Double Outlet Left Ventricle

Definition

Double outlet left ventricle (DOLV) is a cardiac anomaly in which both great arteries arise from the left ventricle (LV). ¹ The great arteries are assigned to one or the other ventricle by the rules described under Definition in Chapter 53 .

1 The adjectives left and right used to modify atrium or ventricle mean morphologically left and morphologically right. Position of the chamber is referred to as right-sided or left-sided .

DOLV may occur with atrioventricular (AV) concordant or discordant connection, as does double outlet right ventricle (DORV; see Chapter 53 ). DOLV with AV discordant connection is discussed in Chapter 55 . DOLV, like DORV, may also occur in patients with univentricular AV connections (see Chapter 56 ) and in those with atrial isomerism (see Chapter 58 ).

Historical Note

Marechal is credited with describing the first case of DOLV in 1819, but this was in a heart with double inlet LV with an infundibular outlet chamber. The first reported case in a heart with two ventricles and without pulmonary stenosis was that of Sakakibara and colleagues in 1967, for which they performed a successful intraventricular repair. DOLV is therefore another congenital cardiac anomaly that remained, for all practical purposes, undescribed until the advent of intracardiac surgery. It is also of interest that the first case reported by Potts and colleagues as tetralogy of Fallot and receiving a side-to-side aortopulmonary artery anastomosis underwent subsequent repair for well-documented DOLV with pulmonary stenosis (John Kirklin: personal communication; 1983). A unique case of DOLV with an intact ventricular septum was reported by Paul and colleagues in 1970, establishing with certainty the existence of the entity. Subsequent reports expanded the surgical possibilities by reporting reconstruction of the pulmonary pathway in cases in which a completely intraventricular repair was not possible, usually by a valved extracardiac conduit from the right ventricle to pulmonary trunk. Anderson and colleagues reported the sixth case of DOLV in 1974. Sharratt and colleagues in 1976 reported use of a Fontan-type procedure in hearts with DOLV and severe right ventricular hypoplasia.

Five cases were added to the literature in 1976. Additional cases have been reported by Urban and colleagues and Stegmann and colleagues.

Morphology and Morphogenesis

As with DORV, there is great variability among hearts with DOLV and AV concordant connection. Because of its rarity, generalizations are even more difficult than for DORV. Diagnosis can be ambiguus, because some override of one of the great arteries is commonly present. Defining a DOLV based on 50% or more of great arterial override may result in a substantially higher number of cases being reported. Many patients with complete transposition of the great arteries with subaortic ventricular septal defect (VSD), pulmonary stenosis, and a variable degree of aortic override have been misclassified as having DOLV. An exclusive or near-exclusive origin of both great arteries from the left ventricle (<20% override) will identify the classic form of DOLV and prevent misdiagnosis. Although it was initially thought bilateral absent conus was a prerequisite for the diagnosis of DOLV, all possible conal configurations have been described: subpulmonic, subaortic, bilaterally present, and bilaterally absent. When present, the length of conus under either great artery is typically relatively short and is an important factor in causing the great artery to embryologically align with the left ventricle.

A segmental approach is necessary for complete understanding of this malformation (see “Terminology and Classification of Heart Disease” in Chapter 1 ). DOLV occurs in each of the four basic hearts ( Fig. 54-1 ) but is most common in hearts with atrial situs solitus and ventricular right-handedness or D-loop (S,D,D). Morphologic characteristics of the VSD and its relationship to the great arteries at the level of the semilunar valves are similar to those in DORV and described by terms defined in “Ventricular Septal Defect” under Morphology in Chapter 53 . Subaortic VSD is the most common, followed by subpulmonic, and then by doubly committed. VSD remote from the great arteries is rare ( Table 54-1 ). Absence of a VSD (intact ventricular septum) is also rare but has been described.

Atrial Situs Solitus and Ventricular Right-Handedness (D-Loop) (Atrioventricular Concordant Connection)

In this subset, the aorta is usually in D-malposition (S,D,D), but examples occur with it in L-malposition (S,D,L) (see “Symbolic Convention of Van Praagh” in Chapter 1 ). In the former, the great arteries may appear in relatively normal position (aorta to the right and somewhat posterior to pulmonary trunk), side to side, or with aorta somewhat anterior to the pulmonary trunk.

Ventricular Septal Defect

The ventricular septum is rarely intact. Usually, a large VSD is present and lies between the limbs of the trabecula septomarginalis (septal band).

Most commonly, the VSD is subaortic in position ( Fig. 54-2 ; see Table 54-1 ). It may extend back to the tricuspid anulus, or it may be separated from the anulus by a muscular bridge. When the aorta overrides the VSD and arises in part from the right ventricle, the VSD is juxtaaortic , and this entity begins to merge with transposition of the great arteries.

When the VSD is subpulmonary, it is usually more anterior and well separated from the tricuspid valve by a rather wide band of muscle. In some cases, the pulmonary trunk origin overrides the VSD and lies in part over the right ventricle. Malalignment of conal septum may be present and can cause aortic outflow obstruction and be associated with aortic arch hypoplasia.

Occasionally the VSD is juxtaarterial and lies immediately below both great arteries ( doubly committed ; see Chapter 53 , Fig. 53-6 ). The VSD is typically very large, and there is absence or near absence of conus bilaterally, resulting in aortic-mitral and pulmonary-mitral fibrous continuity and side-by-side great arteries. It is frequently difficult to decide whether DOLV or DORV is present, in which case the term double outlet both ventricles is appropriate.

Conal Pattern

Most often there is absence of a subaortic conus and presence of aortic-mitral fibrous continuity and a subpulmonary conus displaced into the LV ( Fig. 54-3 ). Rarely, bilaterally absent conus permits aortic-mitral-tricuspid and pulmonary-tricuspid fibrous continuity (see Fig. 54-2 ). In this event, both semilunar valves arise at the same level. Very rarely, only a subaortic conus is present. There may be a conus bilaterally.

Pulmonary Stenosis

Pulmonary stenosis is present in most cases and is either valvar (sometimes with anular stenosis) or subvalvar when it is due to a restrictive subpulmonary conus with secondary fibrosis of the ostium. When the VSD is subaortic and there is infundibular pulmonary stenosis, the great arteries are usually relatively normally interrelated.

Right Ventricular and Tricuspid Valve Hypoplasia

There is a tendency for the right ventricular sinus and tricuspid valve to be at least somewhat hypoplastic. The extreme example is coexistence of tricuspid atresia, with the two reported cases having ventricular right-handedness (S,D,D). Rarely, the tricuspid valve may show an Ebstein anomaly.

Left Ventricle

The LV is usually well formed. One case of mitral atresia with large LV and infundibular outlet chamber (S,D,D segmental arrangement) has been reported.

Conduction System

Position of AV node and bundle of His is normal. Thus, the bundle penetrates from a normally positioned posterior AV node through the right trigone in the region of the commissure between tricuspid septal and anterior leaflets and at the base of the noncoronary aortic cusp, and its two branches distribute in normal fashion. Whether it is at risk during repair depends on the relationship of the lower VSD margin to the tricuspid anulus (see “Location in Septum and Relationship to Conduction System” under Morphology in Section 1 of Chapter 35 ).

Clinical Features and Diagnostic Criteria