Overview

Definition

A ventricular septal defect (VSD) is a malformation of the interventricular septum (IVS) resulting in an abnormal communication between the left ventricle (LV) and the right ventricle (RV). This defect may present in isolation, or be a part of another anomaly, such as tetralogy of Fallot Tetralogy of Fallot Tetralogy of Fallot is the most common cyanotic congenital heart disease. The disease is the confluence of 4 pathologic cardiac features: overriding aorta, ventricular septal defect, right ventricular outflow obstruction, and right ventricular hypertrophy. Tetralogy of Fallot.

Classification

There are 4 main subtypes of VSD based on location along IVS:

1. Membranous (75% of cases):
   • Also called perimembranous or conoventricular
   • Most common subtype
   • Located at distal conal septum (just inferior to aortic valve)
   • In proximity to bundle of His
2. Muscular (20%):
   • Located along trabeculated muscular septum
   • Classified as anterior, mid-muscular, apical, or posterior
   • Common in premature infants
   • May be multiple
   • Most likely to undergo spontaneous closure
3. Inlet (5%):
   • Also called AV canal defect
   • Located around tricuspid annulus (inlet)
   • Always accompanies other endocardial cushion defects
   • Will not close spontaneously
4. Supracristal (5%):
   • Also called outlet defect
   • Located inferior to pulmonic valve at right ventricular outflow tract
   • More common in Asian population
   • Will not close spontaneously

Epidemiology

• The most common congenital heart defect (CHD): 25% of all CHDs
• Incidence: 5–50/1,000 live births
• Increased risk:
  • Family history: 3x increase
  • Maternal factors:
    • Obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity
    • Diabetes
    • Alcohol use → muscular VSD

Etiology

Exact mechanism is unknown. Genetic syndromes:

• Down syndrome Down syndrome Down syndrome, or trisomy 21, is the most common chromosomal aberration and the most frequent genetic cause of developmental delay. Both boys and girls are affected and have characteristic craniofacial and musculoskeletal features, as well as multiple medical anomalies involving the cardiac, gastrointestinal, ocular, and auditory systems. Down Syndrome (Trisomy 21)
• Patau’s syndrome ( Trisomy 13 Trisomy 13 Trisomy 13, or Patau syndrome, is a genetic syndrome caused by the presence of 3 copies of chromosome 13. As the 3rd most common trisomy, Patau syndrome has an incidence of 1 in 10,000 live births. Most cases of Patau syndrome are diagnosed prenatally by maternal screening and ultrasound. More than half of the pregnancies result in spontaneous abortions. Patau Syndrome (Trisomy 13))
• Edwards’ syndrome ( Trisomy 18 Trisomy 18 Edwards syndrome, or trisomy 18, is a genetic syndrome caused by the presence of an extra chromosome 18. The extra chromosome is either from 3 full copies of chromosome 18 or an additional segment of chromosome 18. As the 2nd most common trisomy, Edwards syndrome is seen in 1 out of every 5,500 live births. Edwards Syndrome (Trisomy 18))

Pathophysiology and Clinical Presentation

Pathophysiology

Physiologic changes occur based on the size of the defect and the resistance across which the blood has to flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure.

• Small VSD:
  • < 4 mm
  • Minimal left-to-right shunting due to high resistance within defect
  • Maintains RV pressure to normal
  • Rarely causes heart failure
• Moderate VSD:
  • 4–6 mm
  • Left-to-right shunt
  • Higher resistance (smaller defect) → pulmonary artery pressure < 50% of systemic pressure → least amount of change within ventricles and pulmonary circulation
  • Lower resistance (larger defect) → pulmonary artery pressure is > 50% of systemic pressure → pulmonary congestion and LV remodeling
• Large VSD:
  • > 6 mm
  • Very little resistance to flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure across defect
  • Left-to-right shunt equalizes pressure between RV and LV
  • After birth, as fetal pulmonary vascular resistance Vascular Resistance Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Vascular resistance is directly related to the diameter of the vessel (smaller vessels have higher resistance). Vascular Resistance, Flow, and Mean Arterial Pressure (PVR) decreases → increased pulmonary blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure → pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure, which can lead to chronic progressive right heart failure. Pulmonary hypertension is grouped into 5 categories based on etiology, which include primary PAH, and PH due to cardiac disease, lung or hypoxic disease, chronic thromboembolic disease, and multifactorial or unclear etiologies. Pulmonary Hypertension → RV hypertrophy
  • Eisenmenger’s syndrome can occur once RV pressure is higher → right-to-left shunting and cyanosis

Clinical presentation

Age of presentation is usually around 2 months, unless a larger defect is present which becomes symptomatic within weeks of birth.

• Small VSD:
  • Usually asymptomatic
  • Incidental murmur
• Moderate/large VSD:
  • Poor feeding (sweating or fatigue)
  • Poor weight gain
  • Shortness of breath
  • Recurrent lung infections
  • Infective endocarditis Endocarditis Endocarditis is an inflammatory disease involving the inner lining (endometrium) of the heart, most commonly affecting the cardiac valves. Both infectious and noninfectious etiologies lead to vegetations on the valve leaflets. Patients may present with nonspecific symptoms such as fever and fatigue. Endocarditis

Diagnosis

Physical examination

• General appearance:
  • Pallor
  • Failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive
• Precordial exam:
  • Displaced apex
  • Systolic thrill
  • Murmur:
    • Small VSD:
      • Harsh holosystolic
      • Grade 2 or 3
      • Left lower sternal border
    • Large VSD:
      • Systolic murmur with diastolic rumble (apex)
      • No murmur, if severe
• Signs of respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure:
  • Tachypnea
  • Grunting
  • Nasal flaring
  • Retraction
  • Hypoxia
• Signs of heart failure:
  • Hepatomegaly
  • Tachycardia
  • S3 and S4 heart sounds Heart sounds Heart sounds are brief, transient sounds produced by valve opening and closure and by movement of blood in the heart. They are divided into systolic and diastolic sounds. In most cases, only the first (S1) and second (S2) heart sounds are heard. These are high-frequency sounds and arise from aortic and pulmonary valve closure (S1), as well as mitral and tricuspid valve closure (S2). Heart Sounds

Imaging

• Echocardiography with color doppler: 
  • Confirmatory (can be done prenatally)
  • Evaluates:
    • Type and location
    • Size of defect
    • Extent of left-to-right shunt
    • Pulmonary arterial pressure
• Chest X-ray:
  • Increased pulmonary vascularization
  • Cardiomegaly
• ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG):
  • Normal in smaller defects
  • Moderate-to-large defects may show LV and RV hypertrophy

Management

Management

The management of a VSD is based on the size of the defect and the clinical symptoms of the patient.

• Small VSD/asymptomatic infant:
  • Re-evaluate every 2 years, if murmur present.
  • Follow up yearly to assess development of symptoms.
  • Majority will close spontaneously.
• Asymptomatic moderate-to-large VSD:
  • Regular follow-up with echocardiogram to assess hemodynamic stability.
  • Surgically repair once LV dilation occurs.
• Symptomatic patient:
  • Mild:
    • Adequate growth with mild tachypnea
    • Medical management
  • Moderate:
    • Signs of failure to thrive
    • Medical management with caloric intake
    • Bridge to surgical repair
  • Severe: 
    • Symptoms of heart and/or respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure
    • Inpatient medical stabilization followed by immediate surgical repair
• Medical management:
  • Nutritional support
  • Heart failure → diuretics
  • Up-to-date vaccines
• Surgical management involves repairing defect with patch, usually before age of 1.

Prognosis

• Excellent long-term survival
• Majority of small and asymptomatic moderate VSD spontaneously close.
• Complications post-surgical repair are rare

Clinical Relevance

The following conditions are associated with VSD and can cause or modify the disease:

• Congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure: large VSD may result in severe left-to-right shunt causing reduced LV stroke volume, plus higher cardiac output from RV. This leads to pulmonary congestion and eventually right-sided heart failure.
• Failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive: suboptimal weight gain and growth in children. As with majority of CHDs, 1st presentation of VSD may be infant or child failing to meet necessary caloric requirement for growth due to increased demand of overworking heart.
• Endocarditis: growth of infectious vegetations on endothelium of heart. Patients with VSDs are at increased risk of developing it.
• Aortic insufficiency: inability of AV to remain shut during diastole, causing reversed flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure into LV. Due to low-pressure zone created in LV through VSD, AV prolapses and becomes insufficient.