Quantitative assessment and functional correlates of cardiac mechanics and energetics in newborn infants

Abstract

Introduction: As preterm birth and survival rates continue to rise, circulatory failure remains a leading cause of mortality and morbidity. Structural and functional variations in circulatory physiology within the preterm population have been described, secondary to pre and post natal factors. This study applied magnetic resonance imaging techniques to assess cardiac function; analysed suitable techniques for indexing functional parameters by body size and applied a novel method of body composition quantification to investigate the impact of varying growth patterns on cardiac measures. Methods: Steady state free precession MRI imaging was used to analyse cardiac function in 78 preterm neonates. Analysis techniques were validated by comparison to phase contrast measures in 40 infants. Current methods of indexing for body size were compared. A modified DIXON whole body MRI scan utilising chemical shift was validated in phantoms and in vivo and successfully applied to 20 infants to assess adipose tissue content. Results: Validation of acquisition and analysis techniques demonstrated an acceptable level of accuracy. Functional measures indexed by body weight generally decreased with increasing corrected gestational age but patterns were altered when indexed by body surface area. Allometric transformation did not significantly improve correlation between size and function. Full body MDIXON scans demonstrated variations in body fat percentage of between 15 and 25%. Indexing cardiac function by lean body mass gave differing trends to total weight. Conclusions: Analysis of cardiac function in preterm neonates using MRI can be used to describe normative ranges and causes of variation for functional parameters. However, until an appropriate indexing technique for body size can be determined, the impact of pre and post natal factors cannot be fully understood. Analysis of body composition using MRI imaging may present a new indexing technique and allow us to investigate the effects of different growth patterns on cardiac function.Open Acces