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Measurement of myocardial velocities in preterm neonates using Tissue Doppler Imaging

Presented at the Neonatal Society 2007 Summer Meeting (programme).

Negrine RJS1, Chikermane A2, Wright JGC2, Ewer AK1

1 Neonatal Intensive Care Unit, Birmingham Women’s Hospital, UK
2 Department of Paediatric Cardiology, Birmingham Children’s Hospital, UK

Background: Assessment of neonatal cardiac function has significant limitations. Tissue Doppler imaging (TDI ) measures Doppler signals from the myocardium allowing myocardial velocities to be calculated and used as an indicator of cardiac function (1). TDI has been studied, and used, in adults for several years, however only two studies have specifically investigated TDI velocities in term neonates (2,3) and none have investigated preterm infants.

Objective: To assess the myocardial velocities in preterm neonates using TDI.

Methods: Preterm neonates were scanned by a single investigator (RN) at less than 24 hours of age (D1) and/or at one week (W1). Myocardial velocities were acquired from an apical four chamber view. A Doppler pulse-wave sample gate of 0.12cm was positioned at the lateral tricuspid annulus, lateral mitral annulus and basal interventricular septum. Peak velocities in systole, early diastole and late diastole were obtained from each site. Average readings were taken from 3-5 cardiac cycles. Ethical approval was gained from the South Birmingham Research Ethics Committee.

Results: Thirty subjects were recruited with median gestational age 29.5 weeks (range 25-36) and birthweight 1414g (range 724-2230g). 19 D1 and 24 W1 scans were performed with 13 subjects undergoing both. The mean (SD) velocities (cm/sec) obtained are shown:

Consistent with the published data from children and term infants2, the velocities obtained from the septum were significantly lower than those from the tricuspid or mitral annuli, and the tricuspid annulus had significantly greater velocities than the mitral annulus during systole and late diastole. There was a trend for velocities to increase from day one to week one. As might be predicted these velocities were lower than the published velocities in term infants2. The smaller, sicker babies, or those with a large PDA, had lower velocities at all sites although numbers are very small.

Conclusion: Our study shows that myocardial velocities can be measured in preterm infants and provides a pattern of relative velocities which is consistent with those reported in term infants2, although, as might be expected, the overall velocities were lower. This pilot study suggests that TDI may be useful in the quantification of neonatal cardiac function and may be a valuable tool in the assessment of myocardial dysfunction in the critically ill preterm infant.

1. Weidemann F et al. Pediatric Cardiology 2002;23:292 – 306.
2. Mori K et al. Heart 2004;90:175 – 180.
3. Ekici et al. Echocardiography 2007;24:61-67.

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