Sildenafil exposure and hemodynamic effect after Fontan surgery

Abstract

Objective: Determine sildenafil exposure and hemodynamic effect in children after Fontan single-ventricle surgery.

Design: Prospective dose-escalation trial.

Setting: Single-center pediatric catheterization laboratory.

Patients: Nine children post Fontan single-ventricle surgical palliation and undergoing elective cardiac catheterization: median (range) age and weight, 5.2 years (2.5-9.4 yr) and 16.3 kg (9.5-28.1 kg). Five children (55%) were boys, and six of nine (67%) had a systemic right ventricle.

Interventions: Catheterization and echocardiography performed before and immediately after single-dose IV sildenafil (0.25, 0.35, or 0.45 mg/kg over 20 min).

Measurements and main results: Peak sildenafil and desmethyl sildenafil concentration, change in hemodynamic variables measured by cardiac catheterization and echocardiography. Maximum sildenafil concentrations ranged from 124 to 646 ng/mL and were above the in vitro threshold needed for 77% phosphodiesterase type-5 inhibition in eight of nine children and 90% inhibition in seven of seven children with doses more than or equal to 0.35 mg/kg. Sildenafil improved stroke volume (+22%, p = 0.05) and cardiac output (+10%, p = 0.01) with no significant change in heart rate in eight of nine children. Sildenafil also lowered systemic (-16%, p = 0.01) and pulmonary vascular resistance index in all nine children (median baseline pulmonary vascular resistance index 2.4 [range, 1.3-3.7]; decreased to 1.9 [0.8-2.7] Wood Units × m; p = 0.01) with no dose-response effect. Pulmonary arterial pressures decreased (-10%, p = 0.02) and pulmonary blood flow increased (9%, p = 0.02). There was no change in myocardial performance index and no adverse events.

Conclusions: After Fontan surgery, sildenafil infusion acutely improves cardiopulmonary hemodynamics, increasing cardiac index. For the range of doses studied, exposure was within the acute safety range reported in adult subjects.

Trial registration: ClinicalTrials.gov NCT01169519.

Figure 1

Sildenafil effect on trans-pulmonary gradient, pulmonary blood flow and pulmonary vascular resistance. WU: Wood Units

Figure 2

Sildenafil effect on systemic vascular resistance, indexed cardiac output and stroke volume. WU: Wood Units

Figure 3

Peak sildenafil and des-methyl sildenafil levels by dosage group. Peak sildenafil levels predictive of varying degrees of PDE-5 inhibition (from in vitro data) are indicated. PDE-5: phosphodiesterase type-5.