Hypertension & Hypertensive Crisis

Start with whose numbers you are using. The US definition (ACC/AHA) is ≥ 130 and/or ≥ 80 mm Hg; the WHO/international threshold is ≥ 140 and/or ≥ 90 mm Hg measured on two different days — always name the authority with the number. The AHA/ACC categories: normal < 120 and < 80 · elevated 120–129 and < 80 · stage 1 hypertension 130–139 or 80–89 · stage 2 hypertension ≥ 140 or ≥ 90 — unchanged in the 2025 guideline. A diagnosis requires at least two office measurements on at least two separate occasions: one reading is a data point, not a disease.

In essential hypertension no single villain is found — most cases are idiopathic. Instead, several regulators drift in the same direction: increased salt absorption drives volume expansion, the renin–angiotensin–aldosterone system responds abnormally, and sympathetic activation increases — the combined result is increased total peripheral resistance and increased afterload. The pressure the ventricle must pump against rises and stays risen.

"Silent killer" is the WHO’s own label for hypertension, and the rationale is simple: most people with hypertension feel no symptoms, and a blood-pressure check is the only way to find it — while, untreated, it goes on to cause kidney disease, heart disease and stroke. The WHO estimates 600 million adults with hypertension (44%) are unaware they have it, and only about 23% have it controlled — the damage is done in the years nobody is looking.

What the damage looks like: the sustained pressure load produces left ventricular hypertrophy and progressive vascular and end-organ injury, making hypertension one of the most significant comorbidities contributing to stroke, myocardial infarction, heart failure, and renal failure. The screening trail follows the same four targets — LVH on ECG or echo, retinopathy/maculopathy on eye exam, rising creatinine or falling eGFR, and albuminuria. Each finding means the pressure has already been high, and already been harmful, for a long time.

Most hypertension is idiopathic (essential/primary), but a treatable cause hides in more patients than the classic teaching suggested: historical estimates said 5–10%, while contemporary data run higher — one 2024 study found secondary hypertension in 29.6% of confirmed hypertension in adults aged 18–40, about 17% in adults ≥ 65, and 70–85% of hypertension in children under 12 is secondary. The cause list to know: renal parenchymal disease (3–5% of all hypertension), renal artery stenosis (1–5%), primary aldosteronism (5–10% of all hypertension — up to 20% of resistant cases), pheochromocytoma, obstructive sleep apnea, thyroid disease, Cushing syndrome, aortic coarctation, pregnancy/preeclampsia, and drug-induced (NSAIDs, oral contraceptives, stimulants/sympathomimetics).

Suspect a secondary cause when the story doesn’t fit essential hypertension: onset before age 40 without traditional risk factors; a new or abrupt worsening of previously stable pressure; resistant hypertension — BP still at or above goal despite confirmed adherence to maximally tolerated doses of three or more agents; or BP above 180/110 with end-organ damage. Primary aldosteronism deserves a specific look: the 2025 Endocrine Society guideline now recommends screening all hypertensive patients, and a normal potassium does not exclude it.

A hypertensive crisis is conventionally BP higher than 180 systolic and/or higher than 120 diastolic (ACC/AHA) — but the sources themselves stress these cut-points are "arbitrary": the rate of rise and the presence of organ damage matter more than the absolute number. Only 1–2% of hypertensives ever have a crisis, yet about a quarter of ED crisis patients have no prior hypertension diagnosis — and among known hypertensives, the leading precipitant is nonadherence to antihypertensive therapy, followed by sympathomimetic (stimulant) use and thyroid dysfunction. Pain and anxiety can acutely push the number higher still.

Mechanistically a crisis is an abrupt rise in systemic vascular resistance driven by enhanced vasoconstriction, and it feeds itself: the pressure forces a pressure natriuresis that depletes volume, which triggers more vasoconstrictor release. Small vessels develop the characteristic lesion — fibrinoid necrosis — and downstream tissue becomes hypoperfused and ischemic. The hallmark of hypertensive emergency is loss of cerebral autoregulation: the brain’s vessels can no longer buffer the pressure they are handed.

Everything at the bedside now hangs on one fork. Hypertensive emergency = acute, marked elevation with acute target-organ damage — encephalopathy, intracerebral hemorrhage, acute ischemic stroke, MI or unstable angina, acute LV failure with pulmonary edema, aortic dissection, acute renal failure, eclampsia. Hypertensive urgency = the same severe number without acute target-organ injury — managed with oral agents and gradual reduction over 24–48 hours, close outpatient follow-up within a week, and generally no hospital admission. Treat the patient’s overall condition, never an isolated number.