Please assess the completion status of the following clinical trial:

Trial Title: Sildenafil After the Fontan Operation

Study Design Characteristics:
- Allocation: RANDOMIZED
- Intervention Model: CROSSOVER
- Observational Model: None
- Primary Purpose: TREATMENT
- Time Perspective: None
- Masking: QUADRUPLE
- Phase: PHASE2
- Number of Arms: 2.0

Eligibility Criteria:
Inclusion Criteria:~* 8 years of age or older~* All participants must have had Fontan completion~Exclusion Criteria:~* Height less than 132 cm~* Unable to participate in exercise testing due to medical restrictions or physical limitations~* Fontan baffle obstruction or single lung physiology~* Coarctation of the aorta or neo-aorta (BP gradient \> 20 mmHg)~* Severe ventricular dysfunction assessed qualitatively by echocardiography~* Severe atrioventricular valvar regurgitation assessed qualitatively by echocardiography~* Presence of electronic pacemaker~* History of treatment with sildenafil in the six weeks prior to enrollment in study~* Patients with severe renal impairment~* Patients with severe hepatic impairment~* Patients taking medications that inhibit or induce Cytochrome P450 3A4 (CYP3A4) (including grapefruit juice and St. John's Wort)~* Patients taking alpha-blockers and nitrates~* Parents/guardians or subjects who, in the opinion of the investigator, may be non-compliant with study schedules or procedures

- Gender: ALL
- Minimum Age: 8 Years
- Maximum Age: 40 Years
- Healthy Volunteers: f

Study Arms:
- Sildenafil, then Placebo (Type: ACTIVE_COMPARATOR): Sildenafil will be given at a dose of 20 mg three times-a-day for six weeks followed by a six week washout period followed by placebo for an additional six weeks.
- Placebo, then Sildenafil (Type: ACTIVE_COMPARATOR): Placebo will be given for six weeks followed by a six week washout period followed by Sildenafil which will be given at a dose of 20 mg three times-a-day for six weeks

Based on this trial design, predict the completion outcome and termination type (if applicable).