Ann Thorac Surg 1996;61:823-827
© 1996 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Double-Horned or Caplike Right Ventricle: Diagnosis and Operative Treatment
Alexander J. Muster, MD,
Constantine Mavroudis, MD,
Carl L. Backer, MD,
Kaliope Berdusis,
Ernerio T. Alboliras, MD,
Michel N. Ilbawi, MD
Divisions of Cardiology and Cardiovascular-Thoracic Surgery, Children's Memorial Hospital, and Northwestern University Medical School, Chicago, Illinois
Accepted for publication October 26, 1995.
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Abstract
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Background. Three patients reported here and 4 from the literature serve as background for the state-of-art diagnostic and operative considerations for an unusual congenital cardiac malformation-double-horned or caplike right ventricle.
Methods. This is a retrospective analysis of cardiac catheterization, cineangiography, and two-dimensional echocardiography findings, as well as palliative and corrective operations in 3 previously unreported patients. Four patients from the literature are reviewed.
Results. Characteristic morphologic features recognizable by invasive and noninvasive imaging distinguish double-horned right ventricle from complex malformations such as criss-cross hearts, superior-inferior ventricles, and univentricular hearts with a small outflow chamber.
Conclusion. Double-horned or caplike right ventricle is a congenital malformation characterized by an unusual ventricular morphology, which may be the result of incomplete development of the right ventricle. The two-horned appearance may be secondary to an absence of the apical trabeculated compartment, with the left ventricle wedged between the two horns. It is invariably associated with double right ventricular outlet. Surgical experience so far suggests that most patients with typical double-horned right ventricle should be considered for anatomic surgical correction.
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Introduction
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See also page 828.
Double-horned or caplike right ventricle has been reported previously as a variant of double outlet right ventricle. Ciavarella and associates [1] reported 2 patients with a peculiarly structured right ventricle that was straddling the left ventricle. The inflow tract (proximal horn) was sequestered from the outflow tract (distal horn), part of which was ``sitting caplike'' above the left ventricle. In both patients, the great arteries originated from the right ventricular outflow tract. There was a large inflow ventricular septal defect with tricuspid chordal attachments to the crest of the defect and to the outflow tract. One of the reported patients underwent a Fontan-type repair at 21 years of age, and the other had only intracardiac exploration.
Beitzke and colleagues [2] reported 2 infants with similar right ventricular morphology in an article entitled ``Two-chambered right ventricle simulating two-chambered left ventricle.'' One infant was diagnosed angiographically and the other by autopsy; neither had operation.
On superficial examination, these hearts may be misinterpreted as having a criss-cross atrioventricular relationship [3], superior-inferior ventricles [4], transposition of the great arteries (D or L), or double-chambered (divided) right ventricle [2]. However, the reported hearts and those presented in this article possess distinct characteristics that can be readily recognized by diagnostic imaging. In contrast to patients with more complex cardiac malformations, most patients with double-horned right ventricles appear to be candidates for definitive corrective operations.
We report 3 additional patients with this anatomy, all diagnosed preoperatively, who have undergone successful corrective operations.
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Case Reports
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Patient 1
This boy was initially diagnosed by two-dimensional echocardiography as having upstairs-downstairs (superior-inferior) ventricles, large ventricular septal defect, straddling tricuspid valve, double-outlet right ventricle, and multilevel pulmonic stenosis. Results of cineangiocardiography at 6 months of age indicated that the relation between the atria and the ventricular inflow tracts was concordant (solitus atria and D-loop ventricles). The great arteries were malposed, with the large aorta arising from the right ventricular outflow tract anteriorly, superiorly, and to the left of the severely stenosed main pulmonary artery, which was situated posteriorly and inferiorly (Fig 1
). The contrast agent passed from the right atrium through the right ventricular inlet (proximal horn) directly into the right ventricular outlet (distal horn) and the left-sided aorta. A filling gap between the right ventricular inflow and outflow tracts created the appearance of a straddling double-horned right ventricle.
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Fig 1. . Cineangiogram in patient 1. (A) Right atrial (RA) injection, anteroposterior view. The right ventricular inflow tract (RVi) representing the right horn, the ventricular septal defect (VSD), the right ventricular outflow tract (RVo) representing the left horn, and the ascending aorta (AO) are featured. The gap created by the absence of the right ventricular apex indicates the position of the left ventricle (LV). (B) Right ventricular injection, lateral view. The relation between the anterior aorta (AO) and the posterior main pulmonary artery (MPA) is shown, separated by a prominent crista supraventricularis (CS). (RV = right ventricle.)
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This patient underwent a right-sided unidirectional Glenn anastomosis at 21 months of age in anticipation of a future Fontan-type operation. At recatheterization at 6 years of age, the angiographic appearance was essentially the same, except that the subpulmonic stenosis had become nearly atretic. The Glenn anastomosis was functioning well. Right ventricular volume determination was not possible because of its configuration.
Corrective operation was performed 4 weeks later (Fig 2A). There were multiple chordal attachments of the tricuspid valve to the crest of the ventricular septal defect, but this did not interfere with placement of a patch to partition the subaortic outflow tract from the rest of the right ventricle. The ventricular septal defect remained as a communication between the left ventricle and the aorta. Because the right-sided subpulmonic conus was hypoplastic and nearly atretic, the small pulmonary valve was closed with suture, and a 20-mm valved homograft conduit was placed between the right ventricular inflow segment and the main pulmonary artery. The Glenn anastomosis was left intact. The patient remains free of symptoms 5 years postoperatively, with no echocardiographic evidence of significant hemodynamic abnormalities.
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Fig 2. . The operative anatomic repair when the aorta is situated above the left ventricle (LV). (A) Patient 1. The ventricular septal defect (asterisk) connects the left ventricle and the aorta (shaded arrows). The operative patch separates the two outflow tracts. Because of severe subpulmonic stenosis, a valved homograft conduit connects the left pulmonary artery and the right ventricle (RV) (open arrows). There is a right-sided Glenn anastomosis. (B) Patient 2. The arterial and venous sides are separated as in patient 1. The pulmonary artery was debanded and patched. (RVo = right ventricular outflow tract.)
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Patient 2
This male infant had cardiac catheterization at 1 month of age at an outside institution that revealed a double-outlet right ventricle, ventricular septal defect, and pulmonary hypertension. The angiograms were reviewed at a second outside institution, and the diagnosis of corrected transposition was entertained. After transfer to the Children's Memorial Hospital at 2.5 months of age, pulmonary artery banding was performed to control the excessive pulmonary blood flow.
At the second cardiac catheterization at our institution at 1 year of age, the morphologic diagnosis was initially the same as on the previous study. The pulmonary artery banding was adequate. The angiograms were subsequently reviewed at a third outside institution, and the probability of a caplike right ventricle with double outlet was raised.
The patient continued to do well clinically and underwent cardiac catheterization at 5 years of age in anticipation of a more definitive operation. The diagnosis of caplike double horned right ventricle with both great arteries originating from the right ventricular outflow tract, levo-malposed aorta {S-D-Lmal}, and a large inflow ventricular septal defect was confirmed both angiographically and by two-dimensional echocardiography (Fig 3).
At operation, the large inflow ventricular septal defect extending into the outflow tract was left open, and the subaortic outflow tract was added to the left ventricle by partitioning the double right ventricular outlet with a patch (Fig 2B
). Partial resection of the infundibular septum allowed unobstructed flow from the left ventricle to the aorta and from the right ventricle to the pulmonary artery. The pulmonary artery band was removed. The patient did well postoperatively and remains asymptomatic 6 years after operation, with no echocardiographic evidence of significant residual hemodynamic abnormalities.
Patient 3
This girl was born in Europe. The echocardiographic diagnosis at 3 months of age was dextrocardia, situs inversus, double-inlet left ventricle with rudimentary outflow chamber, L-transposition of the great arteries, and a large ventricular septal defect. Pulmonary artery banding was performed shortly thereafter. After a second cardiac catheterization at 6 years of age at the same institution, the diagnosis of superior-inferior ventricles or criss-cross atrioventricular connections was suspected, along with corrected transposition of the great arteries and an adequate operative pulmonary artery band.
The patient was admitted to the Children's Memorial Hospital at 7 years of age for further operation. Her previous single-plane cineangiogram was reviewed (Fig 4), and the anatomy was recognized as that of a mirror-image dextrocardia {I-L-Lmal}, double horned right ventricle, and a large inlet ventricular septal defect.
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Fig 4. . Cineangiogram in patient 3. (A) Right ventricular injection, anteroposterior view, showing mirror-image dextrocardia in diastole. The right ventricular inflow tract (RVi) represents the left-sided proximal horn, and the right ventricular outflow tract (RVo) represents the right-sided distal horn. There is a double outlet with levo-malposed ascending aorta (Ao). The banded main pulmonary artery (MPA) is on the right. (B) Same views in ventricular systole. There is catheter-induced tricuspid regurgitation into the left-sided right atrium (RA). There is a subaortic conus with parietal band (PB) on the left and supraventricular crest (CS) on the right. The gap between the horns is filled by the left ventricle (LV). There is a large ventricular septal defect (VSD).
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The corrective operation (Fig 5) differed from those of the other 2 patients. The right-sided morphologic left ventricle was tunneled through the large ventricular septal defect to the left-sided aorta, while the right-sided main pulmonary artery remained related to the left-sided morphologic right ventricle. The conal musculature was not resected. The early postoperative course was benign, and both intraoperative and postoperative echocardiograms revealed no significant hemodynamic abnormalities.
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Fig 5. . Intracardiac repair in patient 3. Because of the discordant relation of the ventricles and great arteries, the ventricular septal defect (asterisk) is tunneled across the right ventricle (RV) to the aorta (shaded arrows). The venous blood (open arrows) passes over the operative tunnel to the subpulmonic outflow tract (RVo) and the pulmonary artery. (LV = left ventricle.)
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Comment
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The first published reports of double-horned caplike double-outlet right ventricle appeared in 1979 [1, 2]. To our knowledge, there have been no further publications dealing with this anatomic entity. Including our 3 patients, a total of 7 patients with this entity have been reported.
Some of the anatomic characteristics of this malformation resemble those associated with more complex cardiac defects (Fig 6). Because the distal segment of the double-horned right ventricle sits caplike above the left ventricle and the septum separating these two chambers is horizontal, the appearance may lead to the erroneous impression of superior-inferior or upstairs-downstairs ventricles [4]. Because of its location, dimension, and configuration, the ``distal horn'' has also been confused with the vestigial outlet chamber associated with single or double-inlet left ventricle. However, with an appropriate angiographic or two-dimensional echocardiographic technique, a sizeable right ventricular inflow segment (proximal horn) with a sagittal septum and a normal-sized tricuspid valve is demonstrated. Echocardiographic (rather than tomographic) sweeps from subcostal views will allow three-dimensional mental reconstruction of this unusual malformation.
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Fig 6. . Anatomic entities that may resemble the caplike right ventricle, which can be considered a variant of double-outlet right ventricle {S-D-Lmal} with absent apical portion. The others share the horizontal septum situated above the left ventricle. (Star = ventricular septal defect.)
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Double-horned right ventricle can also resemble criss-cross hearts with atrioventricular concordance [3], especially when the two ventricles and the great arteries are geometrically discordant (aorta above the morphologic right ventricle). However, in double-horned right ventricle, the inflow tract and the tricuspid valve are side by side with the left ventricle and the mitral valve (see Figs 2, 4), whereas in all variants of criss-cross atrioventricular relationship, the right ventricular inflow and the tricuspid valve are situated craniad to the left ventricle and the mitral valve.
Embryologic Implications
Double-horned right ventricle may be the result of failure to develop an apical trabeculated portion during formation of the primitive right ventricle. Development of a normal tripartite [5] right ventricle requires a sinus (inflow) compartment, an outlet (conus) compartment, and a trabeculated apical compartment. Absence of the latter allows the two existing compartments of the right ventricle to be split by the left ventricle, giving its characteristic double-horned configuration.
Operative Considerations
In previously reported cases [1, 2], a Fontan-type correction was accomplished in 1 patient, whereas the long-term outcome in the other surviving patients remains unreported. All 3 of our patients underwent anatomic correction. In considering the operative options, one should keep in mind the unusual anatomic features. The sequestration of the caplike right ventricular outflow tract above the left ventricle may give the impression that the entire right ventricle is hypoplastic and incapable of accommodating the systemic venous return. In patients reported so far, the sizes of the right ventricular sinus portion and of the tricuspid valve appeared normal and should be adequate for biventricular repair. Chordal attachments of the tricuspid valve to the crest of the ventricular septal defect may be encountered, but in none of the 7 patients was there a straddling tricuspid valve. In the event that the right ventricle cannot handle the entire systemic venous return postoperatively, a pulsatile bidirectional cavopulmonary anastomosis (one-and-a-half ventricular repair) would be preferable to a Fontan operation [6].
The anatomic repair will differ depending on the proximity of the aorta to the left ventricle. When the aorta sits atop the left ventricle, the ventricular septal defect provides free communication between the left ventricle and the aorta. The operative patch simply separates the venous and arterial sides (see Figs 2A, 2B). When the aorta is above the right ventricle, the ventricular septal defect is tunneled through the right ventricle to the distant aorta (see Fig 5). The abnormal tricuspid valve attachments may not interfere with tunneling of the ventricular septal defect; if needed, they may be cut and reattached to the septal patch. This was not required in any of our patients, but has been performed successfully in other patients with this type of ventricular septal defect.
Conclusion
Double-horned or caplike double-horned right ventricle is a distinct congenital cardiac malformation that should be readily recognizable using current diagnostic imaging methods. It is characterized by a right ventricle seemingly split into an inflow and outflow horn that straddle the ventricular septal defect and the left ventricle. Two variants have been encountered so far, with either the aorta or the pulmonary artery sitting atop the left ventricle. This relation determines the type of anatomic repair. Although the right ventricle may appear small, anatomic correction was possible in all of our patients.
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Acknowledgments
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We thank Arlee Frantz and Melanie Gevitz for preparing the manuscript.
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Footnotes
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Address reprint requests to Dr Muster, Division of Cardiology, Children's Memorial Hospital, M/C 21, 2300 Children's Plaza, Chicago, IL 60614.
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References
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- Ciavarella JM, McGoon DC, Hagler DJ, Fulton RE. Caplike double-horned double-outlet right ventricle: report of two cases. J Thorac Cardiovasc Surg 1979;77:536–42.[Abstract]
- Beitzke A, Anderson RH, Wilkinson JL, Shinebourne EA. Two-chambered right ventricle simulating two-chambered left ventricle. Br Heart J 1979;42:22–6.[Abstract/Free Full Text]
- Anderson RH, Shinebourne ER, Gerlis LM. Criss-cross atrioventricular relationships producing paradoxical atrioventricular concordance and discordance: their significance to nomenclature of congenital heart disease. Circulation 1974;50:176–80.[Abstract/Free Full Text]
- Van Praagh S, LaCorte M, Fellows KE, et al. Superior-inferior ventricles: anatomic and angiocardiographic findings in 10 postmortem cases. In: Van Praagh R, Takao A, eds. Etiology and morphogenesis of congenital heart disease. Mount Kisco, NY: Futura Publishing, 1980:317.
- Goor DA, Lillelei WC, Rees R, Edwards JE. Isolated ventricular septal defect. Development basis for various types and presentation of classification. Chest 1970;58:468–82.[Abstract/Free Full Text]
- Muster AJ, Zales VR, Ilbawi MN, Backer CL, Duffy CE, Mavroudis C. Biventricular repair of hypoplastic right ventricle assisted by pulsatile bidirectional cavopulmonary anastomosis. J Thorac Cardiovasc Surg 1993;105:112–9.[Abstract]
Related Article
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Invited Commentary
- Stella Van Praagh
Ann. Thorac. Surg. 1996 61: 828.
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Abstract
Introduction
