Imaging Studies
Chest radiography
Chest radiography may reveal either a left-to-right shunt with increased pulmonary vascular markings or a severe right ventricle (RV) obstruction with diminished pulmonary vascularity. The usual arrangement includes atrial situs solitus, levocardia, and left aortic arch. Cardiomegaly may be seen in some patients.
Echocardiography
Echocardiography currently enables diagnosis on a 2-dimensional Doppler echocardiogram; before its advent, diagnosis of double-chambered right ventricle (DCRV) could not be made noninvasively. In infancy, subxiphoid imaging is optimal; parasternal short-axis views may be more useful in older patients. The cardinal feature is demonstration of muscle bundles that traverse the RV cavity, with an accompanying gradient starting proximal to the infundibulum. See the images below.
Double-Chambered Right Ventricle. Subcostal right anterior oblique (RAO) echocardiograph view demonstrating right ventricle muscle bundles separating proximal from distal (*) chamber. PV = Pulmonary valve (Image courtesy of J. Smallhorn, MD)
Double-Chambered Right Ventricle. Subcostal right anterior oblique (RAO) echocardiograph view with color Doppler demonstrating ventricular septal defect jet to proximal chamber. (*) = Distal chamber (Image courtesy of J. Smallhorn, MD).
Wong et al described a "displacement index," which is determined by dividing the distance from the pulmonary annulus to the septal insertion of the moderator band by the tricuspid annulus diameter. [8] An index less than 1 may predict that infants with ventricular septal defect (VSD) are at risk of developing an obstruction from a displaced moderator band.
Transesophageal echocardiography has been used to define structures in older patients with poor windows.
Further evidence of double-chambered right ventricle includes the angiographic demonstration of a filling defect dividing the RV, as well as the absence of infundibular hypoplasia. Double-chambered right ventricle should be differentiated from tetralogy of Fallot by the absence of infundibular hypoplasia and pulmonary artery anomalies in double-chambered right ventricle. Entering both components of the RV is important; ideally, perform angiography from the RV apex in the frontal and lateral projections with craniocaudal angulation.
MRI and CT scanning
Magnetic resonance imaging (MRI) and contrast computed tomography (CT) scanning have been used in addition to echocardiography. These modalities may add to the anatomic delineation of the muscle bundles, although echocardiography is typically sufficient.
Electrocardiography
Electrocardiography (ECG) findings in double-chambered right ventricle were reviewed in one series of 30 patients. [9] Almost 50% of the patients had evidence of right ventricular hypertrophy (RHV), 40% of them demonstrated an upright T wave in V3 R in the absence of other findings of RVH, and the remainder had normal ECG findings. Similar findings are reported in other series.
Double-Chambered Right Ventricle. Electrocardiogram of an 18-month-old boy with double-chambered right ventricle. Note the upright T waves in the right precordial leads.
Procedures
Cardiac catheterization still has a role in ruling out other lesions that may be difficult to detect and that may influence operative strategy, although the diagnosis can be made accurately based on echocardiography findings. Recording of the pressure gradient (which widely varies in magnitude) within the right ventricle cavity, remote from the infundibulum, strongly suggests a diagnosis of double-chambered right ventricle.
-
Double-Chambered Right Ventricle. Electrocardiogram of an 18-month-old boy with double-chambered right ventricle. Note the upright T waves in the right precordial leads.
-
Double-Chambered Right Ventricle. Right anterior oblique (RAO) angiogram demonstrating proximal and distal chambers of right ventricle (Image courtesy of R.M. Freedom, MD).
-
Double-Chambered Right Ventricle. Lateral right ventriculography of a patient with double-chambered right ventricle. Large arrow indicates the presence of a fibromuscular obstruction with division of the right ventricle; small arrows outline pulmonary valve stenosis (Image courtesy of R.M. Freedom, MD).
-
Double-Chambered Right Ventricle. Subcostal right anterior oblique (RAO) echocardiograph view demonstrating right ventricle muscle bundles separating proximal from distal (*) chamber. PV = Pulmonary valve (Image courtesy of J. Smallhorn, MD)
-
Double-Chambered Right Ventricle. Subcostal right anterior oblique (RAO) echocardiograph view with color Doppler demonstrating ventricular septal defect jet to proximal chamber. (*) = Distal chamber (Image courtesy of J. Smallhorn, MD).
