Effects of Pulmonary Vasodilation Upon VA Coupling in Fontan Patients

• Effective arterial elastance (Ea) [ Time Frame: Acute, approximately 10-15 minutes ] [ Designated as safety issue: No ]
  Patients will undergo hemodynamic evaluation while receiving inhaled nitric oxide. After the measurements are made the nitric oxide will be discontinued. The primary outcome is the change in effective arterial elastance, a value obtained from ventricular pressure-volume assessment, before and while receiving nitric oxide.
  
  

Patients with complex congenital heart disease and single ventricle physiology typically undergo a staged surgical palliation to a situation where the single ventricle is recruited as the systemic pumping chamber and some (following a Glenn surgery) or all (following a Fontan surgery) systemic venous return flows passively to the lungs. While this physiology eliminates ventricular volume loading and normalizes systemic arterial oxygen saturations, there remain a number of physiologic burdens that limit functional capacity and life expectancy. Evidence suggests that this surgical imposition of the systemic and pulmonary vascular beds in series results in ventricular loading conditions that adversely affect ventricular function. At present, there exist limited means by which to mitigate these burdens, however, new therapies directed at reducing total pulmonary resistance may favorably affect patients with this physiology by reducing systemic venous pressures and improving both ventricular preload and afterload. One such therapy is inhaled nitric oxide (iNO), which is a selective pulmonary vasodilator that has been shown to reduce total pulmonary resistance and improve systemic venous pressures in this patient population. However limited data exist regarding the affects of pulmonary vasodilators like iNO on ventricular loading and ventricular-arterial coupling. This study proposes to assess the effects of pulmonary vasodilator therapy upon ventricular loading and ventricular-arterial coupling in single ventricle patients with passive pulmonary blood flow presenting for elective cardiac catheterization. The study components include obtaining routine (they would be obtained as a part of the clinically-indicated catheterization) hemodynamic measurements with hi-fidelity catheters rather than standard fluid-filled catheters, as well as simultaneous additional measurements with the same catheters at rest and during administration of iNO.