A 52-year-old man from Delhi presents to the emergency department with sudden-onset severe headache, blurred vision, and epistaxis. His blood pressure is 210/140 mmHg. Physical examination reveals papilledema and retinal hemorrhages. Serum creatinine is 2.8 mg/dL (baseline 0.9 mg/dL) and urine shows proteinuria with RBC casts. Which of the following mechanisms is primarily responsible for the acute elevation in diastolic blood pressure in this patient?

Explanation

## Hypertensive Emergency Pathophysiology This patient presents with **hypertensive emergency** (malignant hypertension) with evidence of end-organ damage: acute kidney injury, papilledema, and retinal hemorrhages. ### Mechanism of Acute Diastolic Hypertension in Malignant Hypertension **Key Point:** In malignant hypertension, the primary pathological mechanism is **endothelial injury** with loss of protective vasorelaxant factors and unopposed vasoconstrictor activity. **High-Yield:** The pathophysiological sequence in malignant hypertension: 1. **Endothelial injury** → loss of nitric oxide (NO) and prostacyclin production 2. **Increased endothelin-1** secretion (potent vasoconstrictor) 3. **Arteriolar necrosis** (acute arteriolonecrosis) → "onion-skinning" on histology 4. **Positive feedback loop** → further pressure elevation → further endothelial damage ### Why Endothelial Dysfunction is Central | Feature | Normal BP Regulation | Malignant Hypertension | |---------|---------------------|------------------------| | Endothelial NO | Adequate vasodilation | Severely reduced | | Endothelin-1 | Balanced by NO | Unopposed vasoconstriction | | Vascular tone | Autoregulated | Loss of autoregulation | | Outcome | Stable BP | Spiral of increasing pressure | **Clinical Pearl:** The acute diastolic elevation (often >120 mmHg) in malignant hypertension reflects **loss of the endothelial protective mechanisms** rather than simple sympathetic overdrive. This is why acute vasodilators (nitroprusside, nicardipine) that bypass endothelial dysfunction are effective. **Mnemonic — ENDOTHELIN in malignant HTN:** **E**ndothelial injury → **N**itric oxide loss → **D**iastolic spike → **O**rgan damage → **T**herapy with vasodilators → **H**ealing of endothelium → **E**levation controlled → **L**ong-term BP normalization → **I**ntensity of therapy tailored → **N**eed for follow-up [cite:Harrison 21e Ch 297]