Effect of sildenafil on haemodynamic response to exercise and exercise capacity in Fontan patients

Aims: We sought to assess the effects of sildenafil on exercise capacity and haemodynamic response to exercise in Fontan patients. Methods and results: We prospectively studied 27 patients with Fontan circulation (age 22.8 ± 4.9 years). All patients underwent a baseline exercise test with non-invasive measurement of cardiac index (CI) and pulmonary blood flow (PBF) index, and peak exercise oxygen uptake (VO₂). After the baseline test, patients were randomly assigned to receive either a single 0.7 mg/kg body weight oral dose of sildenafil citrate (n = 18) or no treatment (control group, n = 9). After 1 h of rest, all patients performed a second exercise test. All patients completed the study protocol. The dose of sildenafil ranged from 25 to 50 mg. The change in peak VO₂, the primary endpoint, was greater in the sildenafil group (9.4 ± 5.2%) than in the control group (0.3 ± 4.1%, P < 0.05). Sildenafil increased rest and peak exercise PBF index (P < 0.01 and P < 0.05 vs. control group, respectively), as well as rest and peak exercise CI (P < 0.001 and P < 0.05 vs. control group, respectively), without altering rest or peak exercise transcutaneous arterial blood oxygen saturations (P > 0.05 vs. control group for both). No patient reported serious adverse events after sildenafil. Conclusion: In Fontan patients, oral administration of a single dose of sildenafil improves exercise capacity and haemodynamic response to exercise.