Stroke Volume Calculator Echo

Stroke Volume Equation:

\[ SV = \pi \times \left(\frac{LVOT\ diameter}{2}\right)^2 \times VTI \]

Stroke Volume (SV):

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1. What is Stroke Volume?

Stroke Volume (SV) is the volume of blood pumped from the left ventricle per beat. It's a key parameter in assessing cardiac function and is calculated using echocardiography measurements of the left ventricular outflow tract (LVOT) diameter and velocity time integral (VTI).

2. How Does the Calculator Work?

The calculator uses the stroke volume equation:

\[ SV = \pi \times \left(\frac{LVOT\ diameter}{2}\right)^2 \times VTI \]

Where:

\( SV \) — Stroke volume (mL)
\( LVOT\ diameter \) — Left ventricular outflow tract diameter (cm)
\( VTI \) — Velocity time integral (cm)
\( \pi \) — Mathematical constant (~3.1416)

Explanation: The equation calculates the cylindrical volume of blood passing through the LVOT using the cross-sectional area (πr²) multiplied by the distance traveled (VTI).

3. Clinical Importance

Details: Stroke volume is fundamental for calculating cardiac output (CO = SV × HR) and assessing ventricular function. It helps in diagnosing and monitoring conditions like heart failure, valvular disease, and shock.

4. Using the Calculator

Tips:

Measure LVOT diameter in parasternal long-axis view during systole
Obtain VTI from pulsed-wave Doppler at the LVOT
Enter values in centimeters
Normal SV range: 60-100 mL in adults

5. Frequently Asked Questions (FAQ)

Q1: Why is LVOT diameter squared in the formula?
A: The formula calculates cross-sectional area (πr²) where radius is half the diameter, hence the squared term.

Q2: How accurate is echo for stroke volume measurement?
A: Reasonably accurate when measurements are precise, but errors in LVOT diameter measurement are squared in the calculation.

Q3: What's the difference between SV and ejection fraction?
A: SV is absolute volume per beat, while EF is the fraction of end-diastolic volume ejected (EF = SV/EDV).

Q4: When might this calculation be inaccurate?
A: With irregular LVOT shape, significant aortic regurgitation, or poor Doppler alignment.

Q5: How does this relate to cardiac output?
A: Cardiac output = SV × heart rate. Multiply SV (mL) by HR (bpm) and divide by 1000 for L/min.