[Reference ranges for Doppler echocardiographic measurements within seven days of age in preterm infants]

Objective: To establish reference ranges for Doppler echocardiography in preterm infants within 7 days after birth based on different gestational age (GA), birth weight (BW) and body surface area (BSA). Methods: This retrospective study analyzed Doppler echocardiographic measurements 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⁺⁶ weeks, 32-33⁺⁶ weeks and 34-36⁺⁶ weeks; and five groups according to BW:<1 000 g, 1 000-1 499 g, 1 500-1 999 g, 2 000-2 499 g and ≥ 2 500 g;and 14 groups according to BSA from 0.07-0.20 m². The Doppler values among groups were compared by independent sample KW test, and based on which, the 95%CI were established as reference ranges. Results: Among the 489 preterm infants, males were 264 and females were 225. Their GA, BW and BSA were 32.0 (30.0,33.9) weeks, 1 700 (1 260,2 040) g and 0.13 (0.11,0.15)m², respectively. Measurements are presented charting as 95%CI with respect to GA,BW and BSA for preterm infants aged 0-7 days. Aortic valve(AV) flow rate, mitral valve E peak (MV-E), mitral valve E/A (MV-E/A) and tricuspid valve E peak (TV-E) were all correlated with GA, BW and BSA (r = 0.263, 0.256, 0.324 and 0.114 for GA; 0.292, 0.261, 0.281 and 0.135 for BW; 0.287, 0.268, 0.312 and 0.140 for BSA, all P<0.05). Within the first 7 days after birth, the greater the GA, birth weight and BSA, the greater the AV, MV-E, MV-E/A and pulmonary valve flow rate(all P<0.05). According to the above grouping of GA, the 95%CI of AV were 48-54, 52-57, 58-63 and 60-65 cm/s, respectively; and the 95%CI of MV-E were 32-37, 33-36, 39-42 and 40-45 cm/s, respectively; and the 95%CI of MV-E/A were 0.66-0.73, 0.74-0.80, 0.81-0.90 and 0.92-1.06. And according to the above grouping of BW, the 95%CI of AV were 45-53, 49-53, 59-64, 60-66 and 56-65 cm/s, respectively; 95%CI of MV-E were 29-35, 32-36, 38-41, 40-44 and 38-46 cm/s, respectively; 95%CI of MV-E/A were 0.65-0.74, 0.74-0.81, 0.81-0.99, 0.86-0.99 and 0.84-1.07. Conclusion: The 95%CI of Doppler echocardiographic measurements established based on GA, BW and BSA could provide a reference for preterm infants aged 0-7 days.