Ann Thorac Surg 2007;84:668-670
© 2007 The Society of Thoracic Surgeons
Case Reports
Isolated Pseudohypoplasia of the Right Ventricle
Esteban Pastor, MDa,
José I. Aramendi, MDb,*,
Maite Luis, MDa,
Roberto Voces, MDb,
Miguel A. Rodríguez, MDb,
José M. Galdeano, MDa
a Division of Pediatric Cardiology, Hospital de Cruces, Barakaldo, Spain
b Division of Cardiac Surgery, Hospital de Cruces, Barakaldo, Spain
Accepted for publication January 23, 2007.
* Address correspondence to Dr Aramendi, Division of Cardiac Surgery, Hospital de Cruces, Plaza de Cruces, Barakaldo, 48903, Spain. (Email: jiaramendi{at}hcru.osakidetza.net).
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Abstract
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We present a case of a 12-year-old girl with severe cyanosis due to abnormal moderator band producing a hidden trabecular component of the right ventricle, mimicking isolated hypoplasia of the right ventricle. A marked hypoplasia was confirmed by echocardiography and catheterization. At operation an anomalously thickened moderator band obstructing the apical infundibulum was found. Repair consisted of a section of the moderator band and closure of the atrial septal defect. Postoperatively the right ventricle showed normal dimension and function.
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Introduction
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The isolated hypoplasia of the right ventricle (RV) is a rare anomaly that is characterized by the absence of the trabecular portion of the RV and an atrial septal defect (ASD) resulting in a right-to-left shunt [1]. Since the initial publication of Gasul and colleagues [2] in 1959, 60 patients (most of them in infancy) were reported with cyanosis and heart failure [3]. There are some cases diagnosed in adulthood [4]. Surgery is almost always indicated due to persistent cyanosis.
A 12-year-old girl was referred to our hospital for diagnosis. She complained of cyanosis since birth. At admission there was severe cyanosis (arterial oxygen saturation, 75%) and clubbing of the fingers. Electrocardiogram showed sinus rhythm, left axis deviation, and left ventricular hypertrophy. The roentgenogram findings showed no cardiomegaly, an enlarged right atrium, and diminished pulmonary blood flow. An echocardiogram showed the presence of a large ASD of 22 mm. The RV seemed hypoplastic due to underdevelopment of the trabecular portion. The inlet portion and the infundibulum were normal, the pulmonary valve had a normal diameter, but the tricuspid valve diameter was slightly diminished (Z value, –2). A cardiac catheterization was done with an arterial oxygen saturation of 78%. A right-to-left shunt through a large ASD was confirmed with a pulmonary-to-systemic blood flow ratio of 0.58. A right ventriculogram (Fig 1A) showed absence of the trabecular portion with normal tricuspid valve and outflow tract.
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Fig 1. (A) Preoperative cardiac catheterization shows left diastole, normal inlet portion, and absent trabecular portion and right systole, normal infundibulum, and pulmonary valve. (B) Postoperative magnetic resonance imaging scan shows left diastole, normal end-diastolic volume, and right systole with normal right ventricular ejection fraction.
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The patient was operated on through a median sternotomy using standard cardiopulmonary bypass, moderate hypothermia, and cold blood cardioplegia. Externally, a marked hypoplasia of the RV was evident (Fig 2). An indentation in the mid portion of the diaphragmatic wall of the RV could be identified. A right atriotomy was done and a large ASD of more than 2 cm wide was found. The tricuspid valve was normal in shape and dimension. Through the tricuspid valve, the RV was inspected, which showed that the inlet portion, infundibulum, and pulmonary valve had normally developed. The moderator band was abnormally hypertrophied, occluding the trabecular portion laying anteriorly and inferiorly, the so-called infundibular apex [5]. An abnormal extension of the moderator band ran from the origin of the anterior papillary muscle to the mid portion of the diaphragmatic wall corresponding to the external indentation. Repair consisted of a section of the moderator band, which liberated a hidden trabecular component. There was no need for further resection of other trabeculations. Direct closure of the ASD completed the repair. Mean ischemic and pump times were 17 and 39 minutes. The patient was weaned off bypass with good hemodynamics and normal right atrial pressure (8 mm Hg). An intraoperative echocardiogram showed good dimension and function of the right ventricle. The postoperative course was normal. The patient was discharged on postoperative day 10 with no medication.
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Fig 2. Surgical images. (A) The right ventricle (RV) is small compared with the left ventricle (LV). (B) The black arrow indicates the left anterior descending artery separating the right ventricle from the left ventricle. The white arrow indicates the indentation in the diaphragmatic wall. (C) A right atriotomy and normal tricuspid valve; the white arrow indicates the moderator band and anterior papillary muscle. (D) The white arrow indicates a hypertrophied muscular band extending from the moderator band to the diaphragmatic wall corresponding to the outside indentation.
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At follow-up (5 months after surgery) the patient is asymptomatic with normal oxygen saturation of 95%. An echocardiogram and magnetic resonance imaging scan were performed (Fig 1B) that showed a RV end-diastolic volume of 74 mL, an end-systolic volume of 41 mL, and an ejection fraction of 49%. An echocardiogram showed right ventricular dimensions of a 5-cm length area of 17.8 cm2. The tricuspid valve transverse diameter was 32 mm (Z value, –1).
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Comment
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The main feature of isolated hypoplasia of the right ventricle is the absence of the trabecular portion of the RV with the presence of normally developed tricuspid and pulmonary valves. The inlet portion and the infundibulum may be slightly small but not restrictive. Right ventricular myocardium has normal thickness as opposed to Uhl’s disease. The right atrium is dilated and hypertrophied as a response to the diminished distensibility of the RV. As a consequence, there is an ASD with a right-to-left shunt. In this way the cardiac output is normal at the expense of severe cyanosis and decreased pulmonary blood flow. The cause of this disease is unknown; however it is believed to be due to a primary defect in the development of the right ventricle. Our case masquerades the true hypoplasia of the RV and shares the same hemodynamic features, but there is a trabecular component rendering this case exceptional. The presence of an abnormal moderator band producing an obstruction of the infundibular apex explains the occurrence of the hypoplasia of the RV in the absence of valvular lesions. The mere section of the moderator band expanded a collapsed trabecular portion producing a near normal right ventricular dimension for the size of the patient. In the presence of apical ventricular septal defect, the moderator band produces a compartmentalization of the RV, and the infundibular apex becomes a part of the left ventricle with the shape of a wind sock [6]. In our case there is a hidden trabecular component, but is not committed to the left ventricle because there is no ventricular septal defect [7]. In the postoperative magnetic resonance image scan there was some thickening of the apical myocardium of the RV that could be seen. This is a typical finding in noncompaction of ventricular myocardium, but other characteristics (such as the presence of deep endomyocardial spaces or the involvement of the left ventricle) were absent [8]. The treatment of isolated hypoplasia is essentially surgical. In most cases direct closure of the ASD is only required, but in some severe cases a cavopulmonary anastomosis has been added. A mild increase of right atrial pressure occurs, but the RV is capable of handling the extra volume by increasing the stroke volume and raising the systolic pressure. An ASD occlusion test at the catheterization laboratory has been proposed to verify the feasibility of the ASD closure [4].
In conclusion, the presence of an abnormally hypertrophied moderator band is a rare cause of isolated hypoplasia of the RV due to occlusion of the trabecular portion rather than true absence. The resection of the moderator band increases the dimension and distensibility of the RV and may be curative without the need for a cavopulmonary anastomosis.
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References
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- Gasul BM, Weinberg M, Luan LL, Fell EH, Bicoff J, Steiger Z. Superior vena cava right main pulmonary artery anastomosis; surgical correction for patients with Ebstein’s anomaly and for congenital hypoplastic right ventricle JAMA 1959;171:1797-1801.[Abstract/Free Full Text]
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- Stellin G, Padalino M, Milanesi O, et al. Surgical closure of apical ventricular septal defects through a right ventricular apical infundibulotomy Ann Thorac Surg 2000;69:597-601.[Abstract/Free Full Text]
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Abstract
Introduction
