Pulsatility index (PI) quantifies arterial blood flow resistance by assessing the ratio of peak systolic velocity to end-diastolic velocity. To calculate PI, use Doppler ultrasound to measure these velocities in the vessel of interest. The systolic velocity is the maximum velocity during the cardiac ejection phase, while the end-diastolic velocity is the minimum velocity during diastole. PI is dimensionless and typically ranges from 0 to 1. A higher PI indicates increased arterial resistance, while a lower PI suggests reduced resistance. PI is commonly used to evaluate blood flow dynamics in various clinical settings, such as assessing vascular health and monitoring vascular interventions.
