deflection, or using a different approach to achieve cannulation. The other structures described can affect catheter navigation in the right atrium in their own ways, but they do not typically block the coronary sinus ostium itself: the Eustachian valve is at the IVC entrance and can misdirect catheters, the Chiari network is a net-like RA structure that can entangle wires, and the Thebesian vein is a small intramural drainage vessel not involved in obstructing the CS ostium.