Right Atrial Anatomy

Objectives
 
At the completion of this chapter the user should be able to:
 
  1. Understand normal right atrium, vena cava, coronary sinus and IAS anatomy
  2. Obtain TEE views of right atrium, vena cava, coronary sinus and IAS and hepatic vein anatomy
  3. Identify normal and abnormal right atrium, vena cava, coronary sinus and IAS structures
  4. Evaluate PWD of right atrium, vena cava, coronary sinus and IAS, Hepatic vein
  5. Obtain quantitative Doppler measurements for right atrium, vena cava, coronary sinus, hepatic vein
Anatomy
 
The right atrium is an ovoid structure with slightly thinner walls than the left atrium. The right atrial appendage is anterior to the right atrium.  The right atrial appendage and the right atrial walls contain pectinate muscles which may appear as small ridges on an echocardiography exam.  The left border is the interatrial septum and the right border is the free wall which is parallel to the right side of the sternum. There are 4 openings of the right atrium:
 
(1) The Superior Vena Cava (SVC)
(2) The Inferior Vena Cava (IVC)
(3) The Coronary Sinus (CS)
(4) The Tricuspid Valve (TV)
 
The superior vena cava (SVC) empties into the right anterior portion of the superior wall of the right atrium. The inferior vena cava (IVC) empties into the right posterior margin of the inferior wall of the right atrium.  The coronary sinus empties into the infero-posterior portion of the right atrium.  The coronary sinus is posterior to the inferior border of the interatrial septum and superior to the posterior portion of the tricuspid valve annulus. The right atrium receives blood from the SVC, IVC, and coronary sinus. Blood exits the right atrium via the tricuspid valve.
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Right Atrial Anatomy
 
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Superior Vena Cava - Short Axis Superior Vena Cava - Short Axis
   
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Superior Vena Cava - Long Axis Superior Vena Cava Long Axis
   
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Inferior Vena Cava - ME 4CV Inferior Vena Cava - ME 4CV
   
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Inferior Vena Cava - BCV Inferior Vena Cava - BCV
   
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Coronary Sinus - BCV Coronary Sinus - BCV
   
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Coronary Sinus/Tricuspid Valve Coronary Sinus/Tricuspid Valve
 
The interatrial septum is a thin muscular membrane that separates the right and left atrial chambers. An oval indentation is in the middle of the septum, the fossa ovalis, corresponds to the foramen ovale in the fetal heart. The coronary sinus may contain a valve, the thesbian valve.  The superior vena cava has a ridge called the crista terminalis.   The inferior vena cava usually has a fetal remnant of a valve called the eustachian valve.  A filamentous collection attached to the inferior vena cava and sometimes extending to the foramen ovale is called a chiari network. The chiari network , found in about 2% of patients, is a congenital remnant of the right valve of the sinus venosus and is associated with a patent foramen ovale or an interatrial septal aneurysm.
RIght Atrial Anatomy
 
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Chiari Network Chiari Network
   
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Interatrial Septum Interatrial Septum
   
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Eustachian Valve Eustachian Valve
   
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Crista Terminalis Crista Terminalis
 
Normally, the right atrium is smaller than the left atrium.  A right atrium of equal size or larger than the left atrium is interpreted as right atrial enlargement.  The superior vena cava is usually a small vessel, usually less than 2 cm in diameter.  The inferior vena cava's width depends upon the volume status and the respiration status of the patient.