Double Outlet Right Ventricle

Summary of DORV

Double Outlet Right Ventricle (DORV) is a group of congenital heart defects where both great arteries (the aorta and the pulmonary artery) arise exclusively or predominantly from the right vSummary entricle (RV). A ventricular septal defect (VSD) is almost always present. In classifying DORV, if a great vessel overrides the ventricular septum, the type of connection is determined using the 50% rule, meaning more than 50% of the vessel's circumference must be committed to the RV for it to be considered arising from the RV. While the historical definition required a well-developed conus beneath both great arteries, the currently accepted definition is broader and includes various arrangements of the subarterial conus. Absence of aorto-mitral continuity may also be used from a morphological standpoint. This condition may present in various spectrum. DORV-Tetralogy of Fallot type has the LVOT committed more than 50% to the right ventricle with an associated pulmonary stenosis. The DORV-TGA subtype has inversion of great vessels. More on DORV here and here.

Anatomy and Morphology 

DORV is a highly variable set of anomalies. Key anatomical features include the relationship of the great vessels to each other and to the ventricular cavity, and critically, the location and size of the ventricular septal defect (VSD). VSDs in DORV are usually large. The position of the infundibular septum influences the VSD location.

Classification schemes often categorize DORV based on the VSD location relative to the great arteries. Common types described include:

• Subaortic VSD: The VSD is located beneath the aorta. This is the most common type.

• Subpulmonary VSD: The VSD is located beneath the pulmonary artery. The Taussig-Bing malformation is a variant of DORV with a subpulmonary VSD.

• Doubly Committed VSD: The VSD is located beneath both great arteries. This results from absent or markedly attenuated infundibular septum. These defects are close to both semilunar valves and may be referred to as juxta-arterial.

• Remote (Noncommitted) VSD: The VSD is located far from both great arteries. This can include perimembranous inlet or muscular defects. Defects of this type are sometimes associated with Atrioventricular Septal Defects (AVSD).

The relationship of the great arteries to each other is also variable. Normal relations (aorta posterior and right of the pulmonary artery) are most common. Parallel arrangements are also seen. In most DORV hearts, the aortic and pulmonary valves are situated at the same level, unlike normal hearts, due to the presence of a muscular conus under each great artery.

Physiology and Clinical Presentation 

The physiology of DORV is diverse and depends heavily on the location of the VSD and whether there is pulmonary or systemic outflow obstruction. It can resemble the physiology of a simple VSD, Tetralogy of Fallot (TOF), or Transposition of the Great Arteries (TGA).

• VSD-type physiology (typically with subaortic or doubly committed VSD and no pulmonary stenosis) presents with signs of congestive heart failure, usually within the first 4–6 weeks of life.

• TOF-type physiology (typically with subaortic VSD and pulmonary stenosis) presents with cyanosis. There is often a short systolic ejection murmur due to stenotic RVOT flow.

• TGA-type physiology (typically with subpulmonary VSD, like Taussig-Bing anomaly) presents with cyanosis due to reduced effective pulmonary blood flow. If associated with coarctation of the aorta (CoA) or interrupted aortic arch (IAA), neonates may present with severe heart failure, respiratory distress, and low cardiac output.

• Systemic outflow obstruction (e.g., subpulmonary VSD with aortic arch obstruction) presents with signs of low cardiac output neonatally.

• Single ventricle physiology can occur in some complex forms, such as DORV with heterotaxy, leading to cyanosis with complete mixing of blood.

Associated Lesions DORV can be associated with a variety of other cardiac anomalies. These include:

• Pulmonary valvar or infundibular stenosis.

• Aortic obstruction, such as subaortic stenosis, Coarctation of the Aorta (CoA), or Interrupted Aortic Arch (IAA).

• Atrioventricular Septal Defects (AVSD).

• Hypoplastic ventricle, leading to functional single ventricle physiology.

• Atrioventricular discordance (ccTGA).

• Pulmonary atresia.

• Right atrial isomerism (heterotaxy).

• Total Anomalous Pulmonary Venous Drainage (TAPVD).

• Unusual coronary artery patterns are seen in about 60% of cases. Identifying these, especially courses anterior to the RVOT, is important for surgical planning.

Diagnosis 

Diagnosis of DORV is primarily made through imaging studies.

• Echocardiography is the mainstay and usually diagnostic. It is used to determine the location and size of the VSD, the relationship of the great arteries and AV valves to the ventricles, the presence of outflow obstruction, and associated defects. Fetal echocardiography can detect DORV and associated findings like pulmonary stenosis and evaluate for potential 22q11 deletion syndrome.

• Electrocardiography (ECG) findings are non-characteristic and variable. It may show signs of atrial enlargement or right ventricular hypertrophy (RVH), sometimes left-axis deviation if associated with AVSD.

• Chest X-ray (CXR) reflects the underlying physiology. It can show cardiomegaly and pulmonary vascularity which varies depending on the presence of pulmonary stenosis.

• Cardiac Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) may be used to provide detailed anatomical information, particularly regarding the aortic arch, pulmonary arteries, and coronary arteries, especially when echocardiography is insufficient. CT is sometimes considered a second choice for cross-sectional imaging. MRI can also be used to quantify ventricular volumes and shunts.

• Cardiac Catheterization is rarely needed solely for diagnosis. It may be used to assess pulmonary vascular resistance, especially in older patients or those with suspected pulmonary hypertension, to determine operability.

Management and Surgical Strategy 

Management of DORV is complex and highly variable due to the wide spectrum of anatomy and physiology. The position of the VSD relative to the great vessels is a key factor in determining the surgical approach.

• The goal is often to achieve an unobstructed concordant ventriculoarterial connection, though this may not always be feasible.

• Biventricular repair is generally considered optimal when possible. This usually involves closing the VSD and creating an unobstructed pathway from the left ventricle (LV) to the aorta. The VSD may need enlargement to ensure unobstructed flow.

• For simple DORV with subaortic VSD, repair involves VSD closure and rerouting to the aorta.

• For DORV with subpulmonary VSD (Taussig-Bing), repair typically involves VSD closure (rerouting the PA to the LV) and an Arterial Switch Operation (ASO).

• For DORV with Remote VSD, biventricular repair may be attempted, but a single ventricle palliation (Fontan) may be necessary if a complex intraventricular tunnel would be required. Atrial switch procedures may be used in rare cases with AV discordance.

• Alternative biventricular repair procedures like REV/Lecompte or Nikaidoh may be used for complex anatomy.

• If biventricular repair is not possible, patients are managed with a staged single ventricle palliation pathway, culminating in the Fontan circulation. Initial palliation may include BTT shunts, ductal stenting, or pulmonary artery banding.

Timing of intervention varies depending on the specific anatomy and physiology, ranging from neonatal repair to 2-4 months of age.

Outcome Outcomes for patients with DORV are generally good across the spectrum of lesions, but are less favourable in specific subgroups. Patients with outflow tract obstructions and associated arch hypoplasia have worse outcomes. Outcomes are also worse for those managed as single ventricle patients. Potential long-term issues after repair can include residual or recurrent outflow tract obstruction, ventricular dysfunction, pulmonary hypertension, and arrhythmias.

References

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Echocardiographic Example

Parasternal long axis showing that the aorta is overriding and committed to the right ventricle. 

Parasternal long axis shows that the pulmonary valve is unobstructed.