An echocardiographic study of myocardial performance and baroreceptor reflexes in preterm neonates: Cardiovascular response to head up tilting to 30 and 60 degrees. 141

Abstract

Background: The development of myocardial performance and baroreceptor responses in preterm infants is not clear. Purpose: To evaluate myocardial performance and baroreceptor reflexes in stable convalescent preterm infants using 2D, M-mode and Doppler echocardiography at supine, 30° & 60°. Methods: 14 preterm infants with gestational age (GA) (mean ± SD) 31 ± 3.8 wks.(range 25-35.5 wks.), birth weight of 1811 ± 790 g. (range 520-3260 g.) studied. All infants studied in supine, 30° and 60° head up positions. Heart rate(HR), respiratory rate (RR), systolic blood pressure (SBP), O2 saturation, transcutaneous O2 and CO2 monitored during test.Results: We found a progressive improvement in myocardial functioning with increasing GA. A linear increase in stroke volume (SV) and cardiac output (CO) was seen with increasing GA (slope ± SE, b=0.021± 0.006, p=0.001). The left ventricular ejection time (LVET) increased with GA (slope b=2.5 ± 1.29, p=0.06). Likewise the end systolic wall stress (ESWS) increased significantly with GA (slope b=3.16 ± 1.02, p=0.0036). GA had no effect on velocity of circumferential fiber shortening(VCFS) (p=0.16) and left ventricular filling pattern as seen by early / late atrial doppler flow velocity ratios (E/A) (p=0.72). An inverse relationship was found between VCFS and ESWS (slope b= -0.0197 ± 0.008, p=0.003). GA had a significant effect on HR (p=0.007), SBP (p=0.029), left ventricular end diastolic dimensions (LVEDD) (p=0.0002) and left ventricular end systolic dimensions (LVESD) (p=0.001).