Segmental Approach to Imaging of Congenital Heart

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Segmental Approach to Imaging of Congenital Heart Disease:

Segmental Approach to Imaging of Congenital Heart Disease DR PREM D N B RESIDENT MEDWIN 5 TH JAN 2010

Slide 2:

The segmental analysis of congenital heart disease was introduced 25 years ago and is now used worldwide . This approach is flexible and easy to understand (even for nonexperts ), applicable to any imaging modality, and thus particularly useful in clinical practice.

Slide 3:

In the segmental approach, the cardiac anatomy is assessed first by dividing the heart into three distinct segments, which are based on 10 embryologic regions. These segments are the visceroatrial situs , which is evaluated in step 1; the ventricular loop, evaluated in step 2; and the position of the great vessels, evaluated in step 3

Slide 4:

These segments are fundamental building blocks of the cardiac anatomy, and the morphologic and anatomic features specific to each segment are assessed separately . Next, the relationships between the segments (blocks) are assessed at the atrioventricular and ventriculoarterial levels. Finally, associated abnormalities in individual segments are sought and described.

Slide 5:

The notation system developed by Van Praagh (a series of three letters, separated by commas, within parentheses) may be used in conjunction with this approach.

Assessment of Cardiac Anatomy:

Assessment of Cardiac Anatomy Step 1 : Determining the Visceroatrial Situs Step 2 : Determining the Orientation of the Ventricular Loop Step 3 : Determining the Origin and Position of the Great Vessels

Step 1: Determining the Visceroatrial Situs :

Step 1 : Determining the Visceroatrial Situs There are three types of situs : solitus (S,–,–), inversus (I,–,–), and ambiguus (A,–,–). By definition, the type of situs is determined by the relationship between the atria and the adjacent organs, and only one type of situs anomaly is possible in any patient.

Slide 9:

Thus, the first step in the assessment of the cardiac anatomy is to locate and identify the left and right atria. Anatomically, the atrial chamber differentiation is based on the morphologic aspect of the atrial appendages. The atrial appendages are earlike extensions of the atria

Slide 10:

Typically, the right atrial appendage is broad and blunt (triangular), whereas the left atrial appendage is narrow, pointed, and tubular (fingerlike) .

Slide 11:

Most of the time, the appendages are not reliably identifiable at radiologic imaging, and the localization of noncardiac organs is more helpful for determining the situs .

Slide 12:

Determination of the orientation of the atria is the first step in segmental analysis. A universal rule exists which makes atrial location easy. Because of a fixed developmental pattern in early embryogenesis, atrial situs is almost always concordant with visceral situs . In other words, the left atrium is always found on the same side as the stomach .

Slide 13:

The right atrium stays in parallel with the liver. Locating the abdominal organs by physical exam or x-ray thus provides atrial situs . The term “ solitus ” means “usual.” Thus “ situs solitus ” refers to normal position of the atria. “ Situs inversus ” describes mirror-image reversal of the atria and the visceral contents

Slide 14:

At the thoracic level, the bronchial (pulmonary) anatomy, especially the relationship between the main right and left bronchi and the pulmonary arteries, is a reliable indicator of the atrial arrangement .

Slide 15:

At the abdominal level, the positions of the liver, stomach, and spleen are of paramount importance. The supradiaphragmatic portion of the inferior vena cava (IVC) also provides a reliable landmark for locating the anatomic right atrium (because of the rule of venoatrial concordance) .

Slide 16:

The position of the heart in the thorax and the orientation of the cardiac apex are contributive to but not determinative of the situs , and, accordingly, they must be described separately.

Slide 17:

There are three possible types of cardiac malposition , as determined by the orientation of the cardiac base-apex axis: dextrocardia , mesocardia , and levocardia .

Slide 18:

dextrocardia

Slide 19:

With regard to the global location of the heart within the chest cavity, levoposition describes a location mainly in the left chest; dextroposition , a location predominantly in the right chest; and mesoposition , a midline location of the heart; In all three variants, the cardiac base-apex axis may be oriented normally (toward the left chest) .

Slide 20:

dextroposition

Slide 21:

Usually, dextrocardia refers to a heart located in the right thorax, with the base-apex axis tilted toward the right. Dextrocardia may be present with any type of situs .

Slide 23:

In general, cardiac and situs anomalies are less frequently found with a concordant position of the cardiac apex, stomach, and aortic arch and occur more frequently with a discordant position of one or more of these landmarks It is therefore important to detect any thoracic or pulmonary anomalies that might lead to displacement of the heart .

Slide 24:

Situs ambiguus with complex congenital heart disease. Frontal chest radiograph shows discordant positions of the cardiac apex (white arrow), aortic arch (black arrow), and stomach (arrowhead), findings indicative of severe congenital anomalies and heterotaxy

Slide 25:

For example, a hypoplastic right lung induces dextroposition with a left-sided cardiac apex, and the presence of this pulmonary abnormality implies a reduced probability of underlying congenital heart disease .

Slide 26:

Chest radiograph shows cardiac dextroposition due to right lung hypoplasia after a right diaphragmatic hernia repair .

Slide 27:

Systemic and pulmonary venous characteristics are not, strictly speaking, part of the segmental approach, but they must be described at this point in the report because they have surgical implications.

Slide 28:

For the systemic venous structures, the main abnormalities that should be sought at CT, MR imaging, or both are as follows: (a) a left superior vena cava with or without an innominate vein that drains either into the right atrium via the coronary sinus or directly into the left atrium

Slide 29:

(b) a retroaortic position of the innominate vein, behind the ascending aorta; and (c) an interrupted inferior vena cava with azygos vein continuation .

Slide 30:

The pulmonary veins are examined to identify their connections and any stenotic lesions . An abnormal pulmonary venous connection may be total or partial.

Situs Solitus :

Situs Solitus Situs solitus is the normal anatomic configuration, with the right atrium and liver on the right side; the left atrium, stomach, and spleen on the left side; a right-sided trilobed lung with an early origin of the upper lobe bronchus from the right main stem bronchus; and a left-sided bilobed lung with a more distal origin of the upper lobe bronchus .

Situs solitus :

Situs solitus

Slide 33:

The right pulmonary artery of the right bronchus ( eparterial bronchial position ), and the left pulmonary artery crosses above the left bronchus ( hyparterial bronchial position ).

Situs inversus:

Situs inversus In situs inversus , the anatomic configuration is an exact inversion of that in situs solitus .

Situs inversus :

Situs inversus

Slide 36:

Situs inversus

Slide 37:

Situs inversus

Slide 38:

Radiograph of the upper abdomen from a barium enema examination in a 40-year-old man with situs inversus and dextrocardia . This image shows the liver ( L ) in the left upper quadrant of the abdomen. The positions of the splenic flexure ( SF ) and hepatic flexure ( HF ) are reversed

Slide 39:

Radiograph of the lower abdomen from a barium enema examination in a 40-year-old man with situs inversus and dextrocardia . This image shows the sigmoid colon ( SC ) on the right and the cecum ( C ) on the left

Slide 40:

Appendicolith Situs inversus

Slide 41:

Situs inversus

Slide 42:

Coronal70-mm-thick RARE MR cholangiopancreatogram shows the biliary tract (arrow) and gallbladder ( GB) in the left upper quadrant and the pancreatic duct (arrowheads) coursing toward the right. The high-signal-intensity focus in the right upper quadrant ( S) represents fluid in the stomach

Situs Ambiguus:

Situs Ambiguus When the situs is neither solitus nor inversus , it is referred to as situs ambiguus or heterotaxy . Situs ambiguus may manifest with various abnormal visceroatrial configurations that are associated with extracardiac anomalies ( eg , splenic abnormalities, biliary atresia , and intestinal malrotation ) as well as cardiac anomalies .

Slide 44:

Because of potential morbidity associated with intestinal malrotation , a barium enema examination is recommended in patients with heterotaxy . Abdominal ultrasonography also may contribute useful information in the work-up of extracardiac diseases. In situs ambiguus , the venoatrial connections are frequently abnormal.

Slide 45:

Two subsets of situs ambiguus are well recognized: right isomerism ( asplenia ) IVERMARKS SYNDROME and left isomerism ( polysplenia ) .

Slide 46:

In the presence of right isomerism, bilateral trilobed lungs, a large symmetric liver, absence of the spleen , and total anomaly of the pulmonary venous return are frequently observed.

Situs ambiguus with right isomerism :

Situs ambiguus with right isomerism asplenia

Slide 48:

Left isomerism is usually indicated by bilateral bilobed lungs, interruption of the IVC, multiple spleens , and pulmonary veins that drain into both the right and the left atria

Situs ambiguus with left isomerism :

Situs ambiguus with left isomerism polysplenia

Slide 50:

Frontal chest radiograph demonstrates a left-sided aortic arch, a left-sided cardiac apex, location of the stomach on the right (arrow), and bilateral left bronchi. Polysplenia ( heterotaxy ) with congenital heart disease.

Slide 51:

Coronal volume-rendered CT image helps confirm the presence of bilateral left bronchi.

Step 2: Determining the Orientation of the Ventricular Loop:

Step 2 : Determining the Orientation of the Ventricular Loop The ventricular loop or ventricular situs may tend rightward ( dextro -loop; hereafter, d-loop) (–,D,–) or leftward ( levo -loop; hereafter, l-loop) (–,L,–).

Developmental Anatomy:

Developmental Anatomy

Slide 59:

Figure 10. Schema shows the spectrum of possible configurations of the great vessels, from classic normal variants such as those in situs solitus and situs inversus to abnormal variants such as d-transposition (solid arrow), l-transposition (arrowhead), and double outlet right ventricle (dashed arrow). AD = anterior descending coronary artery, Ant = anterior, Ao = aorta, AoV = aortic valve, BC = bulbus cordis , D = dextro , Inf = inferior, L = levo , Lt = left, LV = left ventricle, MGA = malposition of the great vessels, PA = pulmonary artery, Post = posterior, PV = pulmonary valve, Rt = right, RV = right ventricle, Sup = superior, TGA = transposition of the great vessels, V = embryonic left ventricle. (Reprinted, with permission, from reference 28.)

Slide 61:

Other variants of cardiac malposition may occur during early development: The term isolated dextrocardia has been used to distinguish a situs solitus with a d-loop from true dextrocardia with an l-loop . Isolated levocardia as a result of congenital cardiac malposition occurs only with situs inversus and situs ambiguus .

Identification of Right and Left Ventricles:

Identification of Right and Left Ventricles The cardiac structures are identifiable on the basis of their specific morphologic features . The features that help differentiate between the right and left ventricles are the texture and distribution of internal trabeculae

Slide 63:

In the right ventricle, the trabeculae are coarse, and the presence of an apical moderator band is characteristic. The trabeculae of the left ventricle are thin and delicate, and the septal surface is smooth.

Slide 64:

Four-chamber cardiac views coarse trabeculae

Slide 65:

In addition, the papillary muscles of the right ventricle are attached to both the interventricular septum and the free wall, whereas the two papillary muscles of the left ventricle are attached only to the free wall .

Slide 66:

The fine-textured trabeculae , smooth septal surface, and two papillary muscles of the left ventricle

Slide 67:

The position of the atrioventricular valves is correlated with the orientation of the ventricular loop . In a d-loop, the tricuspid valve is located to the right of the mitral valve; in an l-loop, it is to the left of the mitral valve.

Slide 68:

In general, the mitral valve is associated with the morphologic left ventricle, and the tricuspid valve is associated with the morphologic right ventricle .

Step 3: Determining the Origin and Position of the Great Vessels:

Step 3 : Determining the Origin and Position of the Great Vessels Several variants may be observed with regard to the positions of the great vessels. The vessels may be in normal position ( solitus ) (–,–,S); inverted position ( inversus ) (–,–,I); d-transposition (–,–,D-TGV) or l-transposition (–,–,L-TGV); or d- malposition (–,–,D-MGV) or l- malposition (–,–,L-MGV).

Developmental Anatomy:

Developmental Anatomy According to Van Praagh et al , the embryonic aortic valve is anterior to the pulmonary valve but at the same level in the straight cardiac tube. As the loop begins to form, the great vessel valves are side by side. Muscle ( conus ) is interposed under each semilunar valve, and there is no fibrous continuity with the atrioventricular valves.

Slide 71:

Axial CT angiographic image . Normal relationship of the great vessels

Slide 73:

axial MR image

Slide 74:

Normally, the muscle under the aortic valve is subsequently resorbed , giving rise to the mitroaortic fibrous continuity, whereas the subpulmonary conus grows.

Slide 75:

The location of the aortic valve after resorption of the conus is more posterior, and the pulmonary valve is farther removed from the atrioventricular valves, without fibrous continuity

Slide 76:

The pulmonary valve is located anterior to and left of the aortic valve, which is normally located in the center of the thorax . The semilunar valves undergo an estimated 150° dextrorotation (counterclockwise rotation, if viewed from below).

Identification of the Great Vessels:

Identification of the Great Vessels Disruption may occur at any stage in the developmental positioning of the great vessels, with various resultant malformations known as conotruncal anomalies

Slide 78:

There are four possible types of conal anatomy: subpulmonary conus (normal), subaortic conus , bilateral conus , and bilaterally absent conus . Some correlations are commonly seen between the type of conus and the ventriculoarterial connection

Slide 79:

Typically, subaortic conus without subpulmonary conus is found in cases of d- or l-transposition. In such cases, the aorta, which lacks atrioventricular fibrous continuity, is anterior to the pulmonary valve, which shows evidence of atrioventricular valve continuity .

Slide 80:

Bilateral conus is seen in cases of double outlet right ventricle, and bilaterally absent conus is observed in cases of double outlet left ventricle

Slide 81:

In double outlet cardiopathies , the great vessels are side by side, in an anterior position in a double outlet right ventricle (without atrioven-tricular fibrous continuity) and in a posterior po-sition in double outlet left ventricle (with atrioventricular fibrous continuity).

Slide 82:

The presence of conus under a semilunar valve usually indicates that the vessel originates from the right ventricle; however, exceptions may occur

Slide 83:

If the ventricular origin of an abnormal vessel cannot be determined or if the great vessels arise from a single ventricle, as occurs in a double outlet ventricle, the term malposition is more suitable than transposition. The term transposition usually applies when the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle .

Slide 84:

Two types of transposition exist: d-transposition ( S,D,D-TGV ) and l-transposition ( S,L,L-TGV ).

Slide 85:

Axial images from thoracic CT angiography show l-transposition of the great vessels. Situs solitus (step 1) is depicted, with the liver, cardiac apex, IVC, and right lung (with eparterial bronchus) on the right and with the stomach, spleen, and left auricle (arrowhead in c) on the left. Both right and left superior venae cavae (solid arrows in d) are shown

Slide 86:

A left-oriented ventricular loop (step 2) is depicted, with the right ventricle (identified on the basis of the moderator band [arrow in b]) located to the left of the left ventricle, and with the aorta anterior to and left of the pulmonary artery (step 3). A conduit is seen between the left ventricle and pulmonary artery (dashed arrow in d), a result of pulmonary valve stenosis . The final report showed S,L,L-TGV , with atrioventricular discordance, ventriculoarterial discordance, and dextrocardia

Slide 87:

S,L,L-TGV

Slide 88:

In d-transposition, the atrial and ventricular positions are normal. The anomaly is located only at the conus level: the right-sided aorta anteriorly positioned arises from the right ventricle with a subaortic conus , and the left-sided pulmonary artery posteriorly positioned arises from the left ventricle with mitropulmonary fibrous continuity.

Slide 89:

In l-transposition, despite an abnormal conal anatomy and abnormal positioning of the great vessels, the circulation is “corrected” because the ventricular position is also inverted (l-loop). Accordingly, the right ventricle in a left-sided position is connected to the left atrium and the anteriorly positioned left-sided aorta with subaortic conus , whereas the left ventricle in a right-sided position is connected to the right atrium and the right-sided pulmonary artery with mitropulmonary fibrous continuity.

Slide 90:

l-transposition also has been described as ventricular inversion, double discordance, and physiologically corrected transposition .

Assessment of Connecting Segments:

Assessment of Connecting Segments Atrioventricular Connections Ventriculoarterial Connections

Atrioventricular Connections :

Atrioventricular Connections According to the approach developed by Anderson and colleagues , there are five types of atrioventricular connection: concordant (normal), discordant, ambiguous, double inlet, and absent right or left connection.

Slide 93:

With a normal or concordant connection, the right atrium drains into the right ventricle, and the left atrium drains into the left ventricle. With a discordant connection, the right atrium drains into the left ventricle, and the left atrium drains into the right ventricle.

Slide 94:

Transposition of the great vessels frequently occurs in association with discordant atrioventricular connection . In cases of heterotaxy , the connection is described as ambiguous. Concordant, discordant, and ambiguous may be used to describe the connections when two ventricles are present, whereas double inlet and absent right (or left) connection are used for a univentricular heart .

Ventriculoarterial Connections:

Ventriculoarterial Connections Besides permanent truncus arteriosus , four types of ventriculoarterial connection may develop: concordant connection (the pulmonary artery arises from the right ventricle, and the aorta arises from the left ventricle); discordant connection , which is synonymous with transposition of the great vessels (the pulmonary artery arises from the left ventricle, and the aorta arises from the right ventricle) double outlet right ventricle (the great vessels arise from the right ventricle); and double outlet left ventricle (the great vessels arise from the left ventricle).

Assessment of Associated Malformations:

Assessment of Associated Malformations Descriptions of other abnormalities that are intrinsic to individual parts or segments of the cardiovascular anatomy also might be useful in the radiologic report. Such malformations are frequently major lesions that influence the surgical approach and have profound physiologic significance

Slide 97:

The search for such anomalies also may be conducted in a segmental fashion: At the level of the heart , the presence, size, and location of atrial and ventricular septal defects and the size of the ventricles should be documented, and the presence and degree of any ventricular outflow tract stenosis should be noted .

Slide 98:

The aorta and pulmonary artery also should be carefully examined for evidence of hypoplastic and stenotic lesions ( eg , aortic coarctation and hypoplasia of the aortic arch) as well as for a pa-tent ductus arteriosus

Conclusions:

Conclusions Detailed knowledge about the cardiac anatomy allows accurate diagnosis and successful management of congenital heart disease, and the capabilities of multidetector CT and MR imaging for depicting this anatomy ensure an increasing role for radiologists. Moreover, a systematic segmental approach to imaging evaluation, which emphasizes the proximal-to-distal positions and relationships of cardiac chambers and great vessels, greatly facilitates the detection and characterization of congenital heart disease

Quiz :

Quiz

Slide 102:

Large pneumothorax on the right with almost complete collapse of the right lung. The heart and aorta are in the right hemithorax . Gastric air bubble is beneath the right diaphragm.

Slide 104:

Transverse contrast-enhanced CT scan ofthe abdomen shows a midline liver, multiple spleens ( S) in the right upper quadrant adjacent to the collapsed stomach ( St), and IVC interruption with azygous continuation (arrow). The low attenuation of the spleens is related to infarctions , which cause liquefaction and subcapsular hematomas. Note the absence of splenic tissue in the left upperquadrant ()

Slide 105:

Situs ambiguous with polysplenia

Slide 107:

As the use of imaging increases, situs anomalies will likely be detected with greater frequency In adults. Therefore, it is important for radiologiststo become familiar with these anomalies, the spectrum of their manifestations, and their significance. This information is crucial in diagnosing disease and planning interventional procedures.

Than q:

Than q