Accelerated (Malignant) Hypertension

Definition and Terminology

• Accelerated hypertension: Severe BP elevation with retinal hemorrhages/exudates (grade III retinopathy) but without papilledema
• Malignant hypertension: Same, but with papilledema (grade IV retinopathy) - reflecting higher intracranial pressure

Pathophysiology

1. Sudden severe BP rise exceeds vascular autoregulatory capacity
2. Endothelial injury triggers fibrin deposition and platelet aggregation in arteriolar walls
3. Two characteristic vascular lesions develop:
   • Fibrinoid necrosis - breakdown of arteriolar walls with deposition of eosinophilic fibrin-containing material and perivascular inflammation
   • "Onion skin" lesion (hyperplastic arteriolosclerosis) - concentric intimal proliferation in larger arterioles causing near-obliteration of the lumen
4. Ischemia from these lesions stimulates renin-angiotensin activation, perpetuating the cycle
5. Endothelial injury leads to microangiopathic hemolytic anemia (MAHA) in severe cases

• Robbins & Cotran Pathologic Basis of Disease
• Harrison's Principles of Internal Medicine 22E

Cerebral Autoregulation and PRES

• Cerebral vasodilation and endothelial dysfunction
• Posterior reversible encephalopathy syndrome (PRES) - vasogenic edema preferentially in the posterior parieto-occipital regions (sparse sympathetic innervation of the vertebrobasilar territory makes it more susceptible)
• PRES is reversible with BP control; 68% of cases are due to hypertension
• Symptom to Diagnosis: An Evidence Based Guide, 4th Edition

Causes / Precipitants

• Medication non-adherence (most common in treated hypertensives)
• Cocaine or other sympathomimetic drugs
• Renal artery stenosis / renal disease
• MAOI interactions (tyramine-containing foods, tricyclics, meperidine, levodopa)
• Pheochromocytoma
• Scleroderma renal crisis
• Pre-eclampsia / eclampsia
• Abrupt withdrawal of beta-blockers or clonidine (rebound)

Clinical Features

Symptoms

• Severe headache, visual disturbances, nausea/vomiting
• Altered consciousness, confusion, seizures (encephalopathy)
• Chest pain, dyspnea (cardiac involvement)

End-organ damage - the hallmarks

Fundoscopy

• Grade III: Hemorrhages + exudates (accelerated HTN)
• Grade IV: All of above + papilledema (malignant HTN) - bilateral disc swelling indistinguishable from other causes of raised ICP

Prognosis Without Treatment

• Without dialysis, 1-year mortality >90% (before antihypertensives)
• 5% of hypertensive patients may develop malignant phase
• With modern antihypertensive therapy, 5-year survival now exceeds 50%

Investigations

• Urinalysis: Proteinuria, hematuria, casts
• Renal function: Creatinine, electrolytes (look for AKI)
• FBC: Schistocytes (MAHA), anaemia
• LDH, haptoglobin, reticulocytes: Assess haemolysis
• ECG: LVH, ischemia
• CXR: Pulmonary oedema
• CT head: Rule out haemorrhagic stroke before BP lowering
• MRI brain: PRES - T2/FLAIR signal in posterior regions; more sensitive than CT for acute ischaemic stroke (83% vs 16% sensitivity)
• Echocardiography: LV function, wall motion
• Screen for secondary causes (renal artery stenosis, phaeochromocytoma, Conn syndrome)

Treatment

Urgency vs Emergency

• Hypertensive urgency: BP >180/110 but no acute target-organ injury - can be managed with oral agents and prompt outpatient follow-up; rapid IV reduction is NOT indicated
• Hypertensive emergency: Severe BP + active target-organ injury - requires ICU admission with IV titratable agents

General BP lowering targets

• Reduce MAP by no more than 25% in the first hour
• Then target 160/100-110 mmHg over 2-6 hours
• Do not normalize BP acutely - risks cerebral ischemia (the autoregulatory curve is shifted in chronic hypertensives)
• Exception: Aortic dissection, acute pulmonary oedema, ACS, haemorrhagic stroke - more aggressive immediate reduction warranted

IV Agents Used

• Goldman-Cecil Medicine; Symptom to Diagnosis 4e; Lippincott Illustrated Reviews Pharmacology

Special situations

• Stroke (ischaemic): Generally avoid treating BP <220/120 unless thrombolysis planned (target <185/110 before tPA); nicardipine preferred over nitroprusside
• Haemorrhagic stroke: Target SBP <140 per INTERACT2 trial; nicardipine preferred
• Aortic dissection: Aggressive reduction to SBP <120 using esmolol + vasodilator
• Eclampsia: Labetalol, hydralazine, or nicardipine; MgSO4 for seizure prophylaxis
• Cocaine-induced: Benzodiazepines first; avoid beta-blockers alone (risk of unopposed alpha stimulation)
• Phaeochromocytoma: Phentolamine first; beta-blocker only AFTER alpha blockade

Recent Evidence (PubMed 2024-2025)

Harrison's 22E (2025) - Accelerated/Malignant Hypertension: Exact Data

Hypertensive Urgencies and Emergencies

"Adults presenting with a very high level of BP, usually designated as an SBP/DBP ≥180/100 mmHg, should be classified as having a hypertensive urgency if they are asymptomatic or a hypertensive emergency if there is evidence of active ongoing hypertensive end-organ damage such as hypertensive encephalopathy, often manifesting with headaches, vision defects, nausea, vomiting, seizures, acute left ventricular failure, or acute kidney failure.

Hypertensive urgency is far more common than hypertensive emergency and should be treated with institution, reinstitution, or intensification of oral antihypertensive agents in an outpatient setting. In contrast, a hypertensive emergency requires immediate, carefully supervised management with intravenous antihypertensive agents in an emergency room or inpatient setting.

A hypertensive emergency associated with acute aortic dissection, eclampsia or severe preeclampsia, or a pheochromocytoma in crisis signals the need for particularly rapid care."

"Malignant" Hypertension - Pathology

"Some individuals develop rapidly progressive BP elevations with target organ injury including retinal hemorrhages, encephalopathy, and declining kidney function. Placebo arms during the early controlled trials of hypertension therapy identified progression to severe levels in 20% of subjects over 5 years."

"If untreated, patients with target organ injury including papilledema and declining kidney function suffered mortality rates in excess of 50% over 6-12 months, hence the designation 'malignant.'"

"Postmortem studies of such patients identified vascular lesions, designated 'fibrinoid necrosis,' with breakdown of the vessel wall, deposition of eosinophilic material including fibrin, and a perivascular cellular infiltrate. A separate lesion was identified in the larger interlobular arteries in many patients with hyperplastic proliferation of the vascular wall cellular elements, deposition of collagen, and separation of layers, designated the 'onionskin' lesion."

"For many of these patients, fibrinoid necrosis led to obliteration of glomeruli and loss of tubular structures. Progressive kidney failure ensued and, without dialysis support, led to early mortality in untreated malignant-phase hypertension."

"These vascular changes could develop with pressure-related injury from a variety of hypertensive pathways, including but not limited to activation of the renin-angiotensin system and severe vasospasm associated with catecholamine release. Occasionally, endothelial injury is sufficient to induce microangiopathic hemolysis."

Harrison's Data on Prognosis

"Whereas prior reports before the era of drug therapy suggested that 1-year mortality rates exceeded 90%, current survival over 5 years exceeds 50%."

Treatment

"Antihypertensive therapy is the mainstay of therapy for malignant hypertension. With effective BP reduction, manifestations of vascular injury, including microangiopathic hemolysis and renal dysfunction, can improve over time."

Epidemiology / Precipitants

"Malignant hypertension is less common in Western countries, although it persists in parts of the world where medical care and antihypertensive drug therapy are less available. It most commonly develops in patients with treated hypertension who neglect to take medications or who may use vasospastic drugs, such as cocaine."

Renal Manifestations

"The hemodynamic stress of malignant hypertension leads to fibrinoid necrosis of small blood vessels, thrombotic microangiopathy, a nephritic urinalysis, and AKI. In the setting of kidney injury, chest pain, or papilledema, the condition is treated as a hypertensive emergency."

"Renal abnormalities typically include rising creatinine [and] microangiopathic hemolysis."

Cerebral Autoregulation Data

Harrison's BP Threshold Summary

Key Harrison's Data Points (exact figures)