Hypertension¶
Chapter 288 | Part 6: Disorders of the Cardiovascular System
KEY CLINICAL POINTS¶
- Hypertension is a leading risk factor for cardiovascular disease (CVD), stroke, heart failure, and chronic kidney disease (CKD).
- The ACC/AHA classification system defines normal BP as <120/80 mmHg, stage 1 hypertension as 130-139/80-89 mmHg, and stage 2 as ≥ 140/ ≥ 90 mmHg.
- Nonpharmacologic interventions (DASH diet, weight loss, sodium reduction, physical activity) reduce BP by 5-10 mmHg in most patients.
- First-line pharmacologic therapy includes thiazide diuretics, ACEIs, ARBs, and CCBs, with combination therapy often required for stage 2 hypertension.
- Resistant hypertension requires evaluation for secondary causes (e.g., renovascular disease, obstructive sleep apnea) and adjustment of medication regimen.
1. DEFINITION & OVERVIEW¶
Hypertension is defined as sustained elevation of arterial pressure ≥ 130/80 mmHg. It is a major modifiable risk factor for CVD, stroke, and CKD. Primary hypertension accounts for 90-95% of cases, while secondary hypertension (e.g., renal artery stenosis, pheochromocytoma) accounts for 5-10%.
American College of Cardiology/American Heart Association Blood Pressure Classification System¶
| BP CATEGORY | SYSTOLIC BP, mmHg | DIASTOLIC BP, mmHg |
|---|---|---|
| Normal BP | <120 | <80 |
| Elevated BP | 120-129 | <80 |
| Stage 1 Hypertension | 130-139 or 80-89 | |
| Stage 2 Hypertension | ‡140 or ‡90 |
1.1 Pathophysiology¶
Hypertension results from complex interactions between genetic, environmental, and physiological factors. Key mechanisms include increased cardiac output, peripheral vascular resistance, and renal sodium retention. The RAAS, sympathetic nervous system, and endothelial dysfunction play central roles.
1.2 Clinical Significance¶
Hypertension is the leading cause of preventable morbidity and mortality worldwide. It contributes to 40% of CVD deaths and 50% of stroke cases. Early detection and treatment reduce cardiovascular risk by 25-30%.
2. EPIDEMIOLOGY¶
Global prevalence exceeds 1.28 billion adults (46%). In the U.S., ~46% of adults have hypertension, with higher rates in non-Hispanic blacks (59%) compared to whites (45%). Prevalence increases with age, doubling from 30% in adults aged 40-49 to 60% in those ≥ 75 years. Obesity and sedentary lifestyles contribute to rising rates in low- and middle-income countries.
2.1 Demographics¶
Non-Hispanic blacks have highest prevalence (59%) and poorest control (37% vs 52% in whites). Men have higher BP than women until age 65, after which women's risk surpasses men's.
2.2 Global Trends¶
Prevalence has increased by 60% since 1970. In low-income countries, prevalence is rising due to urbanization, dietary changes, and aging populations. Global control rates remain below 50%.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Primary hypertension (90-95% of cases) involves complex interactions of genetic, environmental, and physiological factors. Secondary hypertension (5-10%) has identifiable causes like renal artery stenosis, coarctation of the aorta, or endocrine disorders.
Common Causes of Secondary Hypertension¶
| Cause | Prevalence | Key Features |
|---|---|---|
| Renovascular disease | 1-2% | Abdominal bruit, resistant hypertension |
| Primary aldosteronism | 5-10% | Hypokalemia, resistant hypertension |
| Obstructive sleep apnea | 15-25% | Nocturnal hypertension, daytime sleepiness |
| Renal parenchymal disease | 3-5% | Renal dysfunction, proteinuria |
3.1 Primary Hypertension¶
Involves genetic predisposition, sodium sensitivity, and vascular remodeling. Key mechanisms include RAAS activation, sympathetic overactivity, and endothelial dysfunction.
3.2 Secondary Hypertension¶
Causes include renal parenchymal disease (3-5%), renovascular disease (1-2%), primary aldosteronism (5-10%), obstructive sleep apnea (15-25%), and drug-induced hypertension (e.g., NSAIDs, COX-2 inhibitors).
4. CLINICAL FEATURES¶
Most patients are asymptomatic. When symptoms occur, they include headache, dizziness, epistaxis, and visual disturbances. Target organ damage manifests as left ventricular hypertrophy, retinopathy, or chronic kidney disease.
4.1 Complications¶
Cardiovascular complications include coronary artery disease, heart failure, and stroke. Renal complications include proteinuria, glomerulosclerosis, and CKD progression.
4.2 Hypertensive Emergencies¶
Defined as BP ≥ 180/120 mmHg with evidence of end-organ damage (e.g., encephalopathy, acute kidney injury, retinal hemorrhage). Requires immediate intravenous antihypertensive therapy.
5. DIFFERENTIAL DIAGNOSIS¶
Differentiate from secondary causes (e.g., pheochromocytoma, Cushing's syndrome) and other conditions causing elevated BP (e.g., hyperthyroidism, renal artery stenosis).
5.1 Secondary Causes¶
Include endocrine disorders (e.g., hyperthyroidism, Cushing's), renal disease, and drug-induced hypertension (e.g., NSAIDs, oral contraceptives).
5.2 White Coat vs Masked Hypertension¶
White coat hypertension: BP ≥ 140/90 mmHg in clinic but <130/80 mmHg out-of-office. Masked hypertension: BP <130/80 mmHg in clinic but ≥ 140/90 mmHg out-of-office.
6. INVESTIGATIONS & DIAGNOSIS¶
Confirm hypertension with ≥ 2 readings on different days. Use ambulatory BP monitoring (ABPM) or home BP monitoring (HBPM) for better accuracy. Exclude secondary causes with imaging and laboratory tests.
Diagnostic Criteria for Hypertension¶
| Criteria | Definition |
|---|---|
| Elevated BP | SBP 120-129 mmHg and/or DBP 80-89 mmHg |
| Stage 1 Hypertension | SBP 130-139 mmHg or DBP 80-89 mmHg |
| Stage 2 Hypertension | SBP ‡140 mmHg or DBP ‡90 mmHg |
| Hypertensive Crisis | SBP ‡180 mmHg and/or DBP ‡120 mmHg |
6.1 BP Measurement¶
Use validated devices. Average of 2-3 readings from different visits. Avoid white coat hypertension by using HBPM or ABPM.
6.2 Diagnostic Tests¶
Include urine analysis (proteinuria), renal ultrasound, renal artery Doppler, and plasma renin activity. Consider 24-hour urine for aldosterone or catecholamines in suspected secondary causes.
7. MANAGEMENT & TREATMENT¶
Lifestyle modifications (DASH diet, weight loss, sodium restriction) are first-line. Pharmacologic therapy includes thiazides, ACEIs, ARBs, and CCBs. Combination therapy is often required for stage 2 hypertension.
Major Antihypertensive Drug Classes¶
| Class | Examples | SBP Reduction (mmHg) | Common Side Effects |
|---|---|---|---|
| Thiazide Diuretics | Hydrochlorothiazide | 12 | Hypokalemia, hyperglycemia |
| ACE Inhibitors | Lisinopril | 12 | Dry cough, hyperkalemia |
| ARBs | Losartan | 12 | Hyperkalemia, dizziness |
| CCBs (DHP) | Amlodipine | 10 | Peripheral edema, headache |
7.1 Nonpharmacologic Therapy¶
DASH diet reduces SBP by 5-11 mmHg. Weight loss of 10 kg reduces SBP by 5-20 mmHg. Sodium restriction to <2,300 mg/day lowers SBP by 2-8 mmHg.
7.2 Pharmacologic Therapy¶
First-line agents: thiazide diuretics (hydrochlorothiazide), ACEIs (lisinopril), ARBs (losartan), and CCBs (amlodipine). Combination therapy is needed for most patients with stage 2 hypertension.
8. PROGNOSIS & COMPLICATIONS¶
Uncontrolled hypertension increases risk of CVD by 2-3 times. Mortality risk is 2-3 times higher in patients with uncontrolled hypertension. Complications include myocardial infarction, stroke, and end-stage renal disease.
8.1 Cardiovascular Risk¶
Each 10 mmHg reduction in SBP lowers CVD risk by 20-25%. Hypertension contributes to 40% of CVD deaths and 50% of stroke cases.
8.2 Renal Complications¶
Hypertension accelerates CKD progression. Blood pressure control reduces risk of ESRD by 50% in patients with CKD.
9. SPECIAL CONSIDERATIONS¶
Management differs by age, gender, and comorbidities. Pregnancy, elderly, and patients with diabetes require tailored approaches.
9.1 Pregnancy¶
Hypertension in pregnancy includes gestational hypertension (BP ≥ 140/90 mmHg) and preeclampsia (with proteinuria). ACEIs/ARBs contraindicated in pregnancy.
9.2 Elderly¶
Focus on preventing falls and syncope. Target SBP <150 mmHg for adults ≥ 65 years. Use of diuretics over CCBs for isolated systolic hypertension.
10. KEY POINTS & CLINICAL PEARLS¶
- Hypertension is the leading preventable cause of CVD. 2. Nonpharmacologic therapy should be the first approach. 3. Combination therapy is needed for most patients with stage 2 hypertension. 4. Monitor for secondary causes in patients with resistant hypertension. 5. Target SBP <130 mmHg for most adults.