Relative Atrial Index

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Relative Atrial Index
Medical diagnostics
Purposeassess for cardiac shunt defects.

The Relative Atrial Index (RAI) is a numeric parameter used to assess for cardiac shunt defects. It is calculated from the standard transthoracic Doppler echocardiogram measurements of the right atrial area divided by the left atrial area. RAI = right atrial area / left atrial area.[1] These measurements are made from the apical four chamber view.

Large validation studies[2] 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 echocardiograms. The RAI rapidly normalizes within 24 hours of percutaneous closure[3] of atrial septal defects.[4] Secondary validation studies have confirmed the data in discrete patient populations.[5] This parameter has been shown to predict long-term survival after acute pulmonary embolism.[6]

The RAI was conceptualized in response to observed clinical inadequacies of standard transthoracic echocardiography in some shunt conditions. The same author[7] had developed several Doppler echocardiographic numeric parameters over the last two decades to assess cardiac diastolic function.[8][9]

See also


  1. 54. The Relative Atrial Index (RAI) – A Novel, Simple, Reliable and Robust Transthoracic Echocardiographic Indicator of Significant Atrial Defects. Kelly, N; Walters, L; Walters, D; Burstow, D; Presneill, J, Scalia, G. Heart, Lung and Circulation Vol. 16Supplement 2, Page S44 2007 CSANZ Christchurch 2007
  2. “The Relative Atrial Index (RAI) – A Novel, Simple, Reliable and Robust Transthoracic Echocardiographic Indicatory of Atrial Defects”. Natalie F Kelly, Darren Walters, Lisa Hourigan, Darryl J Burstow, Gregory M Scalia. J Am Soc Echocardiogr 2010;23:275-81.
  3. Percutaneous patent foramen ovale closure: outcomes with the Premere and Amplatzer devices. Naylin Bissessor, Allison W. Wong, Lisa A. Hourigan, Rohan S. Jayasingheb, Gregory M. Scalia, Darryl J. Burstow, Lyn R. Griffiths, Michael Savage, Darren L. Walters. Cardiovascular Revascularization Medicine (2010)
  4. 55. Rapid Normalization Following Percutaneous Secundum Atrial Septal Defect Device Closure. A Study Using The Relative Atrial Index Kelly, N; Walters, D; Walters, L; Burstow, D; Scalia, G Circulation. 2007; 116:II_329. AHA Florida 2007
  5. The Relative Atrial Index - A Transthoracic Echocardiographic Indicator of Intracardiac Shunt Status Pre and Post Amplatzer Atrial Septal Defect Closure. Tegan E Draheim; Natalie F Kelly; Sudhir Wahi; Stephen V Cox; Darren L Walters; Darryl J Burstow; Gregory M Scalia. Circulation. 2011; 124: A11559
  6. Right atrial to left atrial area ratio on early echocardiography predicts long-term survival after acute pulmonary embolism. Vincent Chow, Austin Chin Chwan Ng, Tommy Chung, Liza Thomas and Leonard Kritharides. Cardiovascular Ultrasound 2013, 11:17 doi:10.1186/1476-7120-11-17
  7. "Greg Scalia". 
  8. Non-Invasive Assessment of the Ventricular Relaxation Time Constant (τ) in Humans by Doppler Echocardiography. Gregory M. Scalia, Neil L. Greenberg, Patrick M. McCarthy, James D. Thomas, Pieter M. Vandervoort. Circulation 1997;95:151-5
  9. 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.

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