Intracardiac Ultrasound Imaging During Transseptal Catheterization

Study objective: The purpose of this study was to assess the feasibility of using small 12.5- or 20-MHz intracardiac ultrasound catheters to image the fossa ovalis and guide transseptal catheterization.

Design: The study was performed in three phases. First, in vitro imaging of human autopsy hearts was performed to define the intracardiac ultrasound appearance of the fossa ovalis and transseptal apparatus. Subsequently, the optimum approach for imaging the fossa ovalis in vivo was established in 30 patients. Finally, intracardiac ultrasound imaging was performed during transseptal catheterization of 10 patients undergoing percutaneous mitral commissurotomy.

Interventions: Intracardiac ultrasound imaging was performed with a 12.5- or 20-MHz single-element mechanical device in which a central imaging core is rotated within a 6F polyethylene sheath. Measurements and results: In both in vitro and in vivo studies, the fossa ovalis was easily identifiable as a thin membranous region surrounded by the thicker muscular portion of the interatrial septum. Initial in vivo studies established venous access by the femoral route to be superior to the internal jugular approach for catheter introduction. Studies performed during transseptal catheterization established the utility of using the fluoroscopic image of the catheter adjacent to the fossa ovalis to generate a guiding shot for positioning the transseptal apparatus. In addition, distention of the fossa prior to needle perforation could be demonstrated. However, since it was often difficult to track the tip of the needle, actual puncture of the fossa was rarely demonstrated.

Conclusions: Intravascular ultrasound imaging can precisely locate the fossa ovalis in virtually all subjects. It therefore may assist transseptal catheterization.