Echocardiography (Echo) has been used to define restrictive physiology as any presence of end-diastolic forward flow (EDFF) on the pulmonary artery, despite constant small amount of EDFF is present in healthy children, being values lesser than in children with repaired right ventricular outflow tract obstructive lesions (RVOT). No information regarding EDFF quantitative assessment has been made in adult healthy controls (HC).
METHODS: 81 consecutive patients (mean age: 37 years; 53% men) with RVOT lesions were studied. Forty-three age-and-sex matched HC were evaluated. Echo parameters were: EDFF peak velocity in inspiration (EDFF_i), in expiration (EDFF_e), EDFF_i/EDFF_e ratio, maximum velocity-time integral EDFF (VTI_EDFF).
RESULTS: A small constant EDFF was present in HC. Mean values of EDFF_i, EDFF_e, VTI-EDFF were significantly lower in HC compared to patients: 26 cm/s (SD 6) vs 49.6 cm/s (SD ±22), 25 cm/s (SD ±6) vs 40 cm/s (SD ±19), 2.3 cm (±0.6) vs 6.2 cm (±3.5), respectively, p < 0.001. The EDFF_i/EDFF_e ratio was 1 (±13) in HC vs 1.25 (±0.25) in patients p< 0.001. Based on their normal distribution in HC, we propose cut-off values > 2SD for the different parameters. VTI-EDFF could easily be used as a non-invasive parameter to distinguish patients from HC and provide a new definition of RP; the presence of respiratory variation should be considered a key factor to differentiate HC from patients. In conclusion, any amount of EDFF throughout the respiratory cycle is not useful for identifying abnormal EDFF. A new approach based on cut-off values obtained from HC and quantitative EDFF assessment is proposed to provide a new definition of abnormal EDFF.
