Double outlet right ventricle (DORV) refers to a congenital cardiac malformation in which most of the pulmonary artery and the aorta arise from the right ventricle, one subtype of which is known as the Taussig–Bing heart. Such an abnormality is generally compatible with life only when there is an additional malformation that allows blood flow from one side of the heart to the other, most commonly a ventricular septal defect (VSD).

Attempts have been made to define the malformation based on the relative area of each outflow tract arising from the right ventricle, with an anatomic threshold of 50% being used. The surgical definition of DORV requires that at least 90% of the area of the outflow tracts arise from the right ventricle. The most commonly used definition requires one great artery to arise fully over the right ventricle and at least 50% of the other great artery to also originate from the right ventricle (Aoki et al., 1994). Therefore, cases of tetralogy of Fallot (see Chapter 52) in which the majority of the aortic outflow tract arises from the right ventricle could also be defined as DORV. Such anomalies may arise because of arrest of normal rotation of the outflow tracts (Bostrom and Hutchins, 1988). DORV has also been classified based on the relationship of the outflow tracts. The most common is where the aortic outflow tract is situated posterior to the pulmonary outflow tract, each spiraling around the other as they exit the heart (Romero et al., 1988). The Taussig–Bing heart is a subtype of DORV in which the aortic outflow tract ascends posterior to the pulmonary outflow tract in a parallel fashion. In the third type of DORV, the aortic outflow tract ascends anterior to the pulmonary outflow tract in a parallel fashion. DORV may also be classified based on the location of the VSD, either subaortic or subpulmonary; in the Taussig–Bing heart the VSD is subpulmonary (Bashore, 2007).

Because of this confusion in classification of DORV anatomically, the Society of Thoracic Surgeons (STS) and the European Association of Cardiothoracic Surgery (EACTS) have agreed a new classification system based on clinical presentation and surgical management (Walters et al., 2000). The four types are: (1) VSD-type, (2) tetralogy of Fallot-type, (3) transposition of great arteries-type (Taussig–Bing), and (4) DORV with noncommitted VSD. Patients with a subaortic VSD present clinically very similar to tetralogy of Fallot (Bashore, 2007).

Additional cardiac malformations are almost always present, with the most common being a VSD. Other coexisting cardiac malformations include atrial septal defect, atrioventricular canal defect, pulmonary stenosis, coarctation of the aorta, and anomalous venous return. Noncardiac malformations may also be present, including chromosomal abnormalities, such as trisomy 18 or 13, tracheoesophageal fistula, cardiosplenic syndrome, and orofacial clefting (Rowe et al., 1981; Wladimiroff et al., 1989; Kim et al., 2006).

DORV is rare and accounts for approximately 1% of all congenital cardiac malformations. However, this incidence may be higher if cases of tetralogy of Fallot that can also be defined as DORV are included. In one multicenter series, DORV accounted for 4.1% of all cases of prenatally diagnosed congenital heart disease (Paladini et al., 1996). The presence of pre-existing maternal diabetes mellitus seems to be a significant risk factor for the development of DORV, with an odds ratio of 21.3 (Ferencz et al., 1990). The incidence of DORV is approximately 1 to 2 per 10,000 livebirths (Hoffman and Kaplan, 2002).

Definitive prenatal sonographic diagnosis of DORV is difficult, as successful prenatal diagnosis requires careful examination of both the four-chamber view and the outflow tracts. On the four-chamber view, a VSD is almost always present, either in a subpulmonary or a subaortic location. In DORV, both outflow tracts are visible arising from the right ventricle and are often in a side-by-side, or parallel position (Figures 53-1 to 53-3) (Stewart et al., 1985).

In one series of 24 fetuses with parallel outflow tracts, 7 were found to have transposition of the great arteries, while the remaining 17 had DORV (Allan, 1997). In that series, most of the mothers were referred for fetal echocardiography because of an initial abnormal four-chamber cardiac view. In another series, 13 cases of DORV were correctly diagnosed by fetal echocardiography, 5 of which had an abnormal four-chamber cardiac view (Paladini et al., 1996). A transverse three-vessel view through the upper fetal mediastinum, demonstrating the main pulmonary artery, ascending aorta, and superior vena cava, may also be helpful in diagnosing DORV (Yoo et al., 1997). In a population-based study from Australia, 54 of 73 (74%) cases of DORV were correctly identified prenatally (Chew et al., 2007). When DORV is suspected prenatally, the diagnosis will subsequently be proven correct in approximately 75% of cases (Gelehrter et al., 2007). It appears clear, therefore, that maximal prenatal detection of DORV requires careful visualization of both the four-chamber view and the cardiac outflow tracts.