An Approach to Cardiac Malposition and the Heterotaxy Syndrome Using 99mTc Sulfur Colloid Imaging P. M. FITZER A diagnostic approach to cardiac malposition and the heterotaxy syndrome is outlined. The 9Tc sulfur colloid intravenous forward angiocardiogram and plain chest radiograph are used to determine the two key diagnostic points: position of the venous atrium and stomach. If locatad on the opposite sides of the body, four basic situs configurations are possible, and the presence of associated cardiac anomalies may be predicted. For the two configurations in which the cardiac apex is on the same side as the stomach, the incidence of associated cardiac anomalies is low; when on opposite sides, the incidence is high. If the venous atrium and stomach are on the same side, then abdominal heterotaxy with associated splenic abnormality is present. Dynamic Tc sulfur colloid imaging will usually show interruption of the inferior vena cava, if present, and multiple or absent spleens. To the general diagnostic radiologist, probably no subject is as difficult and uncertain as cardiac malposition and the heterotaxy syndrome. Considering the complex possibilities, such attitudes are understandable. This paper presents a simplified diagnostic approach based on the plain chest radiograph and simple imaging techniques. In most instances, a presumptive diagnosis can be established with considerable accuracy. Definitions and Associations The position, or situs, of the heart in the thorax is best defined by the position of the atnia [1 1. In this discussion, the atrium receiving the systemic venous return is termed the venous atrium. In the usual situation, the inferior vena cava, venous atrium, and liver are on the right side, and the aortic arch and stomach are on the left side. This is called situs solitus. In some individuals these relationships are reversed, the mirror image of the normal situation. This is called situs inversus. The position of the ventricles and, consequently, the position of the cardiac apex is not relevant to determination of the basic thoracoabdominal situs. In early fetal life the ventricles migrate from the opposite side of the thorax to their ultimate position. While this migration may fail to occur, it does not affect the basic situs which depends on the position of the atria. The term malposition, then, refers simply to a reversed position of the atnia, ventricles, or both. Four basic configurations are possible [1]: (1) situs solitus, apex on left; (2) situs solitus with failure of migration of ventricles, apex on right; (3) situs inversus (mirror image of 1), apex on right; and (4) situs inversus (mirror image of 2), apex on left. In most instances, the aortic arch and stomach lie on the opposite side of the venous atrium, and this relationship has been proposed for locating the atnia [1 1. However, an isolated anomaly of the aortic arch may occur in otherwise normal individuals [21. Or, rarely. the stomach may be located abnormally. To avoid these problems, a Tc sulfur colloid forward angiogram may be used to ascertain the position of the venous atrium. A 5-1 0 mci bolus of 9 Tc sulfur colloid is injected intravenously in the lower extremity. Dynamic imaging of the upper abdomen and heart is performed. A low energy diverging collimator may be useful. This will show the side of the inferior vena cava, venous atrium, and ventricles. Subsequent multiple static views of the upper abdomen to outline the liver and spleen may be made if indicated. The plain chest radiograph usually shows the position of the stomach, but administration of a single teaspoon of thick barium paste may be helpful. The position of the cardiac apex is usually evident on the chest radiograph but will also be shown by dynamic cardiac imaging. The position of the inferior vena cava and venous atrium may be established by other techniques as well. Simple catheter exploration or venous angiocardiography are effective, but there are disadvantages associated with invasive catheter manipulation or sensitivity to contrast media. Ultrasound imaging may identify the side of the inferior vena cava and, hence, the position of the venous atrium. However, unlike dynamic 99mTc sulfur colloid imaging, none of these techniques combine a noninvasive, virtually morbidity-free cardiovascular imaging modality with the valuable additional information derived from subsequent liver and spleen imaging. The most important factors are the positions of the venous atrium and stomach. In each of the four basic configurations described, the venous atrium and stomach are on opposite sides of the body. If the cardiac apex is on the same side as the stomach, there is a low incidence of associated congenital cardiac anomalies. This is the case in basic configurations 1 and 3, normal situs solitus and situs inversus. If the cardiac apex fails to migrate normally during fetal life and is opposite the stomach, then the incidence of associated cardiac anomalies is high (table 1 ). The incidence of cardiac anomalies in situs inversus is about 5% [31 and is higher than that for situs solitus. Many cardiac anomalies, of course, occur in situs solitus (configuration 1 ). Also, while it is possible to have a normal heart with any configuration, this would be unusual in configurations 2 or 4. Received February 1 1, 1976; accepted after revision July 27. 1976. 1 Nuclear Radiology Section, Department of Radiology. Riverside Hospital. J. Clyde Morris Boulevard, Newport News. Virginia 23601. Am J Roentgenol 127:1021-1025, 1976 1021
1022 FITZER TABLE 1 Cardiac Anomalies Associated with Configurations 2-4 TABLE 3 Common Abnormalities Associated with Asplenia Configurations 2 and 4 Configuration 3 Corrected transposition Corrected transposition accompanied by: accompanied by: VSD and pulmonary stenosis VSD with pulmonary stenosis Tricuspid atresia Isolated VSD P ulmonary stenosis E bstein s malformation Isolated VSD Other: Ebstein s malformation C omplele transposition Other: with VSD ASD Endocardial cushion defect Coarctation of aorta Isolated VSD Complete transposition Con biloculare Anomalous origin left pulmonary artery Note. - Data from [ 1, 31. The incidence of cardiac anomalies associated with configurations 2 and 4 is 95%compared to 5%for configuration 3. Corrected transposition with an associated anomaly is the most common defect in both groups. ASD = atrial septal defect; VSD = ventricular septal defect. Type TABLE 2 Common Abnormalities Associated with Polysplenia Approximate Reported lncidence(%) Cardiac: Endocardial cushion defect (ASD, VSD. common atrium or ventricle) 85 Interruption of hepatic segment of inferior vena cava with azygous on hemiazygous continuation Anamolous pulmonary venous return.... Bilateral superior vena cava 0-100 60-80 50 Coronary sinus rhythm on electrocardiogram 75 Pulmonary: Bilateral bibbed lungs, hypartenial broichus 50-70 Abdominal: Heterotaxy Malrotation of gut Hepatic symmetry Absent gallbladder Extrahepatic biliary atnesia 65-100 50-80 30-60 1 50 Note-Data from (5. 7-12). The cardiac anomalies of polysplenia are characteristically less severe than in asplenia. A normal heart is found in approximately 6% of cases. ASD = atrial septal defect; VSD = ventricular septal defect. If the venous atrium and stomach lie on the same side of the body, then abdominal heterotaxy is usually present. The term abdominal heterotaxy means an abnormal position of one or more abdominal organs. [4]. A simple form would be location of the stomach on the right with all other organs in their normal positions. While abdominal heterotaxy can be an isolated anomaly, it is frequently associated with cardiac malpositions and other cardiac Type Approximate Reported Incidence 1%) Cardiac: Transposition with pulmonary stenosis, ASDand/onVSD 95 Anomalous pulmonary venous return.... 50 Malposition of aortic arch 30-50 Pulmonary: Bilateral tnilobed lungs, bilateral epiantenial bronchi 60-100 Abdominal: Heterotaxy 95 Malnotation of gut 50 Hepatic symmetry 80 Midline gallbladder? Rare Microgastnia 4 Miscellaneous: Howell-Jolly bodies 70 Abnormal P wave? Note-Data from [5. 9. 12-16]. Many other less common anomalies have been reported. ASD = atrial septal defect; VSD = ventricular septal defect. anomalies. Abdominal heterotaxy is also commonly associated with abnormalities of the spleen [51. Multiple or absent spleens are usually demonstrable by 99mTc sulfur colloid imaging [4]. Multiple views, sometimes including obliques, are mandatory. The same information may be provided by imaging with 5tCr-Iabeled erythrocytes [6]. Conventional contrast angiography has been advocated for the evaluation of splenic abnormalities in all patients [7] but has significant disadvantages compared to the simplicity of radionuclide imaging. When multiple spleens are present, the body may tend toward bilateral left-sidedness with absence of normal right-sided structures (table 2) [7, 8]. The inferior vena cava may terminate at the hepatic level with venous continuation via the azygous or hemiazygous system. Malpositions or other associated cardiac anomalies are not always present [7]. Absence of the spleen is associated with a tendency toward bilateral night-sidedness with absence of normal left-sided structures (table 3) [5, 1 7, 1 8]. Cardiac malpositions or other cardiac anomalies are invariably present. The physiologic cardiac lesion in usually severe and resembles tetralogy of Fallot: pulmonary stenosis or atresia with a right-to-left shunt across a ventricular septal defect. Total anomalous pulmonary venous return may also be present. Howell-Jolly bodies may be seen in the blood smear. Polysplenia and asplenia are thought to be closely related defects of early embryogenesis reflecting persistence of normally symmetrical embryonal structures [8, 1 3]. These conditions represent a spectrum of abnormalities; whereas there may be a tendency to bilateral left-sidedness or night-sidedness, some patients show intermediate features [13, 19].
RADIONUCLIDE IMAGING IN CARDIAC MALPOSITION 1023 Determine position of venous atrium and stomach Same side. Same side Determine position of cardiac apex and stomach Opposite sides Normal inferior vena cava, absent spleen Opposite Sides Left Right Stomach left. - Stomac right. Solitus with Inversus with Normal solitus iriversus of failure of lconfiguration 11 (Configuration 3) ventricular ventricular migration migration (configuration 2( (configuration 4( Table 1 Fig. 1. - Diagnostic approach. Interruption of inferior vena cava. multiple spleens Tables 2 and 3 -...,;:,. Fig. 2.-Case 1. A. Chest radiograph showing aortic arch on right; position of cardiac apex not obvious. Stomach bubble is on right. and liver shadow appears to be on left. B,99mTc sulfur colloid forward angiocardiogram (anterior view), showing superior vena cava and venous atrium on left (small arrow). Right ventricle and cardiac apex (large arrow) are on right; main pulmonary artery is filled (double arrow). C. Static anterior abdominal images showing spleen on right and liver on left. Diagnosis: situs inversus, configuration 3.
1024 FITZER I, 0 -.,t Iit.].H! - i;-.-:1 c.......i of...., Venous atrium is on right (upper arrow). D, Static anterior view showing liver on right and a spleen on left. E and F, Posterior and right lateral views showing spleen on left and another spleen posterior to liver on right (arrow). Diagnosis: polysplenia.
RADIONUCLIDE IMAGING IN CARDIAC MALPOSITION 1025 In summary, the important diagnostic features include the positions of the right or systemic venous atrium, the stomach, and the cardiac apex; interruption of the inferior vena cava and absent or multiple spleens are also key points. A diagnostic approach based on these points is outlined in figure 1. Two examples are presented below. Case 1 Case Reports A 26-year-old female hospitaj employee was referred for an annual chest radiograph. She had no history of cardiac disease. An appendectomy had been performed at age 1 6; she was told that there had been some difficulty in locating the appendix. The chest radiograph (fig. 2A) showed marked thoracolumban scoliosis. The aortic arch was on the right, but the position of the cardiac apex was not obvious. The stomach bubble was on the right, and the Ii yen shadow appeared to be on the left. A OOnlTc sulfur colloid forward angiocandiognam (left arm injection) showed the venous atrium on the left and right ventricle and main pulmonary artery on the right (fig. 2B). Subsequent static images showed the liver on the left and spleen on the right (fig. 2C). Using the flow chart outlined in figure 1. a diagnosis of situs inversus (configuration 3) was made. There was no evidence of associated congenital cardiac abnormality by history. physical examination, or electrocardiogram. Case 2 A 33-year-old female psychiatric patient was referred for an admission chest radiograph. She had no previous history of cardiac disease. The radiograph (fig. 3A) showed the aortic arch and cardiac apex on the left. There was a prominent venous shadow in the right paratracheal area. The gastric bubble appeared to be on the right. This was confirmed by a previous upper gastrointestinal examination (fig. 3B). The OOmTc sulfur colloid forward angiocardiogram (pedal injection, only 2 mci) showed the venous atrium on the right. There was apparent interruption of the inferior vena cava with hemiazygous continuation to the left innominate vein (fig. 3C). The liver was on the night; multiple spleens were present (figs. 3D and 3E). Using the approach outlined in figure 1, a diagnosis of polysplenia was made. The pulmonary vasculanity on the chest radiograph was considered normal. There was no evidence of cardiac disease by history, physical examination, or electrocardiogram. The patient refused further evaluation. It is presumed that she represent one of the small group of polysplenia patients without associated congenital cardiac anomaly (table 2). ACKNOWLEDGMENTS Many of the concepts discussed are based on classic works by L. P. Elliott, K. Amplatz, and others; my debt to them must be acknowledged. 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This article has been cited by: 1. Abraham H. DachmanAnomalies and Anatomic Variants of the Spleen 1993-2004. [CrossRef] 2. M. Bakir, A. Bilgic, M. Özmen, M. Çaĝlar. 1994. The value of radionuclide splenic scanning in the evaluation of asplenia in patients with heterotaxy. Pediatric Radiology 24:1, 25-28. [CrossRef]