The Limbic Ledge

SINCE its initial description,' transseptal left heart catheterization has been increasingly used as a diagnostic and a research technic. While refinements in instrumentation have emerged 2, 3 the method of septal puncture has remained unchanged. The original description of septal puncture required that the catheter and needle assembly be positioned in the right atrium at a point near the junction of the lower and middle thirds of the atrium against the septal wall. With the tip pointing posteriorly and to the left, the needle was unsheathed and passed through the septum into the left atrium. The uncertainty and anxiety in locating the best puncture site are implied by Cope 4 and Aldridge5 who have used the aortic valve, visualized by a retrograde aortic catheterization as an indirect aid to septal puncture site, but to our knowledge no direct, right atrial landmark has been utilized for this objective. In addition no modification of the puncture site has been. suggested to accommodate the anatomic variations found in abnormal hearts. This paper describes an aid to transseptal catheterization based on the identification of the limbus fossa ovalis, the ledge overhanging the fossa. The application of this modified technic and its increased safety are presented in a series of 145 patients.