Muscular Ventricular Septal Defect

Updated: Jan 04, 2016
Author: Michael D Taylor, MD, PhD; Chief Editor: Stuart Berger, MD 



Trabecular (muscular) ventricular septal defect (VSD) is the second most common type of VSD, occurring in 5-20% of most series. Trabecular muscular VSDs are divided into separate distinct regional groups, including midmuscular, apical, anterior, and posterior.[1] Midmuscular is the most common subtype of muscular VSD. Defects occurring centrally or along the margin of the interventricular septum and free wall are termed anterior VSDs. (See Epidemiology.)

When multiple muscular VSDs occur with a very large communication between the ventricles, it is also known as "Swiss cheese" VSD. Frequently, spontaneous closure of small muscular VSDs occurs in the first 2 years of life (usually by age 6 mo). (See Prognosis.)

Normal closure of the ventricular septum occurs through multiple concurrent embryologic mechanisms that help to close the membranous portion of the septum: (1) downward growth of the conotruncal ridges forming the outlet septum, (2) growth of the endocardial cushions forming the inlet septum, and (3) growth of the muscular septum forming the apical and midmuscular portions of the septum.

VSDs occur when any portion of the ventricular septum does not correctly form or if any of components do not appropriately grow together. The ventricular septum is complete by 6 weeks' gestation. VSDs are typically classified according to the location of the defect in one of the 4 ventricular components: the inlet septum, trabecular septum, outlet/infundibular septum, or membranous septum. This article specifically addresses defects in the trabecular muscular septum. (See Etiology.)

The precise etiology of muscular septal defect formation is unknown. However, the proposed mechanisms are many. Muscular defects may occur because of a lack of merging in the walls of the trabecular septum or because of excessive resorption of muscular tissue during ventricular growth and remodeling. (See Etiology.)


Complications of VSDs may include the following (see Clinical and Workup):

  • Congestive heart failure

  • Bacterial endocarditis

  • Eisenmenger syndrome

  • Aortic insufficiency

  • Subaortic stenosis

  • Double-chambered right ventricle

Patient education

Advise the patient and/or his or her parents regarding the risks of bacterial endocarditis and the importance of oral hygiene. Educate them concerning signs and symptoms of CHF.

For patient education information, see the Heart Health Center, as well as Ventricular Septal Defect.


Independent of the type of ventricular septal defect (VSD), the hemodynamic significance of a VSD is determined by 2 factors: the size of the defect and the resistance to flow out of the right ventricle, including the pulmonary vascular resistance (PVR) and anatomic right ventricular outflow obstruction.

In small to moderate VSDs, left-to-right shunting is primarily limited by the size of the defect. Conversely, in large VSDs without right ventricular outflow obstruction, the left-to-right shunting is determined by the relative degree of PVR and systemic vascular resistance.

Because PVR is high at birth and does not reach its nadir until age 6-8 weeks, the development of significant left-to-right shunting and pulmonary overcirculation, often termed congestive heart failure (CHF), can be delayed until the second or third month of life. Additional cardiac lesions that increase left-to-right shunting (eg, atrial septal defect, patent ductus arteriosus) may predispose patients to earlier development of CHF. Noncardiac abnormalities, including prematurity, infection, anemia, or other congenital anomalies, also may predispose infants to significant symptoms of heart failure.

Additional congenital heart lesions (eg, muscular right ventricular outflow tract obstruction, pulmonary valve stenosis, pulmonary venous obstruction, persistent elevation of PVR, mitral stenosis) can restrict shunting, possibly leading to right-to-left trans-VSD flow, depending on the ultimate resistance balance between the systemic and the total right-sided resistances.


Muscular ventricular septal defects (VSDs) have a multifactorial etiology and are predominantly the result of spontaneous abnormalities in development.[2] No correlation with maternal age or birth order is observed.

VSD is the most common congenital heart lesion in most chromosomal anomalies and syndromes. VSD is especially common in patients with trisomy 13, trisomy 18, and trisomy 21. In addition, there are numerous single-gene deletion syndromes associated with VSDs. However, the majority of VSDs (>95%) are not associated with chromosomal abnormalities.[3]

Noncardiac conditions associated with VSD are prematurity, syndromes, and chromosomal anomalies. Regular maternal cannabis slightly increases the incidence of VSD, as does the use of selective serotonin reuptake inhibitors (SSRIs) during early pregnancy.[4, 5]


Ventricular septal defects (VSDs) are slightly more common in females than in males. Large muscular VSDs may not present until age 6-8 weeks, when decreased PVR allows significant left-to-right shunting and the appearance of clinical signs and symptoms of CHF. Most muscular VSDs present clinically in the neonatal period. Typically, these defects, especially the smaller ones, are not suspected at birth and may not be identified by auscultation until the PVR begins to fall in the first few days to weeks of life.

The VSD may manifest soon after birth if it is associated with significant additional congenital heart lesions or if it occurs with an associated chromosomal anomaly or syndrome.

Occurrence in the United States

Without regard to type, VSD is the most common congenital heart defect in the first 3 decades of life, with an incidence between 1.5-4.2 cases for every 1000 live term infants. One study described an incidence of muscular VSD of 2.7 cases per 1000 live births.[6]

VSD is more common in premature infants, with an incidence of 4.5-7 cases for every 1000 live births. Clinically significant VSD that requires medical or surgical management accounts for only 15% of such defects (0.35-0.50 cases for every 1000 live births). When viewing congenital heart disease in total, solitary VSD cases account for 20% of congenital heart disease.

Muscular VSD is the second most common type of VSD, accounting for as many as 40% of VSD cases identified in most surgical or autopsy series.

International occurrence

The prevalence of VSD worldwide is relatively constant. However, the type of VSD that predominates in a region widely varies. In the United States, perimembranous VSDs are most common. In Asia, subaortic VSDs (outlet type) are most common.[7]


Children with small to moderate-sized ventricular septal defects (VSDs) have an excellent prognosis. Infants and children with large VSDs have a good, overall prognosis. Optimal medical management with appropriate timing of surgical intervention in these patients has the best outcome. However, patients with multiple muscular VSDs have a more variable prognosis.

Muscular VSDs may spontaneously decrease in size and eventually close. Small muscular VSDs have the greatest likelihood of spontaneous closure, with closure rates approaching 80-90% by age 2 years. Muscular defects in these patients decrease in size due to growth of the ventricular myocardium, which fills in the defect. One study that used fetal echocardiography showed that 33% of all defects closed in utero, 44% of defects spontaneously closed within the first postnatal year, and 23% of defects did not close.[8]

Morbidity and mortality

Morbidity and mortality associated with VSDs are influenced by the number and size of the defects, the degree of left-to-right shunting, the presence of associated congenital heart defects, the presence of associated noncardiac defects and syndromes, and the patient’s age at repair of the VSD.

For patients with large muscular VSDs, surgical repair is indicated at any time during the first year of life if the infant fails to grow appropriately despite optimal medical management. Surgical risk and mortality for patients with large VSDs are higher in the first 2 months of life (10-20%) than after age 6 months (1-2%), although these figures are currently decreasing. Elective surgical closure of large VSDs should be planned within the first year of life to prevent development of irreversible pulmonary vascular obstructive disease (ie, Eisenmenger syndrome).

Multiple muscular VSDs, also known as Swiss cheese ventricular septum, are significantly more complex. Patients often show early signs of CHF. This lesion may require staged surgical palliation.





Most patients with small muscular ventricular septal defects (VSDs) are asymptomatic and come to medical attention due to the discovery of a systolic murmur. Most murmurs have a delayed presentation in the newborn period, occurring in the first few days to weeks following birth.

At birth, PVR is high, which maintains an elevated right ventricular pressure equal to the left ventricular pressure. As the PVR falls, the developing pressure gradient from the left ventricle to the right ventricle allows high-velocity left-to-right shunting across the muscular VSD, producing the typical holosystolic murmur.

Progression of symptoms

Patients with an isolated, large muscular VSD are typically asymptomatic in the immediate newborn period. As PVR falls, the degree of left-to-right shunting is proportional to the size of the defect and the relative degree of PVR. The larger the VSD and the lower the PVR, the greater is the degree of left-to-right shunting.

Typically, infants with large VSDs present with signs and symptoms of CHF at age 6-8 weeks or later as PVR continues to fall and the degree of left-to-right shunting increases. CHF signs include inadequate weight gain and growth, along with recurrent lower respiratory tract infections in patients with a large VSD without evidence of CHF but with elevated pulmonary artery pressure (>50% systemic pressure) or or a pulmonary artery – to – systemic flow ratio greater than 2:1.

Signs and symptoms of CHF also include poor feeding, tachypnea, tachycardia, sweating (especially after feeding), and lethargy.

Chromosomal anomalies

VSD is the most common congenital heart lesion (20-30%) in infants with chromosomal anomalies or syndromes. Defects may be discovered in the first days of life due to additional diagnostic evaluation to exclude multiple congenital defects.

Physical Examination

Typical physical examination findings are influenced to a significant degree by the size of the ventricular septal defect (VSD) and the degree of left-to-right shunting.

Small VSD

Symptoms of a small VSD (defined as a VSD with a dimension less than half the size of the aortic annulus diameter) include the following:

  • Vital signs and weight gain are normal

  • The precordium is quiet, with a normal apical impulse

  • The first heart sound is normal

  • The second heart sound is typically narrowly split; the pulmonary component may be accentuated

  • A third heart sound is generally not present

  • A palpable thrill may be observed at the middle to lower left sternal border

  • A grade III-VI/VI holosystolic murmur, which widely radiates throughout the precordium, is present along the left sternal border

The intensity of the murmur is inversely proportional to the size of the defect, the left ventricle–to–right ventricle pressure gradient, and the degree of left-to-right shunting. In general, smaller defects produce the loudest murmur.

Systolic murmurs are usually holosystolic but may occasionally be crescendo or crescendo-decrescendo. No diastolic murmur is typically present.

Large VSD

The symptoms of a large VSD (defined as a defect size equal to the diameter of the aortic annulus) are as follows:

  • Poor growth and poor weight gain are common

  • Signs and symptoms of CHF may be present, including tachypnea, tachycardia, sweating, and pallor

  • Hyperdynamic precordium, with or without a precordial bulge secondary to underlying cardiomegaly

  • Abnormal apical impulse with or without right ventricular tap is present; a thrill is uncommon with large VSDs

  • A normal first heart sound and a narrowly split second heart sound with a loud pulmonary component are evident

  • A prominent third heart sound is typically present at the apex, producing a gallop rhythm

  • A II-III/VI holosystolic murmur is maximal at the left sternal border, with wide precordial radiation

  • A diastolic flow rumble may be present at the cardiac apex; this diastolic murmur is caused by a significant left-to-right shunt (at least a 2:1 left-to-right shunt), with excessive flow across a normal-sized mitral annulus





Approach Considerations

For children with small ventricular septal defects (VSDs), no specific laboratory blood tests are indicated. Occasionally, in the evaluation of children with a large, symptomatic VSD, brain natriuretic peptide (BNP) is measured as a marker of CHF severity. Electrolytes should be periodically measured in children who are maintained on diuretics and angiotensin-converting enzyme (ACE) inhibitors.

Electrocardiographic findings vary depending on the VSD size and the degree of intracardiac shunting. Patients with small VSDs have normal ECG findings.

Large VSDs show left ventricular hypertrophy (LVH) (ie, volume overload), right ventricular hypertrophy (RVH) (ie, pressure overload), and left atrial enlargement.

Histologic findings

No specific histologic abnormality is present. However, lung biopsy findings are sometimes used to stage degrees of pulmonary vascular obstructive disease.

Imaging Studies

Chest radiography

Small ventricular septal defects (VSDs) show normal cardiac size and normal pulmonary vascularity. Large VSDs demonstrate cardiac enlargement and increased pulmonary vascular markings proportional to the size of the left-to-right shunt, left atrial and left ventricular enlargement, the posterior displacement of the left ventricular apex, and the prominence of the main pulmonary artery segment.

Two-dimensional echocardiography and Doppler

Two-dimensional (2D) echocardiography with Doppler color flow mapping is the most reliable noninvasive modality to identify the presence, size, number, and location of VSDs. Muscular VSD is readily identified from the apical, 4-chamber, parasternal long-axis and parasternal short-axis scan planes.

Small VSDs are usually isolated defects with otherwise normal cardiac anatomy and function. Large VSDs typically have left atrial and left ventricular dilation, with normal left ventricular systolic and diastolic function. Dilation of the main and branch pulmonary arteries is also common.

Echocardiography is also useful in determining the presence of associated intracardiac findings including right ventricular muscle bundles, infundibular stenosis, pulmonary valve stenosis, and associated left-sided lesions (eg, subaortic membrane, aortic stenosis, aortic cusp prolapse, coarctation of the aorta).

Doppler echocardiography can be used to predict the intracardiac pressure gradient from the left ventricle to the right ventricle using the continuous wave Doppler tracing (modified Bernoulli equation = 4 [velocity squared] and subtracting the calculated gradient from the aortic systolic blood pressure [in the absence of aortic stenosis]).[9]

Color Doppler ultrasonography is useful in determining VSD location and size as well as the degree of intracardiac shunting.

These tests are also essential to rule out other commonly associated congenital heart lesions including atrial septal defects, patent ductus arteriosus, pulmonary valve stenosis, and complex congenital heart disease with associated VSD.

Three-dimensional echocardiography

Real-time 3-dimensional echocardiography (RT3DE) can be applied to the characterization of the ventricular septum. RT3DE allows accurate determination of VSD size, shape, and location. The short acquisition time and acceptable reconstruction time make this technique clinically applicable.

RT3DE is especially helpful in the characterization of multiple muscular VSDs (Swiss cheese VSD). It allows for more precise interventional and surgical planning for this very challenging anatomy.[10]

Magnetic resonance imaging

Cardiac magnetic resonance imaging (MRI) is a useful adjunct in the evaluation of large muscular VSDs. Black blood imaging at end-diastole reliably shows the anatomy of the ventricular septum, ventricular chambers, and great vessels. Bright blood gradient-echo dynamic images are useful for evaluating the anatomy in all segments of the cardiac cycle. Tiny muscular VSDs are not well seen using cardiac MRI.

Flow-sensitive phase contrast imaging is the criterion standard for determining the direction and magnitude of shunting. It can alleviate the requirement for cardiac catheterization in some cases.

Diagnostic Cardiac Catheterization and Angiography


Routine diagnostic cardiac catheterization is no longer required for muscular ventricular septal defects (VSDs). However, it is indicated in some situations, such as inadequate noninvasive assessment of the size, number, or location of VSDs by echocardiography.

Other indications include a requirement to determine additional hemodynamic data prior to medical management or surgical repair (eg, determination of PVR and its reactivity, quantitation of left-to-right shunting, exclusion of associated congenital heart defects).

Older children and adults with a large, unoperated VSD usually require cardiac catheterization prior to surgical closure to assess PVR.


Muscular VSDs are best demonstrated in the long axial oblique orientation; anterior muscular defects are best demonstrated in right anterior oblique angulation, while posterior muscular defects are best visualized in the hepatoclavicular view. Angiography can be a useful adjunct to identify multiple defects in the muscular septum.



Approach Considerations

Small muscular ventricular septal defects (VSDs) have a high spontaneous closure rate (80-90%) within the first 2 years of life and often require no medical or surgical management. Larger defects may not close but may become smaller with time.

Medical therapy may be required with large muscular VSDs due to excessive left-to-right shunting and the development of CHF. Therapy is directed at alleviating the symptoms of pulmonary overcirculation and typically includes increased-calorie feedings, diuretics, and, sometimes, an ACE inhibitor.

Diuretic therapy with furosemide is used to lessen volume overload. Significant potassium wasting may warrant the addition of spironolactone or potassium supplementation.

The use of afterload reduction to improve systemic-pulmonary flow ratios may be beneficial in selected cases. ACE inhibitors also inhibit the tissue-based renin-angiotensin system, preventing deleterious remodeling. Be aware that ACE inhibitors have a potassium-sparing effect. When these are used, spironolactone or supplemental potassium should be avoided or judiciously used.

Surgical indications

Failure of medical management to alleviate symptoms in the first 6 months of life requires intervention. Growth failure despite optimal medical therapy and maximized calorie intake is the most important evidence of failure of medical therapy. Intervention is either by surgery or by cardiac catheterization. Very large left-to-right shunts are usually electively repaired within the first year of life.

Elevated pulmonary arteriolar resistance of more than 12 Wood units that does not decrease with oxygen or selective pulmonary vasodilator therapy may be regarded as inoperable.


In patients with small muscular VSDs, no special diet is required. For patients with large muscular VSDs and significant CHF, caloric supplementation is often required using fortified formula or breast milk.


Patients with small muscular VSDs can maintain normal activity. Patients with moderate to large defects with significant symptomatology may self-limit strenuous exercise until the defect is repaired. Patients with repaired VSD and no residual cardiac sequelae can resume regular activity.

Inpatient care

Routine inpatient monitoring of infants and children with a small muscular VSD is not necessary. Hospitalization for severe CHF usually indicates the need for early intervention for VSD closure.


Transfer to a tertiary care center may be required for further diagnostic evaluation or surgical intervention in patients with large VSDs or multiple VSDs.


Consultations may be indicated with the following specialists:

  • Pediatric cardiologist

  • Pediatric cardiothoracic surgeon

Surgical Treatment

Surgical repair is the most common intervention currently performed.[11] New surgical approaches using smaller incisions have proven effective in single ventricular septal defect (VSD) closure.[12] Surgical repair of an isolated large VSD involves closure of the muscular defect with a Gore-Tex patch.

Surgical intervention in younger infants, especially those younger than 1 month, is associated with an increased risk of mortality (historically as high as 10-20%, although currently much lower). Surgical mortality is now very low (approximately 1%) in patients older than 6 months with isolated large muscular VSDs.

Patients with multiple muscular VSDs may undergo pulmonary artery banding if primary repair is deemed too risky. This palliative procedure limits the degree of left-to-right shunting and allows additional time for these defects to decrease in size or undergo spontaneous closure.

Cardiac Catheterization and Hybrid Procedures

Devices are now available for closure of muscular ventricular septal defects (VSDs).[13] VSD closure devices typically have 2 opposing discs (one for the right ventricular side and one for the left ventricular side), which are released during catheterization under fluoroscopic and transesophageal echocardiographic guidance to occlude the defect. Data suggest that closure of small muscular VSDs in patients with otherwise normal anatomy offers less short-term morbidity with similar results. However, the long-term morbidity is unknown.[14, 15, 16, 17, 18, 19]

The closure devices can be percutaneously placed in the cardiac catheterization laboratory or in the operating room during a "hybrid procedure."[20, 21, 22] Hybrid procedures may involve inserting the device through a very small incision in the free wall of the right ventricle.

Ongoing investigational trials are currently being performed to assess indications and outcomes in VSD closure with these devices. Data suggest that the ventricular septal occluder does not cause interventricular conduction disturbances in greater numbers than does surgical repair.

Outpatient Care

Mild to moderate congestive heart failure (CHF) secondary to left-to-right shunting from a ventricular septal defect (VSD) may be managed in an outpatient setting. For routine muscular VSDs, prophylactic antibiotics for the prevention of bacterial endocarditis are no longer recommended by the American Heart Association, except under special circumstances.[23] A modest risk of endocarditis is still observed; thus, the importance of vigilant oral hygiene should be reinforced.

Small muscular VSDs have a high incidence of spontaneous closure. Serial follow-up care should be performed until spontaneous closure occurs. Moderate-sized VSDs can also be followed in the outpatient setting while awaiting evidence of reduction in size or spontaneous closure. Patients with a large VSD but without significant CHF can be followed as outpatients, with frequent evaluations.

Serial patient follow-up care is required for assessment of patient growth and ongoing evaluation of the need for elective surgical closure.



Medication Summary

Diuretics are the mainstay of medical therapy in infants and children with large ventricular septal defects (VSDs), large left-to-right shunts, and evidence of congestive heart failure (CHF). Many centers also use digoxin, but some debate surrounds its efficacy, especially in infants. The patient’s hemoglobin level should be adequate.

Afterload reduction may be beneficial in certain situations. As previously mentioned, ACE inhibitors have a potassium-sparing effect. When these are used, spironolactone or supplemental potassium should be avoided or judiciously used.


Class Summary

These agents relieve ventricular volume load and peripheral and pulmonary congestion. They promote excretion of water and electrolytes by the kidneys and are used to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention has resulted in edema or ascites.

Furosemide (Lasix)

Furosemide increases the excretion of water by interfering with the chloride-binding cotransport system, which, in turn, inhibits sodium and chloride reabsorption in the ascending loop of Henle and distal renal tubule.

Spironolactone (Aldactone)

Spironolactone is used for the management of edema resulting from excessive aldosterone excretion. It competes with aldosterone for receptor sites in distal renal tubules, increasing water excretion while retaining potassium and hydrogen ions.

Angiotensin Converting Enzyme (ACE) Inhibitors

Class Summary

These afterload reduction agents decrease systemic afterload and, therefore, may decrease left-to-right shunting through a large ventricular septal defect (VSD). They are used to improve preoperative or postoperative cardiac output, reducing systemic vascular resistance and increasing blood flow resulting from myocardial dysfunction and/or significant mitral valve insufficiency.

Enalapril (Vasotec)

Enalapril is a competitive ACE inhibitor; it reduces angiotensin II levels, decreasing aldosterone secretion.


Captopril prevents the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in lower aldosterone secretion.

Cardiac Glycosides

Class Summary

These inotropic agents are used to augment ventricular contractility. Positive inotropic agents increase the force of contraction of the myocardium and are used to treat acute and chronic CHF. Some may also increase or decrease the heart rate (ie, positive or negative chronotropic agents), provide vasodilatation, or improve myocardial relaxation. These additional properties influence the choice of drug for specific circumstances. Digoxin is predominantly used for its inotropic effect.

Digoxin (Lanoxin)

Digoxin is a cardiac glycoside with direct inotropic effects in addition to indirect effects on the cardiovascular system. It acts directly on cardiac muscle, increasing myocardial systolic contractions. Digoxin's indirect actions result in increased carotid sinus nerve activity and enhanced sympathetic withdrawal for any given increase in mean arterial pressure.