Pulmonary arterial wall stiffness and its impact on right ventricular afterload in patients with repaired tetralogy of Fallot.

Abstract

Recent histologic studies involving patients with tetralogy of Fallot (TOF) have revealed a reduction in normal elastic fibers in the pulmonary trunk. Such histologic changes may significantly alter the mechanical properties of the arterial wall and may thereby augment the pulsatile afterload on the right ventricle (RV) and propagate RV dilation and dysfunction. We studied 29 patients with repaired TOF (median age, 5.9 years) and 29 age-matched controls. Pulmonary arterial hemodynamics were investigated by measuring the pulmonary input impedance during cardiac catheterization. Patients with TOF had higher characteristic impedance (p = 0.0002), lower total pulmonary vascular compliance (p < 0.0001), and enhanced wave reflection (p < 0.0001). Consistent with these changes, patients with TOF were subject to higher pulsatile load, measured by fundamental frequency impedance (p < 0.0001), which was significantly related to both reduced RV output and increased RV end-diastolic volume (p = 0.006 and 0.003, respectively). Moreover, pulmonary arterial compliance was strongly related to RV end-diastolic volume (r = -0.69, p = 0.0001). In multivariate analysis, pulmonary arterial compliance was a significant predictor of RV dilation independent of pulmonary regurgitation and pulmonary stenosis (p = 0.03). In line with known histologic changes, pulmonary arterial stiffness is increased and is significantly related to reduced RV ejection and RV enlargement in patients with repaired TOF. These results suggest that not only pulmonary valvular function (pulmonary regurgitation/pulmonary stenosis) but also pulmonary vascular pulsatile properties can be an important therapeutic target to improve prognosis in this population.