Aortic valve area calculation

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  Comparison of results from Gorlin, Agarwal-Okpara-Bao, and Clinical data

Aortic Valve Area Calculation

The calculation of the aortic valve area (AVA) is a critical component in the assessment of aortic stenosis, a condition characterized by the narrowing of the aortic valve opening. Accurate determination of the AVA is essential for diagnosing the severity of aortic stenosis and guiding clinical management.

Anatomy and Physiology

The aortic valve is one of the four main heart valves and is located between the left ventricle and the aorta. It ensures unidirectional blood flow from the heart into the systemic circulation. The normal aortic valve area ranges from 3 to 4 square centimeters. A reduction in this area due to calcification or other pathological processes can lead to aortic stenosis.

Methods of Calculation

Several methods are used to calculate the aortic valve area, each with its own advantages and limitations.

Gorlin Formula

The Gorlin formula is a classic method used to calculate the AVA based on hemodynamic measurements obtained during cardiac catheterization. The formula is:

\[ \text{AVA} = \frac{\text{CO}}{\text{HR} \times \text{SEP} \times 44.3 \times \sqrt{\Delta P}} \]

where: - \( \text{CO} \) is the cardiac output in liters per minute, - \( \text{HR} \) is the heart rate in beats per minute, - \( \text{SEP} \) is the systolic ejection period in seconds, - \( \Delta P \) is the mean transvalvular pressure gradient in mmHg.

Continuity Equation

The continuity equation is a non-invasive method that uses Doppler echocardiography to calculate the AVA. It is based on the principle of conservation of mass, which states that the flow through the left ventricular outflow tract (LVOT) must equal the flow through the aortic valve. The equation is:

\[ \text{AVA} = \frac{\text{CSA}_{\text{LVOT}} \times \text{VTI}_{\text{LVOT}}}{\text{VTI}_{\text{AV}}} \]

where: - \( \text{CSA}_{\text{LVOT}} \) is the cross-sectional area of the LVOT, - \( \text{VTI}_{\text{LVOT}} \) is the velocity time integral of the LVOT, - \( \text{VTI}_{\text{AV}} \) is the velocity time integral of the aortic valve.

Clinical Significance

The severity of aortic stenosis is classified based on the calculated AVA: - Mild: AVA > 1.5 cm_ - Moderate: AVA 1.0 - 1.5 cm_ - Severe: AVA < 1.0 cm_

Accurate assessment of the AVA is crucial for determining the appropriate timing of aortic valve replacement or transcatheter aortic valve implantation (TAVI).

Related Pages

• Aortic stenosis
• Echocardiography
• Cardiac catheterization
• Heart valve disease

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