Note: Davidson's Principles and Practice of Medicine is not available in this medical library. The response below draws from Goldman-Cecil Medicine (International Edition, 2-Volume Set) - the closest equivalent comprehensive internal medicine textbook available - supplemented by Braunwald's Heart Disease and other sources. The content is clinically equivalent and covers all major Davidson's topics on hypertension.

Hypertension - Detailed Overview

1. Definition

• Averaging multiple readings over several temporally spaced visits
• Confirmation via home blood pressure monitoring or ambulatory blood pressure monitoring (ABPM)

• Observer training
• Use of validated, calibrated devices
• Adherence to a rigorous measurement protocol

2. Epidemiology

• At the 140/90 mm Hg threshold, hypertension affects nearly 1.4 billion adults worldwide, with ~75% living in low- and middle-income countries.
• At the 130/80 mm Hg threshold, prevalence in the United States is 45%, affecting >115 million U.S. adults aged ≥20 years.
• Prevalence is higher in men (49%) than women (43%), but reverses after age 65.
• Worldwide prevalence is highest in Eastern Europe and Central Asia, lowest in South Asia.
• In high-income countries, hypertension is more common in rural areas; in low/middle-income countries, it is more common in urban areas.
• Prevalence is inversely related to educational attainment in the United States.
• Hypertension is the leading cause of preventable death globally and the #1 reason for ambulatory office visits.
• Systolic BP is a more important cardiovascular risk determinant than diastolic BP, especially after middle age.

3. Classification / Staging

Types:

• Primary (Essential) Hypertension - No identifiable secondary cause; accounts for ~90-95% of cases
• Secondary Hypertension - Identifiable underlying cause; includes renovascular hypertension, primary hyperaldosteronism, obstructive sleep apnea, chronic kidney disease, pheochromocytoma, Cushing's syndrome, coarctation of the aorta, thyroid disorders

4. Pathophysiology

Key Mechanisms:

• Renin (released by juxtaglomerular cells) converts angiotensinogen to angiotensin I
• ACE converts angiotensin I → angiotensin II (potent vasoconstrictor)
• Angiotensin II stimulates aldosterone secretion → sodium retention → volume expansion → elevated BP

• Increased catecholamine activity raises heart rate, cardiac output, and vasoconstriction
• Obesity, sleep apnea, and psychosocial stress amplify sympathetic tone

• Impaired renal ability to excrete sodium shifts the pressure-natriuresis relationship
• Leads to volume expansion and sustained BP elevation

• Chronic hypertension causes vascular remodeling: medial hypertrophy, reduced lumen diameter
• Increases vascular stiffness (arteriosclerosis) → elevated systolic BP and pulse pressure
• Rising pulse pressure with age due to loss of aortic compliance

• Reduced nitric oxide (NO) production impairs vasodilation
• Increased oxidative stress, inflammation, and endothelin-1 activity promote vasoconstriction

• Heritability estimated at ~50%
• Multiple genes involved in sodium transport, RAAS, and sympathetic tone

• Systolic BP rises progressively with age in industrialized societies
• Diastolic BP plateaus in the 6th decade, then declines
• Result: isolated systolic hypertension becomes dominant in older adults

5. Risk Factors

• Age (risk increases with age)
• Male sex (until age 65)
• Family history / genetics
• Race (higher prevalence and severity in Black Americans)

• High dietary sodium intake
• Obesity / overweight
• Physical inactivity
• Excessive alcohol consumption
• Cigarette smoking
• Psychosocial stress
• Low dietary potassium intake
• Obstructive sleep apnea

6. Clinical Presentation and Target Organ Damage

Symptoms (when present):

• Headache (classically occipital, worse in the morning)
• Visual disturbances
• Chest pain
• Shortness of breath
• Epistaxis

Target Organ Damage:

7. Hypertensive Emergencies and Urgencies

• Hypertensive urgency: BP >180/120 mm Hg without evidence of acute target organ damage. Managed with oral antihypertensives with gradual BP reduction over 24-48 hours.
• Hypertensive emergency: Severely elevated BP with acute target organ damage (hypertensive encephalopathy, acute aortic dissection, acute MI, flash pulmonary edema, eclampsia). Requires immediate IV antihypertensive therapy (e.g., IV labetalol, nicardipine, nitroprusside) with BP reduction by ~25% within first hour.

8. Diagnosis and Evaluation

Measurement:

• Patient seated quietly ≥5 minutes, arm at heart level, back supported, feet flat
• No caffeine/smoking within 30 minutes
• Use appropriate cuff size (cuff bladder encircling ≥80% of arm)
• Average ≥2 readings, ≥2 visits

Blood Pressure Measurement Types:

• Office BP: Most common; may overestimate (white coat hypertension) or underestimate (masked hypertension) true BP
• Home BP monitoring (HBPM): Preferred for confirming diagnosis and monitoring treatment; typical threshold ≥135/85 mm Hg
• Ambulatory BP monitoring (ABPM): Gold standard; captures 24-hour profile; daytime threshold ≥130/80, nighttime ≥110/65, 24-hour average ≥125/75

Initial Workup:

• Urinalysis (protein, blood, casts)
• Urine albumin-to-creatinine ratio
• Serum creatinine, eGFR
• Serum electrolytes (sodium, potassium)
• Fasting glucose / HbA1c
• Fasting lipid panel
• Thyroid-stimulating hormone (TSH)

Screening for Secondary Causes (when suspected):

9. Non-Pharmacological (Lifestyle) Management

10. Pharmacological Management

First-Line Drug Classes:

Compelling Indications (Drug Choice by Comorbidity):

Resistant Hypertension:

11. Special Populations

• Elderly: Isolated systolic hypertension predominates; treatment beneficial even in very elderly (>80 years); start low, go slow; avoid orthostatic hypotension
• Pregnancy: Hypertension in pregnancy includes gestational hypertension, preeclampsia, eclampsia, chronic hypertension, and superimposed preeclampsia; ACEi/ARBs are contraindicated
• Diabetes: Aggressive BP control (<130/80 mm Hg) recommended; ACEi/ARBs first-line
• CKD: ACEi/ARBs preferred to slow progression; monitor potassium and creatinine
• Black patients: Higher prevalence, earlier onset, more severe disease; thiazide diuretics and CCBs particularly effective; ACEi monotherapy less effective

12. Prognosis and Prevention

• Untreated hypertension significantly increases risk of stroke, MI, heart failure, CKD, and premature death
• Primordial prevention (preventing hypertension in the first place) is key - most BP-related cardiovascular events occur in people with BP below the pharmacologic treatment threshold
• Treated hypertensives retain residual cardiovascular risk higher than untreated individuals with the same BP level, emphasizing the need to address all global CV risk factors (dyslipidemia, diabetes, smoking)
• Rate of hypertension control in the U.S. has been worsening in recent years after decades of improvement

• Goldman-Cecil Medicine, International Edition (2-Volume Set), Chapter 64: Arterial Hypertension
• Braunwald's Heart Disease, 15th Edition: Hypertension sections
• Comprehensive Clinical Nephrology, 7th Edition: Hypertension chapters