Ventricular Septal Defect (VSD)

Overview

VSDs are the most common congenital cardiac anomaly in children and the second most frequent congenital abnormality in adults, behind only bicuspid aortic valves. A ventricular septal defect (VSD) is a cardiac birth abnormality in which there is a hole in the wall that divides the heart's two lower chambers (ventricles). The ventricular septum is another name for this wall.

While many VSDs repair naturally, severe defects can cause problems such as pulmonary arterial hypertension (PAH), ventricular dysfunction, and an increased risk of arrhythmias.

What is Ventricular septal defect (VSD)?

A ventricular septal defect (VSD) is a hole or flaw in the wall that connects the heart's lower two chambers. These chambers are known as ventricles, and the wall that separates them is known as the ventricular septum. A child's ventricular septal defects might be solitary or numerous. Ventricular septal abnormalities can sometimes arise in conjunction with more severe cardiac disorders such as Tetralogy of Fallot and great vessel transposition.

Ventricular septal defects can be further described by:

1. Size of the defect,
2. Location of the defect, 
3. Whether there is more than one defect present, and
4. The presence or absence of a ventricular septal aneurysm. 

The flaw is often classified as mild, moderate, or major. Small abnormalities, in general, create no symptoms throughout birth or childhood and frequently heal spontaneously. Moderate and large abnormalities are less likely to heal naturally, may cause congestive heart failure, and require surgical closure more frequently. The extent of the flaw is sometimes described using the terms restrictive or non-restrictive.

Small abnormalities that allow little or no blood flow from the left side of the heart to the right side of the heart are referred to as restrictive defects. Non-restrictive defects are big abnormalities that allow substantial blood flow from the left to the right side of the heart. This causes increased blood flow to the lungs, elevated pulmonary artery pressures, more strain for the heart, and congestive heart failure. 

Epidemiology

Isolated VSD is responsible for 37% of all congenital heart disease in children. Isolated VSD affects around 0.3 percent of neonates. Because up to 90% of adults may ultimately seal spontaneously, the incidence is substantially lower in children. VSDs exhibit no preference for one gender over another. In the pathophysiology section, the proportion of each category is shown.

VSD Causes

VSD occurs when there is a developmental error or stoppage in the establishment of the interventricular septum during the intricate embryologic heart morphogenesis. VSDs are often solitary; however, they can coexist with other congenital heart abnormalities such as atrial septal defects, patent ductus arteriosus, right aortic arch, and pulmonic stenosis.

They are also seen in aortic coarctation and subaortic stenosis, and they are a common component of complicated congenital cardiac disease such as Tetralogy of Fallot and transposition of the major arteries. VSDs are caused by a variety of genetic causes, including chromosomal, single gene, and polygenic inheritance. 

Non-inherited risk factors for VSDs have been identified, including maternal infection (rubella, influenza, and febrile sickness), maternal diabetes mellitus, and phenylketonuria. VSDs have also been associated to pollutants such as alcohol, marijuana, cocaine, and some drugs such as metronidazole and ibuprofen.

Pathophysiology

Because of the pressure differential between the ventricular chambers, the interventricular septum is an asymmetric curving structure. It is made up of five sections: the membranous, muscular (also known as trabecular), infundibular, atrioventricular, and inlet.

Failure of one of the above components to develop or fuse during embryonic heart morphogenesis leads in a VSD in the associated component. VSDs' many anatomic sites and histologic differences have resulted in a number of categorization and naming schemes. Complexities in characterizing VSDs and many synonyms have been reduced with the establishment of a new unified categorization that categorizes VSDs into four primary groups:

• Type 1: (infundibular, outlet) This VSD is positioned below the semilunar valves (aortic and pulmonary) in the right ventricle's outflow septum above the crista supraventricularis, which is why it is also known as supracristal. It is the most uncommon kind, accounting for just 6% of all VSDs, with the exception of the Asian population, where it accounts for around 30%. Aortic valve prolapse and regurgitation are widespread due to the lack of support of the aortic valve's right and/or noncoronary cusps. It is rare for these flaws to close on their own.
• Type 2 (membranous): This VSD is by far the most prevalent, accounting for around 80% of all defects. It is found underneath the crista supraventricularis in the membranous septum. When it is referred to be perimembranous, it frequently affects the muscular septum. The septal leaflet of the tricuspid valve can sometimes develop a "pouch," reducing the shunt and resulting in spontaneous closure.
• Type 3 (inlet or atrioventricular canal): Within the intake region of the right ventricular septum, this VSD is positioned immediately inferior to the inlet valves (tricuspid and mitral). It accounts for just 8% of all defects. It is present in Down syndrome individuals.
• Type 4 (muscular, trabecular): This VSD is found in the muscular septum, and it is frequently surrounded by muscle in the apical, middle, and outlet sections of the interventricular septum. They can be many, like "Swiss cheese." They account for up to 20% of VSDs in babies. However, because to the tendency of spontaneous closure, the prevalence is decreased in adulthood.

The primary pathophysiologic mechanism of VSD is the formation of a shunt between the right and left ventricles. The hemodynamic importance of the VSD is determined by the volume of blood shunted and the direction of the shunted flow. These variables are influenced by the size, location, and pulmonary vascular resistance of the VSD.

While VSDs are classed geographically, they may also be classified by size. The size is stated in relation to the aortic annulus diameter. They are classified as small if they are less than or equal to 25% of the aortic annulus diameter, medium if they are larger than 25% but less than 75%, and big if they are greater than 75% of the aortic annulus diameter.

Long-standing massive left-to-right shunts cause permanent alterations in the pulmonary vascular endothelium, resulting in chronic PAH. When the pulmonary circulation pressure surpasses the systemic circulation pressure, the shunt direction reverses and becomes a right-to-left shunt. This is known as Eisenmenger syndrome, and it affects 10% to 15% of people with VSD.

VSD Symptoms

The appearance of unrepaired VSDs is primarily reliant on the presence of hemodynamically significant shunt; hence, the size of the defect is directly connected to it. Small VSDs cause just a little left-to-right shunt without causing left ventricular (LV) fluid excess or PAH; they are frequently asymptomatic or discovered inadvertently on physical examination. Medium-sized VSDs cause moderate LV volume overload with absent to mild PAH; they manifest late in childhood as mild congestive heart failure (CHF).

Due to significant LV overload and severe PAH, those with substantial defects develop CHF early in childhood. VSD murmurs are often pan-systolic and best heard in the left lower sternal border; they are sharp and loud in minor faults but softer and less intense in big defects. Handgrips enhance afterload, which strengthens the murmur. The pulmonic region is the finest place to hear infundibular problems.

In the presence of aortic regurgitation, a diastolic decrescendo murmur and a broad pulse pressure might be heard. The mid-diastolic rumbling at the lower left sternal border may be caused by increased LV flow. A septal aneurysm's systolic click can occasionally be heard in membranous defects. Eisenmenger syndrome is characterized by cyanosis, desaturation, dyspnea, syncope, secondary erythrocytosis, and clubbing; the usual murmur of VSD may be missing, and an exaggerated pulmonic component of the second heart sound may be detected.

VSD Diagnosis

• Because of its great sensitivity, color Doppler transthoracic echocardiography (TTE) is the most valuable diagnostic tool. Color Doppler TTE may identify up to 95% of VSDs, particularly non-apical lesions bigger than 5 mm; it offers morphologic information such as size, position, and number of defects, as well as hemodynamic information such as jet size, severity, and pulmonary artery pressure assessment. TTE can identify any related aortic insufficiency as well as other congenital cardiac abnormalities. Finally, TTE may be used to assess the size and function of the right and left ventricular chambers. Operator dependency and a weak acoustic window are two drawbacks. When standard TTE is inconclusive, a trans-esophageal echo (TEE) is advised.
• Electrocardiography (ECG) is completely normal in 50% of VSD patients. When the ECG is aberrant, it can reveal LV hypertrophy in patients who have big shunts. Right bundle branch block, right axis deviation, and right ventricular (RV) hypertrophy and strain may be seen on the ECG in PAH patients.
• Chest radiography (CXR) is frequently normal in people with minor flaws. Larger abnormalities and increased LV size might result in an enlarged cardiac silhouette. PAH patients may have RV enlargement and increased pulmonary diameter.
• Cardiac MRI and computed tomography (CT) are effective in situations where the anatomy is complicated, such as VSD in conjunction with other congenital cardiac malformations, and in lesions in atypical places that are difficult to identify with standard TTE.
• Cardiac catheterization provides reliable hemodynamic information on pulmonary vascular resistance and response to vasodilators; this is especially beneficial in patients undergoing surgical closure. It goes into further depth about concomitant aortic regurgitation, numerous VSDs, and coronary artery disease.

VSD Treatment

During the first year of life, around 85 to 90 % of tiny isolated VSDs close spontaneously. Patients with minor, asymptomatic VSDs and no PAH have a favorable prognosis without treatment. Otherwise, the management strategy calls for VSD closure. Due to the difficulty of such instances, patients with Eisenmenger syndrome are generally addressed in advanced centers. Historically, the sole alternative for VSD correction was surgical repair; however, new improvements in interventional procedures now allow for percutaneous VSD closure.

Antibiotic prophylaxis for infective endocarditis is no longer regularly provided for individuals with unrepaired ventricular septal defects. Endocarditis prophylaxis is most needed in patients with cyanotic congenital heart disease, past bouts of endocarditis, and those who have prosthetic heart valves or have had prosthetic heart valve repair. VSD closure is often suggested in medium to large defects with considerable hemodynamic compromise, such as those with symptomatic LV failure.

Surgical repair

Surgical repair lowers the incidence of endocarditis, may improve PAH, and improves overall survival. The surgical mortality rate without PAH is around 1%. Residual or recurrent VSD, valvular incompetence such as tricuspid regurgitation and aortic insufficiency, arrhythmias, LV dysfunction, and development of PAH are among complications.

Arrhythmias associated with VSD repair include atrial fibrillation, total heart block, and, in rare cases, ventricular tachycardia. The existence of irreversible PAH is the principal contraindication for surgical VSD closure, due to the significant surgical perioperative mortality and pulmonary complications.

Percutaneous system VSD closure is reserved for patients whose operation is extremely dangerous due to severe PAH, several comorbidities, or past cardiothoracic surgery, such as residual or recurrent VSD. Muscular VSDs are the most common kind susceptible to this surgery; nevertheless, the closeness of other abnormalities to the input valves makes this approach difficult to conduct in such patients.

Despite its unpopularity in the United States, current statistics show great results with full closure and minimal mortality. The most common problem is total atrioventricular block, which is usually caused by perimembranous abnormalities.

What are the effects of this defect on my child's health?

In general, the consequences of a ventricular septal defect are proportional to its magnitude. Small ventricular septal defects, as previously mentioned, do not elicit symptoms in infancy or youth and seldom require surgical or medicinal treatment. The majority of muscle VSDs close on their own throughout childhood. If a ventricular septal aneurysm is present, a membraneous VSD can close at any time. Small ventricular septal abnormalities are unlikely to have an impact on the child's growth or development.

A modest ventricular septal defect is usually associated with a slightly higher risk of subacute bacterial endocarditis (SBE). This is a cardiac infection caused by bacteria in the bloodstream. It frequently arises after a dental or other medical operation and may usually be avoided by taking an antibiotic before the surgery.

Larger ventricular septal defects cause increased blood flow to the lungs due to shunting of blood over the defect. Normally, the resistance or pressure on the left side of the heart is substantially higher than the pressure on the right side. When there is a significant defect, the blood follows the "way of least resistance" and returns to the right ventricle rather than leaving the body. This causes pulmonary overcirculation and additional effort for the heart.

Excessive perspiration (a cold, clammy sweat typically seen during feeding), poor feeding, delayed weight growth, irritability or lethargy, and/or fast breathing occur when the heart is unable to match this increased workload. When this happens, medications are frequently begun. If the medications do not work, surgery is typically advised.

A relatively tiny percentage of ventricular septal defects placed near the pulmonary valve might cause aortic valve injury. When this happens, the aortic valve begins to leak. Because leaking frequently worsens with time, surgical closure of the breach is often advised, even if the defect is minor.

What is the outlook for children with ventricular septal defects?

The prognosis for a kid with a ventricular septal defect is favorable. As previously stated, the majority of problems close on their own or are so little that no treatment is required. The surgical outcomes are also great. If the kid simply has a ventricular septal defect and a normal heart, the surgical death rate approaches 0%. Major problems are uncommon and include cardiac block and inadequate defect closure. Major problems occur in fewer than 1% of cases.

• What activities can my child do?

If the VSD is tiny or has been surgically closed, your kid may not require any additional care about physical exercise and can engage in routine activities without danger.

• What will my child need in the future?

Depending on the location of the VSD, your child's pediatric cardiologist will evaluate him or her on a regular basis to search for unusual abnormalities, such as an aortic valve leak. If a leak develops in this heart valve, older children with minor VSDs may require surgery. Following VSD surgery, your kid will be examined on a regular basis by a pediatric cardiologist. The cardiologist will examine the heart to ensure that it is functioning appropriately. Long-term prognosis is favorable, and typically no medications or additional surgery are required.

• What about preventing endocarditis?

Ask about your child's endocarditis risk. Your child's cardiologist may advise him or her to take antibiotics before some dental treatments for a period of time following VSD surgery. For further information, see the Endocarditis section.

Conclusion 

Finally, VSD is the most prevalent congenital birth defect. A ventricular septal defect is a hole in the ventricular septum, which is the separating wall between the right and left ventricles of the heart. VSD is a heart abnormality that is present at birth.

When the VSD is big, the heart may need to work harder to pump adequate oxygen into the body. Patients with a minor VSD often have no symptoms. Something happens to the fetus during the first eight weeks of pregnancy that affects heart development, resulting in a VS. Other cardiac abnormalities can occur in children with VSD.

Small flaws are anticipated to heal naturally in the first year of life, while bigger defects can cause significant difficulties. The primary solution for big problems is surgical VSD closure and device closure.