Mechanics of the Functionally Univentricular Heart-How Little Do We Understand and Why Does It Matter?

Despite improved surgical techniques, preoperative and postoperative care, patients with functionally univentricular hearts (UVH) continue to have high morbidity and mortality and a decreased lifespan. Ventricular systolic and diastolic dysfunction is a major contributing factor to Fontan patient outcome. The evaluation of ventricular function in patients with UVH is particularly challenging. At a cellular and ultrastructural level, there are inherent differences between single and biventricular right and left ventricles. In addition, there are variable loading conditions throughout the stages of single ventricle palliation as well as variable ventricular remodelling in response to these changes. We will discuss the traditional and newer, advanced echocardiographic techniques that have been applied to evaluate ventricular function in patients with UVH. Each method has inherent advantages and disadvantages when applied to this population. The use of novel techniques including deformational imaging and 3-dimensional echocardiography will hopefully provide a more comprehensive understanding of the performance of the single ventricle, and how ventricular dysfunction affects the clinical status of patients after Fontan palliation.