What is transseptal puncture and what is it used for in EP?

• A. A puncture through the interatrial septum to access the left atrium, enabling left-sided ablation including atrial fibrillation
• B. A puncture through the coronary sinus
• C. A puncture through the right ventricle to access the left ventricle
• D. A puncture to access the aorta

Answer: (A)

Transseptal puncture is the technique of crossing the interatrial septum from the right atrium into the left atrium to gain access for left‑sided heart procedures. In electrophysiology, this is essential because many arrhythmia substrates, especially those involved in atrial fibrillation, reside in the left atrium and around the pulmonary veins, which cannot be reached from the right atrium with standard catheters. The puncture is typically performed at the fossa ovalis under imaging guidance, and after access is secured, a sheath and ablation catheters are advanced into the left atrium to map and ablate targets such as isolating the pulmonary veins.

This method is distinct from punctures of the coronary sinus, which is a venous structure around the heart; it is not a route to the left ventricle from the right ventricle, and it does not involve accessing the aorta. Those other punctures serve different purposes and pathways, whereas transseptal puncture specifically provides a passage into the left atrium for left‑sided ablation needs.