Doppler tissue imaging assessment of myocardial velocities and atrioventricular time intervals in term newborn infants during the neonatal period.

BACKGROUND: In both term and premature neonates, changes in the systolic and diastolic function of the left ventricle (LV) and right ventricle (RV) reflect the degree of neonatal myocardial immaturity and the co-existence of foetal circulation as well as the presence of concurrent diseases.

AIM: To evaluate the changes in values of systolic and diastolic LV and RV function using pulse tissue Doppler imaging (TDI) in 20 healthy term newborn infants from birth to the 28th day of life.

METHODS: Ventricular peak myocardial velocities were recorded during early diastole (Em wave), atrial contraction (Am wave), and systole (Sm wave). TDI derived atrioventricular (AV) intervals were measured as the period from atrial contraction (Am) to isovolumic contraction (IV), from Am to ventricular systole (Sm), from Sm to the following Am, and from IV to the following Am. The first measurements were taken as soon as possible after birth, the second on the third day, and the final one on the 28th day of life.

RESULTS: The diastolic myocardial velocities recorded in the RV were higher than those in the LV. Statistically significant differences were observed for time intervals in the RV: Am-IV and Am-Sm (day 1-3), p < 0.02; IV-Am (day 1-28), p < 0.005; Sm-Am (day 1-28), p < 0.01. Statistically significant differences for time intervals were also evident in the LV: Am-IV (day 1-28), p < 0.05; and for Sm-Am (day 1-28), p < 0.01. Mean isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) intervals remained stable for all measurements recorded in the RV. However, a statistically significant difference was evident for both ICT and IRT intervals in the LV between days 1 and 28 of life (p < 0.01).

CONCLUSIONS: 1. Cardiac TDI is feasible in the neonate. 2. In neonates, the diastolic and systolic function recorded in the RV was better than that in the LV. This may reflect the 'persistent' foetal status of this ventricle in the first day of life. 3. The differences observed in conduction times also reflect the haemodynamic changes which occur in the circulatory system of the neonate in the first month of life. 4. Further investigation of a larger population of neonates throughout the whole neonatal period is indicated.