Segmental imaging is a popular method for diagnosing congenital heart disease. It involves a three-step assessment of cardiac anatomy. Step 1 determines the visceroatrial position. Visceroatrial situations are the relative position of the atria to the surrounding anatomy (including the stomach and liver) There are three possible anatomic configurations: situs solitus, situs inversus, and situs ambiguous. Step 2 evaluates the left-or rightward orientation of the ventricular loop. The positions of ventricles are then identified based on their internal morphologic characteristics. Step 3 determines the position of the great vessels and then any anomalies are noted.
Abnormalities in the origin of the great vessels, or conotruncal anomalies, are predominantly of three types: D-transposition (dextrotransposition), L-transposition (levotransposition), and D-malposition with double outlet right ventricle. The relationships between the atria, ventricles, and the great vessels, are then determined at two levels: the atrioventricular level (concordant or discordant with ambiguous double inlet, absence right or left connection), and the ventriculoarterial level (concordant discordant double outlet).
The final step is to search for associated abnormalities in the cardiac chambers and septa, outflow tract, and great vessels. The radiologist can interpret the image more accurately if they execute these steps in sequence during image review. For congenital heart disease, multiplanar reconstructions from cross-sectional images obtained using computed tomography and magnetic resonance imaging are especially useful.
After reading the article and passing the test, you will be able to:
- Describe the steps involved in the segmental approach for evaluating congenital cardiac disease.
- Describe the three types of visceroatrial situations.
- Identify the most significant anomalies in cardiac development that can lead to congenital heart diseases.
Multidetector computed tomography (CT), and cardiac magnetic resonance imaging (MR) has sparked interest in radiologists for the diagnosis of congenital cardiac disease. This has encouraged the reexamination of the classifications and definitions used to diagnose the condition by cardiologists and cardiac surgeons. Segmental analysis of congenital cardiac disease was first introduced 25 years ago. It is now widely used. This method is easy to use and flexible, even for non-experts. It can be applied to any imaging modality and is therefore particularly useful in clinical practice. This article briefly reviews Van Praagh’s basic concepts and how they have been further developed in clinical settings across Europe and the United States.
A Segmental approach assesses the cardiac anatomy by first dividing it into three segments. These are based upon 10 embryologic regions.
These segments form the fundamental building blocks of cardiac anatomy. Each segment’s morphologic and anatomic characteristics are evaluated separately. The relationships (or blocks) between segments are then assessed at the ventriculoarterial and atrioventricular levels. Finally, abnormalities that may be associated with individual segments are described. This approach can be combined with the Van Praagh notation system (a series consisting of three letters separated by commas within parentheses), as shown in the sections below.
How to determine the Visceroatrial Situs
There are three types: solitus, I ,-,-), inversus, and ambiguus (A ,-,-).). The relationship between the atria, adjacent organs, and the patient’s atria determines the type of situs. Only one type of abnormality is allowed in each patient. The first step in assessing the cardiac anatomy is to identify and locate the right and left atria. The morphologic aspects of the atrial appendages are what determine the anatomy of the atrial chamber. The atrial appendages can be thought of as ear-like extensions of the Atria. The right atrial appendage (triangular) is usually broad and blunt. While the left atrial is narrow, pointed and tubular (fingerlike), it is typically narrower, pointed and more tubular. Appendages can be difficult to identify on radiologic imaging. It is easier to locate noncardiac organs than appendages.
The bronchial anatomy (or pulmonary) at the thoracic level is an indicator of the atrial arrangement. It includes the relationship between the main left and main right bronchis and the pulmonary vessels.
The positions of the liver and stomach at the abdominal level are crucial. Because of the rule of Venoatrial Concordance, the supradiaphragmatic portion (IVC), also serves as a landmark to locate the anatomic right of the atrium.
The location of the heart in the chest and the orientation at the cardiac apex can be contributing factors to the situs. However, it is not essential. These factors can be used to predict the likelihood of congenital heart disease (Table). Based on the orientation of your cardiac base-apex, there are three types of cardiac malposition: mesocardia (dextrocardia), mesocardia (levocardia), and mesocardia (levocardia).
Levoposition refers to the location of the heart in the chest cavity. Dextroposition is a location in the right chest. Mesoposition is a midline location. In all three cases, the base-apex of the cardiac axis can be oriented normal (towards the left chest). Dextrocardia is a condition where the heart is located in the right chest cavity, with the base apex axis tilted to the right. Any type of situation can cause dextrocardia.
The general rule is that cardiac and situs anomalies are more common when the position of the stomach, heart or aortic arch is concordant. They also occur less often when there’s a discordant position for one or more landmarks (Fig. 1). It is important to identify any thoracic and pulmonary anomalies that could lead to the displacement of your heart. Hypoplastic right lung can cause dextroposition and a left-sided cardiac arpeggio. This explains why there is a lower chance of congenital heart disease.