eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology
Ventricular Septal Defect, Supracristal
Updated: Oct 10, 2008
Introduction
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 defects in the western hemisphere.1 Its location adjacent to the pulmonary and aortic valves accounts for the unique natural history associated with this defect. The spiraling course of the ventricular septum may make diagnosis of the supracristal VSD more difficult.
Definition
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 in this part of the septum are generally referred to as supracristal defects. The term is generally reserved for defects lying immediately under the pulmonary valve, so that aortic and pulmonary valve tissue are in fibrous continuity and not separated by septal tissue.
Embryology
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 is 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.2 By exposing neural crest tissue to homocysteine, supracristal VSDs have been induced in a high percentage of chick embryos. Disruption of apoptosis and myocardialization has been proposed to explain these findings.3
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.4
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 muscular fairly rigid support for the aortic valve, especially the right coronary cusp.5
Numerous synonyms indicate the confusion often associated with describing this particular type of ventricular defect. The term supracristal may be misleading because the entire conus septum (or a major portion of the septum) may be missing. However, the term is commonly used and underscores the superior location of the defect along with the close approximation of the aortic and pulmonary valve leaflets.
The lack of support for the right aortic leaflet is crucial to the natural history of this type of VSD.6
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.5 7
Unlike the more common perimembranous type of VSD, 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.
Natural history
The natural history of supracristal VSDs depends on the location and size of the defect.
Patients with small isolated supracristal VSDs may have no early symptoms or signs of congestive failure such as would be observed with a large shunt. Progressive aortic insufficiency may develop late in the first decade of life. However, larger defects of the outlet septum frequently are associated with severe 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 show early signs of decompensation from a large left-to-right shunt. Because these defects are not surrounded by muscular tissue, spontaneous closure is less common.8 However, the defect may decrease in size by progressive prolapse of aortic valve tissue (the right coronary cusp or, possibly, the right sinus of Valsalva).9 This valve prolapse is believed to result from negative pressure by shunt flow because of the Venturi effect. This progressive distortion of the aortic leaflet or sinus may lead to increasing aortic valve insufficiency or to formation of an aneurysm in the sinus of Valsalva.
Pathophysiology
The unique location of the supracristal ventricular septal defect with its close proximity to the aortic root 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.
Frequency
United States
VSDs account for approximately 25-30% of significant congenital heart disease. Of these, approximately 5-7% are supracristal VSDs. These rates are similar throughout the Western Hemisphere.
International
Supracristal VSDs are much more common in persons of Asian descent than in individuals of other races. Supracristal VSDs account for approximately 25% of all VSDs in patients from the Eastern Hemisphere.
Mortality/Morbidity
Morbidity/mortality is generally not the result of large left-to-right shunt. Rather, it is caused by progressive development of aortic valve insufficiency, with development of left ventricular enlargement and eventual congestive heart failure if the problem is not addressed early enough.
Race
Although the overall incidence of VSDs is no higher in Asians than in other groups, supracristal VSDs account for approximately 30% of VSDs in Asians1 and only approximately 5% of VSDs in other groups. The higher occurrence of supracristal VSDs in Asians has not been adequately explained.
Sex
No predilection based on sex is observed.
Clinical
History
In patients with supracristal ventricular septal defects (VSDs), symptoms and severity are a function of size and location of the defect, the relative systemic and pulmonary vascular resistances, and 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
Because congestive heart failure is unusual in the patient with a small supracristal VSD, general examination findings should be normal, with no signs of respiratory distress or growth failure. Infants with larger defects, especially with associated left ventricular outflow obstruction (eg, doubly committed subarterial defect with interrupted aortic arch), may present within the first week of life with profound congestive heart failure and cardiogenic shock.
- The murmur from a supracristal VSD is systolic and located at the upper left sternal border (ie, second or third intercostal space). The murmur is often crescendo-decrescendo in character, unlike the holosystolic regurgitant murmur of VSDs in other locations of the septum. It may radiate laterally and posteriorly because of shunt flow directed into the pulmonary outflow tract.10
- When a patient is known to have a supracristal VSD, the examination should focus on whether aortic insufficiency is present. A high-pitched diastolic murmur beginning with the second heart sound may be heard along the left sternal border. The combined systolic and diastolic murmurs may be likened to the sound of sawing wood.
- The systolic-diastolic murmur of supracristal VSD with aortic insufficiency may be confused with a continuous murmur (eg, patent ductus arteriosus, arteriovenous malformation or fistula).
- Maneuvers to increase the diastolic murmur of aortic insufficiency include isometric handgrip, leaning forward in a sitting position, and holding the breath during expiration.10
- With increasing severity of aortic insufficiency, pulse pressure (ie, difference between systolic and diastolic blood pressures) and pulse intensity may increase.
More on Ventricular Septal Defect, Supracristal |
 Overview: Ventricular Septal Defect, Supracristal |
| Differential Diagnoses & Workup: Ventricular Septal Defect, Supracristal |
| Treatment & Medication: Ventricular Septal Defect, Supracristal |
| Follow-up: Ventricular Septal Defect, Supracristal |
| Multimedia: Ventricular Septal Defect, Supracristal |
| References |
| Next Page » |
References
McDaniel NL, Gutgesell HP. Ventricular septal defects. In: Allen HD, Driscoll DJ, Shaddy RE, Feltes TF. Moss and Adams' Heart Disease in Infants, Children, and Adolescents. 7th ed. Philadelphia: Wolters Kluwer/ Lippincott Williams & Wilkins; 2008:667-682.
Gittenberger-De Groot AC, Poelmann RE. Normal and abnormal cardiac development. In: Moller JH, Hoffman JI, eds. Pediatric Cardiovascular Medicine. New York, NY: Churchill Livingstone; 2000:3-20.
Boot MJ, Steegers-Theunissen RP, Poelmann RE, van Iperen L, Gittenberger-de Groot AC. Cardiac outflow tract malformations in chick embryos exposed to homocysteine. Cardiovasc Res. Nov 1 2004;64(2):365-73. [Medline].
Momma K, Ando M, Matsuoka R, Joo K. Interruption of the aortic arch associated with deletion of chromosome 22q11 is associated with a subarterial and doubly committed ventricular septal defect in Japanese patients. Cardiol Young. Sep 1999;9(5):463-7. [Medline].
Anderson RH, Wilcox BR. The surgical anatomy of ventricular septal defects associated with overriding valvar orifices. J Card Surg. Mar 1993;8(2):130-42. [Medline].
Cheung YF, Chiu CS, Yung TC. Impact of preoperative aortic cusp prolapse on long-term outcome after surgical closure of subarterial ventricular septal defect. Ann Thorac Surg. Feb 2002;73(2):622-7. [Medline].
Ho SY, Baker EJ, Rigby ML. Color Atlas of Congenital Heart Disease: Morphologic and Clinical Correlations. St Louis, MO: Mosby-Wolfe; 1995.
Eroglu AG, Oztunc F, Saltik L, et al. Evolution of ventricular septal defect with special reference to spontaneous closure rate, subaortic ridge and aortic valve prolapse. Pediatr Cardiol. Jan-Feb 2003;24(1):31-5. [Medline].
Mori K, Matsuoka S, Tatara K, et al. Echocardiographic evaluation of the development of aortic valve prolapse in supracristal ventricular septal defect. Eur J Pediatr. Mar 1995;154(3):176-81. [Medline].
Zuberbuhler JR. Ventricular septal defect. In: Clinical Diagnosis in Pediatric Cardiology. London, England: Churchill Livingstone; 1981:39-45.
Cheng TO, Xie MX, Wang XF, Wang Y, Lu Q. Real-time 3-dimensional echocardiography in assessing atrial and ventricular septal defects: an echocardiographic-surgical correlative study. Am Heart J. Dec 2004;148(6):1091-5. [Medline].
Masaki N, Iwatsuka R, Nagahori W, et al. Three-dimensional echocardiography could distinguish a ventricular septal defect adjacent to asymptomatic ruptured sinus of valsalva aneurysm. J Cardiol. Apr 2008;51(2):139-43. [Medline].
Freedom RM, Mawson JB, Yoo SJ. Ventricular septal defect. In: Freedom RM, et al, eds. Congenital Heart Disease: Textbook of Angiocardiography. Futura Publishing Co; 1997:189-218.
Wang ZJ, Reddy GP, Gotway MB, et al. Cardiovascular shunts: MR imaging evaluation. Radiographics. Oct 2003;23 Spec No:S181-94. [Medline]. [Full Text].
Yacoub MH, Khan H, Stavri G, et al. Anatomic correction of the syndrome of prolapsing right coronary aortic cusp, dilatation of the sinus of Valsalva, and ventricular septal defect. J Thorac Cardiovasc Surg. Feb 1997;113(2):253-60; discussion 261. [Medline].
Komai H, Naito Y, Fujiwara K, Noguchi Y, Nishimura Y, Uemura S. Surgical strategy for doubly committed subarterial ventricular septal defect with aortic cusp prolapse. Ann Thorac Surg. Oct 1997;64(4):1146-9. [Medline].
Leung MP, Chau KT, Chiu C, Yung TC, Mok CK. Intraoperative TEE assessment of ventricular septal defect with aortic regurgitation. Ann Thorac Surg. Mar 1996;61(3):854-60. [Medline].
Levine HJ, Gaasch WH. Vasoactive drugs in chronic regurgitant lesions of the mitral and aortic valves. J Am Coll Cardiol. Nov 1 1996;28(5):1083-91. [Medline].
Leung MP, Beerman LB, Siewers RD, et al. Long-term follow-up after aortic valvuloplasty and defect closure in ventricular septal defect with aortic regurgitation. Am J Cardiol. Oct 1 1987;60(10):890-4. [Medline].
Rhodes LA, Keane JF, Keane JP, et al. Long follow-up (to 43 years) of ventricular septal defect with audible aortic regurgitation. Am J Cardiol. Aug 1 1990;66(3):340-5. [Medline].
Elgamal MA, Hakimi M, Lyons JM, Walters HL III. Risk factors for failure of aortic valvuloplasty in aortic insufficiency with ventricular septal defect. Ann Thorac Surg. Oct 1999;68(4):1350-5. [Medline].
Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. Oct 9 2007;116(15):1736-54. [Medline]. [Full Text].
Further Reading
Keywords
supracristal ventricular septal defect, doubly committed ventricular septal defect, doubly-committed VSD, subarterial ventricular septal defect, juxtaarterial ventricular septal defect, subpulmonic ventricular septal defect, conal ventricular septal defect, type I ventricular septal defect, supracristal VSD, outlet VSD, arch abnormalities, aortic insufficiency, cardiogenic shock, exercise intolerance, dyspnea, left ventricular outflow obstruction, patent ductus arteriosus, arteriovenous malformation, arteriovenous fistula
