Embryology, anatomy, and pathology of ventricular outflow tracts related to cardiac mapping and arrhythmias

Ventricular arrhythmias, especially those of non-ischemic heart diseases, arise mostly from the outflows. Differences in embryonic origin and phenotype may account for arrhythmogenic propensity of right ventricular outflow tract (RVOT). The anatomy of the ventricles may be divided into inflow, apex, and outflow. The RVOT and left VOT (LVOT) have a common origin, which may point to a common mechanism underlying outflow tract arrhythmias. During the fetal stage of development, the embryonic outflow tract (OFT) is fully incorporated into the RV myocardium and forms the RVOT and LVOT. Most of the tachyarrhythmias arising from the ventricular outflow have a substrate, accounting for triggered activity or reentry circuits, and are mostly non-ischemic. Arrhythmogenic cardiomyopathy is heredo-familial disorder due to mutations of genes encoding cell junction proteins, characterized by a pathognomonic substrate, namely fibro-fatty replacement of the ventricular myocardium. RVOT or LVOT tachyarrhythmias may occur in the absence of structural myocardial disease.