[Reference ranges for M-mode echocardiographic measurements within seven days after birth in preterm infants].

Objective: To establish reference ranges for M-mode echocardiography in preterm infants within 7 days after birth based on different gestational age (GA) and birth weight. Methods: This retrospective study analyzed M-mode echocardiographic values of 489 premature infants, who were admitted to the neonatal intensive care unit of Department of Pediatrics, Peking University Third Hospital from March 2017 to February 2020. These infants were divided into four groups according to GA:<28 weeks, 28-31+6weeks, 32-33+6weeks and 34-36+6weeks; and five groups according to birth weight:<1 000 g, 1 000-1 499 g, 1 500-1 999 g, 2 000-2 499 g and ≥2 500 g. The M-mode values among groups were compared by independent sample K-W test, and based on which, the 95% confidence interval (CI) and the Z-value reference ranges were established. Results: The gestational age of these infants was 32.0 (24.0-36.7) weeks, and the birth weight was 1 700 (650-3 180) g. The interventricular septum end-diastolic thickness (IVSd), left ventricular posterior wall end-diastolic thickness (LVPWd), left atrial diameter (LAD), left ventricular end-diastolic diameter (LVED), left ventricular end-systolic diameter (LVES), right ventricular outflow tract (RVOT) and the right ventricular end-diastolic diameter (RVED), were all correlated with GA and birth weight (r = 0.209, 0.216, 0.430, 0.608, 0.495, 0.464, 0.447; r = 0.275, 0.288, 0.445, 0.609, 0.496, 0.499, 0.464;all P<0.01). While the left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) had no correlation with GA or birth weight (all P<0.05). Within the first 7 days after birth, the greater the GA and birth weight, the greater the inner diameters of the heart chambers, and the thicker the ventricular wall. The LVEF and LVFS maintained a high and stable level within the first week of life (95%CI: 67%-69%, 34%-36%). Conclusions: According to different GA and birth weight, the reference ranges for chamber diameters, interventricular septal thickness and left ventricular wall thickness within 7 days were established. The 95% CI and Z score ranges for M-mode echocardiographic measurements established based on gestational age and birth weight can provide a reliable reference for preterm infants aged 0-7 days.