Double Outlet Right Ventricle: Pathophysiology, Physiology, Diagnosis, Management

Double Outlet Right Ventricle (DORV)

~Introduction

Double Outlet Right Ventricle (DORV) is a rare congenital heart defect characterized by both the aorta and the pulmonary artery arising predominantly or entirely from the right ventricle. In a normal heart, the aorta arises from the left ventricle and carries oxygenated blood to the body, while the pulmonary artery arises from the right ventricle and carries deoxygenated blood to the lungs. In DORV, this normal anatomical relationship is disrupted, resulting in abnormal mixing of oxygenated and deoxygenated blood.

This malformation accounts for approximately 1–2% of all congenital heart diseases, and its presentation can vary depending on the position of the great arteries, the presence and location of a ventricular septal defect (VSD), and the existence of other associated cardiac anomalies such as pulmonary stenosis or coarctation of the aorta. Because of this variability, DORV represents not a single defect but a spectrum of anatomical variations with different physiological and clinical implications.

~Embryology and Pathophysiology

Embryological Basis

The normal development of the outflow tracts occurs between the 5th and 8th week of gestation. The conotruncal septum divides the embryonic truncus arteriosus into the aorta and the pulmonary artery. This process involves complex spiral rotation and fusion of the bulbar ridges. Failure in the normal alignment or septation of these structures leads to conotruncal anomalies, one of which is DORV.

In DORV, both great arteries are connected predominantly to the right ventricle due to abnormal conal development and malalignment. The ventricular septal defect acts as the only outlet for the left ventricle, and the physiological outcome largely depends on its relation to the great arteries and the presence of obstruction in either outflow tract.

~Anatomical Variants of DORV

DORV is a heterogeneous condition with several anatomical subtypes classified according to the position of the VSD and the relationship of the great arteries. The most widely used classification is based on the location of the VSD:

1. Subaortic VSD Type

• The VSD lies just beneath the aortic valve.

• Blood from the left ventricle flows primarily into the aorta through the VSD.

• Hemodynamics are similar to those in Tetralogy of Fallot (TOF) if pulmonary stenosis is also present.

• If no pulmonary stenosis exists, physiology resembles a large VSD with left-to-right shunting.

2. Subpulmonary VSD Type (Taussig–Bing Anomaly)

• The VSD is located beneath the pulmonary valve.

• Blood from the left ventricle mainly enters the pulmonary artery.

• Systemic and pulmonary circulations are parallel rather than in series, similar to transposition of the great arteries (TGA).

• Often associated with increased pulmonary blood flow and congestive heart failure.

3. Doubly Committed VSD Type

• The VSD lies beneath both great arteries.

• Both vessels receive mixed blood from the left and right ventricles.

• Usually associated with mild cyanosis and variable symptoms.

4. Non-committed (Remote) VSD Type

• The VSD is remote from both semilunar valves, located in the inlet or muscular part of the septum.

• Communication between the left ventricle and great arteries depends on intracardiac streaming and the geometry of the defect.

• Surgical correction in this variant is most complex.

~Associated Cardiac Anomalies

DORV rarely exists in isolation. Commonly associated defects include:

• Pulmonary Stenosis or Atresia: Leading to cyanosis by restricting pulmonary blood flow.

• Aortic Arch Obstruction or Coarctation: Causing systemic outflow obstruction.

• Atrioventricular Septal Defects (AVSD): Present in some cases, especially with heterotaxy syndromes.

• Mitral Valve Abnormalities: Affecting left ventricular inflow.

• Coronary Artery Anomalies: Important for surgical planning.

• Right Ventricular Hypertrophy: Secondary to increased workload and pressure.

The combination of these anomalies significantly influences clinical presentation and surgical approach.

~Hemodynamics and Physiology

The hemodynamic pattern in DORV depends on three main factors:

1. VSD location — determines which great artery receives more left ventricular blood.

2. Presence or absence of pulmonary or aortic obstruction — affects the direction and degree of blood flow.

3. Relationship of the great arteries — influences the mixing of oxygenated and deoxygenated blood.

Without Pulmonary Stenosis

• Excess pulmonary blood flow occurs, leading to heart failure and pulmonary hypertension.

• Cyanosis is minimal or absent.

With Pulmonary Stenosis

• Decreased pulmonary blood flow results in cyanosis.

• Physiology resembles Tetralogy of Fallot.

With Subpulmonary VSD

• Physiology mimics Transposition of the Great Arteries.

• Early cyanosis and congestive heart failure are typical.

Thus, the clinical manifestation ranges from acyanotic heart failure to severe cyanosis, depending on the anatomical variant.

~Clinical Presentation

The age at presentation and the symptoms depend on the subtype and associated lesions.

Neonates and Infants

• Cyanosis (especially in DORV with pulmonary stenosis or subpulmonary VSD)

• Poor feeding

• Tachypnea

• Failure to thrive

• Heart failure symptoms due to excessive pulmonary flow

Older Children

• Clubbing and exertional dyspnea

• Polycythemia due to chronic hypoxemia

• Systolic murmur due to turbulent flow across VSD or outflow tract

~Physical Examination

• Cyanosis: Depends on the degree of pulmonary obstruction or mixing.

• Clubbing: In chronic cyanosis.

• Cardiac Thrill: Over left sternal border.

• Heart Sounds:

  • Single S2 or widely split S2.

  • Systolic ejection murmur due to pulmonary stenosis or increased flow.

• Hepatomegaly: Secondary to right heart failure.

• Growth Retardation: In long-standing cases.

~Diagnostic Evaluation

Accurate diagnosis requires a combination of clinical assessment and imaging studies.

1. Chest X-ray

• Cardiomegaly due to right ventricular enlargement.

• Increased or decreased pulmonary vascular markings depending on flow.

• Boot-shaped heart in DORV with pulmonary stenosis.

2. Electrocardiogram (ECG)

• Right ventricular hypertrophy (common finding).

• Right axis deviation.

• Occasionally biventricular hypertrophy.

3. Echocardiography (ECHO)

• The main diagnostic tool for DORV.

• Determines:

  • Origin of great arteries.

  • Location and size of VSD.

  • Presence of pulmonary stenosis or other anomalies.

  • Relationship between ventricles and great vessels.

4. Cardiac MRI

• Provides detailed three-dimensional visualization of complex anatomy.

• Useful for surgical planning and follow-up.

5. Cardiac Catheterization

• Assesses pressures, oxygen saturations, and flow dynamics.

• Defines pulmonary vascular resistance.

• Occasionally used to confirm findings before surgery.

~Differential Diagnosis

• Tetralogy of Fallot (TOF): DORV with subaortic VSD and pulmonary stenosis can mimic TOF.

• Transposition of Great Arteries (TGA): Subpulmonary VSD type resembles TGA (Taussig–Bing anomaly).

• Large VSD with pulmonary hypertension.

• Truncus Arteriosus: Both great arteries arise from a common trunk.
  Accurate differentiation is essential because management strategies differ considerably.

~Management

General Principles

Treatment of DORV is primarily surgical. The goal is to establish physiologic separation of systemic and pulmonary circulations. The choice and timing of surgery depend on the specific anatomical subtype, associated lesions, and the patient’s clinical condition.

~Medical Management (Preoperative Care)

• Prostaglandin E1 infusion: Keeps the ductus arteriosus open in neonates with inadequate pulmonary or systemic flow.

• Diuretics and ACE inhibitors: Manage heart failure due to increased pulmonary blood flow.

• Oxygen therapy and nutritional support: Maintain adequate oxygenation and growth before definitive repair.

• Cyanotic spells: Managed similar to Tetralogy of Fallot with oxygen, beta-blockers, and sedation.

~Surgical Management

1. Definitive Intracardiac Repair

The mainstay of treatment is intraventricular repair—creating a pathway that directs left ventricular blood to the appropriate great artery (usually the aorta) and ensuring right ventricular blood flows to the pulmonary artery.

Subaortic VSD Type

• Intraventricular tunnel (baffle) directs left ventricular blood through the VSD to the aorta.

• If pulmonary stenosis exists, right ventricular outflow tract (RVOT) reconstruction or transannular patch may be needed.

• Physiology after repair approximates normal two-ventricle circulation.

Subpulmonary VSD Type (Taussig–Bing)

• Often treated by arterial switch operation (ASO) with VSD closure.

• Restores normal ventricular–arterial connections (left ventricle → aorta, right ventricle → pulmonary artery).

• Coronary reimplantation is critical in this approach.

Doubly Committed VSD

• Similar repair with appropriate baffling to direct left ventricular outflow.

• May require patch augmentation of outflow tracts.

Non-committed VSD

• Complex anatomy may preclude biventricular repair.

• Single-ventricle palliation (Fontan pathway) is often necessary.

2. Staged or Palliative Procedures

When definitive repair is not feasible initially (due to small ventricles, severe pulmonary hypertension, or complex anatomy), staged procedures are performed:

• Pulmonary artery banding: Reduces excessive pulmonary blood flow and prevents pulmonary hypertension.

• Systemic-to-pulmonary shunt (Blalock–Taussig shunt): Increases pulmonary blood flow in cyanotic infants.

• Bidirectional Glenn shunt: Redirects venous return to pulmonary arteries as part of single-ventricle pathway.

~Postoperative Care and Complications

Immediate Postoperative Period

• Close monitoring of hemodynamics, oxygenation, and arrhythmias.

• Inotropes for ventricular support.

• Management of pulmonary hypertension crises.

Long-term Complications

• Residual VSD or patch leak.

• Right ventricular outflow obstruction.

• Left ventricular outflow obstruction.

• Aortic insufficiency.

• Arrhythmias and conduction disturbances.

• Progressive ventricular dysfunction.

Regular follow-up with echocardiography and cardiac MRI is essential to monitor ventricular function and detect late complications.

~Prognosis

The prognosis of DORV has improved significantly with advancements in surgical techniques and postoperative care.

• Early mortality rates have decreased to less than 10% in many centers for standard forms.

• Long-term survival exceeds 80–90% at 10 years for successfully repaired biventricular cases.

• Complex or single-ventricle variants carry higher morbidity and require lifelong surveillance.

Quality of life is generally good, though exercise tolerance may remain limited in some patients. Lifelong cardiology follow-up is mandatory.

~Genetic and Syndromic Associations

Certain genetic syndromes are associated with DORV:

• 22q11.2 deletion (DiGeorge syndrome)

• Heterotaxy syndrome

• Trisomy 13, 18, and 21

• Congenital heart defect syndromes involving outflow tract malalignment

Genetic counseling and chromosomal studies are recommended in all patients with conotruncal anomalies.

~Recent Advances

• Three-dimensional echocardiography and cardiac MRI have improved anatomical delineation.

• 3D-printed cardiac models assist surgeons in planning complex repairs.

• Hybrid procedures combining catheter-based and surgical techniques are emerging.

• Genetic research into conotruncal development pathways may eventually lead to preventive strategies.

~Conclusion

Double Outlet Right Ventricle is a complex congenital cardiac anomaly that encompasses a wide range of anatomical and physiological variations. Early recognition and detailed anatomical evaluation are essential for appropriate surgical planning. Modern imaging modalities and advanced surgical techniques have transformed DORV from a fatal neonatal condition to a manageable, often curable heart defect with excellent long-term outcomes. However, lifelong follow-up remains crucial to detect late complications, manage residual lesions, and optimize the quality of life for affected individuals.