Individuals who have undergone the Fontan procedure are uniquely dependent upon respiratory mechanics to support pulmonary blood flow (PBF). The investigators hypothesized that enhanced respiratory muscle function via inspiratory muscle training (IMT) would improve performance on cardiopulmonary exercise stress testing (CPET).

Adult Fontan subjects were recruited from 2 academic medical centers. Following characterization of pulmonary function and functional class, CPET was performed using incremental and constant work rate protocols. Subjects performed 6-8 weeks of IMT using a handheld inspiratory loading device (Threshold®, Philips); both exercise tests were then repeated. Patient-centered outcome data were collected before and after IMT (RAND-36 assessment and New York Heart Association (NYHA) functional class).

Inclusion Criteria:

Single ventricle physiology status post Fontan palliation

Exclusion Criteria:

• The presence of a sub-pulmonary ventricle
• Pregnancy or any contraindication to stress testing (e.g., uncontrolled symptomatic arrhythmia, severe systemic ventricular outflow tract obstruction or uncontrolled symptomatic heart failure).
• Height less than 4'11" due to limitations of the cycle ergometer.