High blood pressure (hypertension): causes, symptoms, pathophysiology, investigations and treatment medications

Hypertension: A Comprehensive Guide for Medical Students (Harrison-Based Explanation)

Hypertension is one of the most common chronic medical conditions worldwide and a major preventable cause of cardiovascular, cerebrovascular, and renal disease. Although often silent, uncontrolled hypertension significantly increases the risk of stroke, myocardial infarction, heart failure, chronic kidney disease, and premature death. This article provides a clear, detailed, Harrison-style overview for MBBS Li students, interns, and early-career clinicians.

• What is Hypertension?

Blood pressure (BP) is the force exerted by circulating blood on the arterial walls. Hypertension is diagnosed when this pressure is persistently elevated beyond established normal ranges.

• BP Classification

Category Systolic BP and Diastolic BP

Normal blood pressure <120 and <80

Elevated 120–129 and <80

Stage 1 Hypertension 130–139 and diastolic 80–89 

Stage 2 Hypertension ≥140 and ≥90

Hypertensive Crisis ≥180 and ≥120

cardiovascular risk increases in a continuous, graded manner even within “high-normal” BP ranges

Types of Hypertension

hypertension and high blood pressure

1. Primary (Essential) Hypertension

Accounts for 90–95% of all cases.

No single cause; instead results from a combination of genetic, environmental, and lifestyle factors.

Major contributors:

Increased sympathetic nervous system (SNS) activity

Impaired pressure-natriuresis (kidneys retain sodium)

Endothelial dysfunction (reduced nitric oxide)

Obesity and insulin resistance

Family history

2. Secondary Hypertension

Occurs due to an underlying, identifiable cause. Suspect when BP is:

1. Severe, resistant to >3 drugs
2. Onset <30years or sudden after 55
3. Associatedwith specific symptoms

what could cause high blood pressure?

1. Renalparenchymal diseases (most common)
2. Renovascularhypertension (RAS)
3. Primary aldosteronism
4. Pheochromocytoma
5. Cushingsyndrome
6. Hypo- or hyperthyroidism
7. Obstructivesleep apnea
8. Coarctationof the aorta
9. Drugs: NSAIDs, oral contraceptives, steroids, decongestants, cocaine

• Pathophysiology of Hypertension

Hypertension results from abnormalities in mechanisms regulating cardiac output and systemic vascular resistance.

1. RAAS Overactivity

Produces angiotensin II, a strong vasoconstrictor.

Stimulates aldosterone → sodium and water retention → ↑ blood volume.

2. Sympathetic Nervous System Activation

Increases heart rate, vasoconstriction, and cardiac output.

Seen in stress, obesity, sleep apnea.

3. Renal Regulation Problems

Kidneys fail to excrete sodium effectively.

Causes expansion of intravascular volume.

4. Endothelial Dysfunction

Reduced nitric oxide availability → vasoconstriction.

5. Vascular Remodeling

Structural changes in arteries increase peripheral resistance.

• Clinical Features

Hypertension is mostly called the “silent killer” because patients often have no symptoms for years.

Some of the blood pressure too high symptoms are:

1. Morningheadaches
2. Dizziness
3. Palpitations
4. Fatigue
5. Epistaxis
6. Blurred vision

Signs of Target Organ Damage

Eyes: Retinopathy (AV nicking, hemorrhages, papilledema)

Heart: Left ventricular hypertrophy (LVH), HF

Brain: Stroke, TIA

Kidneys: Proteinuria, reduced GFR

Peripheral Arteries: Claudication

• Evaluation of a Hypertensive Patient

A structured evaluation helps confirm diagnosis, look for secondary causes, and assess organ damage.

1. BP Measurement

Take ≥2 readings on at least 2 different visits.

Measure in both arms initially.

Ambulatory BP monitoring (ABPM) is preferred for borderline cases.

2. Routine Investigations

Fasting glucose, HbA1c

Lipid profile

Serum creatinine, eGFR

Electrolytes (especially potassium)

Complete blood count

Urinalysis (albumin/protein)

ECG (for LVH)

3. Special Tests (if secondary HTN suspected)

Renal Doppler

Plasma aldosterone–renin ratio

Thyroid function tests

24-hour urinary catecholamines

Cortisol testing

Sleep study (OSA)

• Treatment of Hypertension

Management includes lifestyle changes, drug therapy, and regular follow-up.

1. Lifestyle Modifications

These are essential for all patients, regardless of BP level.

Weight reduction (most impactful)

Regular aerobic exercise

Low-sodium diet (<2 g/day)

DASH diet (fruits, vegetables, low-fat dairy)

Limit alcohol

Quit smoking

Stress management

2. Pharmacologic Therapy

First-Line Drugs

1. ACE Inhibitors

2. Angiotensin Receptor Blockers (ARBs)

3. Calcium Channel Blockers (CCBs)

4. Thiazide Diuretics

These are supported by large outcome trials for reducing:

Stroke

Heart failure

MI

CKD progression

When to Start Medication

BP ≥140/90 in general population

BP ≥130/80 in:

Diabetes

CKD

High CV risk

Second-Line / Add-On Drugs

Beta blockers – useful post-MI, HF, arrhythmia

Aldosterone antagonists – resistant HTN

Alpha blockers – BPH

Vasodilators – hydralazine, minoxidil

Combination Therapy

Often needed when:

Stage 2 hypertension

BP >20/10 mmHg above target

Hypertensive Emergencies

A medical emergency where severely elevated BP is accompanied by acute organ damage.

Examples of Organ Damage are:

Hypertensive encephalopathy

Stroke

Acute LV failure

Aortic dissection

Acute kidney injury

Myocardial ischemia

Management

Admit to ICU

IV medications:

Nicardipine

Labetalol

Nitroprusside (rare now)

Reduce mean arterial pressure by ≤25% in first hour

Avoid rapid or excessive lowering

Long-Term Management

Regular BP monitoring

Annual kidney function tests

Lifestyle reinforcement

Ensure medication adherence

Screen for complications periodically (eyes, ECG, urine protein)

Target BP Goals:

<130/80 mmHg → most patients

Elderly >65 years: SBP 130–139 mmHg (individualized)

Diabetes or CKD: <130/80 mmHg

Conclusion

Hypertension is a chronic but highly manageable disease. Early diagnosis, lifestyle modification, evidence-based pharmacotherapy, and consistent follow-up greatly reduce the risk of cardiovascular and renal complications. Medical students should understand the mechanisms, evaluation protocol, and management strategies to ensure optimal patient care.