Effects of Pulmonary Vasodilation Upon VA Coupling in Fontan Patients

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.

Inclusion Criteria:

- All consecutive patients with single ventricle hearts having passive pulmonary blood
flow presenting to the cardiac catheterization laboratory for clinically indicated
cardiac catheterization.

Exclusion Criteria:

- Patients with coarctation of the aorta or known bilateral femoral arterial obstruction

- Patients with known severe systemic venous/Fontan obstruction

- Patients already receiving sildenafil or other vasodilator therapy