To the Editor— The anatomy of para-Hisian arrhythmias

In the “Hands On” vignette published in relation to para-Hisian arrhythmias, 1 Enriquez A. Tapias C. Rodriquez D. Liang J. Marchlinski F. Saenz L. Garcia F. How to map and ablate parahisian ventricular arrhythmias. Heart Rhythm. 2018; 15: 1268-1274 Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar the authors referenced one of the early publications by one of us. 2 Soto B. Becker A.E. Moulaert A.J. Lie J.T. Anderson R.H. Classification of ventricular septal defects. Br Heart J. 1980; 43: 332-343 Crossref PubMed Scopus (243) Google Scholar Our insights of ventricular septal anatomy have now changed significantly, aided by virtual dissection of computed tomography data sets. 3 Mori S. Spicer D.E. Anderson R.H. Revisiting the anatomy of the living heart. Circulation J. 2016; 80: 24-33 Crossref PubMed Scopus (43) Google Scholar It is incorrect to suggest that the muscular ventricular septum can be separated into inlet, apical, and outlet components. Because of the “wedged” position of the subaortic outflow tract, the so-called “inlet” septum separates the inlet of the right ventricle from the outlet of the left. The “outlet” septum is no more than the free-standing muscular subpulmonary infundibular sleeve. It is best, therefore, to describe the ventricular septum as having muscular and membranous components.