Measuring Velocity Time Integral in the Carotid Artery

Equipment and Technique

The American Heart Association recommends using a duplex ultrasound system with pulsed-wave Doppler capability and a high-frequency linear array transducer (typically 5-12 MHz) for measuring VTI in the carotid artery 1
The American Society of Hypertension suggests positioning the probe on the neck to visualize the common carotid artery in longitudinal view, typically 1-2 cm proximal to the carotid bifurcation, and applying minimal pressure to avoid compressing the vessel 2
The American College of Cardiology recommends placing the sample volume in the center of the vessel lumen, avoiding the vessel walls, to ensure accurate velocity measurements 1
The American Society of Hypertension advises ensuring the sample volume size encompasses the full diameter of the vessel to capture peak velocities, and using Doppler ultrasound to distinguish vessels: the internal carotid has more pulsatile flow, while the external carotid exhibits continuous diastolic flow 2

The European Society of Cardiology notes that cardiac dysfunction reduces all velocities and may cause underestimation of flow changes, and contralateral carotid disease can elevate velocities in the less-diseased artery through compensatory flow 3
The American Heart Association recommends recognizing that monophasic waveforms (instead of normal triphasic patterns) indicate severe proximal disease or cardiac dysfunction and invalidate standard VTI interpretation 3