HYPERTENSION (HIGH BLOOD PRESSURE)

 

HYPERTENSION (HIGH BLOOD PRESSURE)

Introduction

Hypertension (HTN) or high blood pressure is a chronic cardiovascular disorder in which the arterial blood pressure remains persistently elevated above normal values. It is one of the most important risk factors for heart disease, stroke, kidney failure, and premature death worldwide.

Hypertension is often called the “Silent Killer” because most patients remain asymptomatic for years until serious organ damage develops.

Definition of Blood Pressure

Blood pressure (BP) is the pressure exerted by circulating blood on the walls of arteries. It is measured in millimeters of mercury (mmHg).

Components of Blood Pressure

1. Systolic Blood Pressure (SBP)

• Pressure during ventricular contraction (systole)
• Normal value ≈ 120 mmHg

2. Diastolic Blood Pressure (DBP)

• Pressure during ventricular relaxation (diastole)
• Normal value ≈ 80 mmHg

Normal BP: 120/80 mmHg

Definition of Hypertension

Hypertension is generally defined as: BP ≥140/90 mmHg

Traditional definition commonly uses ≥140/90 mmHg. Recent ACC/AHA guidelines define hypertension beginning at:  SBP ≥130 mmHg or DBP ≥80 mmHg

Classification of Hypertension

Category	Systolic BP	Diastolic BP
Normal	<120	<80
Elevated BP	120–129	<80
Stage 1 HTN	130–139	80–89
Stage 2 HTN	≥140	≥90
Hypertensive Crisis	≥180	≥120

Types of Hypertension

1. Primary (Essential) Hypertension

• No identifiable cause
• Accounts for 90–95% cases
• Multifactorial origin

Causes/Risk Factors

• Genetic predisposition
• Obesity
• Excess salt intake
• Stress
• Smoking
• Alcohol
• Sedentary lifestyle

2. Secondary Hypertension

Occurs due to an identifiable disease.

Causes

Renal Causes

• Chronic kidney disease
• Renal artery stenosis

Endocrine Causes

• Hyperthyroidism
• Cushing syndrome
• Pheochromocytoma
• Hyperaldosteronism

Cardiovascular Causes

• Coarctation of aorta

Drug-Induced

• Oral contraceptives
• Steroids
• NSAIDs
• Cocaine

Physiological Basis of Blood Pressure

Blood pressure depends mainly on:

BP=Cardiac Output × Peripheral Resistance

Where:

• Cardiac Output (CO) = amount of blood pumped by heart/min
• Peripheral Resistance = resistance offered by blood vessels

Pathophysiology of Hypertension

Major Mechanisms

1. Increased Cardiac Output

Occurs due to:

• Increased sympathetic activity
• Increased blood volume

2. Increased Peripheral Resistance

Due to:

• Vasoconstriction
• Narrowing of arterioles

3. Renin-Angiotensin-Aldosterone System (RAAS)

Important mechanism in hypertension.

Mechanism

Step 1

Kidney releases Renin

Step 2

Renin converts angiotensinogen → Angiotensin I

Step 3

ACE converts Angiotensin I → Angiotensin II

Step 4

Angiotensin II causes:

• Vasoconstriction
• Aldosterone secretion

Step 5

Aldosterone increases:

• Sodium retention
• Water retention

Result:

• Increased blood volume
• Increased BP

Role of Sympathetic Nervous System

Overactivity causes:

• Increased heart rate
• Increased vasoconstriction
• Increased cardiac output

Result:

• Persistent hypertension

Risk Factors of Hypertension

Non-Modifiable Risk Factors

• Age
• Family history
• Genetics
• Male sex

Modifiable Risk Factors

• Obesity
• High salt intake
• Smoking
• Alcohol
• Physical inactivity
• Stress
• Diabetes mellitus
• Hyperlipidemia

Obesity and Hypertension

Obesity increases BP by:

• Increasing cardiac workload
• Increasing sympathetic activity
• Increasing insulin resistance

Important Fact

Abdominal obesity has strong association with hypertension.

Salt and Hypertension

Excess sodium intake:

• Causes water retention
• Increases blood volume
• Raises arterial pressure

WHO recommends limiting salt intake to: <5 g/day

Symptoms of Hypertension

Most patients are asymptomatic.

Common Symptoms

• Headache
• Dizziness
• Fatigue
• Palpitations
• Blurred vision

Severe Hypertension

• Chest pain
• Breathlessness
• Neurological symptoms

Why Is Hypertension Called A “Silent Killer”?

Because:

• Usually no symptoms initially
• Organ damage occurs silently
• First presentation may be:
• Stroke
• Heart attack
• Kidney failure

Target Organ Damage

1. Heart

Left Ventricular Hypertrophy (LVH)

Heart pumps against high resistance → muscle thickening.

Coronary Artery Disease

Can cause:

• Angina
• Myocardial infarction

Heart Failure

Long-standing HTN weakens heart.

2. Brain

Stroke

Most dangerous complication.

Types:

• Hemorrhagic stroke
• Ischemic stroke

Hypertensive Encephalopathy

Severe HTN causing brain dysfunction.

3. Kidney

Nephrosclerosis

Damage to renal blood vessels.

Chronic Kidney Disease (CKD)

4. Eyes

Hypertensive Retinopathy

Findings:

• Arteriolar narrowing
• Hemorrhages
• Exudates
• Papilledema

Hypertensive Crisis

Severe elevation in BP: BP≥180/120 mmHg

Two types:

1. Hypertensive Urgency

• Severe BP elevation
• No organ damage

2. Hypertensive Emergency

• Severe BP elevation
• Organ damage present

Medical emergency requiring immediate treatment.

Diagnosis of Hypertension

Blood Pressure Measurement

Measured using:

• Sphygmomanometer

Methods

• Mercury sphygmomanometer
• Aneroid apparatus
• Digital BP monitor

Rules for BP Measurement

• Patient relaxed
• Seated comfortably
• Avoid caffeine/smoking before test
• Arm at heart level
• Multiple readings required

Investigations In Hypertension

Blood Tests

• Blood glucose
• Lipid profile
• Kidney function tests

Urine Examination

• Proteinuria

ECG

• Left ventricular hypertrophy

Echocardiography

• Cardiac changes

Fundoscopy

• Retinal damage

Management of Hypertension

A. Non-Pharmacological Management

Lifestyle Modifications

1. Weight Reduction

Most effective lifestyle intervention.

2. Reduced Salt Intake

Less sodium → lower BP.

3. Exercise

At least 30 min/day.

4. DASH Diet

Diet rich in:

• Fruits
• Vegetables
• Whole grains

Low in:

• Saturated fats

5. Stop Smoking

6. Limit Alcohol Intake

7. Stress Reduction

B. Pharmacological Management

Major Drug Classes

Drug Class	Example	Mechanism
Diuretics	Hydrochlorothiazide	Reduce blood volume
ACE inhibitors	Enalapril	Block Angiotensin II formation
ARBs	Losartan	Block Angiotensin II receptor
Beta blockers	Atenolol	Reduce heart rate
Calcium channel blockers	Amlodipine	Vasodilation

 

ACE Inhibitors

Mechanism

Prevent: Angiotensin I → Angiotensin II

Effects:

• Vasodilation
• Reduced aldosterone
• Lower BP

Examples:

• Enalapril
• Ramipril

Beta Blockers

Action

• Decrease heart rate
• Decrease cardiac output

Examples:

• Atenolol
• Metoprolol

Calcium Channel Blockers

Prevent calcium entry into vascular smooth muscle.

Result:

• Vasodilation
• Reduced BP

Examples:

• Amlodipine
• Nifedipine

Prevention of Hypertension

Primary Prevention

• Healthy diet
• Exercise
• Weight control
• Avoid smoking

Secondary Prevention

• Early diagnosis
• Proper treatment
• Regular monitoring

Complications of Untreated Hypertension

Cardiovascular

• Heart attack
• Heart failure
• Aneurysm

Neurological

• Stroke
• Dementia

Renal

• Renal failure

Ophthalmic

• Blindness

 

Important Terms

Term	Meaning
Normotension	Normal BP
Hypertension	High BP
Hypotension	Low BP
Systolic pressure	Pressure during contraction
Diastolic pressure	Pressure during relaxation
Pulse pressure	SBP − DBP
Mean arterial pressure	Average arterial pressure

Pulse Pressure

Pulse Pressure=Systolic BP−Diastolic BP

Example: 120 - 80 = 40 mmHg

Normal pulse pressure ≈ 40 mmHg.

Mean Arterial Pressure (MAP)

MAP=DBP+​(SBP−DBP)

Hypertension In Young VS Old

Young	Elderly
Often secondary HTN	Usually essential HTN
Sympathetic overactivity	Arterial stiffness
Diastolic HTN common	Isolated systolic HTN common

Isolated Systolic Hypertension

Definition:

• High systolic BP
• Normal diastolic BP

Common in elderly due to:

• Reduced arterial elasticity

Malignant Hypertension

Severe rapidly progressive hypertension associated with:

• Retinal hemorrhage
• Papilledema
• Renal failure

Medical emergency.

Hypertension and Kidney

Kidneys both:

• Cause hypertension
• Are damaged by hypertension

Important relation:

• RAAS activation
• Sodium retention
• Reduced renal perfusion

Hypertension and Stroke

Hypertension is the most important modifiable risk factor for stroke.

Can cause:

• Cerebral hemorrhage
• Cerebral infarction

Important Facts

Remember Values

Parameter	Value
Normal BP	120/80 mmHg
Hypertension	≥140/90 mmHg
Hypertensive crisis	≥180/120 mmHg
Normal pulse pressure	40 mmHg
Normal MAP	~93 mmHg

Flowchart Summary

Pathogenesis of Hypertension

Genetic factors + Lifestyle factors
↓
↑ Sympathetic activity + ↑ RAAS
↓
↑ Vasoconstriction + ↑ Blood volume
↓
↑ Peripheral resistance
↓
Persistent hypertension
↓
Target organ damage

Quick Revision Table

Topic	Key Point
Hypertension	BP ≥140/90 mmHg
Silent killer	Usually asymptomatic
Most common type	Essential HTN
RAAS role	Vasoconstriction + Na retention
Major complications	Stroke, MI, CKD
Diagnosis	Repeated BP readings
Best prevention	Lifestyle modification
Severe HTN	≥180/120 mmHg

One-Line Exam Pearls

• Hypertension is the leading preventable cardiovascular risk factor.
• Most hypertension cases are primary/essential.
• Long-standing hypertension damages heart, kidneys, brain, and retina.
• RAAS plays a major role in BP regulation.
• Salt restriction is important in BP control.
• ACE inhibitors block Angiotensin II formation.
• Hypertension may remain asymptomatic for years.
• Isolated systolic hypertension is common in elderly.

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