The malformation known as superoinferior (SI) ventricles is characterized typically by a superior morphologically right ventricle (RV), an inferior morphologically left ventricle (LV), and a relatively horizontal ventricular septum (VS). Rarely, the LV can be superior and the RV can be inferior.
Our Cardiac Pathology database indicates that we have seen and studied 22 cases of SI ventricles out of a total series of 3216 autopsied cases of congenital heart disease (0.68%). Of these 22 cases, 21 had a superior RV and an inferior LV (0.65% of the total series), whereas only 1 patient had a superior LV and an inferior RV (0.03%).
This chapter is based primarily on our 11 published cases. ,
Sex: Males 9, females 2; males 82%, females 18%; males-to-females = 9/2 (4.5/1). Thus, a strong male preponderance was found in this small series.
Age at Death: Mean, 982 days (2.69 years) ± 2572 days (7.05 years), minimum 7 days, maximum 23 10/12 years.
Segmental Anatomy
Double-outlet right ventricle (DORV) was the most common diagnosis, with 6 of 11 (54.55%). The variations in DORV segmental anatomy were: DORV {S,L,D} in 3; DORV {S,D,D} in 2; and DORV {S,L,L} in 1.
Transposition of the great arteries (TGA) was second in frequency, with 4 of 11 (36.36%). The variations in TGA segmental anatomy were: TGA {S,D,L} in 3 and TGA {S,L,L} in 1.
Solitus normally related great arteries with isolated ventricular inversion was the least frequent segmental anatomic set: {S,L,S} in 1 in 11 (9.09%).
These findings are summarized in Table 18.1 .
| Anatomic Types | No. of Cases n = 11 | % of Series ∗ |
|---|---|---|
| 3 | 27 |
| 2 | 18 |
| 1 | 9 |
| 3 | 27 |
| 1 | 9 |
| 1 | 9 |
Status of the Atrioventricular Valves
The atrioventricular (AV) valves were morphologically normal in only 3 of 11 cases (27%); all 3 patients had AV valves that were in situs solitus. The AV valves were malformed in 8 of these 11 cases of SI ventricles (73%). Specifically, the AV valvar anomalies were as follows:
The mitral valve (MV) overrode the VS in 2 patients. The MV was left-sided with a ventricular D-loop (solitus ventricular situs) in 1 case, and the MV was right-sided with a ventricular L-loop (inverted ventricular situs) in 1 case.
The MV (left-sided) was cleft in 1 patient.
The MV (right-sided) was atretic in 1 case.
The left-sided tricuspid valve (TV) obstructed the ventricular septal defect (VSD) in 1 patient with {S,L,S}.
A left-sided TV had Ebstein anomaly with tricuspid stenosis and tricuspid regurgitation in 1 case.
Both inverted AV valves overrode the VS in 1 patient.
Why is the frequency of AV valvar anomalies so high (73%) in these cases of SI ventricles? We think that the answer, at least in part, is because the ventricular malformations frequently result in significant ventriculoatrial malalignments.
Ventricular Situs.
In these 11 patients with SI ventricles, a ventricular D-loop (solitus organizational pattern) was present in 5 (45%) and a ventricular L-loop (inversus organizational pattern) was found in 6 (55%). So no predilection for either type of ventricular situs was apparent.
Typical Superoinferior Ventricles With a Small Superior Right Ventricle
All 10 patients (100%) had a small-chambered superior right ventricular sinus, body, or inflow tract, that is, hypoplasia of the true RV. This was the only anatomic constant that all 10 cases of SI ventricles with a small RV had in common ; all other findings were anatomic variables. The LV was always well developed.
Developmental Hypothesis
These observations concerning SI ventricles with a small superior RV and a well-developed inferior LV led to the following developmental and anatomic hypothesis. SI ventricles with a small superior right ventricular sinus and a well-developed inferior LV is closely related to single LV with an infundibular outlet chamber and absence of the right ventricular sinus. When the right ventricular sinus is absent, the subarterial chamber is composed of the infundibulum only. But when a small right ventricular sinus develops beneath the infundibular ring composed of the septal band, the moderator band, the infundibular septum, and the parietal band, the subarterial chamber enlarges and cardiac loop formation begins.
Initially, the developing right ventricular sinus is above the left ventricular sinus. Consequently, the VS is approximately horizontal. But as the right ventricular sinus develops, it starts to descend anteriorly on the right (D-loop formation), or anteriorly on the left (L-loop formation). With descent of the right ventricular sinus on the right, or on the left, the spatial orientation of the VS normally changes from horizontal to approximately vertical. But not in typical SI ventricles. The VS remains approximately horizontal, and the hypoplastic right ventricular sinus remains superior and undescended. Cardiac loop formation does not occur, or it remains very incomplete.
If any of the foregoing concepts are unfamiliar, please look them up elsewhere in this book: straight heart tube, D-loop formation, L-loop formation, chirality for diagnosing atrial and ventricular situs, the four components that make up the normal RV and LV. Reiteration is avoided here for brevity.
As will be seen, SI ventricles with a small superior LV is a very different malformation.
Degrees of Right Ventricular Sinus Underdevelopment
In these 10 cases, right ventricular sinus underdevelopment was described as follows: mild, 2; moderate, 3; severe, 4; and normal development, 1.
Anatomic Types of Ventricular Septal Defect
In these 10 cases of typical SI ventricles with small superior RV, the anatomic types of VSD were VSD of the AV canal type, 6 (large 5, medium 1); membranous, subpulmonary, small, 1; infundibuloventricular, subpulmonary, large, 2; and infundibular septal defect, small 1.
Anatomic Types of Infundibulum
The anatomic types of infundibulum found in these 10 typical cases of SI ventricles were as follows:
- 1.
Bilateral (subaortic and subpulmonary), 6
DORV {S,L,D}, 3
DORV {S,D,D}, 2
TGA {S,L,L}, 1
- 2.
Subaortic, 3
TGA {S,D,L}, 3
- 3.
Subpulmonary, 1
{S,L,S}, 1
The most common type of infundibulum was bilateral (60%), found in DORV in 5 of 6, and also observed in 1 patient with TGA. The second most frequent type of infundibulum was subaortic (30%), found only in 3 cases of TGA. The least frequent type of infundibulum found in SI ventricles with a small superior right ventricular sinus was noted in 10%, in a patient with solitus normally related great arteries with isolated ventricular inversion {S,L,S}.
Given that the type of relationship between the great arteries is largely determined by infundibuloarterial situs concordance or discordance, , the types of relationships between the great arteries observed in these 10 cases of SI ventricles are as expected.
All of these cases have infundibuloarterial situs nonconcordance, except for {S,L,S} with a subpulmonary infundibulum (situs solitus) and solitus normally related great arteries. , Hence, infundibuloarterial situs concordance is present (both the subarterial infundibulum and the great arteries are in situs solitus). Please see Chapter 15 for more information concerning infundibuloarterial situs equations.
Figures of SI ventricles with a small superior RV are presented in Figs. 18.1 to 18.10 inclusive.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
