|FOCUS ISSUE - CONGENITAL HEART DISEASE
|Year : 2020 | Volume
| Issue : 3 | Page : 344-349
Systemic Venous Anomalies: Echocardiographic Evaluation
Nandeeswari Subramanian, Anuradha Sridhar
Department of Pediatric Cardiology, Apollo Children Hospital, Chennai, Tamil Nadu, India
|Date of Submission||20-Aug-2020|
|Date of Acceptance||02-Oct-2020|
|Date of Web Publication||18-Dec-2020|
Dr. Nandeeswari Subramanian
15, Shaffi Mohammed Road, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Systemic venous anomalies can occur in isolation but are more commonly found in association with other structural heart diseases. Echocardiography has become a routine tool in the diagnosis of these anomalies, which although hemodynamically insignificant, can cause significant morbidity in the setting of cardiac catheterisation and surgical intervention in patients with congenital heart disease if not identified correctly.
Keywords: Coronary sinus, inferior vena cava, superior vena cava
|How to cite this article:|
Subramanian N, Sridhar A. Systemic Venous Anomalies: Echocardiographic Evaluation. J Indian Acad Echocardiogr Cardiovasc Imaging 2020;4:344-9
|How to cite this URL:|
Subramanian N, Sridhar A. Systemic Venous Anomalies: Echocardiographic Evaluation. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2020 [cited 2023 Jan 29];4:344-9. Available from: https://jiaecho.org/text.asp?2020/4/3/344/303943
| Introduction|| |
Assessment of systemic veins is an important step in the sequential segmental analysis of the heart by echocardiography. In the echocardiography of complex congenital heart diseases, describing the systemic veins as a first step will help in accurate description of all the cardiac chambers. Congenital systemic venous anomalies [Table 1] can occur in isolation, often with little hemodynamic significance, or in association with other structural heart defects. Because of the wide variability within this class of anomalies, evaluation of the systemic venous return must involve a systematic approach with a comprehensive description of each individual segment. Assessment of systemic veins can have important implications in the management of any patient who requires cardiac catheterization or surgical intervention and cardiopulmonary bypass, since the systemic venous return is cannulated in these procedures. Preoperative identification and complete characterization of any abnormalities in systemic venous return are also crucial in patients with single ventricle circulation because their surgical palliation ultimately requires connection of the systemic venous return directly into the pulmonary arteries.
| Anomalies of Superior Vena Cava|| |
Persistent left superior vena cava draining into the right atrium
Persistence of the left superior vena cava (LSVC) is the most common systemic venous anomaly. It results from failure of the left anterior and left common cardinal veins to involute. LSVC drains into the right atrium (RA) through the coronary sinus (CS) in 92% of cases. The LSVC may also drain directly into the left atrium (LA) because of absent or unroofed CS. LSVC begins at the junction of the left jugular and subclavian veins and joins the CS in the posterior left atrioventricular (AV) groove.
When the LSVC drains into the RA through the CS, it is physiological and does not present with clinical manifestations. Its association with other congenital cardiac malformations such as tetralogy of Fallot, AV septal defects may pose diagnostic and technical difficulties during catheterization, cannulation approach for cardiopulmonary bypass, and planning for bilateral Glenn surgery. Persistent LSVC joining an enlarged CS in the posterior left AV groove may interfere with blood flow from the LA into the left ventricle.
The presence of LSVC can be suspected on a chest radiogram based on a shadow along the left upper border of the mediastinum. Echocardiography is the most widely used noninvasive method to detect an LSVC. The detection of LSVC by two-dimensional echocardiography had a specificity of 100% and a sensitivity of 96%.
Imaging of a dilated CS is often the first clue to the diagnosis of an LSVC during the course of an echocardiographic examination. The CS can be imaged from the subcostal long-axis view during posterior to anterior sweep, posterior sweep of apical, and in the posterior AV groove in parasternal windows. It appears as a tubular structure in the posterior left AV groove with an opening into the posteroinferior aspect of the RA adjacent to the orifice of the inferior vena cava (IVC) in the apical four-chamber view [Figure 1].
|Figure 1: Apical four chamber view in most posterior plane showing dilated coronary sinus (CS) running along the floor of left atrium. RA- right atrium, LV-left ventricle, RV-right ventricle, DAo: Descending aorta|
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Suprasternal view – short axis shows aortic short axis in the middle flanked by the RSVC on the right side and the LSVC on the left side. Color mapping shows the direction flow from LSVC into CS [Figure 2].
|Figure 2: Suprasternal short axis view with color flow mapping showing bilateral SVC and absence of bridging vein. Ao-aorta,PA -pulmonary artery, RSVC-right superior vena cava, LSVC- left superior vena cava|
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There is an inverse relationship between the caliber of the LSVC and the left innominate vein (LIV).
If the left SVC cannot be delineated easily by imaging and/or color mapping, saline contrast injection into the left arm will result in the presence of contrast in the dilated CS before its presence in the RA.
In fetal echo, the persistent LSVC can be identified in cross section on three-vessel view as an additional fourth vessel to the left of the pulmonary artery and its long axis can be seen with leftward sagittal sweep [Figure 3]. Color Doppler to determine the direction of the blood flow is important in differentiating between an LSVC and other veins that may connect with the innominate vein such as total or partial pulmonary venous connections, a left superior intercostal vein, and a levoatrialcardinal vein. Unlike LSVC draining to an intact CS, the direction of blood flow in these veins is expected to be into the innominate vein (ascending venous channel).
|Figure 3: Fetal echocardiography showing additional 4th vessel in the cross-section three-vessel view. LSVC: Left superior venacava, RSVC: Right superior venacava, PA: Pulmonary artery, Ao: Aorta|
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Bilateral superior venae cavae with an unroofed coronary sinus anatomy
The common wall between the LA and the CS is either partial or completely absent, thereby leading to the LSVC draining into the LA. The highest incidence is seen in visceral heterotaxy with asplenia.
Isolated persistent LSVC draining to a partially or completely unroofed CS is known to be associated with a large CS ostium that functions as an interatrial communication (Raghib syndrome). The hemodynamic consequences of the Raghib syndrome are cyanosis and left-to-right shunting through the atrial septal defect (ASD). The degree of arterial desaturation is related to the net right-to-left shunt, which, in turn, depends on the amount of systemic venous blood carried by the LSVC and the proportion of systemic venous blood that crosses the atrial septum and reaches the pulmonary circulation.
The LSVC may appear as a shadow along the left upper border of the mediastinum on the chest radiogram. The electrocardiographic features of isolated LSVC to an unroofed CS are similar to secundum ASD. The frontal axis of the P wave may be abnormal in patients with heterotaxy syndrome, reflecting a left sinoatrial node or an ectopic atrial rhythm.
The drainage of the LSVC into the LA can be imaged in the subcostal view and suprasternal view. The posterior left AV groove is examined thoroughly to ascertain the extent of deficiency of the CS septum. When the CS septum is completely unroofed, the LSVC terminates in the upper left posterior corner of the LA between the left upper pulmonary vein posteriorly and the left atrial appendage anteriorly.
Color Doppler is useful in demonstrating flow from the LSVC into the LA, which will reveal antegrade flow along the left SVC. If the diagnosis is still in doubt, a contrast injection in a left arm vein establishes the diagnosis by the demonstration of microbubbles in the LA before they appear in the RA.
The CS defect of a partially or completely unroofed CS that receives an LSVC must be repaired to avoid complications of cyanosis and its sequelae and of chronic left-to-right shunting.
Absent right superior vena cava in visceroatrial situs solitus
The right innominate veins drain into the left SVC, which in turn drains into the RA through a dilated CS. There are no clinical manifestations in this condition in the absence of additional cardiovascular malformations. It can rarely be associated with rhythm disturbances. Echocardiographic examination shows the absence of right SVC connecting to RA in subcostal short-axis view and the presence of left SVC draining to the dilated CS.
Fetal echo shows the absence of RSVC, and the LSVC is found on the left of the pulmonary artery in the three-vessel view [Figure 4].
|Figure 4: (a) Fetal echo showing the three-vessel view. (b) Note the absence of RSVC. Ao: Aorta, LSVC: Left superior vena cava, PA: Pulmonary artery, SVC: Superior venacava|
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The clinical relevance of establishing the diagnosis of absent right SVC with a persistent LSVC to the CS in visceroatrial situs solitus is mainly to avoid difficulties during cardiac catheterization and the surgical procedures which require venous cannulation.
Left atrial or biatrial drainage of right superior vena cava
Left atrial or biatrial drainage of right superior vena cava (SVC) results from the deficiency of the common wall between the SVC and right upper pulmonary vein (RUPV), thereby unroofing the RUPV [Figure 5]. The unroofed RUPV then drains into SVC, and its LA orifice becomes the interatrial communication. There is a sinus venosus defect of the SVC type in association with atresia of the right SVC orifice.
|Figure 5: Subcostal view showing the drainage to right superior vena cava into LA through a deficient wall between the right superior vena cava and right upper pulmonary vein. RSVC: Right superior venacava, LA: Left atrium, RA: Right atrium, IVC: Inferior venacava|
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Cyanosis is the dominant clinical feature. The risk of right-to-left shunt sequelae increases with age.
The common entrance site of the RSVC and RUPV in the roof of the LA can be demonstrated by echo from the subcostal short-axis view or the right sternal border long-axis view.
Surgical transection the SVC and anastomosis to the RA appendage.
Retroaortic innominate vein
The LIV normally courses anterior to the aortic arch from left to right in the superior mediastinum finally joining the right innominate vein to form the RSVC. In retroaortic innominate vein, the confluence of the left subclavian and left common jugular veins forms the LIV which runs horizontally behind the ascending aorta to reach the SVC below the insertion of the azygous vein [Figure 6].
|Figure 6: Suprasternal short-axis view of a retroaortic innominate vein. Ao: Aorta, LIV: Left innominate vein; RSVC: Right superior vena cava|
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The LIV should be tracked from its origin through its retroaortic course to the SVC. It should be differentiated from persistent LSVC which will connect with the CS or with the LA if the CS is unroofed.
| Anomalies of the Coronary Sinus|| |
Visualizing a dilated CS should mandate a systematic approach with an evaluation of the LIV, the individual pulmonary veins, the hepatic veins, and the roof of the CS. It is important to evaluate the CS in the posterior sweep of an apical view as well as a high left parasagittal view with the probe in a nearly vertical orientation where the roof is perpendicular to the ultrasound beam.
A coronary sino-septal defect (partial or complete unroofing of the CS) is often associated with a left SVC, is located along the superior aspect of the CS as it passes behind the LA, can present like a left SVC to the LA, and may or may not be associated with an additional interatrial communication. Saline contrast injection into the left arm may result in the appearance of contrast in the LA.
Coronary sinus defect and unroofed coronary sinus
Unroofed CS almost always is associated with a persistent LSVC. A CS defect without an associated LSVC is rare, and the physiology is the same as in ASD. Echocardiographic diagnosis can be made by imaging the CS septum in the posterior left AV groove as described earlier.
Coronary sinus orifice atresia
Atresia or severe stenosis of the right atrial orifice of the CS is rare. The CS is usually well formed, and the orifice is covered by a thin membrane-like tissue that appears to be related to the Thebesian valve. Myocardial ischemia, infarction, and death have been reported in several patients in whom there was no alternative exit for the CS blood.
| Anomalies of the Inferior Vena Cava|| |
Interrupted inferior vena cava
Interrupted IVC (absence of the hepatic segment of the IVC) with azygos continuation occurs in up to 84% of patients with left isomerism or polysplenia syndrome. It is also known to occur in patients with situs solitus and rarely in patients with right isomerism or asplenia syndrome. There is a prevalence of approximately 0.6% among patients with congenital heart disease and less than 0.3% among those without other heart defects.
Embryologically, right subcardinal vein fails to connect to the right vitelline and right hepatocardiac veins. The right supracardinal vein enlarges and ultimately becomes the azygos continuation to the right SVC. Rarely, the infrahepatic segment of the IVC may continue to both right and LSVC through bilateral azygos veins.
Interrupted IVC with azygous continuation does not cause any physiological abnormality. The hemodynamic significance of such an anomaly is usually determined by the associated intracardiac anomalies. It is important to diagnose the azygos continuation of the IVC by echocardiography because cardiac catheterization and intraoperative venous cannulation may be difficult in these patients. Patients with left isomerism and an interrupted IVC are at increased risk for complete heart block, and emergency placement of a pacemaker can be difficult to place through an azygos vein.
In patients with single ventricle circulation, the timing for staged palliation is affected by an interrupted IVC since a bidirectional superior cavopulmonary anastomosis will result in the connection of the entire systemic venous system except for the hepatic veins to the pulmonary arteries (Kawashima procedure).
The diagnosis is based on imaging of the size, location, and course of the IVC and the azygos vein from the subcostal window. Subcostal short-axis (sagittal) and long-axis (transverse) views with posterior angulation usually demonstrate hepatic venous drainage to the RA without IVC connection to the RA [Figure 7].
Subcostal short-axis (sagittal) views are especially useful in delineating the following anatomic features:
- The length of the IVC from the level of the kidneys to its junction with the RA to avoid erroneously identifying a prominent hepatic vein as the IVC
- A prominent azygos vein coursing parallel to and along the rightward and posterior aspect of the descending aorta (a prominent hemiazygos vein courses along the leftward and posterior aspect of the descending aorta) [Figure 8]
- On color flow mapping, there is the opposite direction of flow in the azygos or hemiazygos vein and the descending aorta by color mapping
- Right sternal border long-axis (parasagittal) and the suprasternal long-axis views can also demonstrate the arch of the azygos vein as it connects to the posterior aspect of the right SVC.
|Figure 8: Subcostal sagittal view with leftward tilt showing the whole length of azygos arch in a child with interrupted inferior vena cava and azygos continuation. SVC: Superior venacava, RPA: Right pulmonary artery|
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Fetal echocardiography usually reveals the absence of the full length of the IVC during sagittal sweeps of the fetal chest and abdomen. Identification of the prominent azygos vein behind and to the right of the descending aorta is often the first clue to an interrupted IVC in utero.
Bilateral inferior vena cava
Bilateral suprahepatic IVC (a normal IVC and contralateral hepatic vein) associated with heterotaxy syndromes. The left-sided hepatic vein drains into the CS. This variation in anatomy does not cause any hemodynamic disturbances.
Inferior vena cava drainage into the left atrium
During fetal life, about half of the IVC blood that enters the RA is directed toward the LA with the help of two venous valves: the eustachian valve and the valve of the foramen ovale.
The eustachian valve may persist with little or no change from its fetal size and attachments. If the foramen ovale is patent or if there is an ostium secundum defect, the IVC blood will continue to drain into both atria.
Partial or complete drainage of the IVC into the LA results in cyanosis. The clinical manifestations are the result of right-to-left shunting including polycythemia, brain abscess, and paradoxical emboli.
The diagnosis can be established by echocardiography, cardiac MRI, computed tomography, or cardiac catheterization. Echocardiographic evaluation involves careful Doppler color mapping of IVC flow in subcostal and right sternal border view. Saline contrast injection into a lower extremity systemic vein can confirm the diagnosis with the immediate appearance of contrast in the LA.
Surgical redirection of the IVC into the RA.
| Conclusion|| |
Systematic assessment while performing echocardiography is indispensable for identifying and describing congenital cardiac defects. Importance of identifying systemic venous anomalies in the management of any patient requiring cardiac catheterization or surgical procedures involving cannulation of the systemic veins cannot be reemphasized more. Preoperative identification of these anomalies is also pivotal for the planning of palliative procedures in single ventricle physiology.
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Conflicts of interest
There are no conflicts of interest.
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