This retrospective study included 22 SVP patients (Figure2) who underwent CT between February to September 2019. All data was acquired on a 256 slice scanner. Nonionic contrast medium was given intravenously via 20–22 G catheter with power dual injector at a rate of 1.5–4 mL/s followed by a saline chaser.Exams started from the thoracic inlet level to below the diaphragm.Images were acquired using optimised FLASH protocol.The test bolus technique was used with 4-second delay time after the peak contrast enhancement of a region of interest in the ascending aorta.Images with 0.6 mm slice thickness were reconstructed for multiplanar reformation.Images were evaluated using a 3D post processing workstation where various image reformatting techniques were used to get relevant information.
All patients were assessed in a systemic approach as outlined below(Figure3)
- Determination of atrial situs.
- Classification into single left ventricle (LV), single right ventricle (RV) or indeterminate on the basis of dominant ventricle morphology(Figure 4).The LV was recognizable by fine septal and apical trabeculations,smooth walls and lack of septal chordal attachments to the atrioventricular(AV)valve while RV has coarse apical-trabecular aspect and septal chordal attachments to its AV valve.
- Identification of ventricular topology (d-or l-loop).
- Establishing the type of AV connection [univentricular (two separate AV valves, one AV valve or a common valve)or biventricular].
- Assessing the ventriculoarterial (VA) connections [concordant,discordant ,double outlet or single outlet].
- Assessment of associated anomalies3.
A) ONE DOMINANT VENTRICLE AND ONE HYPOPLASTIC VENTRICLE
1. With univentricular AV connection and one AV valve:
- TRICUSPID ATRESIA: It is characterized by absent communication between the morphologic right atrium and RV.An atrial-level communication is always present.Pulmonary blood flow is provided by intracardiac shunt like ventricular septal defect(VSD) and extracardiac (PDA, aortopulmonary collaterals) sources.In our study all cases showed absent tricuspid valve with hypoplastic RV. A VSD and interatrial communication was seen in all 6 cases.The VA connection was concordant in most cases followed by discordant VA connection and double-outlet left ventricle (DOLV)in one case each.
- MITRAL ATRESIA- Mitral atresia is a rare congenital heart defect when compared to atresia of other valves.In mitral atresia there is a univentricular atrioventricular connection to a dominant RV via a tricuspid valve.The mitral valve is atretic with a posteroinferior incomplete LV as was seen in our case.
2. With univentricular AV connection and two AV valves:
- DOUBLE-INLET LEFT VENTRICLE –DILV includes hearts in which both AV valves are aligned with and connected to one ventricular chamber of LV morphology.Type I DILV has normally related great arteries, type II has a rightward and anterior aorta and rightward RV.Type III has a left-sided RV and a leftward anterior aorta.One case of DILV was encountered in our study.Both atrioventricular valves were seen draining into a single dominant ventricle of LV morphology.The rudimentary RV consisted only of trabecular and outlet portions and communicated with the LV through a VSD and was seen on the left. Aorta was seen arising from the morphological RV and was seen anterior and lateral to the MPA (Type III DILV).
- DOUBLE INLET RIGHT VENTRICLE - It is defined as ventricular morphology in which both atria empty,entirely or predominantly into the morphological RV.One out of 21 patients was diagnosed as DIRV. Both atrioventricular junctions were supported by the same dominant ventricular chamber of RV morphology. Both aorta and pulmonary artery were seen arising from RV(double-outlet arrangement). Hypoplastic LV was located in postero-inferior position on the left and communicated with the RV through a VSD
3. With univentricular AV connection and common AV valve:
- UNBALANCED ATRIOVENTRICULAR SEPTAL DEFECT:In unbalanced AVSD the common AV junction is committed to the RV/LV leading to RV/LV dominance and relative hypoplasia of the opposing ventricle.AVSD with RV dominance is more frequently encountered.Two cases of AVSD with RV dominance and one of AVSD with LV dominance were seen.
4. Biventricular AV connection and single VA connection :
- PULMONARY ATRESIA WITH INTACT VENTRICULAR SEPTUM (PA/IVS) - It is characterized by atresia of the right ventricular outflow tract in the absence of communication at the level of ventricles.PA/IVS was found in two patients evaluated in our study. CT revealed atresia of the pulmonary valve and an intact ventricular septum with hypoplastic RV. A PDA was seen in both cases.
5.With biventricular AV and concordant VA connections (Functionally univentricular heart) :
- SEVERE EBSTEIN’S ANOMALY - It is characterized by caudal displacement and dysplasia of septal and posterior leaflets of tricuspid valve resulting in atrialisation of the RV above the valve.In all three cases diagnosed as severe Ebstein’s anomaly, there was such extreme atrialization of the RV that the residual ventricle unable to sustain the pulmonary circulation and was not amenable for biventricular repair.
B) SOLITARY VENTRICLE OF INDETERMINATE MORPHOLOGY:
Two patients of heterotaxy syndrome were encountered in our study.Heterotaxy syndrome is defined as an abnormal arrangement of viscera across the left/right axis primarily induced by disorders of laterality determination. Classic right isomerism implies that the patient has bilateral trilobed lungs,bilateral minor fissures,eparterial bronchi, bilateral systemic atria, a centrally located liver, and a stomach in indeterminate position. It is associated with cardiac malformations like common atrium, SVP, pulmonary stenosis, total anomalous pulmonary venous connection.Left atrial isomerism is characterized by bilateral bilobed lungs, bilateral pulmonary atria, a centrally located liver, a stomach in indeterminate position, and multiple spleens.One of our patients revealed right isomerism with a common atrium of right atrial morphology which was seen draining into a single ventricle of indeterminate morphology.
C) WELL DEVELOPED TWO VENTRICLES :
1. Biventricular AV connection and single outlet truncus areterosus
- Truncus arteriosus :It is a cono-truncal anomaly characterized by a single arterial vessel originating from the heart and supplying the systemic, pulmonary, and coronary circulation. SVP with two well formed ventricles is seen due to presence of a large non restrictive shunt.In our study two cases of Truncus arteriosus were seen. One of them showed a single arterial vessel with a single dysplastic truncal valve originating from the heart, overriding the ventricular septum, and giving rise to both aorta and main pulmonary artery.(Type I).In the second patient pulmonary arteries were seen arising separately from the posterior aspect of trunk with negligible main pulmonary artery segment (Type II).
2. Biventricular AV connection and double outlet VA connection:
- DORV WITH NON-ROUTABLE VSD : One case of DORV with unroutable VSD was encountered in which it was difficult to create an unobstructed pathway from left ventricle to one of the great vessels therefore it was not amenable for biventricular repair.