A 62-year-old man with a 10-year history of hypertension presents with resistant hypertension despite being on three antihypertensive medications including a diuretic. Duplex renal Doppler ultrasound is performed. The structure marked **A** in the diagram shows a peak systolic velocity of 240 cm/s at the renal artery stenosis. Based on this finding, which of the following statements about the hemodynamic significance of this stenosis is most accurate?
A. This peak systolic velocity suggests mild stenosis that does not activate the renin-angiotensin-aldosterone system
B. This peak systolic velocity is within normal limits and excludes the diagnosis of renal artery stenosis
C. This peak systolic velocity indicates hemodynamically significant stenosis (>60-70% luminal narrowing) and warrants further evaluation for revascularization candidacy
D. This peak systolic velocity is diagnostic of fibromuscular dysplasia and indicates need for immediate percutaneous balloon angioplasty
Explanation
Why option 1 is correct
A peak systolic velocity (PSV) >200 cm/s at the renal artery stenosis is the key diagnostic criterion for hemodynamically significant (>60-70% luminal narrowing) renal artery stenosis on duplex Doppler ultrasound. This patient's PSV of 240 cm/s exceeds the diagnostic threshold and indicates flow acceleration through a stenotic segment, confirming hemodynamic significance. In this clinical context of resistant hypertension in a 62-year-old (typical for atherosclerotic RAS), this finding warrants further evaluation with CTA or MRA and assessment for revascularization candidacy according to the 2017 ACC/AHA guidelines and CORAL trial criteria (refractory hypertension on ≥3 drugs is a potential indication for intervention).
Why each distractor is wrong
Option 2: PSV >200 cm/s is abnormal and diagnostic of hemodynamically significant stenosis, not normal. Normal renal artery PSV is typically <180 cm/s. This misinterprets the diagnostic criterion.
Option 3: Hemodynamically significant stenosis (>60-70% narrowing) by definition activates the renin-angiotensin-aldosterone system, leading to renovascular hypertension. A PSV of 240 cm/s indicates significant stenosis, not mild stenosis.
Option 4: While PSV >200 cm/s indicates hemodynamically significant RAS, it does not distinguish between atherosclerotic RAS (90%, typically ostial/proximal, in older patients) and fibromuscular dysplasia (10%, typically mid-distal, in young women). The patient's age (62) and clinical presentation favor atherosclerotic RAS. FMD diagnosis requires angiographic findings (string-of-beads appearance), not PSV alone.
High-YieldNEET PG
Peak systolic velocity >200 cm/s is the primary Doppler criterion for hemodynamically significant RAS; renal-aortic ratio >3.5 and tardus-parvus waveform are confirmatory findings.
