Supracristal Ventricular Septal Defect 

Updated: Aug 31, 2015
Author: Ira H Gessner, MD; Chief Editor: Howard S Weber, MD, FSCAI 

Overview

Background

Supracristal (or doubly committed) ventricular septal defect (VSD) is the least common type of VSD in the Western Hemisphere, accounting for approximately 5-7% of such defects in this part of the world, including in the United States.[1] The location of the supracristal VSD, with its close proximity to the aortic valve, accounts for the common development of aortic insufficiency with this defect. Left-to-right shunting of blood through the defect is believed to progressively pull aortic valve tissue (especially the right coronary cusp) through a Venturi effect (see the image below). (See Pathophysiology.)

Parasternal long-axis echocardiogram view showing Parasternal long-axis echocardiogram view showing supracristal ventricular septal defect (arrow) with buckling and prolapse (***) of the right coronary cusp of the aortic valve.

The crista supraventricularis can be considered synonymous with the infundibular (or conus) ventricular septum. It is the portion of the septum that separates the tricuspid and pulmonary valves. Defects above this part of the septum are referred to as supracristal defects. The term is generally reserved for defects lying immediately under the pulmonary valve. A defect, usually small, may occur within the conus septum, and, technically can be termed supracristal. (See Anatomy and Etiology.)

The spiraling course of the ventricular septum may make diagnosis of supracristal VSD more difficult. (See Clinical and Workup.)

Anatomy

The infundibular (or conus) septum separates the tricuspid and pulmonary valves and accounts for the more superior placement of the pulmonary valve relative to the aortic valve. This portion of the septum also provides fairly rigid, muscular support for the aortic valve, especially the right coronary cusp.[3]

Numerous synonyms indicate the confusion often associated with describing supracristal ventricular septal defects (VSDs). The term supracristal may be misleading because the entire conus septum (or a major portion of the septum) may be missing. The term is commonly used, however, emphasizing the superior location of the defect along with its close approximation to the aortic and pulmonary valve leaflets. Lack of support for the right aortic leaflet is crucial to the natural history of this type of VSD.[4]

The plane of the conus septum in the right ventricular outflow tract lies almost perpendicular to that of the remainder of the septum. From a surgical perspective, a defect lying in the conus septum may not be visualized from the standard right atriotomy approach, looking through the tricuspid valve.[3, 5]

Unlike the more common perimembranous type of VSD, the supracristal VSD does not lie near the tricuspid valve. Unless the supracristal defect is large, extending inferiorly to the perimembranous septum, the tricuspid valve is not involved in partial closure of the defect.

Conduction system tissue lies inferior to the supracristal VSD. The conduction system may lie closer to a larger defect that crosses from the outlet septum into the perimembranous area.

Pathophysiology

The natural history of supracristal ventricular septal defects (VSDs) depends on the location and size of the defect. Patients with small, isolated supracristal VSDs may have no symptoms or signs of congestive failure such as might be observed with a large shunt. Progressive aortic insufficiency may develop later in life. Larger defects of the outlet septum frequently are associated with forms of aortic outflow obstruction (eg, coarctation, interrupted aortic arch). In such cases, symptoms of congestive heart failure and possible circulatory collapse appear early.

Patients with larger, isolated supracristal VSDs may develop congestive heart failure early in infancy due to a large left-to-right shunt. While spontaneous closure is not common,[6] a decrease in the magnitude of the left-to-right shunt may occur due to progressive prolapse into the defect of aortic valve tissue (the right coronary cusp or, possibly, the right sinus of Valsalva).[7] This valve leaflet prolapse is believed to result from the Venturi effect, as the high-velocity shunt flow produces negative pressure. Progressive distortion of the aortic leaflet or sinus as it prolapses into the VSD may lead to increasing aortic valve insufficiency.

Etiology

The muscular outlet septum is primarily formed from the proximal endocardial ridges (similar to endocardial cushion tissue). Semilunar valve tissue and the actual connection between the septum and the arteries are formed by the more distal endocardial ridges. Extracardiac mesenchyme, derived from neural crest tissue, condenses as prongs (which act as a welding agent) with the most superior portion of the distal cushions to form the aortopulmonary septum.[8] By exposing neural crest tissue to homocysteine, supracristal ventricular septal defects (VSDs) have been induced in a high percentage of chick embryos. Disruption of apoptosis and myocardialization has been proposed to explain these findings.[9]

The frequent association between arch abnormalities and significant conal VSDs suggests a common mechanism involving a chromosome band 22q11 microdeletion. Deletions in this area have not been linked with isolated supracristal VSDs.[10]

Epidemiology

As stated above, supracristal ventricular septal defect (VSD) accounts for approximately 5-7% of VSDs in the Western Hemisphere.[1] In the Eastern Hemisphere, however, the incidence of this condition is much higher, reaching 25% of all VSDs in patients from this part of the world, as supracristal VSDs are much more common in persons of Asian descent than in individuals of other races. Although the overall incidence of VSDs is no greater in Asians than in other groups, supracristal VSDs account for approximately 30% of VSDs in Asians.[1] Higher occurrence of the condition in this population has not been adequately explained, but one may assume that it is genetically determined.

Prognosis

The prognosis in patients with supracristal ventricular septal defect (VSD) should be considered good to excellent when the potential complication of aortic valve insufficiency is recognized and aggressively treated.[11, 12] Delayed recognition of or surgical treatment for progressive aortic valve insufficiency may lead to severe distortion of the aortic valve leaflet, making eventual valve replacement more likely.[13]

Morbidity or mortality in supracristal VSD is generally not the result of a large left-to-right shunt. Rather, it is caused by the development of aortic valve insufficiency. When progressive and severe, this results in left ventricular enlargement and eventual congestive heart failure, hence the admonition to address this problem early.

The appearance of aortic insufficiency as a complication of supracristal VSD is related to age. Young infants and toddlers presenting with supracristal VSDs are more likely to have findings of pulmonary overcirculation from the left-to-right shunt. While it may occur earlier in infancy, onset of aortic valve prolapse and progressive aortic insufficiency generally begins in children aged 6-10 years.

Patients with supracristal ventricular septal defect (VSD) are at increased risk of infective endocarditis. The risk is higher if aortic valve insufficiency is present.

Patient Education

The patient’s risk of developing infective endocarditis is higher for supracristal VSD with aortic insufficiency than it is for an isolated VSD. Patients and families should be educated on the importance of good oral and dental hygiene. Routine prophylaxis for dental or surgical procedures is no longer recommended unless there has been a prior episode of endocarditis.[2]

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

 

Presentation

History

In patients with supracristal ventricular septal defects (VSDs), symptoms and severity are a function of the size of the defect, the relative systemic and pulmonary vascular resistances, and the presence of associated abnormalities. Symptoms may range from severe congestive failure and cardiogenic shock in patients with large conal defects and left heart obstruction to complete absence of symptoms in patients with small, isolated defects.

Exercise intolerance and dyspnea suggest progressive aortic insufficiency, although early detection and treatment for valve insufficiency should obviate any significant symptoms.

Physical Examination

Congestive heart failure does not occur in the patient with an isolated, small supracristal ventricular septal defect (VSD). General examination findings consist of a long harsh systolic murmur and no signs of respiratory distress or growth failure. Infants with larger defects, especially those associated with significant left ventricular outflow obstruction (eg, doubly committed subarterial defect with interrupted aortic arch), may present as early as the first week of life with profound congestive heart failure and cardiogenic shock as the ductus arteriosus closes. Infants with only a large left-to-right shunt usually develop symptoms before the second month of life.

The murmur of an isolated, small supracristal VSD is similar to that of other types of small VSDs. While it may be loudest in the third left intercostal space (ie, more superior than other VSDs), it begins with the first heart sound and has a similar harsh, noisy quality. As with other types, a large defect may produce no murmur from the defect itself. In this case, a murmur may result from turbulent flow through the pulmonic valve, thus becoming crescendo-decrescendo in character. This murmur may radiate laterally and posteriorly because of shunt flow directed into the branch pulmonary arteries.[14]

Second heart sound findings depend on volume of shunt flow as well as pulmonary artery pressure and resistance. With a small shunt, the second heart sound splits and varies normally with respiration, and the pulmonary component is normal in intensity. With a large shunt, and elevated pulmonary artery pressure, the pulmonary component of S2 increases in intensity. Intensity of this sound is further increased if pulmonary resistance is increased, in which case the splitting interval of S2 is decreased. With a large left-to-right shunt, one should hear a short, low-frequency, middiastolic apical murmur due to increased flow across the mitral valve. With significantly elevated pulmonary vascular resistance, shunt flow decreases and this diastolic murmur does not occur.

When a patient is known to have a supracristal VSD, physical examination should focus on whether aortic valve insufficiency is present. Blood pressure must be carefully evaluated for pulse pressure (ie, the difference between systolic and diastolic blood pressures) and pulse amplitude, as these increase with increasing aortic valve insufficiency unless heart failure also occurs. With significant aortic valve insufficiency, the aortic component of S2 decreases in intensity. If left ventricular end diastolic pressure increases, left atrial pressure increases, thus causing an increase in intensity of the pulmonic component of S2. Aortic valve insufficiency causes a high-pitched diastolic murmur beginning with the aortic component of the second heart sound. It is best heard along the left sternal border, usually in the third left intercostal space at the sternal edge.

The combined systolic and diastolic murmurs of supracristal VSD with aortic valve insufficiency may be likened to the sound of sawing wood. This systolic-diastolic murmur combination should not be misinterpreted as a continuous murmur (eg, patent ductus arteriosus, arteriovenous malformation or fistula). Significant aortic valve insufficiency may cause a late diastolic murmur at the apex resulting from atrial contraction augmenting late ventricular filling. This is the Austin Flint murmur.

 

DDx

Diagnostic Considerations

In addition to the conditions listed in the differential diagnosis of ventricular septal defect (VSD), other problems to be considered include the following:

  • VSD with associated defects

  • Atrioventricular (AV) septal defect

  • Double-outlet right ventricle (RV) with normally related great arteries

  • Mild or moderate subaortic stenosis

Differential Diagnoses

 

Workup

Approach Considerations

The recurrence risk for the offspring of mothers with supracristal ventricular septal defect (VSD) is estimated at 4-5%; the recurrence risk for the offspring of fathers with the condition is approximately 2-3%. Detailed prenatal fetal echocardiography (ECHO) may be indicated. Supracristal VSD cannot be identified from a routine prenatal 4-chamber view.

Electrocardiographic findings may be normal in infancy, because the defect may not be large enough to cause a significant left-to-right shunt and ventricular hypertrophy. With larger defects and beyond the first few months of life, the electrocardiogram (ECG) may show left atrial enlargement, as well as both left and right ventricular hypertrophy.

With progressive aortic valve insufficiency in the older child or adult, electrocardiography usually reveals evidence of left heart enlargement from volume overload (ie, left atrial enlargement and left ventricular hypertrophy [tall R waves in the left precordium with or without ST-T changes]).

A diagnostic pitfall associated with supracristal VSD is the failure to diagnose the condition adequately and, therefore, failure to recognize the potential for aortic valve involvement.

Imaging Studies

Chest radiography

Chest radiography is normal in infancy if the left-to-right shunt is small. If a large shunt is present, eventual cardiomegaly (left heart enlargement, both the left atrium and the left ventricle) with increased pulmonary vascularity from increased pulmonary blood flow will occur.

Radiography in the older child or adult with progressive aortic insufficiency may reveal left heart enlargement (particularly left ventricular enlargement) and prominence of the ascending aorta. Shunt volume is generally smaller, thus pulmonary arterial vascularity is generally normal. Advanced left heart failure produces pulmonary edema.

Two-dimensional transthoracic echocardiography

Echocardiography (ECHO) provides the most efficient means to diagnose supracristal ventricular septal defect (VSD) accurately (see the image below) and the most effective means to monitor progressive aortic insufficiency.[7] An accurate diagnosis can generally be made in infants and children with standard transthoracic ECHO examination findings. In the older child and adult, transthoracic ECHO findings may be inconclusive; in such cases, transesophageal ECHO may be extremely helpful.

Parasternal long-axis echocardiogram view showing Parasternal long-axis echocardiogram view showing supracristal ventricular septal defect (arrow) with buckling and prolapse (***) of the right coronary cusp of the aortic valve.

Two-dimensional (2D) imaging reveals the supracristal VSD in the parasternal short-axis view or the modified apical 3-chamber view (ie, left atrium, left ventricle, aortic root, and pulmonary root, equivalent to the transesophageal view with transducer at 90°). The defect can also be observed well in the subcostal parasagittal view (ie, visualizing the pulmonary and aortic outflow tracts).

A supracristal VSD cannot be imaged from the apical 4-chamber view because of the orientation of the outlet septum. Distortion of the right aortic leaflet may be the only clue to the presence of a significant supracristal VSD, because the aortic leaflet may obstruct the defect.

Color Doppler echocardiography

Color Doppler examination using the parasternal short-axis view reveals left-to-right shunting immediately below the pulmonary valve and directed into the pulmonary outflow tract. If the flow is turbulent, it may be confused with pulmonary stenosis; however, careful, slow-motion review of color flow results (with electrocardiographic timing) may reveal the early appearance of turbulent flow below the pulmonary valve. (See the images below.)

Parasternal short-axis echocardiogram view with co Parasternal short-axis echocardiogram view with color Doppler showing proximity of ventricular septal defect jet to the pulmonic valves. The patient is an infant with neither aortic valve prolapse nor aortic insufficiency.
Subcostal "right ventricular inflow/outflow" view Subcostal "right ventricular inflow/outflow" view showing the close relationship between the aortic and pulmonic valves in the presence of supracristal ventricular septal defect. Turbulent shunt flow is shown directed into the main pulmonary artery. The patient is an infant with neither aortic valve prolapse nor insufficiency.
Transesophageal horizontal view of aortic root and Transesophageal horizontal view of aortic root and right ventricle, showing sinus of Valsalva aneurysm leaking through a supracristal ventricular septal defect (VSD)(>

The best way to detect aortic valve insufficiency is by color Doppler in the parasternal long-axis and apical 5-chamber views. The modified apical 3-chamber view can also be used to detect left-to-right shunting and aortic valve insufficiency. Numerous methods are available to provide semiquantitative information on the severity of aortic valve insufficiency (eg, color jet–to–outflow width ratio, pressure half time).

The best way to identify progression of aortic valve insufficiency by echocardiography is by serial comparison of left ventricular systolic and diastolic dimensions and ventricular function (shortening fraction or ejection fraction). Progressive left atrial enlargement can be a sign of ventricular diastolic dysfunction.

Three-dimensional echocardiography

Three-dimensional (3D) echocardiographic imaging of VSDs closely correlates with surgical findings, although specific findings with supracristal defects have not been reported.[15] Three-dimensional echocardiography may prove useful in differentiating supracristal VSD from unruptured sinus of Valsalva aneurysm.[16]

Angiography

Although rarely performed in the modern era, a supracristal VSD is best delineated in the right anterior oblique projection or in the cranially tilted left anterior oblique projection. Small supracristal defects may not be identified in the standard long-axial oblique projection because of rotation of the septum.[17]

Distortion of an aortic valve cusp may be the only clue to a supracristal VSD of significant size, even though the apparent volume of the left-to-right shunt may be small.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) may be used with appropriate projections and alignment to show the pulmonary outflow tract.[18] Serial MRI studies can be helpful in that they do not expose the patient to ionizing radiation. Blood flow studies can be used to provide quantitative information on regurgitant volume in the assessment of aortic insufficiency.

Catheterization

Although rarely performed in the modern era, cardiac catheterization can quantify shunt volume and pulmonary arterial resistance.[17] Step-up in oxygen saturation may be detected in the distal branch pulmonary arteries rather than in the right ventricular cavity because of streaming of the shunted blood into the pulmonic trunk.

If aortic valve prolapse is significant, left-to-right shunting by oximetry may be fairly unremarkable, because the ventricular septal defect (VSD) in such cases is partially obstructed.

Rare catheterization complications include hemorrhage, pain, nausea and vomiting, arterial or venous obstruction from thrombosis or spasm, tachyarrhythmias, and bradyarrhythmias.

 

Treatment

Approach Considerations

Once the diagnosis of supracristal ventricular septal defect (VSD) has been made, there should be careful followup for the development of aortic valve insufficiency. This necessitates not only periodic physical examination with auscultation but also serial echocardiograms, because these diagnostic studies are more sensitive than auscultation in detecting aortic valve regurgitation.

Because spontaneous closure is uncommon in supracristal VSDs and aortic valve insufficiency is common and surgical closure is recommended in most cases. Aortic valve insufficiency in supracristal VSD is usually progressive and warrants an aggressive approach with early intervention to avoid aortic valve deformity and replacement.

Aortic valve insufficiency caused by supracristal VSD must be differentiated from that caused by an abnormal aortic valve (usually a bicuspid valve). Surgical intervention is usually delayed in the latter disorder, because the abnormal aortic valve typically requires replacement rather than repair in cases of aortic valve insufficiency.

Surgical Treatment

Because of the orientation of the right ventricular outflow tract, a surgical approach from the right atrium may not allow adequate visualization of the ventricular septal defect (VSD).[19, 20] Incision into the main pulmonary artery, which exposes the defect through the pulmonic valve, has proved successful.

Repair may be achieved with patch or suture closure, depending on the size of the defect. Aortic valvuloplasty is often, but not always, necessary, and incision through the aortic root can allow adequate visualization for valve repair (Trusler technique). The approach through the main pulmonary artery avoids the need for incision into the right ventricle. Care should be taken to avoid capturing the aortic cusp into one of the patch sutures.[21, 22]

Intraoperative transesophageal echocardiographic monitoring before and after cardiopulmonary bypass can be extremely helpful in precisely defining aortic valve prolapse and the severity of valve insufficiency, which determine the necessity of valvuloplasty[23] .

More extensive damage to the aortic valve from long-standing prolapse and distortion may require valve replacement.

Follow-up care after supracristal ventricular septal defect (VSD) repair and aortic valvuloplasty is essential to ensure that the aortic insufficiency has been corrected completely.

Activity

Activity level is determined by the age at which signs or symptoms develop. Infants with large left-to-right shunts, particularly with complex left heart obstruction, will present soon after birth with congestive heart failure symptoms of poor feeding, diaphoresis, and tachypnea. Patients with small left-to-right shunts without aortic valve insufficiency or with only trivial aortic valve insufficiency generally should be allowed full activity without restriction.

Older patients with more significant aortic valve insufficiency should be restricted from competitive athletics and from sustained isometric types of activities (eg, weightlifting, rope pulls, sustained heavy lifting on the job).

 

Medication

Medication Summary

For patients who develop aortic valve insufficiency, surgical closure of the ventricular septal defect (VSD) and repair of valve insufficiency is the preferred treatment. If surgical repair must be postponed, diuretics and afterload reducers, such as angiotensin-converting enzyme (ACE) inhibitors or calcium channel blockers, have proved helpful in adults and children.[24] ACE inhibitors that may be employed include enalapril, lisinopril, and captopril. Nifedipine is an effective calcium channel blocker.

Angiotensin Converting Enzyme (ACE) Inhibitors

Class Summary

These agents have proved beneficial in long-term therapy for aortic valve insufficiency. Positive effects include reductions in pulse pressure, regurgitant volume, left ventricular volume, and left ventricular mass (because of beneficial effects on ventricular remodeling).

Enalapril (Vasotec)

Enalapril is considered a reasonable first drug of choice in this group because of its increased dosing interval (q12-24h). A competitive ACE inhibitor, it reduces angiotensin II levels, decreasing aldosterone secretion. Enalapril is available in a liquid suspension.

Lisinopril (Prinivil, Zestril)

Lisinopril is considered a reasonable first drug of choice in this group because of its increased dosing interval (q12-24h). It prevents the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in lower aldosterone secretion.

Captopril

Captopril prevents the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in lower aldosterone secretion. For younger children or infants, this agent can be formulated as a suspension if it is stabilized with ascorbic acid to prevent hydrolysis. The dosing interval is 6-8 hours because of captopril's shorter half-life.

Calcium Channel Blockers

Class Summary

Calcium channel blockers also have proved effective in reducing afterload and lowering pulse pressure and regurgitant volume. Prolonged, regular use may stabilize left ventricular volume, but the effect on left ventricular muscle mass is less pronounced than that of ACE inhibitors.

Nifedipine (Adalat, Procardia, Afeditab CR, Nifedical XL)

Nifedipine is a good first choice because of its primary action on peripheral resistance and its limited effect on cardiac function and heart rate.

Diltiazem (Cardizem, Dilacor XR, Diltzac, Matzim LA)

During depolarization, diltiazem inhibits calcium ions from entering slow channels and voltage-sensitive areas of vascular smooth muscle and myocardium.