Thoratec HeartMate III, Instructions For Use Manual, Page: 27 / 458

Introduction 1
HeartMate III Left Ventricular Assist System Instructions for Use 1-17
Pulsatility Index (PI)
When the left ventricle contracts, the increase in ventricular pressure causes an increase in Pump
flow during cardiac systole. The magnitude of these flow pulses are measured and averaged
over 15-second intervals to produce a Pulsatility Index (occasionally shortened to “PI” for
on-screen messages).
The PI calculation represents cardiac pulsatility. PI values typically range from 1 to 10. In
general, the magnitude of the PI value is related to the amount of assistance provided by the
Pump. Higher values indicate more ventricular filling and higher pulsatility (that is, the Pump is
providing less support to the left ventricle). Lower values indicate less ventricular filling and lower
pulsatility (that is, the Pump is providing greater support and further unloading the ventricle).
PI values should be routinely monitored and should not vary significantly during resting
conditions. Under otherwise stable conditions, a significant drop in value may indicate a
decrease in circulating blood volume. Pulsatility Index values near or above 10 may indicate
potential problems. For PI values near 10 or above, contact Thoratec Corporation. Refer to page
iii
for Thoratec Corporation contact information.
IMPORTANT! One single Pump parameter is not a surrogate for monitoring the overall clinical
status of the patient. Any change in parameters should be evaluated with all clinical
considerations taken into account.