AUTHOR AND EDITOR INFORMATION

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INTRODUCTION

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Background

Like many other lesions associated with congenital heart disease (CHD), the terminology that surrounds double-chambered right ventricle (DCRV) has evolved over the past several decades. DCRV was originally described more than 130 years ago. Clinical series began describing it extensively in the 1960s.

DCRV is better understood as a form of septated right ventricle (RV) caused by the presence of abnormally located or hypertrophied muscular bands.

The abnormally located or hypertrophied muscle bundles divide the RV cavity into a proximal and a distal chamber. Those muscle bundles run between an area located in the ventricular septum, beneath the level of the septal leaflet of the tricuspid valve, and the anterior wall of the RV. Frequent associated lesions include ventricular septal defect (VSD), pulmonary valve stenosis, and discrete subaortic stenosis.

As outlined by Restivo et al, several subtypes of divided RV are noted.¹ These subtypes include anomalous septoparietal band, anomalous apical shelf, hypertrophy of apical trabeculations, anomalous apical shelf with Ebstein malformation, and sequestration of the outlet portion of the ventricle from a circumferential muscular diaphragm in patients with tetralogy of Fallot. DCRV, the most common form, is noted by the presence of anomalous muscle bundles (AMB) that divide the RV into 2 chambers. However, no uniformity is observed in the position of these anomalous muscle bundles or in the manner in which the RV is divided.

Pathophysiology

Anomalous muscle bundles divide the RV into a high-pressure proximal chamber and a lower-pressure distal chamber. Evidence suggests that DCRV is an acquired disorder in those patients with appropriate substrate. Obstruction to pulmonary blood flow usually progresses with hypertrophy of the muscle and further obliteration of the RV cavity, although cases without progression of obstruction and even of spontaneous regression have been described.

The origin of anomalous muscle bands has been debated. The embryologic basis for DCRV was attributed to failure to incorporate bulbus cordis into the RV or an elevated hypertrophied moderator band. However, Byrum et al used the pattern of electrical activation to determine that muscle bundles were not the result of a displaced moderator band and suggested that activation of the DCRV is similar to activation of the normal heart.² Others, however, concluded that both the presence of bundle branch block in some patients and detection of a portion of the right bundle branch in a pathologic sample of the muscle bundle have proven the hypothesis that the moderator band is, in fact, the obstructing bundle.

A contemporary analysis of the origin of the muscle bundles determined the muscular shelf originates from the body of the septomarginal trabeculation. Two positions of muscle bundles are described as high (or horizontal) position and low (or oblique) position. Either position of the shelf divides the apical trabeculated RV in 2. This same analysis determined that the normal moderator band widely varies and that the anomalous muscle bundles do not represent an early takeoff from the moderator band in most cases.

Muscle bundles and the RV itself are usually lined with thickened endothelium. Other, less common, forms of divided RV include those in which a fibromuscular diaphragm or atrioventricular valve tissue partition the RV. These other forms include the anomalous septoparietal band, anomalous apical shelf, hypertrophy of apical trabeculations, anomalous apical shelf with Ebstein malformation, and sequestration of the outlet portion of the ventricle from a circumferential muscular diaphragm in patients with tetralogy of Fallot. These forms are not discussed in this article.

Associated defects are present in approximately 80-90% of patients; a VSD that involves the membranous septum is the most common defect described. A VSD may communicate with either the proximal or distal chamber, leading to a greater shunt in the latter situation. Development of RV outflow tract obstruction occurs in 3-7% of patients with membranous VSDs within the first years of life. The mechanism responsible for acquired RV obstruction may be progressive hypertrophy and obstruction from anomalous RV muscle bundles.

A well-known relationship is described among patients with RV outflow tract obstruction, membranous VSD, and subaortic stenosis. Vogel et al described 36 patients with membranous VSD and DCRV, 88% of whom had echocardiographic evidence of subaortic stenosis, with evidence of progressive left ventricular outflow tract obstruction.³ Progression of subaortic stenosis may occur before or after VSD closure and/or muscle bundles are resected.

The next most common associated lesion is pulmonary valve stenosis. Various other associations have been reported, including double outlet RV, tetralogy of Fallot, anomalous pulmonary venous drainage, complete or corrected transposition of great arteries, pulmonary atresia with intact ventricular septum, and Ebstein anomaly. DCRV has also been reported in patients with Down syndrome and Noonan syndrome, although differentiation from hypertrophic cardiomyopathy in the latter group is not straightforward.

Although Rowland et al considered patients in 4 groups, based on predominant physiology (pulmonary stenosis, tetralogy of Fallot, large VSD with left-to-right shunt, DCRV associated with other more hemodynamically significant lesions), most patients have moderate-to-restrictive VSD.⁴ Most of the remaining patients present with tetralogy physiology or have significant associated lesions.

Natural history varies depending on the presence of associated lesions. Progressive obstruction of the RV outflow tract has been observed and can lead to RV failure, especially in the presence of a VSD. Several report diagnosis in asymptomatic adults in whom anomalous muscle bundles and intact ventricular septum may have been associated with a VSD that underwent spontaneous closure.

Frequency

International

DCRV is relatively rare as an isolated anomaly; a large pediatric center typically diagnoses fewer than 10 cases per year. The lesion makes up approximately 0.5-2% of CHD and occurs in as many as 10% of patients with VSD.

Mortality/Morbidity

Fatalities in the surgical literature are very rare. Much of reported morbidity and mortality results from a failure to diagnose DCRV. This failure has preoperatively led either to closure of one of the portions of the RV, with a fatal outcome, or to reoperation in cases where the VSD was closed, although an obstructed RV remained.

In the larger series, residual mild RV outflow tract obstruction, nonhemodynamically significant residual VSDs, tricuspid valve regurgitation, and aortic valve regurgitation have been described as long-term morbidity issues.

Sex

Male-to-female ratio is 2:1.

Age

Presentation can be as early as the newborn period; however, mean age at diagnosis is in early childhood. Both fetal and adult cases have been reported.

CLINICAL

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History

• Most patients initially present with no symptoms.
• The most common reason for referral is the detection of a murmur.
• Clinically, patients with double-chambered right ventricle (DCRV) and no ventricular septal defect (VSD) resemble patients with isolated pulmonary valve stenosis.
• When a VSD is present, the clinical picture relates to a VSD. Usually, the patient is diagnosed with a VSD or pulmonary outflow tract obstruction and, subsequently, may show signs of progression of the outflow obstruction, such as cyanosis, fatigue, and decreased exercise tolerance.
• Rowland et al describe 4 physiologic groups (see Pathophysiology) with patients presenting usually with left-to-right shunt or tetralogy of Fallot physiology.⁴
• Patients with severe right ventricle (RV) hypertension may present with cyanosis, RV failure, failure to thrive, and fatigue.
• Association with other syndromes is well recognized, and DCRV may be found during their workup.

Physical

Most patients are nondysmorphic and acyanotic with normal peripheral examination findings. Auscultation reveals a variable intensity of the second heart sound. Holosystolic ejection murmur, which peaks in intensity near midsystole, with greatest intensity at mid- and upper-left precordial areas, characterizes DCRV. An RV heave, hepatomegaly, and tachypnea indicate RV hypertension.

Causes

• No inheritance pattern has been described.
• No risk factors for developing the disease have been encountered.
• Sporadic cases have been described in patients with Down syndrome and Noonan syndrome.

DIFFERENTIALS

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Other Problems to be Considered

Foreign body simulating double-chambered right ventricle (one case report)

WORKUP

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Imaging Studies

• 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 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.
• • Wong et al describe 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.⁵ 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 DCRV includes the angiographic demonstration of a filling defect dividing the RV, as well as the absence of infundibular hypoplasia. DCRV should be differentiated from tetralogy of Fallot by the absence of infundibular hypoplasia and pulmonary artery anomalies in DCRV. 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 contrast 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.

Other Tests

• ECG findings in DCRV were reviewed in one series of 30 patients.⁶ Almost 50% of the patients had evidence of right ventricular hypertrophy (RHV), 40% of them demonstrated an upright T wave in V₃R in the absence of other findings of RVH, and the remainder had normal ECG findings. Similar findings are reported in other series.

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 RV cavity, remote from the infundibulum, strongly suggests a diagnosis of DCRV.

TREATMENT

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Medical Care

Symptoms requiring therapy are generally an indication for operative repair.

Surgical Care

• The first successful surgical repair was reported in 1962. The initial approach was through a ventriculotomy; contemporary series describe both transatrial and transventricular approaches.
• Time to intervene naturally depends on the associated lesions; the current practice is to address associated lesions (ventricular septal defect [VSD], subaortic stenosis, pulmonary stenosis) at the time of double-chambered right ventricle (DCRV) repair.
• In the absence of a significant associated lesion, observation may be appropriate as long as the intracavitary gradient is not greater than 40 mm Hg and the degree of obstruction is not progressive.
• Although attempted, balloon dilatation likely has no role in the management of DCRV. Recently, Tsuchikane et al reported a patient who underwent a percutaneous myocardial ablation with an alcohol-induced conus branch occlusion for relief of a significant pressure gradient in DCRV.⁷

Activity

• Before repair, according to the degree of right ventricular outflow tract obstruction and associated lesions, exercise tolerance may be impaired and cyanosis may be present. After surgical repair and without significant residual anatomic lesions, activity tolerance should be normal.

MEDICATION

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Drug therapy is not currently a component of the standard of care for this condition. See Treatment.

FOLLOW-UP

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Further Outpatient Care

• Prior to surgical therapy, the follow-up is based on the degree of obstruction, associated lesions, and symptoms. Regular evaluation by a cardiologist is recommended.
• The residual lesions determine the follow-up of these patients after surgery. The patients are initially frequently evaluated in order to monitor the progress after repair.
• Exercise tolerance and quality of life, endocarditis prophylaxis, and recurrence of obstruction comprise the major issues during the long-term follow-up.

Prognosis

• Long-term results in earlier series are excellent, with current results showing improvement. Ruling out residual lesions and providing follow-up care for patients with recurrent right ventricle (RV) obstruction are important.

Patient Education

• For excellent patient education resources, visit eMedicine's Heart Center. Also, see eMedicine's patient education article Tetralogy of Fallot.

MISCELLANEOUS

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Medical/Legal Pitfalls

• Failure to recognize double-chambered right ventricle (DCRV) in the presence of associated defects, particularly ventricular septal defect (VSD) (may result in reoperation)
• Failure to rule out residual lesions
• Failure to provide follow-up care for patients with recurrent right ventricle obstruction

Special Concerns

• Once the associated lesions have been repaired and the abnormal muscle bundles have been resected, pregnancy carries no additional risks. The same applies if mild gradients across the right ventricular outflow tract exist.

MULTIMEDIA

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Media file 1:  Electrocardiogram of an 18-month-old boy with double-chambered right ventricle. Note the upright T waves in the right precordial leads.
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Media type:  ECG

Media file 2:  Right anterior oblique (RAO) angiogram demonstrating proximal and distal chambers of right ventricle (image courtesy of R.M. Freedom, MD).
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Media type:  CT

Media file 3:  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).
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Media type:  CT

Media file 4:  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)
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Media type:  CT

Media file 5:  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).
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Media type:  CT

REFERENCES

Section 11 of 11

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1. Restivo A, Cameron AH, Anderson RH, Allwork SP. Divided right ventricle: a review of its anatomical varieties. Pediatr Cardiol. Jul-Sep 1984;5(3):197-204. [Medline].
2. Byrum CJ, Dick M 2nd, Behrendt DM, et al. Excitation of the double chamber right ventricle: electrophysiologic and anatomic correlation. Am J Cardiol. Apr 1 1982;49(5):1254-8. [Medline].
3. Vogel M, Smallhorn JF, Freedom RM, et al. An echocardiographic study of the association of ventricular septal defect and right ventricular muscle bundles with a fixed subaortic abnormality. Am J Cardiol. Apr 1 1988;61(10):857-60. [Medline].
4. Rowland TW, Rosenthal A, Castaneda AR. Double-chamber right ventricle: experience with 17 cases. Am Heart J. Apr 1975;89(4):455-62. [Medline].
5. Wong PC, Sanders SP, Jonas RA, et al. Pulmonary valve-moderator band distance and association with development of double-chambered right ventricle. Am J Cardiol. Dec 15 1991;68(17):1681-6. [Medline].
6. Goitein KJ, Neches WH, Park SC, et al. Electrocardiogram in double chamber right ventricle. Am J Cardiol. Mar 1980;45(3):604-8. [Medline].
7. Tsuchikane E, Kobayashi T, Kirino M, et al. Percutaneous myocardial ablation in double-chamber right ventricle. Catheter Cardiovasc Interv. Jan 2000;49(1):97-101. [Medline].
8. Alva C, Ho SY, Lincoln CR, et al. The nature of the obstructive muscular bundles in double-chambered right ventricle. J Thorac Cardiovasc Surg. Jun 1999;117(6):1180-9. [Medline].
9. Ceyran H, Narin N, Tasdemir K, et al. Double-chambered right ventricle mimicking asymmetric septal hypertrophy. Turk J Pediatr. Jan-Mar 2003;45(1):80-2. [Medline].
10. Freedom RM, Mawson JB, Yoo SJ. The divided right ventricle: anomalous right ventricular muscle bundles and other entities. In: Congenital Heart Disease: Textbook of angiocardiography. Futura Publishing Company, Inc; 1997:389-407.
11. Hoffman P, Wojcik AW, Rozanski J, et al. The role of echocardiography in diagnosing double chambered right ventriclein adults. Heart. Jul 2004;90(7):789-93. [Medline]. [Full Text].
12. Kurosawa H, Becker AE. Surgical anatomy of the atrioventricular conduction bundle in anomalous muscle bundle of the right ventricle with subarterial ventricular septal defect. Pediatr Cardiol. 1985;6(3):157-60. [Medline].
13. Kveselis D, Rosenthal A, Ferguson P, et al. Long-term prognosis after repair of double-chamber right ventricle with ventricular septal defect. Am J Cardiol. Dec 1 1984;54(10):1292-5. [Medline].
14. Nagashima M, Tomino T, Satoh H, et al. Double-chambered right ventricle in adulthood. Asian Cardiovasc Thorac Ann. Jun 2005;13(2):127-30. [Medline].
15. Penkoske PA, Duncan N, Collins-Nakai RL. Surgical repair of double-chambered right ventricle with or without ventriculotomy. J Thorac Cardiovasc Surg. Mar 1987;93(3):385-93. [Medline].
16. Pongiglione G, Freedom RM, Cook D, Rowe RD. Mechanism of acquired right ventricular outflow tract obstruction in patients with ventricular septal defect: an angiocardiographic study. Am J Cardiol. Oct 1982;50(4):776-80. [Medline].
17. Puvaneswary M, Indira N, Sreedhar M, Barooah B. Double-chambered right ventricle: magnetic resonance imaging findings. Australas Radiol. Apr 2005;49(2):170-4. [Medline].
18. Vogel M, Freedom RM, Brand A, et al. Ventricular septal defect and subaortic stenosis: an analysis of 41 patients. Am J Cardiol. Dec 1 1983;52(10):1258-63. [Medline].

Article Last Updated: Oct 4, 2007