eROA Calculator
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Formula
EROA = (2 x pi x r^2 x Va) / Vmax
Where r is the PISA radius (distance from aliasing boundary to orifice), Va is the aliasing velocity, and Vmax is the peak regurgitant velocity by CW Doppler. Alternatively, EROA = Regurgitant Volume / Regurgitant VTI.
Worked Examples
Example 1: PISA Method for Mitral Regurgitation EROA
Problem: A patient has a PISA radius of 9mm at an aliasing velocity of 38 cm/s, with a peak regurgitant velocity of 500 cm/s and regurgitant VTI of 150 cm. Calculate the EROA.
Solution: PISA radius = 9mm = 0.9 cm\nFlow rate = 2 x pi x (0.9)^2 x 38 = 2 x 3.14159 x 0.81 x 38 = 193.2 mL/s\nEROA = Flow rate / Peak velocity = 193.2 / 500 = 0.386 cm^2\nRegurgitant Volume = EROA x VTI = 0.386 x 150 = 57.9 mL\nSeverity: Moderate (EROA 0.20-0.39 cm^2)
Result: EROA: 0.39 cm^2 | Regurgitant Volume: 57.9 mL | Severity: Moderate
Example 2: Severe Mitral Regurgitation Assessment
Problem: PISA radius is 12mm, aliasing velocity 40 cm/s, peak regurgitant velocity 450 cm/s, VTI 160 cm. Assess severity.
Solution: PISA radius = 12mm = 1.2 cm\nFlow rate = 2 x pi x (1.2)^2 x 40 = 2 x 3.14159 x 1.44 x 40 = 362.0 mL/s\nEROA = 362.0 / 450 = 0.805 cm^2\nRegurgitant Volume = 0.805 x 160 = 128.8 mL\nSeverity: Severe (EROA >= 0.40 cm^2, RV >= 60 mL)
Result: EROA: 0.80 cm^2 | Regurgitant Volume: 128.8 mL | Severity: Severe
Frequently Asked Questions
What is EROA and why is it important in cardiology?
EROA stands for Effective Regurgitant Orifice Area, a quantitative measurement used in echocardiography to assess the severity of valvular regurgitation, most commonly mitral and aortic regurgitation. It represents the cross-sectional area of the opening through which blood flows backward during valve closure. EROA is considered one of the most reliable parameters for grading regurgitation severity because it is relatively independent of hemodynamic conditions compared to visual assessment alone. An EROA greater than or equal to 0.40 cm squared for mitral regurgitation or 0.30 cm squared for aortic regurgitation indicates severe disease that may warrant surgical intervention.
How does the PISA method work for calculating EROA?
The PISA (Proximal Isovelocity Surface Area) method is based on the principle of conservation of mass in fluid dynamics. As blood converges toward a regurgitant orifice, it forms concentric hemispheric shells of increasing velocity. By setting the color Doppler aliasing velocity appropriately, the echocardiographer can visualize and measure the radius of the hemispheric convergence zone where the velocity equals the aliasing velocity. The flow rate through the PISA shell equals 2 times pi times the radius squared times the aliasing velocity. Dividing this flow rate by the peak regurgitant velocity measured by continuous wave Doppler gives the EROA. This method is widely accepted and recommended by ACC/AHA guidelines for quantitative assessment.
What are the normal values and severity thresholds for EROA?
For mitral regurgitation, the ACC/AHA guidelines define severity based on EROA as follows: mild is less than 0.20 cm squared, moderate is 0.20 to 0.39 cm squared, and severe is 0.40 cm squared or greater. For aortic regurgitation, mild is less than 0.10 cm squared, moderate is 0.10 to 0.29 cm squared, and severe is 0.30 cm squared or greater. These thresholds should be interpreted in conjunction with other parameters including regurgitant volume, regurgitant fraction, vena contracta width, and clinical symptoms. In borderline cases, integration of multiple quantitative and qualitative measures is essential for accurate severity grading.
What is regurgitant volume and how does it relate to EROA?
Regurgitant volume is the total amount of blood that flows backward through the incompetent valve during each cardiac cycle, measured in milliliters. It is mathematically related to EROA through the velocity-time integral (VTI) of the regurgitant jet measured by continuous wave Doppler: Regurgitant Volume equals EROA multiplied by the regurgitant VTI. For mitral regurgitation, a regurgitant volume less than 30 mL indicates mild, 30-59 mL indicates moderate, and 60 mL or greater indicates severe regurgitation. The regurgitant volume provides a volumetric assessment complementary to the EROA, and both should be calculated together for a comprehensive evaluation of regurgitation severity.
What are the limitations of the PISA method for EROA calculation?
The PISA method has several important limitations that clinicians must understand. First, it assumes a hemispheric convergence zone, which may not be accurate when the orifice is eccentrically located (such as in eccentric mitral regurgitant jets), constrained by adjacent structures, or irregularly shaped. Second, accurate measurement of the PISA radius requires optimal image quality and correct aliasing velocity settings, which can be technically challenging. Third, the method assumes a constant orifice area throughout systole, while in reality, the EROA can change dynamically during the cardiac cycle in conditions like mitral valve prolapse. Fourth, the angle correction factor may introduce additional error. Despite these limitations, PISA remains one of the most validated quantitative methods.
When should EROA be used instead of qualitative assessment of regurgitation?
Quantitative EROA measurement should be used whenever there is discordance between qualitative assessments or when clinical decision-making depends on precise severity grading. Qualitative methods like visual assessment of color jet area can be misleading due to technical factors such as gain settings, jet eccentricity (Coanda effect), and hemodynamic conditions. EROA quantification is particularly important when considering surgical or interventional treatment, during serial follow-up to track progression, in patients with borderline severity between moderate and severe grades, and when multiple valve lesions coexist. The ASE guidelines recommend integrating EROA with other quantitative parameters including vena contracta width, regurgitant volume, and regurgitant fraction for comprehensive evaluation.