Methods
Repaired TOF patients with native outflow tracts or RVPA conduits were
referred for TPVR at a single institution between 2008-2019 were
included in the retrospective analysis. All patients had at least
moderate PR by CMR (pulmonary regurgitant fraction >20%). Pre-implantation CMR data was included for volumetric data
analysis: EF, end-diastolic volume indexed (EDVI), end-systolic volume
indexed (ESVI), and PR. RV mass/volume ratio was also calculated on
pre-procedural CMR images available for review. CMR RV cine images were
reanalyzed for RV mass/volume ratio using available software (MedisSuite
MR, Medis Medical Imaging Systems BV, the Netherlands). Pre-implantation
hemodynamic catheterization was included for analysis of degree of RVSP
and pulmonic stenosis. RV end-diastolic pressure (RVEDP) was also
included for analysis.
Myocardial Strain by Speckle Tracking Echocardiography
Serial echocardiography data was used for analysis: (a) prior to valve
implantation, (b) at hospital discharge, and (c) within
18 months post valve
implantation. An internal validation scale was used for assessing
quality of GLS images: 0 = more than 2 segments not tracking; 1 = less
than 1 segment not tracking; 2 = all segments tracking. Patients with
poor quality imaging, assigned a
0, were excluded. GLS analysis using STE was obtained by tracing the RV
and LV endocardium from the apical 4 chamber view using TomTec Imaging
Systems (GmBH, Munich, Germany) (Figure 1). A less negative number is
lower strain or abnormal strain magnitude, and a more negative number is
higher strain magnitude or normal strain. A cut off of -17 is accepted
as normal strain magnitude, previously validated in CMR controls with as
the gold standard [12, 19-21].
Statistical Analysis
To account for the multiple strain measurements per patient, the
univariable and multivariable associations with RV or LV GLS were
modeled using linear mixed models with random intercepts for patients
[22, 23]. The confidence intervals for these associations
used profile likelihoods.
Associations between other metrics, such as RV mass, RVSP
pre-catheterization, were computed using linear models and confidence
intervals were computed with the classical formula.
The associations between RV GLS and RVSP pre-implantation, LV GLS and
RVSP pre- implantation, RV mass and RVSP pre- implantation, RV strain
and RV end diastolic pressure (RVEDP), and RV GLS and RV mass, were
adjusted for type of outflow. Adjusting for the type of outflow tract
did not change the significance of any of the analyses. Other
associations, including RV GLS with RVSP post- implantation, LV GLS with
RVSP post- implantation, RV GLS with age, LV GLS with age, RV GLS with
RV EF, LV GLS with RV EF, and LV GLS with LV end diastolic pressure
(LVEDP), were unadjusted.
Additionally, GLS, grouped by right and left, over time were plotted
using box plots. RV GLS, grouped by RVSP pre-catheterization, was also
plotted over time using boxplots. Similar plots were made for LV GLS
grouped by RVSP pre-catheterization. All analysis was conducted in R
version 4 [24]. Plots were created using ggplot2 [25].