The anatomic substrates for outflow tract arrhythmias.

Much has been learned regarding the cellular and molecular mechanisms involved in producing idiopathic ventricular tachycardias originating from the ventricular outflow tract. Questions remain, however, regarding their genesis. In part, this reflects the uncertainty regarding the anatomic arrangement of their myocardial components. This is exacerbated by the lack of consensus regarding the appropriate terms to describe their components, as shown by the current use of "cusp," used interchangeably to describe either the valvar sinuses or the leaflets of the arterial valves. Such uncertainty can be resolved only by providing precise definitions of leaflets, sinuses, and the sinutubular junction. Further problems are created when the arterial roots are described in an attitudinally incorrect manner. Current techniques reveal the location of the cardiac components as they are positioned within the thorax. In this review, we discuss these potential difficulties, putting them into the context of the anatomy of the ventricular outflow tracts as revealed by virtual dissection of computed tomographic datasets. We provide a brief account of cardiac development, suggesting that such evidence can provide vital clues to the potential origins of arrhythmias originating from the myocardial components of the ventricular outflow tracts.