CASE SERIES OF DOUBLE CHAMBER RIGHT VENTRICLE IN VENTRICULAR SEPTAL DEFECT: SHOULD IT BE MISSED OUT?

was a pansystolic murmur grade 3/6, which was most audible at the left lower sternal edge. The chest radiograph showed mild cardiomegaly with clear lung field. Echocardiography showed mild left atrium (LA) and left ventricle (LV) dilatation, large outlet VSD with a mal-aligned septum, obstruction at the RVOT-infundibular junction with RVOT peak gradient was 50 mmHg, pulmonary stenosis (PS) and


Introduction
Double chamber right ventricle (DCRV) is an uncommon congenital anomaly characterised by aberrant muscle bundles that divide the right ventricle (RV) into a distal low-pressure chamber and a proximal high-pressure chamber.Right ventricular outflow tract (RVOT) obstruction frequently develops in these patients, particularly those whose distance between the moderator bundle and pulmonary valve is excessively short (1).A bizarre arrangement of muscle bundles has the potential to generate a pressure gradient between the RV inflow and outflow.Over time, the obstruction may become more pronounced.The occurrence of isolated DCRV is exceedingly uncommon, comprising a mere 6.2% of patients (2).In contrast, congenital heart defects such as peri-membranous ventricular septal defect (VSD) are the most prevalent, accounting for around 80%-90% of DCRV cases.Despite the frequent occurrence of peri-membranous type VSD in conjunction with DCRV, the precise pathogenesis of the obstructive muscle bundles that result from failing to diagnose DCRV remains a matter of debate (3).Furthermore, it mimics other forms of congenital heart defects, including RV cardiomyopathy and tetralogy of Fallot (TOF).We report these two cases to draw attention to the fact that long term VSD can lead to DCRV, a problem that might be missed during transthoracic echocardiography examination.

Case report Case 1
An 18-month-old boy was referred for an incidental finding of a cardiac murmur.He did not experience any cyanotic episodes or other failure symptoms.Upon assessment, he did not appear syndromic, he was pink with no respiratory distress and no failure to thrive.Vital signs showed a heart rate of 100 beats per minute, blood pressure of 80/65 mmHg, and saturation of 97% in room air.Cardiovascular examination revealed the apex beat was displaced and there was a pansystolic murmur grade 3/6, which was most audible at the left lower sternal edge.
The chest radiograph showed mild cardiomegaly with clear lung field.Echocardiography showed mild left atrium (LA) and left ventricle (LV) dilatation, large outlet VSD with a mal-aligned septum, obstruction at the RVOT-infundibular junction with RVOT peak gradient was 50 mmHg, pulmonary stenosis (PS) and proximal right pulmonary artery (RPA) stenosis (Figure 1 and 2).
Cardiac catheterization was scheduled at the age of 19 months for further assessment before cardiac surgery.Cardiac catheterization showed a stenosis at the RV-infundibular junction due to hypertrophied muscle (Figure 3), with a narrowest diameter of 4 mm; hypoplastic RPA, with proximal and distal RPA diameters of 4.3 mm (z score -3.43) and 6.6 mm (z score -0.82), respectively; and elevated RV pressure of 76/3 mmHg.Pulmonary artery (PA) pressure was normal with the reading was 28/10 mmHg (mean 19).Due to the absence of symptoms, no medication was prescribed, and he was scheduled for surgical intervention.Nevertheless, the timing of operation had to be postponed a few times in view of patient was having recurrent upper respiratory infection.
During the follow-up at the age of 2 years and 5 months, he was cyanosed with saturation of 87% in room air.Upon further questioning, he had episodes of cyanosis two months prior while he was crying and having emotional disturbances.Aside from that, there was no clubbing upon examination.Therefore, a discussion with the cardiothoracic surgeon for an earlier surgical intervention was initiated in view of the worsening RVOT obstruction signs.He underwent PA augmentation, infundibular resection, and surgical closure of the VSD.Following surgery, he was pink and had normal oxygen saturation.The follow up echocardiography showed reducing RVOT peak gradient of 10 mmHg.A nine-year-old boy has been diagnosed with small peri-membranous ventricular septal defect (VSD) since birth.He was asymptomatic and under routine follow up as outpatient.However, he has defaulted the follow-up since he was three years old.At the age of nine, he was referred again for a pre-operative evaluation prior to a dental procedure.
Upon assessment, he was well, pink, and had no signs of respiratory distress.Blood pressure was 90/65 mmHg, pulse rate of 103 beats per minute and SpO2 was 97% under room air.Examination of the cardiovascular system revealed that the apex beat was not displaced and the presence of grade 3/6 pansystolic murmur at left lower sternal edge.Echocardiography revealed a small peri-membranous VSD with turbulent flow in the RV and a peak gradient of 64 mmHg across the RV-infundibular junction (Figure 3a and 3b).
Consequently, a cardiac catheterization was conducted for a comprehensive evaluation.Cardiac catheterization showed a high RV and normal PA pressure of 119/67 mmHg and 33/19 mmHg respectively (Figure 4).As a result, he was diagnosed with peri-membranous VSD with DCRV.He was therefore referred to a cardiothoracic surgeon for surgical intervention.

Discussion
DCRV is an uncommon congenital disease.Although infrequently observed as an isolated disorder, VSD and PS are concurrently present in the majority of patients (4).In the first case, DCRV develops as a consequence of left-to-right shunting of VSD; PS exists as an isolated pathology, necessitating pulmonary artery augmentation by the surgeon due to the small pulmonary valve annulus and branch pulmonary arteries.This condition can be misdiagnosed as TOF with echocardiography.However, in TOF, the obstruction is located in the infundibular area.In contrast, in DCRV, the aberrant bundle crosses the right ventricular cavity and lies proximal to the infundibulum, resulting in no obstruction in the RVOT area (5).The bulbar and endocardial cushion elements, which frequently seal the superior portion of the ventricular septum, would therefore fuse incompletely due to the irregular expansion of the bulbo-ventricular junction.This would account for the frequent occurrence of a VSD in conjunction with this malformation (4).The perimembranous septum is the most common site for the VSD in DCRV, despite occasional observations in the sub-arterial region (1).
DCRV develops in 7% of patients with membranous VSD within the first year of life.Possible causes include progressive hypertrophy and obstruction caused by aberrant muscle bundles in the RV (2).Although manifestations may occur as early as infancy, the average age at which a diagnosis is made is during early childhood.The majority of patients who develop DCRV initially exhibit no symptoms (4).
The most frequent cause of referral is when a murmur is detected.Patients with DCRV and no VSD resemble those with isolated pulmonary valve stenosis from a clinical perspective.The clinical picture corresponds to a VSD when one is present (5).Established symptoms of severe RV hypertension in patients may include right ventricular failure, cyanosis, failure to thrive, and fatigue.In our first case, the patient experienced symptoms and signs suggesting worsening of the RV obstruction at the age of two, including cyanosis.The manifestation could potentially resemble TOF, necessitating surgical correction.In contrast, the second case involved the identification of DCRV in an individual who was older than three years.The natural history exhibits variation reliant upon the existence of concomitant lesions.Progressive RVOT obstruction, particularly when a VSD is present, can lead to RV failure (4).
Echocardiography is typically used to diagnose this lesion.The aberrant muscle bundles can be visualised effectively from either the subcostal or parasternal views.Because an echocardiograph can mimic TOF in an accompanying pulmonary valve stenosis lesion or RV cardiomyopathy, cardiac catheterization is occasionally used to confirm the diagnosis of DCRV (2).A pressure gradient is observed as the catheter is advanced further into the distal, low-pressure chamber, after it has been inserted into the inflow portion of the RV cavity.In most cases, the pressure in the distal chamber and pulmonary artery are equivalent, unless pulmonary valve stenosis is present (5).Filling defects are observed in the right ventricle beneath the crista supraventricularis, in the region between the outflow and inflow zones, as seen on anterior and lateral projections (4).Additionally, left ventriculography should be performed to identify the presence of a VSD.In adult patients, when echocardiographic views are frequently limited, the use of magnetic resonance imaging (MRI) is particularly significant.The anatomical characteristics of a DCRV are easily identifiable via MRI, and flow velocity measurements can even provide a quantitative evaluation of the obstruction's severity.In older patients, MRI is preferable to echocardiography and may eliminate the need for cardiac catheterization in the majority of cases (2).
The prompt diagnosis of DCRV typically necessitates surgical resection of the bundle and repair of any additional anomalies.If the degree of obstruction is not progressive and the intra-cavitary gradient is less than 40 mmHg, surveillance can be suitable in the absence of a substantial associated lesion (4).The associated lesions determine the timing of intervention.Drug therapy is not considered part of the standard treatment for DCRV.Surgical resection is the method of treatment for anomalous muscle bundles.The need for re-operation for recurrent obstruction and fatalities reported in the surgical literature are rare.A recent series reports no hospital or late deaths.Much of the reported morbidity and mortality result from a failure to diagnose the DCRV (5).This failure has pre-operatively led either to the closure of one of the portions of the RV, with a fatal outcome, or to re-operation in cases where the VSD was closed, although an obstructed right ventricle remained.

Conclusion
DCRV is a rare cardiac congenital anomaly in infants and childhood.It is most frequently associated with peri membranous VSD, which typically overlooks and requires definitive identification via echocardiography.Symptoms varied in accordance with the degree of RV obstruction.Prompt identification of DCRV is critical to impede the progression of RV obstruction.

Figure 1 Figure 2 Figure 3
Figure 1 An echocardiography showed turbulence at RV-infundibular junction (red arrow) Pulmonary artery Aorta

Figure 4 .
Figure 4. Cardiac catheterization revealed stenosis at right ventricle before entering the infundibulum, narrowest diameter 7.3 mm (red line)