Abstract 1735: The Relationship of the Ventricular Septum and Right Ventricular Outflow Tract to the Right and Non-coronary Sinuses: Implications for Ablation of Ventricular Tachycardias
Background: Outflow tract ventricular tachycardias (VT’s) have been successfully ablated from the aortic sinuses. However, detailed anatomy of the interventricular septum (IVS) in this region is not well understood.
Purpose: The purpose of this study was to quantify the relationship of the right (RCS) and non-coronary aortic sinuses (NCS) to the IVS and RVOT to delineate the best anatomical approach for the ablation of aortic sinus VT’s.
Methods: Clinical data from 60 patients who underwent ablation of outflow tract VT’s from 12/04 to 3/07 was reviewed. Six patients had VT originating from the RCS of the aorta. Detailed analysis of the relationship of the RVOT and IVS to the aorta was then performed in 50 patients referred for cardiac CT angiography using a 64 slice dual source scanner (1.5 mm slices). This data was validated with histopathological data from 7 autopsy hearts.
Results: All patients whose VT originated from the RCS were successfully ablated from the RVOT. On CT, the IVS extended 18.2 ±2.0 mm superiorly beyond the base of the aortic valve along the RCS. No portion of the IVS was associated with the NCS. Inferior to superior, the amount of myocardium in proximity to the RCS decreased linearly, R2=0.96. Inferiorly, muscle bundles closest to the RCS were 4.7±1.0 mm, and at 18 mm superior to the valve, were 1.3±1.5 mm from the RVOT endocardium. These values were not significantly different from those obtained on histology: 5.1±1.6 mm, P=0.5; and 0.90±1.5, P=0.3; respectively.
Conclusions: Ventricular myocardium extending beyond the aortic valve along the RCS is well within the ablative footprint of catheters from the RVOT. No region of the IVS has exclusive access from the aorta.