Neonates and infants with critical pulmonary stenosis with significant RV pressure load which directly affects RV shape , volumes , functions and morphology with consequent changes in these parameters after balloon pulmonary valvuloplasty (4)
In contrast to the LV the RV is an anterior complex asymmetrical structure which makes its assessment limited by the 2D echo in addition to inability to visualize both it inflow and outflow portion in the same view and the heavily trabeculated myocardium which makes it difficult to track the endocardial border and consequently quantification of RV volumes and function using conventional echo is challenging and lacking accurate assessment (5) .
Accordingly despite thar numerous 2DE quantitative methods based on geometric postulations have been established, for better quantifying of the RV shape and functions , however it still poses a big challenge (6, 7) . 3D echocardiography has become more useful in diagnosis and management of congenital heart disease (CHD) patients, particularly before surgical intervention or cardiac catheter intervention . 3D echocardiography has been used recently in patients with congenital heart disease because of better acoustic window and the non-invasive assessment using this technique (8) .3 DE is currently gaining attention and familiarity as a more accurate and reproducible modality for RV evaluation especially on congenital and structure heart disease ( 9) .
Our Study included 60 patients with critical pulmonary stenosis who were referred for right ventricular function evaluation by 2 dimensional (2DE) and 3 dimensional echocardiography (3DE) before BPV, After BPV immediately and at 6 month follow up in the Cardiology Department at Ain Shams University Hospitals .
The aim of this study was to identify role of 3D echocardiographic in comparison to conventional 2 D echo in assessment of RV volumes and function in infants with critical pulmonary stenosis undergoing balloon pulmonary valvuloplasty pre and post dilatation, and to evaluate these indices as follow up parameters for the procedural success.
In our study we found that RA area indexed and PV annulus were significantly reduced in the 6 month follow up which was comparable to the results with the study of Agha et al. (10 ) , stating that right heart structures improved gradually and started to grow significantly after 3-6 months of BPV.
We also noticed that TAPSE and FAC were significantly increased within 24 hours after , and in 6 months follow up , which were comparable with study of Fukui et al( 11 ) which demonstrated that RV EDVi and ESVi markedly improved with concomitant increase in RV EF and FAC. While Agha et al (10 ) reported that TAPSE significantly improved immediately and in the 3-6 months follow up .
We reported that 3D derived RV EDVI and RV ESVI were significantly decreased in the 6 months follow up from a median of 12.35(8.85-26.55)ml/m2 and 21.6(15.33-32.3)ml/m2 , these results concur with the study of Fukui et a (11 ) . which demonstrated that the RV EDV and RV ESV indexed are markedly improved after BPA in CTEPH patients.
Similarly both 3D RV EF and TASPE were increased significantly within 24 hours after and in the 6 months follow up as follows ( RV EF increased from 41.27% ±9.16% before BPV to a mean of 54.53% ± 6.78% at 3-6 month follow up, while RV TAPSE increased from a mean of 39.5% ± 8.01% before BPV to a mean of 51.07%±7.33% at 3-6 months follow up, which was concur with the study of Tsugu et al. ( 12 ) which showed a significant improvement in RVEF in patient with CTEPH after balloon pulmonary angioplasty, also our results were similar to results published by Moriyama et al.(13) when they studied the effect of pressure overload reduction on the RV EF and TAPSE by 3D echo in patients with chronic thromboembolic pulmonary hypertension (CTEPH).
In our study we also noted that 3D derived RV longitudinal diameter increased significantly in the 6 months follow up while RV basal diameter decreased significantly in the 6 months follow up which could be explained as The anatomy of the RV has a more complex asymmetrical geometry being wrapped around the LV, as the specific arrangement of RV myocardial fibers as the epicardial fibers are arranges obliquely in contagious with the LV fibers and the endocardial fibers are arranged longitudinally (14) which makes the RV increase in the circumferential diameter rather than the longitudinal diameter with increased RV pressure load , on relieving the RV pressure the dilated RV regains its normal elongated geometry ( i.e decrease in the circumferential dimension and increase in the longitudinal dimension ) rather than globular shape. In study done by Fernandez Friera et al ( 15 ) noticed that there were regional differences between the RV segments where the basal segments showed better contractility than others and this is mostly due to variation in the pressure load which affects segments rather than others . In study done by Dambrauskaite et al ( 16 ) he observed apical to basal difference in deformation and deformation rate which can be explained by : Firstly, longitudinal deformation is smaller in structures with straight walls, which can be seen in patients with long standing pulmonary hypertension as apical segments are less affected . Secondly, passive wall stress is also higher when the wall is thin, as in the apical segment of the RV free wall , Anderson RH (17 ) . Thirdly, in Pulmonary hypertension RV remodeled the deformation in the apical segments may be decreased due to the different embryonic origin of the RV or due to difference in the distribution of adrenergic receptors which is more located in the RV base rather than the apex Pierpont et al ( 18 ).
In our study on comparing the RV dimensional and functional parameters measured by 3D echo versus 2D echo , FAC , TAPSE , RV basal and longitudinal diameters were significantly higher and accurately assessed by 3D echo than those measured by 2D echo these results were in concur with study of Van der zwaan et al (19 ) which stated that 3D echo shows better quantitative RV volumes and function assessment compared with 2D echo in patients and in healthy controls.
Also 3D derived FAC , TAPSE and RV geometry serve as an outcome predictors for pediatric patients with RV pressure overload ( infants with critical pulmonary stenosis ) this was also reported by Pei-NI Jone et al (20 ) where 3D RV EF, volumes, FAC, and free wall RV strain serve as outcome predictors for pediatric pulmonary hypertension patients. So because of the RV peculiar morphology and functions , 2D echo has several limitations in the evaluation of right ventricle which can be overcome by 3D echo gated wide angle acquisition, which enable complete assessment of its geometry , volumes and ejection fraction.
Limitations :
Our study is a single center study , only focused on immediate and intermediate term procedural outcomes, in the future we hope to complete a multicenter study with larger sample sizes and long term follow up .