The Fontan operation for children with congenital heart disease places them in a physiological state of mildly elevated systemic venous pressure and low-normal cardiac output. Consequently, close follow-up is imperative, yet currently no method is available to obtain Fontan pressures without direct measurements in the cardiac catheterization laboratory while supine and sedated. We hypothesize that by suturing the CardioMEMS sensor device into the Fontan conduit during the standard Fontan operation for a child with single ventricular physiology, clinicians can accurately retrieve Fontan pathway pressure measurements noninvasively during normal physiological states.