Tissue Doppler–Derived Strain and Strain Rate during the First 28 Days of Life in Very Low Birth Weight Infants

Abstract

Preterm infants may have cardiac stress related to patent ductus arteriosus (PDA) or bronchopulmonary dysplasia (BPD). In this study, we examined the development of cardiac function in preterm infants by measuring tissue Doppler-derived peak systolic strain (PSS) and strain rate (PSSR) in the first 28 days of life. Peak systolic strain and strain rate were measured in series in the free wall of the right (RV) and left (LV) ventricles on days 1, 7, 14, and 28 of life in 119 preterm infants <1500 g birth weight along with weight, heart rate, and presence of hemodynamically significant (hs) PDA or BPD. Both were assigned retrospectively. HsPDA was defined as a PDA requiring intervention whereas BPD was determined based on an infant's need for supplemental oxygen at 36 weeks of gestational age. Peak systolic strain and strain rate of the RV rose significantly during the first 28 days of life (P < 0.01). Infants who developed BPD had significantly lower RV free wall PSS on days 14 and 28 (P < 0.01 and <0.05). HsPDA resulted in a significantly lower PSS in the LV free wall as of day 14 (P < 0.01). After PDA intervention (day 28), LV PSS remained significantly lower (P < 0.05), but showed a tendency to increase (P = 0.18). Peak systolic strain determined in preterm infants appears to reflect increased afterload (decreased RV PSS in BPD infants) and increased preload (decreased LV PSS in hsPDA infants). The merits of such measurements as a basis for making clinical decisions still need to be explored.