Speckle Tracking as a tool for Assessing foetal Cardiac Ventricular Imbalance (STACVI)

Jones, Joanne Elizabeth (2022) Speckle Tracking as a tool for Assessing foetal Cardiac Ventricular Imbalance (STACVI). Doctoral thesis (DClinSci), Manchester Metropolitan University in collaboration with the National School of Healthcare Science and Manchester Academy of Scientific Health Education.

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Abstract

Introduction: Speckle Tracking echocardiography (STE) plays an exciting new role in the assessment of cardiac function. It is now widely used in the adult and paediatric sectors to evaluate the percentage of myocardial deformation, or % strain, with which the contractility of the muscle can be determined. It has proven validity, feasibility, and reproducibility in adult cardiology whilst demonstrating a significant contribution to clinical management, but there is still doubt regarding the clinical use in foetal cardiology due to technical barriers and a vast variation in normative data. There are, however, clinical presentations in foetal cardiology where long-term outcomes need to be counselled with caution. At 20 weeks gestation the foetal heart can be assessed for structural and functional normality, but where this borders on abnormal, there needs to be some discussion about the potential for deterioration. With little diagnostic evidence to support these borderline normal presentations, a functional tool such as speckle tracking could prove useful in predicting outcomes where there is a level of suspicion. Methods: In this study 40 foetal echocardiograms, where there was a discernible size discrepancy between the left and the right ventricles of unknown aetiology, were analysed using Tomtec Cardiac Performance Analysis (CPA) v.1.2 to provide longitudinal strain of left and right ventricular myocardial deformation. In addition, 40 echocardiograms where this imbalance in size was clearly due to a congenital heart defect were also retrospectively analysed for strain quantification. A further 40 foetal echocardiograms of age-related normal anatomy, were also analysed to provide a control group. Results: In total, 118 foetal echocardiograms were successfully analysed using CPA to obtain ventricular size, volume, and functional parameters, including percentage strain, for both the left and right ventricles across 3 groups – 1) foetuses with a foetal cardiac size discrepancy between the ventricles, 2) foetuses with a congenital heart defect and an imbalance between the size of the ventricles and 3) foetuses with normal foetal cardiac presentation. The foetal echocardiograms were retrospectively collected from foetuses between 15-24weeks gestation and results show that there was no significant difference in strain values in a ventricular size imbalance despite significant differences in size and volume of the ventricles. There was, however, a significant difference between the CHD group and control indicating that strain was reduced in the presence of a cardiac heart defect. Discussion: The results of this study show that myocardial deformation is preserved in the foetal heart where there is a ventricular size disproportion at mid-pregnancy. Significantly lowered left ventricular strain values were demonstrated in the CHD group which suggests that myocardial deformation is reduced in the presence of a congenital heart defect. These results support the theory that Speckle Tracking Echo (STE) may be a useful functional assessment tool at mid-gestation, in the presence of a congenital heart defect but not when there is only a ventricular size discrepancy. Further research is required into variations in methods, technique, and reference values to reduce technical variations, and build confidence in using STE to assess foetal cardiac function in congenital heart disease.