Pulsatility Index Calculator

The Pulsatility Index Calculator estimates vascular resistance based on Peak Systolic Velocity, End Diastolic Velocity, and Mean Velocity. This tool helps medical professionals and sonographers assess blood flow characteristics quickly. Whether you are evaluating placental blood flow, checking renal artery stenosis, or diagnosing peripheral vascular disease, this calculator provides accurate results to support your clinical decisions.

Maximum blood flow velocity during systole (cm/s)
Minimum blood flow velocity during diastole (cm/s)
Average blood flow velocity over the cardiac cycle (cm/s)

How Pulsatility Index Is Calculated

The Pulsatility Index represents the ratio of the difference between systolic and diastolic velocities to the mean velocity. This metric helps evaluate vascular resistance without being affected by the angle of the ultrasound beam. The standard formula used is:

PI = (PSV - EDV) / MV

Where:

  • PSV = Peak Systolic Velocity (Maximum flow)
  • EDV = End Diastolic Velocity (Minimum flow)
  • MV = Mean Velocity (Average flow)

First, find the difference between the maximum (PSV) and minimum (EDV) blood flow speeds. This shows the range of flow during a heartbeat. Next, divide this difference by the average speed over the whole cycle (MV). This final ratio reveals how much resistance the blood vessels are facing. This method is widely accepted for its reliability in clinical settings.

What Your Pulsatility Index Means

Your Pulsatility Index result tells you how hard the heart has to work to push blood through the vessels. A higher number means the vessels are tight or blocked, while a lower number suggests wide-open vessels.

Normal Range (0.7–1.3)

Values in this range usually indicate healthy blood flow and typical vascular resistance. Continue routine monitoring during standard examinations to ensure these values stay consistent.

High Resistance (> 1.3)

A score above 1.3 suggests increased resistance, often due to vessel narrowing or rising pressure. You should investigate potential stenosis or intracranial issues immediately.

Low Resistance (< 0.7)

Scores below 0.7 mean blood flows easily with little resistance. While common in some areas, extremely low values might indicate vasodilation or an arteriovenous malformation.

Important Note

Normal values vary by specific vessel and patient age. Always compare results against age-matched reference ranges.

This pulsatility index calculator is a screening tool for educational purposes only and is not a substitute for professional medical diagnosis. Always consult with a qualified healthcare provider for interpretation of results and treatment decisions.

Re-measure if values seem inconsistent with the patient's condition to ensure accuracy.