Heart in the Mirror: Artifacts as a Violation of Ultrasonography Assumptions.

To the Editor,

Echocardiography became the leading method of assessing cardiac anatomy and function. A piezoelectric transducer transmits and records sound waves; subsequently, they are converted into an electrical signal, which is used to construct an image displayed on the monitor. Boundaries between different tissues with different acoustic impedances serve for reflection. Part of the sound waves are reflected to the transducer and the remaining ones are traveling in the original direction.[1]

Despite the constant technological advancements, cardiologists often face the artifacts.[2] Artifacts may present as additional structures, may hide the appearance of existing structures, or alter the size or shape of the original structure.[3] A wide range of diseases such as aortic dissection, left atrial appendage thrombi, loculated pleural effusion, and endocarditis may be falsely presented.[124] In this article, we present a parasternal long-axis view of a 25-year-old patient after syncope with two common echocardiography artifacts present.

Artifacts may be related to the ultrasound beam's physical properties, interactions of sound waves with tissues, or equipment related.[1] During ultrasound image creation, certain assumptions[15] are made concerning wave propagation: (1) Pulses and echoes travel in a straight line; (2) given structure reflects the beam only once; (3) only structures localized in the intended path generates echoes back to the transducer; (4) echoes originate from the main beam; (5) echoes travel at a uniform speed; and (6) pulses and echoes are attenuated uniformly by all tissues. Violation of the assumption that echoes return to the transducer after a single reflection creates reverberation and mirror-image artifacts presented in Figure 1.

Figure 1

Parasternal long axis image. Red arrow = Comet-tail reverberations, Blue arrow = Pericardium-lung interface, Yellow star = Anterior mitral leaflet, Red star = Mirror-image of anterior mitral leaflet

When two strong reflectors are placed on the path of a traveling wave, the pulse, instead of heading back to the transducer, bounces between two surfaces creating reverberations. When the distance between reflectors is small, reverberations create a so-called comet tail [Figure 1. red arrow].[45]

A mirror image appears when there is a strong reflector (for example pericardium, pleura, and diaphragm)[2] behind the assessed structure. A significant difference in acoustic impedances between two structures causes the sound waves to reflect toward the transducer and again reflect from the target structure lying more superficially, which creates a significant delay of returning waves. The transducer interprets the prolonged travel time of a sound wave as if the structure was localized deeper in the initial traveling path. This creates the image of the same structure moving in the opposite direction from the mirror-like object.[15]

The best method of reducing the abovementioned artifacts is removing the strong reflector from the path of waves by changing the probe position.[1] Using Doppler sampling may be helpful in recognizing mirror artifacts as it measures the flow velocity, if it is the same in both mirrored and true structures, we can presume that the artifact is present.[4]

The clinicians should be aware of the presence of artifacts and basic physical properties that may create them.[24] Critical analysis of echocardiography decreases the risk of additional diagnostics and unnecessary intervention.[5]

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Nil.

Conflicts of interest

There are no conflicts of interest.