Ventricular Septal Defects

Introduction to Ventricular Septal Defects

A Ventricular Septal Defect (VSD) is a congenital heart defect characterized by an abnormal opening in the ventricular septum, allowing blood to flow between the left and right ventricles. VSDs are one of the most common congenital heart defects, occurring in approximately 2-6 per 1000 live births.

The significance of a VSD depends on its size, location, and the presence of associated cardiac anomalies. Small VSDs may close spontaneously, while larger defects can lead to significant hemodynamic changes and complications if left untreated.

Embryology of Ventricular Septal Defects

VSDs result from incomplete closure of the interventricular septum during cardiac development. The interventricular septum forms between weeks 4 and 7 of gestation through the fusion of:

Muscular septum: Grows upward from the apex of the heart
Membranous septum: Develops from endocardial cushions
Conotruncal septum: Derived from neural crest cells

Failure of proper fusion or growth of these components leads to different types of VSDs. The timing and location of the developmental disruption determine the specific type and characteristics of the VSD.

Classification of Ventricular Septal Defects

VSDs are classified based on their location in the interventricular septum. The most common classification system is the one proposed by Soto et al.:

Perimembranous VSD (80%): Located in the membranous septum, often extending into adjacent muscular septum
Muscular VSD (15-20%): Completely surrounded by muscular tissue, can be further subclassified as:
- Apical
- Midmuscular
- Anterior
- Posterior
Doubly committed subarterial VSD (5%): Located beneath both great arteries, more common in Asian populations
Inlet VSD (<5%): Located in the inlet septum, often associated with atrioventricular canal defects

VSDs can also be classified based on size:

Small: <4 mm
Moderate: 4-6 mm
Large: >6 mm

Clinical Presentation of Ventricular Septal Defects

The clinical presentation of VSDs varies depending on the size of the defect and the resulting hemodynamic changes:

Small VSDs:

Often asymptomatic
Characteristic harsh holosystolic murmur at the left lower sternal border
Normal growth and development

Moderate to Large VSDs:

Symptoms of heart failure: tachypnea, diaphoresis, poor feeding, failure to thrive
Recurrent respiratory infections
Exercise intolerance in older children
Louder murmur, often with a thrill
Signs of pulmonary overcirculation: tachycardia, hepatomegaly, increased precordial activity

In cases of large VSDs with significant left-to-right shunting, patients may develop Eisenmenger syndrome if left untreated, characterized by reversal of shunt direction and cyanosis.

Diagnosis of Ventricular Septal Defects

Diagnosis of VSDs involves a combination of clinical examination and diagnostic tests:

Physical Examination:

Auscultation: Characteristic harsh holosystolic murmur at the left lower sternal border
Palpation: Precordial thrill may be present in larger defects
Assessment for signs of heart failure in significant defects

Diagnostic Tests:

Chest X-ray: May show cardiomegaly and increased pulmonary vascular markings in larger defects
Electrocardiogram (ECG): Can demonstrate left ventricular hypertrophy or biventricular hypertrophy
Echocardiography: Gold standard for diagnosis
- Transthoracic echocardiography (TTE) to visualize the defect, assess size and location
- Color Doppler to evaluate shunt direction and velocity
- Assessment of ventricular function and pulmonary artery pressure
Cardiac MRI: Useful for complex anatomy or when echocardiography is inconclusive
Cardiac Catheterization: Rarely needed for diagnosis, but may be used to assess pulmonary vascular resistance in complex cases

Management of Ventricular Septal Defects

Management of VSDs depends on the size of the defect, associated symptoms, and complications:

Conservative Management:

Small VSDs often close spontaneously and may only require monitoring
Regular follow-up with serial echocardiography
Endocarditis prophylaxis is no longer routinely recommended for isolated VSDs

Medical Management:

For patients with heart failure symptoms:
- Diuretics (e.g., furosemide) to reduce fluid overload
- ACE inhibitors to reduce afterload
- Digoxin may be considered in some cases
Nutritional support for infants with failure to thrive

Surgical Management:

Indications for closure:
- Large VSDs with significant left-to-right shunt (Qp:Qs > 2:1)
- Failure of medical management
- Evidence of pulmonary hypertension
- Associated lesions requiring surgery
Surgical techniques:
- Primary closure with sutures
- Patch closure (e.g., Dacron or pericardial patch)
Timing of surgery depends on symptoms and defect size, typically performed between 3-9 months of age for symptomatic infants

Catheter-based Closure:

Suitable for some muscular VSDs and selected perimembranous VSDs
Less invasive than open surgery
Devices used include Amplatzer VSD occluder and Nit-Occlud Lê VSD coil

Complications of Ventricular Septal Defects

Untreated or large VSDs can lead to several complications:

Pulmonary Hypertension: Due to chronic pulmonary overcirculation
Eisenmenger Syndrome: Irreversible pulmonary hypertension leading to right-to-left shunting and cyanosis
Heart Failure: Due to volume overload of the left ventricle
Aortic Regurgitation: In subarterial VSDs, prolapse of the aortic cusp can occur
Infective Endocarditis: Risk is higher in uncorrected VSDs
Arrhythmias: Can occur post-surgically or due to ventricular dilatation
Right Ventricular Outflow Tract Obstruction: In some perimembranous VSDs

Prognosis of Ventricular Septal Defects

The prognosis for patients with VSDs is generally good, especially with modern management strategies:

Small VSDs: Excellent prognosis, many close spontaneously
Surgically corrected VSDs: Good long-term outcomes, with most patients leading normal lives
Residual VSDs: May occur in up to 5% of cases post-surgery, usually small and hemodynamically insignificant
Long-term follow-up: Recommended for all patients, especially those with repaired large VSDs

Factors affecting prognosis:

Size and location of the defect
Presence of associated cardiac anomalies
Timing of intervention
Development of pulmonary hypertension

With appropriate management, the majority of patients with VSDs have a normal life expectancy and good quality of life.

Objective QnA: Ventricular Septal Defects

Question: What is the most common congenital heart defect? Answer: Ventricular septal defect (VSD)
Question: Which part of the interventricular septum is most commonly affected in VSD? Answer: Perimembranous (membranous) portion
Question: What is the characteristic murmur of a VSD? Answer: Holosystolic murmur best heard at the left lower sternal border
Question: Which complication is associated with a large, unrepaired VSD? Answer: Eisenmenger syndrome
Question: What is the primary imaging modality used to diagnose and assess VSDs? Answer: Echocardiography
Question: Which type of VSD is most likely to close spontaneously? Answer: Small muscular VSD
Question: What is the indication for surgical closure of a VSD in infancy? Answer: Failure to thrive and congestive heart failure despite medical management
Question: Which medication is commonly used to manage congestive heart failure in infants with large VSDs? Answer: Furosemide
Question: What is the role of pulmonary artery banding in the management of VSDs? Answer: To protect the pulmonary vasculature in infants with multiple VSDs or as a palliative procedure
Question: Which associated cardiac anomaly is commonly found with outlet (supracristal) VSDs? Answer: Aortic valve prolapse
Question: What is the most common chromosomal abnormality associated with VSDs? Answer: Trisomy 21 (Down syndrome)
Question: Which complication can occur with VSDs located near the cardiac conduction system? Answer: Complete heart block
Question: What is the recommended timing for elective surgical closure of an uncomplicated large VSD? Answer: Between 3-6 months of age
Question: Which imaging modality can be used to assess the size and location of VSDs in older children with poor echocardiographic windows? Answer: Cardiac MRI
Question: What is the significance of a Qp:Qs ratio > 2:1 in a child with VSD? Answer: Indicates a hemodynamically significant left-to-right shunt
Question: Which type of VSD is associated with the highest risk of developing aortic regurgitation? Answer: Subarterial (doubly committed) VSD
Question: What is the role of transcatheter device closure in the management of VSDs? Answer: To close suitable muscular VSDs or residual post-surgical VSDs
Question: Which clinical sign suggests the development of pulmonary hypertension in a child with VSD? Answer: Loud, single second heart sound
Question: What is the most common residual lesion after surgical VSD closure? Answer: Small residual VSD
Question: Which medication may be used to reduce pulmonary vascular resistance in children with VSD and pulmonary hypertension? Answer: Sildenafil
Question: What is the significance of a bidirectional shunt across a VSD? Answer: Indicates equalization of right and left ventricular pressures, suggesting pulmonary hypertension
Question: Which type of VSD is most challenging to close surgically? Answer: Multiple (Swiss cheese) VSDs
Question: What is the role of cardiac catheterization in the management of VSDs? Answer: To assess pulmonary vascular resistance and suitability for surgical repair in older children
Question: Which complication can occur after VSD closure in patients with elevated pulmonary vascular resistance? Answer: Right ventricular failure
Question: What is the recommended follow-up interval for small, hemodynamically insignificant VSDs? Answer: Annual follow-up with echocardiography
Question: Which genetic syndrome is associated with conotruncal VSDs? Answer: DiGeorge syndrome (22q11 deletion)
Question: What is the significance of a VSD in the setting of transposition of the great arteries? Answer: It allows for mixing of oxygenated and deoxygenated blood, improving survival
Question: Which type of VSD is most likely to be associated with right ventricular outflow tract obstruction? Answer: Outlet (supracristal) VSD
Question: What is the role of brain natriuretic peptide (BNP) in the management of children with VSDs? Answer: To assess the degree of heart failure and monitor response to treatment
Question: Which complication can occur in unrepaired VSDs during pregnancy? Answer: Worsening of a left-to-right shunt due to the physiological increase in blood volume