Dimensionless velocity index

DVI · LVOT VTI (PW) / aortic VTI (CW), or velocity ratio

Normal range & thresholds

Native AS: DVI <0.25 severe ^[5]. Prosthetic aortic valve: DVI <0.25 suggests obstruction; 0.25–0.29 indeterminate; ≥0.30 normal (valve-type dependent) ^[21,167].

Pathophysiology

By continuity, AVA/LVOT area = LVOT VTI/AV VTI, so the ratio removes the LVOT diameter — the largest error source — and is independent of body size and flow to a first approximation ^[5].

Raised by

• Normal valves (DVI ≈0.7–1.0)

Lowered by

• AS, prosthetic obstruction or patient–prosthesis mismatch

Technique & pitfalls

• PW sample in the LVOT at the diameter level; CW from multiple windows.

Pseudo-change & artefact

• Subvalvular acceleration in the PW sample; missed peak CW velocity.

Treatment thresholds

• Supports severe AS grading when AVA is discordant ^[5,6]; flags prosthetic obstruction for TOE/CT ^[167].

Next step

• Calcium score (card 69) if low-gradient; TOE/CT for prostheses.

Drugs

None.

Reversibility

Normalises after AVR.