Double inlet LV with Fontan Circulation: Assessment for Bi-ventricular Repair
Real Time Three Dimensional Echocardiography (RT3DE) has remarkably enhanced the way we understand cardiac morphology, especially in congenital heart disease.
The most important aspect of 3dimensional echocardiography is the potential to slice the dynamic cardiac structures, in infinite planes through all the three dimensions. I improvised this technique so that the planes are moved systematically thorugh multiple planes throughout the cardiac cycle, in anatomically appropriate planes and in an attitudinally appropriate manner. MPR can be used even when the resolution of the images are poor and traditional 3D imaging has inadequate resolution to display underlying anatomy.
Below are example of some patient who benefitted from 3D MPR.
Septation of complex congenital heart defects
2D TOE and colour Doppler images from a 6 year old girl with Double Inlet LV and TGA. Undervent atrial septostomy on day 1 floowed by PA band and atrial septectomy ( 6 weeks) at another centre. Subsequent bidirectional superior cavo-pulmonary anastomosis at 19 months at a major tirtiary care centre. The image above confirms the right atrio-ventricular valve over-riding the ventricular septum and the RV appears small. The image below shows classic double inlet LV.
Her saturations were low (72%) and has decreasing effort tolerence. Parents are keen on further intervention. Cardiac catheterization showed low PA pressures (PA mean 11) small forward flow through the PA band. No intra-pulmonary AVMs.
Determining adequacy of ventricular volume and degree of commitment of the atriovetricular valve to corresponding ventricles along with connection of the great vessels to appropriate ventricular mass can be difficult in complex heart defects as that of this patient. The 2D images are rather convincing that this defect is unsuitable for septation. Please take a few minutes and go through the steps of MPR in this patient and see the difference MPR makes in understanding the morphology.
The transthoracic images are displayed below to illustrate the anatomic details as understood by standard cross sectional 2D echocardiography
The RV appears small. The septal leaflet of the right AV valve opens fully into the Lv cavity. On colour imaging, there is a wide open, un-restricted atrial communication with right to left shunt. The flow from the right AV valve is seen going into the LV cavity. There is an un-restricted ventricular septal defect.
The subcostal para coronal view shows the full profile of the right AV valve. There is cordal attachement of the septal leaflet attachinto the posterio-medial papillary muscle of the left AV valve. The right AV valve appears to be straddling the VSD. On the colour image at the right the para-sternal long axis view demonstrates the ventriculo-arterial relationship. The PA band is seen well in position with a turbulent flow pattern.
3D analysis and MPR
Video image in the right lower corner is a full volume 3D loop from the 3DTOE. It is sliced into 3 images by aligning the dissecting planes in sagital and coronal planes to illustrate the anatomy ( the upper 2 images). The cross sectional short-axis sliced image is displayed in the left lower corner. The left upper image is the standard 2D view one gets during initial the TOE. By aligning the cutting planes appropriately through the heart, the inlet and outlet aspects of the right heart is brought into view and displayed in the right upper corner. The shows an adequate size right heart. By further aligning the short-axis plane the appropriate right ventricular volume is brought out and the RV now appears slightly larger than the LV.
With further movement of the cutting planes in anatomically appropriate planes the crest of the ventricular septum is brought in line with the crux of the heart. The primum septum and the hinge points of the medial leaf lets of the two AV valve is brought in to view. The arrows illustrates the plane of the patch that may used to close the VSD
The magenda coloured dotted line goes through the the palne where VSD patch would be going through. Here the over riding of the right AV valve is less striking as it is prominent only in diastole. It was envisages that re-attaching the cordal attachments in the posterio-medial papillary muscle to the RV side would result in appropriate septation and a competent right AV valve.
This step of the MPR c(3D visualization or dysplay) is not an important aspect in this patient as all the necessary information is gained from the first two steps.
The post-operative 2D images shows successful septation of the ventricles with no significant intra cardiac shunts or AV valve regurgitation. The child now has normal oxygen saturations and good effort tolerence.
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