A theoretical foundation for relating the velocity time integrals of the left ventricular outflow tract and common carotid artery

A recent investigation by Cheong and colleagues should pique the interest of all clinicians who employ sonography during resuscitation [1].In their report, a novel method of measuring the left common carotid artery, maximum velocity time integral (VTI MAX-CA ) was described and its value was related to the left ventricular outflow tract VTI (VTI LVOT ).Absolute VTI measurements (in centimeters) were made in critically-ill patients, though the population studied was relatively stable, seemingly not on vasoactive medications and with normal cardiac function.Importantly, there was no provocative (i.e., dynamic) maneuver carried out during their investigation.As anticipated, Cheong and colleagues observed a stronger relationship between total (i.e., systolic plus diastolic) VTI MAX-CA and VTI LVOT than between only the systolic portion of the VTI MAX-CA and the VTI LVOT .Of most interest, however, was the near parity between VTI MAX-CA and VTI LVOT in absolute value.Based on their regression equation, the VTI MAX-CA overestimated the VTI LVOT less than 10%.Considering why this might be so elaborates some caveats to their approach.