title: Myocardial performance and baroreceptor reflexes in preterm neonates: an echocardiographic evaluation using the tilt-table test.
abstract: The hemodynamic consequence of head-up position in preterm infants is not known, so we used the tilt-table test to assess changes in myocardial performance and baroreceptor reflexes. Twenty-five preterm infants with gestational age (GA) (mean +/- SD) 31 +/- 2.9 weeks (range 25-35.5 weeks), birth weight of 1612 +/- 642 g (range 520-3260 g) were studied in supine, 30 degrees, and 60 degrees head-up positions. GA had a significant effect on heart rate (HR) (p = 0.007), systolic blood pressure (SBP) (p = 0.03), left ventricular (LV) cavity dimensions (p = 0.001), cardiac output (CO) (p = 0.001), LV ejection time (LVETc) (p = 0.05), and end systolic wall stress (ESWS) (p = 0.003). An inverse relationship was seen between velocity of circumferential fiber shortening (VcFs) and ESWS (slope b = -0.019 +/- 0.008, p = 0.003). Results of tilt tests showed that at supine, 30 degrees, and 60 degrees, respectively, HR was 162 +/- 10.5, 162 +/- 9, and 164 +/-12 (p = NS); SBP (mmHg) was 73 +/- 11, 72.5 +/- 9.5, and 78 +/- 10 (p = NS); CO (L/kg/min) was 0.4 +/- 0.16, 0.4 +/- 0.15, and 0.43 +/- 0.16 (p = NS); ESWS (g/cm2) was 38.7 +/- 8.3, 40.9 +/- 9.9, and 43.4 +/- 10.7 (p = NS); and VcFs (circ/sec) was 1.35 +/- 0.3, 1.28 +/- 0.4, and 1.26 +/- 0.2 (p = NS). LV filling pattern as seen by early/late atrial Doppler flow velocity ratio did not change with tilt (p = NS). Myocardial performance improved with increasing GA. No significant differences in myocardial performance were found between baseline and head-up tilt positions.
authors.affiliation: Department of Pediatrics, Medical College of Wisconsin, Milwaukee, WI 53226, USA. shekhawat_P@kids.wustl.edu
authors.forename: P S
authors.initials: PS
authors.lastname: Shekhawat
authors.forename: P
authors.initials: P
authors.lastname: Sasidharan
authors.forename: D A
authors.initials: DA
authors.lastname: Lewis
mesh_terms: D000704:Analysis of Variance; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D004452:Echocardiography; D005865:Gestational Age; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D016014:Linear Models; D009200:Myocardial Contraction / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D018667:Tilt-Table Test; D016276:Ventricular Function