Anatomy and Pathology of the Tricuspid Valve

The tricuspid valve (TV), the morphologically right atrioventricular valve, guards the inflow junction between the right atrium and right ventricle. In functional anatomy, the valve does not consist only of leaflets. Instead, the valve complex is comprised of the annulus, leaflets, tendinous cords and papillary muscles occupying the inlet part of the right ventricle. Right sided structures have not had the extensive analysis when viewed in comparison to the systemic mitral valve. This is possibly due to the complexity of measuring the geometrically unusual shape of the right ventricular cavity, tricuspid valve, the curvature of the muscular ventricular septum and the right ventricular cavity wrapping around the systemic left ventricle. The route of inflow to outflow in the low pressure right ventricle (RV) is elongated compared to the left side of the heart. The right ventricle itself is an anterior structure forming the sterno-costal border of the heart beneath the sternum. The tricuspid valve is always associated with a morphological right ventricle. The chamber can be arbitrarily demarcated into three regions: inlet, apical and outlet, hence the concept of a tripartite ventricle. But, there are no anatomic borders for these regions within the right ventricle. The inflow region of the tricuspid valve is separated from the outflow pulmonary valve by several muscular structures; the ventricular infundibular fold (VIF), septomarginal trabeculation (SMT), septoparietal trabeculations (SPT) and the free standing subpulmonary infundibulum musculature (Fig. 1.1). Adjacent along the atrial side tricuspid valve complex are important structures like the triangle of Koch, tendon of Todaro, atrioventricular node continuing into the bundle of His and coronary sinus orifice (Fig. 1.2). Continuing improvements of imaging methods such as echocardiography, cardiac magnetic resonance imaging and computed tomography to examine in detail and analyse these structures and to measure the flow of deoxygenated blood to the lungs from the right heart allows critical analysis and on-going follow up of patients in normal and disease states.