Pathophysiology
P-I-3. Hypertension, Case 3
高血圧 症例3
A 60-year-old male patient with a history of IHD (ischemic heart disease) and peripheral vascular disease presents to his 6-monthly follow-up appointment. Being on medication (diuretic, ACE inhibitor, Ca antagonist, Beta blocker, aspirin, statin), he has no complaints, but his blood pressure readings have risen in the past few weeks. On examination, these are the findings: blood pressure: 170/105 mmHg, pulse: 70 beats per minute, a murmur to the right of the umbilicus revealed by physical examination, slightly palpable peripheral blood vessels. No audible bruit above the carotid.
Key Quotes & What They Tell Us
| Quote / Value | Interpretation |
|---|---|
| “history of IHD … and peripheral vascular disease” | Established widespread atherosclerosis → predisposes to atherosclerotic renal artery stenosis |
| BP rising to 170/105 mmHg “on medication (diuretic, ACE inhibitor, Ca antagonist, Beta blocker…)” | Resistant hypertension — uncontrolled despite ≥3 drug classes → search for a secondary cause |
| “a murmur to the right of the umbilicus” | Abdominal bruit → turbulent flow suggesting renal artery stenosis (renovascular hypertension) |
| “slightly palpable peripheral blood vessels” | Reduced peripheral perfusion consistent with generalized atherosclerotic vascular disease |
Key Points
- Diagnosis: Secondary (renovascular) hypertension from atherosclerotic renal artery stenosis, presenting as resistant hypertension.
- Clue: Worsening control despite four drug classes, plus an abdominal bruit.
- Pathophysiology: Renal artery narrowing → reduced renal perfusion → activation of the renin–angiotensin–aldosterone system → sustained hypertension.
- Caution: ACE inhibitors can sharply reduce GFR in bilateral renal artery stenosis — monitor renal function.
- Lesson: In a patient with diffuse atherosclerosis, resistant hypertension warrants investigation for a secondary, correctable cause.
一問一答
▶What is the diagnosis in a patient with diffuse atherosclerosis, resistant hypertension, and an abdominal bruit?
Secondary (renovascular) hypertension from atherosclerotic renal artery stenosis.
▶What is resistant hypertension?
Blood pressure uncontrolled despite treatment with ≥3 drug classes.
▶What does an abdominal bruit (murmur near the umbilicus) suggest?
Turbulent flow from renal artery stenosis (renovascular hypertension).
▶What is the pathophysiology of renovascular hypertension?
Renal artery narrowing reduces renal perfusion, activating the renin–angiotensin–aldosterone system and causing sustained hypertension.
▶Why must ACE inhibitors be used cautiously in bilateral renal artery stenosis?
They can sharply reduce GFR because efferent arteriolar constriction (needed to maintain filtration in low-perfusion kidneys) is lost.
▶What clinical clues point to a secondary cause of hypertension in this case?
Worsening BP control despite four drug classes plus a new abdominal bruit.
▶Why does a history of IHD and peripheral vascular disease predispose to renal artery stenosis?
It indicates widespread atherosclerosis, which can also narrow the renal arteries.
▶What does "slightly palpable peripheral blood vessels" indicate in this patient?
Reduced peripheral perfusion consistent with generalized atherosclerotic vascular disease.
▶What is the key clinical lesson of resistant hypertension in a patient with diffuse atherosclerosis?
It warrants investigation for a secondary, correctable cause.
▶How does activation of the RAAS raise blood pressure in renal artery stenosis?
Angiotensin II causes vasoconstriction and aldosterone causes Na⁺/water retention, both raising blood pressure.
▶Why does the stenotic kidney sense low perfusion and release renin?
Narrowing reduces pressure at the afferent arteriole/juxtaglomerular apparatus, which interprets it as low systemic volume and secretes renin.
▶Why does renal artery stenosis cause an abdominal bruit?
Narrowing produces turbulent blood flow that is audible as a murmur over the abdomen.
▶How does ACE inhibition maintain GFR in a normal kidney but not in bilateral RAS?
Normally efferent constriction by angiotensin II preserves filtration; with low perfusion in RAS, blocking it drops glomerular pressure and GFR.
▶What is the most common cause of renal artery stenosis in older patients?
Atherosclerosis of the renal artery.
▶Why should renal function be monitored after starting an ACE inhibitor?
To detect a significant fall in GFR/rise in creatinine that would suggest underlying renal artery stenosis.
▶What distinguishes secondary from primary (essential) hypertension here?
An identifiable, potentially correctable cause (renal artery stenosis), often with resistant BP and specific signs like a bruit.
▶Why might BP control suddenly worsen after years of stability in this patient?
Progressive atherosclerotic narrowing of the renal artery increases RAAS-driven hypertension over time.
▶What are typical treatment options for atherosclerotic renal artery stenosis?
Risk-factor and medical management; revascularization (angioplasty/stenting) in selected resistant cases.
▶Why is renovascular hypertension considered potentially correctable?
Relieving the stenosis (e.g., by revascularization) can reduce RAAS activation and improve blood pressure.
▶Which medication classes was this patient already taking?
A diuretic, ACE inhibitor, calcium antagonist, beta blocker, aspirin, and a statin.