Free Gorlin Formula Calculator - AVA Calculator

The Gorlin formula calculator allows clinicians and students to indirectly estimate human heart valve areas, primarily the aortic valve area (AVA) and mitral valve area (MVA), using standard hemodynamic measurements. By applying the Gorlin equation, this tool not only computes AVA and MVA but also classifies the results according to established stenosis grading guidelines. The free aortic valve area calculator online is especially useful when evaluating patients for aortic stenosis, as it combines cardiac output, heart rate, and pressure gradients to produce quick, consistent assessments.

Aortic Stenosis and Its Grading

Aortic stenosis (AS) is a common valvular condition in which the aortic valve opening narrows, obstructing blood flow from the left ventricle to the aorta. This forces the ventricle to work harder and can lead to symptoms such as chest pain, shortness of breath, palpitations, and fatigue. AS often develops later in life due to calcification or scarring, though younger individuals with a bicuspid aortic valve may also be affected.

The severity of AS is determined by multiple parameters, including the valve area itself. The 2014 AHA/ACC guidelines provide the following classification based on AVA, mean pressure gradient ($\Delta P$), and maximum aortic velocity ($V_{\text{max}}$):

The table above uses mean transvalvular pressure gradient and peak aortic velocity as additional indicators. Note that the full clinical guidelines incorporate further details such as valve anatomy and symptom status.

Calculating Aortic Valve Area with the Gorlin Formula

The Gorlin formula expresses AVA as a function of cardiac output, heart rate, systolic ejection period, and the mean pressure gradient. The core equation is:

where:

• $CO$ = cardiac output (mL/min)
• $HR$ = heart rate (beats/min)
• $SEP$ = systolic ejection period (sec/beat)
• $\Delta P$ = mean pressure gradient (mmHg)

The calculated AVA is reported in cm². The constant 44.3 is an empirical factor derived from catheterization studies.

Important Consideration: Low‑Flow States

When cardiac output falls below 2.5 L/min, the Gorlin formula tends to underestimate the true AVA, making the stenosis appear more severe than it actually is. In such low‑flow situations, an aortic valve area calculator based on the continuity equation (.e., echocardiographic Doppler) may provide a more reliable estimate.

Hemodynamic parameters needed for the Gorlin formula can be obtained through various methods: ECG for heart rate, echocardiography, CT scanning, or cardiac catheterization.

Mitral Stenosis and Its Grading

Mitral stenosis (MS) restricts blood flow from the left atrium to the left ventricle. The resulting pressure rise in the atrium can transmit to the pulmonary circulation, causing lung congestion. MS symptoms overlap with AS but often include distinct heart sounds on auscultation. Aortic and mitral stenosis can coexist, and AS sometimes occurs alongside mitral regurgitation.

The following table shows the typical grading of mitral stenosis based on MVA, mean pressure gradient, and pulmonary arterial systolic pressure (PASP):

PASP is usually measured via echocardiography or right‑heart catheterization.

Gorlin Equation for the Mitral Valve

The mitral valve area is calculated with a similar form of the Gorlin equation:

Here, $DFP$ = diastolic filling period (sec/beat). The constant 37.7 is used instead of 44.3 because the flow characteristics and discharge coefficient differ between the aortic and mitral valves.

An empirical relationship connects AVA and MVA when both are measured in the same patient:

This approximation can be helpful for cross‑checking results. Alternative echocardiographic methods, such as the proximal isovelocity surface area (PISA) technique, also provide a way to determine MVA directly.

Worked Example: Aortic Valve Area Calculation

Consider a patient undergoing cardiac evaluation with the following data:

• Heart rate: 75 bpm
• Cardiac output: 5.5 L/min (5500 mL/min)
• Mean pressure gradient: 15 mmHg
• Systolic ejection period: 0.25 s/beat

Plug the values into the Gorlin equation:

First, compute the denominator: $44.3 \times 75 \times 0.25 \approx 830.625$ and $\sqrt{15} \approx 3.873$, giving $830.625 \times 3.873 \approx 3216.5$. Dividing $5500$ by $3216.5$ yields an AVA of about $1.71$ cm².

Comparing this result with the grading table shows that it falls into the “mild” aortic stenosis category (AVA between 1.5 and 3 cm²). This outcome illustrates how the Gorlin formula calculator transforms raw hemodynamic numbers into a clinically useful classification.