RESUMO
BACKGROUND: Significant hemodynamic changes, including preload and afterload modifications, occur during the transition from the fetal to the neonatal environment. The ductus arteriosus closes, pulmonary vascular resistance decreases, and pulmonary blood flow increases. Strain rate (SR) and strain (epsilon) have been proposed as ultrasound indices for quantifying regional wall deformation. This study was designed to determine if these indices can detect variations in regional deformation between early and late neonatal periods. METHODS: Data were obtained from 30 healthy neonates (15 male). The initial study was performed at a mean age of 20.1+/-14 hours (exam 1) and the second at 31.9+/-2.9 days (exam 2). Apical and parasternal views were used to quantify regional left ventricular (LV) and right ventricular (RV) longitudinal and radial SR and epsilon, and systolic, early, and late diastolic values were calculated from these curves. A paired-samples t test was performed comparing the two groups. RESULTS: Compared with exam 1, LV radial deformation showed significant reductions in peak systolic epsilon in the basal and mid segments (51+/-15% vs 46+/-9%, P<.01). LV longitudinal deformation behaved similarly, showing significant peak systolic epsilon reductions in all measured segments. Systolic SR showed reductions only in the basal and apical segments of the lateral wall and in the mid portion of the inferior wall (-1.9+/-0.5 vs -1.7+/-0.3 s(-1) and -1.9+/-0.4 vs -1.7+/-0.2 s(-1), respectively, P=.03). RV longitudinal free and inferior wall systolic SR and epsilon values were significantly higher in exam 2. CONCLUSIONS: LV peak systolic epsilon decreases in exam 2 were possibly due to afterload increase and preload decrease. The lower RV initial deformation indices could be attributed to increased afterload caused by physiologic pulmonary hypertension or immature RV contractile properties. SR seemed to be a more robust index than epsilon and less influenced by preload and afterload hemodynamic alteration.
Assuntos
Técnicas de Imagem por Elasticidade/métodos , Coração Fetal/diagnóstico por imagem , Coração Fetal/fisiologia , Interpretação de Imagem Assistida por Computador/métodos , Ultrassonografia Pré-Natal/métodos , Módulo de Elasticidade/fisiologia , Feminino , Humanos , Recém-Nascido , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
BACKGROUND: Color Doppler myocardial imaging (CDMI) allows the calculation of local longitudinal or radial strain rate (SR) and strain (epsilon). The aims of this study were to determine the feasibility and reproducibility of longitudinal and radial SR and epsilon in neonates during the first hours of life and to establish reference values. METHODS: Data were obtained from 55 healthy neonates (29 male; mean age, 20 +/- 14 hours; mean birth weight, 3,174 +/- 374 g). Apical and parasternal views quantified regional longitudinal and radial SR and epsilon in differing ventricular wall segments. Values at peak systole, early diastole, and late diastole were calculated from the extracted curves. CDMI data acquired at 300 +/- 50 frames/s were analyzed offline. Three consecutive cardiac cycles were measured during normal respiration. The timing of specific systolic or diastolic regional events was determined. Multiple comparisons between walls and segments were made. RESULTS: Left ventricular (LV) longitudinal deformation showed basal differences compared with apical segments within one specific wall. Right ventricular (RV) longitudinal deformation was not homogeneous, with significant differences between basal and apical segments. Longitudinal epsilon values were higher in the RV free basal and middle wall segments compared with the left ventricle. In the RV free wall apical segment, longitudinal SR and epsilon were maximal. LV systolic SR and epsilon values were higher radially compared with longitudinally (radial peak systolic SR midportion, 2.9 +/- 0.6 s(-1); radial peak systolic epsilon, 53.8 +/- 19%; longitudinal peak systolic SR midportion, -1.8 +/- 0.5 s(-1); longitudinal peak systolic epsilon, -24.8 +/- 3%; P < .01). Longitudinal systolic epsilon and SR interobserver variability values were 1.2% and 0.7%, respectively. CONCLUSION: Ultrasound-based SR and epsilon imaging is a practical and reproducible clinical technique in neonates, allowing the calculation of regional longitudinal and radial deformation in RV and LV segments. These regional SR and epsilon indices represent new, noninvasive parameters that can quantify normal neonate regional cardiac function. Independent from visual interpretation, they can be used as reference values for diagnosis in ill neonates.