The Relative Atrial Index (RAI) is a numeric parameter used to assess for
cardiac shunt
In cardiology, a cardiac shunt is a pattern of blood flow in the heart that deviates from the normal circuit of the circulatory system. It may be described as right-left, left-right or bidirectional, or as systemic-to-pulmonary or pulmonary-to-s ...
defects. It is calculated from the standard transthoracic Doppler
echocardiogram
Echocardiography, also known as cardiac ultrasound, is the use of ultrasound to examine the heart. It is a type of medical imaging, using standard ultrasound or Doppler ultrasound. The visual image formed using this technique is called an echo ...
measurements of the right atrial area divided by the left atrial area. RAI = right atrial area / left atrial area. These measurements are made from the apical four chamber view.
Large validation studies in patients with known atrial septal defects showed that the RAI > 1.0 in the majority of cases. This is in contrast to matched and population controls, where the RAI was significantly below 1.0. This simple numeric parameter has found a role in the diagnostic work-up for possible shunt defects on standard tranthorcaic
echocardiogram
Echocardiography, also known as cardiac ultrasound, is the use of ultrasound to examine the heart. It is a type of medical imaging, using standard ultrasound or Doppler ultrasound. The visual image formed using this technique is called an echo ...
s. The RAI rapidly normalizes within 24 hours of percutaneous closure of atrial septal defects. Secondary validation studies have confirmed the data in discrete patient populations. This parameter has been shown to predict long-term survival after acute pulmonary embolism.
The RAI was conceptualized in response to observed clinical inadequacies of standard transthoracic echocardiography in some shunt conditions. The same author had developed several Doppler echocardiographic
numeric parameters over the last two decades to assess cardiac diastolic function.
[Color M-mode and Doppler-derived tau (τ) as practical advances in clinical diastology - the TauCoMM project. G.M. Scalia and D.J. Burstow. Heart, Lung and Circulation 1999 Vol. 9, Issue 3, Page A13.]
See also
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Medical ultrasonography
Medical ultrasound includes Medical diagnosis, diagnostic techniques (mainly medical imaging, imaging) using ultrasound, as well as therapeutic ultrasound, therapeutic applications of ultrasound. In diagnosis, it is used to create an image of ...
section:
Doppler sonography
Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids (usually blood), and their relative velocity to the probe. By calculating the frequency shift of a ...
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Echocardiography
Echocardiography, also known as cardiac ultrasound, is the use of ultrasound to examine the heart. It is a type of medical imaging, using standard ultrasound or Doppler ultrasound. The visual image formed using this technique is called an ec ...
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American Society of Echocardiography
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Christian Doppler
References
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External links
Echocardiography Textbook by Bonita AndersonEchocardiography (Ultrasound of the heart)
Cardiac procedures
Diagnostic cardiology
Medical ultrasonography
Medical equipment
Multidimensional signal processing