Background: The transseptal procedure can be stressful for beginning interventional cardiologists and sometimes even for experienced one as well, since this procedure can result in life-threatening complications. Pressure monitoring through the needle gives information on the left atrium only after piercing the septum and is not adequate enough for safety. We evaluated the usefulness of the ���tenting of the membrane of Fossa��� using a contrast agent (contrast cap) before piercing the septum in the transseptal procedures.
Methods and Results : The transseptal punctures were performed 44 times in 41 patients using BRK transseptal needle (SJM짰); 17 patients with rheumatic mitral valve stenosis, 17 with high lateral left sided accessory pathways, 6 with paroxysmal atrial fibrillation and 1 with left atrial ectopic tachycardia. A small amount of contrast agent was injected through the BRK needle when it was assumed to be directed at the Fossa ovalis. When the contrast dye collected under the conical cap of the membranous septum in the LAO projection it always indicated the Fossa. One exception was when it was the roof of the coronary sinus (CS). A ���contrast cap��� under the CS roof was very confusing for the fossa. It occurred in a patient with mitral stenosis who had a dilated CS. However, careful examination of the direction of disappearance of the contrast dye indicated CS blood flow. After piercing the Fossa with needle, contrast agent was injected again to confirm whether it was in the left atrium or not.
Conclusion : 1. A ���Contrast cap��� can be used as a safe landmark before piercing the Fossa ovalis. 2. Pressure monitoring is useful to estimate the chamber entered, but it can be incorrect and not very helpful in some situations such as atrial fibrillation. It could be safely combined or replaced with the contrast test used for assessing the left atrium using the BRK needle.