Single Ventricle

hypoplastic left heart syndrome, pulmonary atresia with intact ventricular septum

A group of anomalies in which the entire atrioventricular junction is connected to only one chamber in the ventricular mass.

Rare, less than 0.5% of all congenital cardiac anomalies.

Single ventricle is a broad category encompassing a wide variety of complex cardiac defects.¹ The two most common types include: 1) double inlet, where each atrium has a separate atrioventricular valve which both empty into a single ventricle, 2) single inlet where there is only one atrioventricular valve connected to only one of the atria with the other atria communicating with the rest of the heart only via the foramen ovale (tricuspid or mitral atresia). Despite the term ‘single ventricle’, an accessory rudimentary ventricle is frequently present, usually communicating through a septal defect with the main chamber. The great vessels are usually transposed, although less frequently they may have a normal relationship. Outflow obstruction, either pulmonary or aortic, is frequently seen. However a single dominant right ventricle with severe obstruction to aortic flow is considered as a separate entity (hypoplastic left heart syndrome), as well as a dominant left ventricle with an intact ventricular septum and pulmonary atresia (pulmonary atresia with intact ventricular septum).

Outflow obstructions are common and have a major influence on the final outcome. Single ventricle is also one of the most common ventricular malformations associated with cardiosplenic syndromes (heterotaxy). Extracardiac malformations including chromosomal aberrations are frequently seen.

Though the anatomy can be variable and complex, there is always one main ventricle to which all atrioventricular valves connect.² The type of ventricular anatomy is important in determining the final outcome, but it is the great vessel anatomy and outflow obstruction that will determine newborn need for palliation.^2-8 Therefore it is important to define this anatomy as well. As in less complex forms of cardiac disease, the outflow obstruction can progress in utero so serial fetal echocardiograms are indicated.

Double inlet and common inlet single ventricle must be differentiated from large ventricular septal defects and atrioventricular septal defects. Tricuspid and mitral atresia are usually a part of pulmonary atresia with intact ventricular septum and hypoplastic left heart syndrome that have a more severe prognosis than other types of single ventricle.

Single ventricles are usually well demonstrated with a standard four chamber view. The most important clues are the demonstration of the absence of the ventricular septum in double inlet forms and the presence of a significant discrepancy among the size of the ventricles or the absence of one ventricle in single inlet forms. In the latter cases the atretic atrioventricular valve appears fixed and thick on real-time examination.

There are many anatomic variations of single ventricle, with a major influence on the final outcome. It is important to assess whether there are extra-cardiac anomalies, or findings of heterotaxia, the morphology of the dominant ventricle, and the connections with the great arteries.

Single ventricle is usually well tolerated during intrauterine life and the clinical presentation occurs only after the closure of the fetal circulation. After birth, palliative procedures and the Fontan operation are usually performed. The final outcome depends upon two main factors: whether the dominant ventricle is of left or right type and the presence of outflow obstruction. The ten years survival rate of infants is in the range of 70 %, but it is significantly lower when the dominant ventricle is of the right type compared to left type (58% versus 86%) and when there is associated obstruction to the systemic circulation.^2-8

In continuing pregnancies no modification of standard obstetric care is required and vaginal delivery at term is not contraindicated. In the presence of severe outflow obstruction survival may be dependent upon fetal circulation and prompt cardiologic treatment is recommended.

1. Williams RG. Echocardiography in the management of single ventricle: fetal through adult life. Echocardiography. 1993;10(3):331-42.

.2. Beroukhim RS, Gauvreau K, Benavidez OJ, Baird CW, LaFranchi T, Tworetzky W. Perinatal Outcomes after Fetal Diagnosis of Single Ventricle Cardiac Defects. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2014. Epub 2014/07/22.

3. Berg C, Lachmann R, Kaiser C, Kozlowski P, Stressig R, Schneider M, Asfour B, Herberg U, Breuer J, Gembruch U, Geipel A. Prenatal diagnosis of tricuspid atresia: intrauterine course and outcome. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2010;35(2):183-90. Epub 2010/01/27.

4. Fesslova V, Hunter S, Stark J, Taylor JF. The long-term clinical outcome of patients with tricuspid atresia. II. Influence of surgical procedures. The Journal of cardiovascular surgery. 1991;32(2):225-32. Epub 1991/03/01.

5. Lan YT, Chang RK, Laks H. Outcome of patients with double-inlet left ventricle or tricuspid atresia with transposed great arteries. Journal of the American College of Cardiology. 2004;43(1):113-9. Epub 2004/01/13.

6. Sittiwangkul R, Azakie A, Van Arsdell GS, Williams WG, McCrindle BW. Outcomes of tricuspid atresia in the Fontan era. The Annals of thoracic surgery. 2004;77(3):889-94. Epub 2004/03/03.

7. Tham EB, Wald R, McElhinney DB, Hirji A, Goff D, Del Nido PJ, Hornberger LK, Nield LE, Tworetzky W. Outcome of fetuses and infants with double inlet single left ventricle. The American journal of cardiology. 2008;101(11):1652-6. Epub 2008/05/21.

8. Wald RM, Tham EB, McCrindle BW, Goff DA, McAuliffe FM, Golding F, Jaeggi ET, Hornberger LK, Tworetzky W, Nield LE. Outcome after prenatal diagnosis of tricuspid atresia: a multicenter experience. American heart journal. 2007;153(5):772-8. Epub 2007/04/25.

This article should be cited as: Gianluigi Pilu,: Single Ventricle. Visual Encyclopedia of Ultrasound in Obstetrics and Gynecology.www.isuog.org, (2014)

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