Echocardiographic analysis
All analyses were carried out offline using the GE Echopac software
(version 113). S’ was derived from colour-derived TVI images where the
sample volume was placed at the annulus of the septal and lateral walls.
S’ was defined as the highest velocity during systole after the end of
isovolumetric contraction. Three cardiac cycles were obtained and S’ was
averaged for each time point. During the full protocol Simpson’s biplane
was measured (in the apical 4-and 2-chamber view), global longitudinal
strain (GLS) in the three apical views and the LVOT velocity time
integral (VTI). Speckle-tracking strain analysis was accepted when the
software and visual inspection indicated adequate tracking. If tracking
was inadequate, manual adjustments were made or the analysis was
excluded from overall analyses. GLS was obtained from the apical
4-chamber view (basal septum, mid septum, apical septum, basal lateral,
mid lateral, and apical lateral), the apical 2-chamber view (basal
inferior, mid inferior, apical inferior, basal anterior, mid anterior,
apical anterior) and the apical long axis view (basal posterior, mid
posterior, basal anteroseptal, mid anteroseptal). If data was of
insufficient quality it was excluded from analyses. This was defined as
poor TVI tracing, exclusion of the mitral valve annulus (for colour TVI
measurements), or poor endocardial border definition (for biplane).
Eleven participants were excluded from analysis.