Doppler pulmonary vascular resistance

PVR (Abbas) · Derived: PVR (WU) ≈ 10 × TR Vmax / RVOT VTI + 0.16

Normal range & thresholds

≤2 WU normal (PH definition: PVR >2 WU, mPAP >20 mmHg — invasive) ^[8,180]. The Doppler equation was validated for screening and is unreliable above ≈6 WU ^[49].

Pathophysiology

Resistance is pressure drop over flow: TR velocity reflects the pressure, RVOT VTI the flow. A high TR velocity with a normal VTI implies high resistance; the same velocity with high flow (shunt, anaemia) does not ^[49].

Raised by

• Precapillary PH (groups 1, 3, 4), combined pre/post-capillary PH

Lowered by

• High-flow states, isolated post-capillary PH

Technique & pitfalls

• Complete TR envelope; RVOT VTI at the same heart rate.

Pseudo-change & artefact

• Underestimated TR velocity; torrential TR; high cardiac output.

Treatment thresholds

Screening only — pulmonary vasodilator therapy requires invasive PVR ^[8].

Next step

• Right-heart catheterisation with wedge pressure when decisions depend on it.

Drugs

Pulmonary vasodilators in group 1; treat the left heart in group 2.

Reversibility

Group dependent.