In this two-part series on arrhythmias occurring above the semilunar valve, we discuss the relevant underlying anatomy and the technique for mapping and ablation above the aortic and pulmonic valve. In part I, we focused on ventricular arrhythmias, and in this paper (part II), we discuss the anatomy and present knowledge of the substrate mapped and ablated above the aortic valve for atrial tachycardia in certain unusual accessory pathways. The background anatomy of the aortic valve has been discussed in part I of this series, to which the reader is referred.
