Normal Reference Ranges for Cardiac Valve Annulus in Preterm Infants

The purpose of this study was to establish normal reference ranges for the cardiac valve annulus size in preterm infants and their correlation with gestational age, body weight and chronological age.

In a prospective study, 268 pre-term babies, who fulfilled the criteria for inclusion, were examined in Kuwait during the years 2008-2010. Echocardiograms were performed to measure the aortic, pulmonary, mitral and tricuspid valve annulus size on 0-6 day(s) of life and at weekly intervals until they reached 36 weeks. The gestational age was grouped into three: 24-27, 28-31 and 32-35 weeks, and body weight into five: ≤999, 1000-1499, 1500-1999, 2000-2499 and ≥2500 g. The overall group differences were compared for each period of life: 0-6 days, 1-2, 3-4 and ≥5 weeks.

The mean gestational age was 29.8 (±2.38 SD) weeks, ranging between 24 and 35, and the mean body weight 1479 (±413 SD) grams, ranging between 588 and 3380. At the first scan (0-6 days of life), all cardiac valve measurements correlated well with both body weight and gestational age (P < 0.001). In the subsequent weeks valve diameters correlated well with body weight, while gestational age was found to have significant correlation (P < 0.01) with aortic and mitral valves only. A significant gradual increase was noticed in all valve annulus measurements with body weight during each period of life. Overall, a progressive and significant increase for all four cardiac valve annulus measurements was observed during the first nine weeks of life.

The cardiac valve annulus measurements were found to have significant correlation with body weight. All the cardiac valve measurements correlated well with gestational age (P < 0.01) only up to 2 weeks. The study also provides reference data, which can be used as a normal reference tool for cardiac valve diameters for preterm infants against the gestational age, body weight and chronological age.