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| Objectives |
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| At the completion of this chapter the user will be able to: |
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- Understand the Normal Anatomy Variants of the Heart
- Describe the Common Pitfalls
- Describe Common Artifacts
- Explain the Common Methods to Avoid Misinterpretation of Artifacts
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| Introduction |
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Normal structures or variants, which can be misinterpreted as pathological conditions, are called anatomic pitfalls. In contrast, artifacts are errors in interpretation of images are due to the inherent properties of the ultrasound technology being used. It is important to be familiar with the normal structures that appear to be abnormal and common artifacts to facilitate recognition and avoid unnecessary interventions . |
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Anatomic Pitfalls by Cardiac Chamber
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| Right Atrium |
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| The crista terminalis is a muscle ridge seen anteriorly in the midesophageal (ME) bicaval view at the junction of the SVC and the right atrium. However anatomically it lies between the SVC and IVC. On TEE, it may appear to protrude into the right atrium and be mistaken for thrombus or tumor. |
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| The eustachian valve can be seen in the ME 4-chamber view or the ME bicaval view of the right atrium; it is seen in approximately 25 - 50% individuals, at the junction of the inferior vena cava (IVC) and right atrium. It appears as an elongated, membranous, possibly undulating structure, with a varying width. It may appear to attach to the fossa ovalis but does not cross the tricuspid valve or right ventricle. It can be confused with the tricuspid valve in a ME 4 chamber view although it is located superior to the tricuspid valve. Usually it is of no physiological consequence, but can be confused with an intracardiac thrombus, cause turbulent atrial blood flow, complicate IVC cannulation or serve as a site for endocarditis formation. However, at least one study has associated a persistent eustachian valve with a patent foramen ovale with the attendant increased risk of paradoxical emboli. |
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| Crista Terminalis |
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| The chiari network is a very mobile, filamentous, thin and possibly perforated structure commonly seen within the right atrium. It is probably a remnant of sinus venosus derived structures, but has also been called a fenestrated eustachian valve'. The chiari network moves about the right atrium with a random movement, not necessarily related to valvular movement. It may impede catheters placement through the right atrium for femoral venous drainage or retrograde cardioplegia. Chiari networks have been associated with a patent foramen ovale, paradoxical embolus and an interatrial septal aneurysm. |
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| The normal foramen ovale appears as thin slice of tissue bound by thicker ridges of tissue; inferiorly it may be seen as a flap of tissue. However, up to 30 % of foramen ovale may be patent (PFO) and interatrial septal anatomic variants are common in adult cardiac surgical patients . Evaluation of the foramen ovale for patency should include color flow mapping and a bubble study with a valsalva maneuver to provoke right to left shunting if it is present. The diagnosis of a PFO rests on the appearance of bubbles in the left atrium in less than 5 cardiac cycles. The importance of a PFO must be evaluated in combination with other information such as a history or paradoxical emboli or the finding of unexpectedly high right-sided cardiac pressures. |
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