Relative Atrial Index

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. 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 echocardiograms.

The RAI was conceptualized in 2008 by Dr Gregory M Scalia (Cardiologist, the University of Queensland, The Prince Charles Hospital) in response to observed clinical inadequacies of standard transthoracic echocardiography in some shunt conditions. This author had developed several Doppler echocardiographic numeric parameters over the last two decades to assess cardiac diastolic function and EPLAR for the assessment of pulmonary hypertension physiology.

References

• Medical ultrasonography section: Doppler sonography
• Echocardiography
• American Society of Echocardiography
• Christian Doppler

External links

• Echocardiography Textbook by Bonita Anderson
• Echocardiography (Ultrasound of the heart)
• Doppler Examination - Introduction
• The Doppler Principle and the Study of Cardiac Flows