Survival of patients with congenital heart disease (CHD) has greatly improved in recent decades, owing to technical advances related to diagnosis and treatment. Many of these patients have had palliative and corrective surgical procedures that make them in continuous need for long-term surveillance by which anatomic parameters can be monitored and complications can be identified on a timely basis [13].

This study was carried out on 56 patients (who were referred for cardiac magnetic resonance imaging for the added value of CMR in postoperative Fallot evaluation by using the conventional congenital CMR protocol in addition to an advanced myocardial deformation analysis done by CMR feature tracking technique), in addition to enrolling 56 healthy volunteers as well to compare the CMR ventricular indices and feature tracking analysis results of those patients to standards gained from these healthy volunteers.

This study was conducted upon 56 rTOF patients (including 26 males representing 46.4% and 30 females representing 53.6% with mean age 19.91 ± 11.25 years) and 56 healthy volunteers served as controls (including 23 males representing 41.1% and 33 females representing 58.9% with mean age 21.3 ± 11.57), when compared to Kutty et al. [14], who studied 171 patients with repaired TOF including 94 male patient 55% with age 18.2 ± 8 years together with 140 matched age and gender healthy controls, the two studies are in line to some extent regarding the mean age and gender distribution among the enrolled cohort.

In this current study, the mean age at surgical repair was 4.41 ± 6.22, compared to that reported by Kalaitzidis et al. [15] who reported mean age at repair as 2.4 ± 3.6 years.

Out of the 56 rTOF patients enrolled in this study, 34 patients underwent the study with contrast (representing 60.7%), the indication for contrast in this study is limited to one of these either; 1. to have a baseline for the ventricular volumes and function which will be needed in further follow-up scans or 2. due to deterioration in the clinical status of the patient in the form of recently developed arrhythmia or exercise intolerance or 3. due to deteriorated ventricular function documented by the last echocardiography, otherwise the scan for the remaining 22 patients (39.3%) was done without contrast in order to estimate RV volumes and function and to quantify Qp/Qs as well (in 20 patients of them).

For those 34 patients (60.7%) having CMR scan with contrast, 23 patients of them were referred for 1st follow-up, 10 patients for ventricular function deterioration and 1 of them for clinical status deterioration, and these indications for contrast in CMR congenital protocol were the same discussed by Geva [16].

The 56 rTOF patients at the current study underwent three main tetralogy of Fallot types of repair; RVOT repair, trans-annular patch repair and RV-PA conduit repair, and they were distributed as follows; 33 patients underwent the first type of repair (58.9%), 18 patients underwent the second type of repair (32.2%), and only 5 patients underwent the third type (8.9%); therefore, the RVOT repair had been the most common applied type of repair as regards to this study and the RV-PA conduit repair was the least common, comparing these three techniques of surgical repair in this study and that done in Davlourous et al. [17], that studied 36 patients with repaired TOF; he stated that 19 patients underwent trans-annular patch repair (representing 52.8%), 16 patients underwent RVOT repair (representing 44.5%), and one patient underwent conduit repair (representing 2.8%), so that it is concordant to some extent with this study findings regarding the techniques but at a bit different percentages.

This study mainly assessed the suspected postoperative complications and sequel in repaired tetralogy of Fallot patients and their impact upon ventricular indices and ventricular deformation (calculated by feature tracking strain analysis), and these sequels included pulmonary regurgitation with subsequent RV dilatation, dysfunction and tricuspid regurgitation as well, together with residual pulmonary stenosis and RVOT dilatation or obstruction, LV dysfunction, aortic dilatation and regurgitation, mitral regurgitation and residual VSD.

This study showed these sequels as follows; the most common postoperative sequel was pulmonary regurgitation, RV dilatation and tricuspid regurgitation (in which 54 patients were presented by each sequel representing 96.4% for each) followed by residual pulmonary stenosis (36 patients representing 64.3%), RV dysfunction (26 patients representing 46.4%), RVOT dilatation (19 patients representing 33.9%), LV dysfunction (16 patients representing 28.6%), aortic regurgitation and mitral regurgitation (13 patients representing 23.2% for each) and eventually residual VSD (11 patients representing 19.6%).

Those sequels were the same discussed by Saraya et al. [18], who studied 23 patients with repaired TOF and stated that, the most common sequel was pulmonary stenosis (9 patients representing 39%) then pulmonary regurgitation (7 patients representing 30.4%) followed by RV dysfunction (4 patients representing 17.4%) and finally tricuspid regurgitation (3 patients representing 13.04%).

Saraya et al. [18], reported the pulmonary stenosis as the most common residual complication in patients with repaired TOF with seven patients had LPA branch stenosis (77.8%) and 2 patients had RPA branch stenosis (22.2%); however, in this study sixteen patients were associated with branch stenosis (twelve of them had LPA stenosis and twelve had RPA stenosis with 8 of them having both branch stenoses.

In this study, right ventricular outflow tract obstruction was one of the residual suspected lesions prior to the CMR scan, and out of the 56 patients enrolled in this study, 32 patients had RVOT obstruction (57.1%) and 24 patients had no RVOT obstruction (42.9%) when compared to Latus et al. [19], who studied 54 patients with repaired TOF (nearly the same number as this study), 27 patients had RVOT obstruction and the same number were not having RVOT obstruction (50% for each).

The right and left ventricular indices reported by this study were; RVEF, RVEDV, RVESV, RVSV, RFEDVI, RVESVI, RVSVI, LVEF, LVEDV, LVESV, LVSV, LVEDVI, LVESVI, LVSVI as follows; 52.24 ± 8.21%, 238.6 ± 114.1 ml, 119.9 ± 68.83 ml, 121.2 ± 50.4 ml, 159.6 ± 54.84 ml/m2, 77.54 ± 32.61 ml/m2 and 82.28 ± 27.09 ml/m2 for RV indices, respectively; however, 57 ± 7.56%, 135.3 ± 58.79 ml, 60.62 ± 34.12 ml, 74.71 ± 28.8 ml, 89.29 ± 24.59 ml/m2, 39.13 ± 15.05 ml/m2 and 49.79 ± 13.26 ml/m2 for LV indices, respectively.

Comparing the ventricular indices of this study to different studies published in the literature, significant agreement could be noticed as follows:

Compared to the study of Kalaitzidis et al. [15] regarding mean RVEF, RVEDVI, RVESVI, LVEF, LVEDVI and LVESVI were 52.24 ± 8.21%, 159.6 ± 54.84 ml/m2, 77.54 ± 32.61 ml/m2, 57 ± 7.56%, 89.29 ± 24.59 ml/m2 and 39.13 ± 15.05 ml/m2 for this study versus 50 ± 9%, 121 ± 33 ml/m2, 62 ± 24 ml/m2, 57 ± 9%, 81 ± 17 ml/m2 and 35 ± 13 ml/m2, this study is in line with their study regarding these indices.

Also this study is concordant with Gonzalez et al. [20] study regarding the CMR mean ventricular indices, RVEF, RVEDVI, RVESVI, LVEF, LVEDVI and LVESVI were 52.24 ± 8.21%, 159.6 ± 54.84 ml/m2, 77.54 ± 32.61 ml/m2, 57 ± 7.56%, 89.29 ± 24.59 ml/m2and 39.13 ± 15.05 ml/m2 versus 51 ± 8%, 129 ± 40 ml/m2, 64 ± 25 ml/m2, 62 ± 9%, 84 ± 16 ml/m2 and 33 ± 13 ml/m2, respectively.

Also there is agreement between mean CMR ventricular indices in this study and Ylilato et al. [21], concerning RVEF, RVEDVI, LVEF and LVEDVI being 52.24 ± 8.21%, 159.6 ± 54.84 ml/m2, 57 ± 7.56% and 89.29 ± 24.59 ml/m2 versus 54.5 ± 6.5%, 131 ± 23.4 ml/m2, 58 ± 6.3% and 88.9 ± 12.8 ml/m2, respectively.

This study also discussed myocardial deformation analysis done by CMR feature tracking technique, being a novel technique that quantitatively calculate the myocardial strain, in which there was no need for additional sequences to be done during the scan (so no added scan time, as it is post-processing technique performed off-line based on the basic congenital cines).

Regarding CMR feature tracking results, the parameters obtained were LV circumferential strain (from the short axis cine), LV radial strain (from short axis cine) and longitudinal strain value (from long axis cine 2, 3, 4 chambers), also RV circumferential strain (from short axis cine) and longitudinal strain (form long axis cine: 4 chamber) and right atrial longitudinal strain (from long axis 4 chamber), as these chambers are the mainly affected at repaired tetralogy of Fallot patients.

This study reported mean CMR feature tracking values as follows; LV circumferential strain − 20.7 ± 4.65%, LV radial strain (short axis) 36.45 ± 8.48%, LV longitudinal strain − 16.92 ± 3.51%, RV circumferential strain − 12.66 ± 2.90%, RV longitudinal strain − 19.78 ± 4.97% and right atrium longitudinal strain 14.43 ± 9.09%.

The RA longitudinal strain mean value (14.43 ± 9.09%) in this study at the postoperative Fallot patients is in line with its value reported by Kutty et al. [14] in their study being (13.6 ± 5.7%) who studied 171 patients with repaired tetralogy of Fallot.

Concerning the right and left ventricular myocardial deformation analysis by CMR FT, there is concordance between this study and that of Ylilato et al. [21] concerning right ventricular circumferential strain, RV longitudinal strain, LV circumferential strain and LV longitudinal strain, being − 12.66 ± 2.90%, − 19.78 ± 4.97%, − 20.7 ± 4.65% and − 16.92 ± 3.51% in this study versus − 16.6 ± 3.6%, − 20.6 ± 3.5%, − 18.6 ± 3% and − 15.6 ± 2.9% in their study.

Correlating the advanced CMR indices of myocardial deformation feature tracking and the CMR conventional volumetric and functional indices, this study showed that RA GLS correlated with RV GLS with p < 0.001 and r = 0.469 denoting statistical significant directly proportional correlation; however, RA GLS did not correlate with either RVEF or RVEDVI with p = 0.109 and 0.565, respectively, these results are in line with those reported by Kutty et al. [14], who documented significant correlation between RA GLS and RV GLS with p < 0.001 and r = 0.3 and also no correlation between RA GLS and either RVEDVI and RVEF as well with p = 0.25 and 0.47, respectively.

Comparing the RV CMR conventional ventricular volumetric indices, this study found that all RV volumes in rTOF patients were found to be significantly increased compared to those of the Hvol (including RVEDV, RVESV, RVEDVI, RVESVI); also RV systolic function was found to be significantly decreased compared to that of the Hvol and that is concordant with those results of Kempny et al. [22].

Also for LV indices, LVEDVI and LVESVI were found to be significantly increased and LV systolic function was found to be significantly decreased compared to Hvol, however Kempny et al. [22] stated no significant difference between the two groups regarding these left ventricular indices.

As regards to feature tracking parameters, this study stated that RV GCS, RV GLS, LV GCS, LV GLS, LV GRS were significantly lower in rTOF patients compared to controls, comparing this study with that of Kempny et al. [22]; the two studies showed agreement regarding RV GLS, LV GCS, LV GLS, LV GRS; however, this study disagreed with that of Kempny et al., regarding RV GCS in which their study reported that RV GCS was significantly higher in rTOF patients compared to control group and also documented that RVEF was significantly correlated with longitudinal strain but not with circumferential strain, suggesting RV GLS as an early indicator for RV systolic function deterioration.

This study is concordant with Kutty et al. [14] who stated that RV GLS is significantly lower in rTOF than controls being − 12.3 ± 4.2% versus − 18.5 ± 5.3% in Kutty et al. [14], compared to − 19.78 ± 4.97% versus − 22.59 ± 3.55% in this study.

Discordance is found between this study and that of Ylilato et al. [21] regarding RV GCS, in which the latter reported that RV GCS is significantly higher in rTOF patients compared to control group which is against the results of this study, the latter assigned this finding to the compensatory changes that occur in the myocardial function that may be considered as an initial temporary increase in RV strain during childhood.

According to pulmonary regurgitant volume indexed, this study reported 32 patients having PRV ≤ 30 ml/m2 (57.1%) and 24 patients having PRV > 30 ml/m2 (42.9%), also PRV indexed was found to be statistically significant with RV GLS with p value 0.027 and nonsignificantly correlated to RV GCS, LV GLS and LV GCS as well, these results are concordant with those of Ylilato et al. [21] who documented that patients with severe pulmonary regurgitant volume (> 30 ml/m2)showed an enhanced longitudinal strain when compared to patients with milder regurgitation with p value 0.018, being (− 22.03 ± 4.04%) in PRV > 30 ml/m2 compared to (− 19.9 ± 4.8%) in PRV ≤ 30 ml/m2 in this study versus (− 22.5 ± 2.9%) and (− 19.7 ± 3.5%) in the other study, respectively.

Concerning the residual RVOT obstruction, this study stated that 32 patients had RVOTO and 24 patients were without RVOTO, in which there was a statistical significance increase of RV GCS in RVOTO group compared to the other group showed no RVOTO that is in line with what Latus et al. [19] had been reported, denoting that residual RVOTO seems to preserve RV strain.

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