Essential Hypertension

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Diagnosis | Management

Definition

Essential hypertension, also known as primary hypertension, is defined as a consistent elevation in blood pressure (BP) of 140/90 mmHg or higher without an identifiable secondary cause. It accounts for the majority of hypertension cases and is often associated with a combination of genetic and lifestyle factors.

Aetiology

While the exact cause of essential hypertension is unknown, several factors are known to contribute to its development:

• Excessive Salt Intake: High sodium intake (>1.5 g/day) can lead to fluid retention, increasing blood pressure.
• Aging: Blood vessels become less elastic and more rigid with age, contributing to increased blood pressure.
• Sedentary Lifestyle: Lack of physical activity is associated with higher blood pressure and increased risk of cardiovascular disease.
• Renal Sodium Retention: Genetic variations in renal sodium handling can lead to fluid retention and hypertension.
• Insulin Resistance: Often associated with metabolic syndrome, insulin resistance can contribute to hypertension.
• High Alcohol Intake: Excessive alcohol consumption can raise blood pressure and contribute to the development of hypertension.
• Obesity: Increased body weight increases the workload on the heart, contributing to hypertension.
• Smoking: Nicotine in cigarettes raises blood pressure and damages blood vessels, leading to hypertension.
• Low Calcium, Magnesium, and Potassium Intake: Deficiencies in these minerals are associated with higher blood pressure.
• Genetics: Family history of hypertension increases the likelihood of developing the condition, suggesting a genetic predisposition.

Pathophysiology

The pathophysiology of essential hypertension involves complex interactions between genetic, environmental, and physiological factors:

• Systemic Vascular Resistance (SVR): Blood pressure is determined by the balance between cardiac output and systemic vascular resistance. An increase in SVR, often due to vascular stiffening or endothelial dysfunction, can lead to hypertension.
• Renin-Angiotensin-Aldosterone System (RAAS): Overactivity of the RAAS leads to vasoconstriction and sodium retention, raising blood pressure.
• Sympathetic Nervous System (SNS): Hyperactivity of the SNS increases heart rate and contractility, contributing to hypertension.
• Arterial Baroreceptors: Dysregulation of baroreceptors, which help regulate blood pressure, may contribute to sustained hypertension.
• Endothelial Dysfunction: Impaired production of vasodilators like nitric oxide can increase vascular resistance and blood pressure.
• Vascular Remodeling: Chronic hypertension leads to structural changes in blood vessels, making them less flexible and more resistant to blood flow.

Risk Factors

Several risk factors are associated with the development of essential hypertension:

• High Salt Intake: Consumption of more than 1.5 g/day of sodium increases the risk of hypertension.
• Obesity and Overweight: Excess body weight is a major risk factor for hypertension.
• Poor Diet and Sedentary Lifestyle: Diets high in fat, sugar, and processed foods, along with lack of exercise, contribute to hypertension.
• Age: The risk of developing hypertension increases with age.
• Ethnicity: Hypertension is more prevalent in individuals of black African or Caribbean descent.
• Medical Conditions: Conditions such as chronic kidney disease (CKD), diabetes, and obstructive sleep apnoea are associated with higher risk of hypertension.

Signs and Symptoms

Essential hypertension is often asymptomatic, earning it the nickname "the silent killer." However, when symptoms do occur, they may include:

• Headache: Often in the morning and located at the back of the head.
• Chest Pain: Can indicate cardiac strain due to high blood pressure.
• Shortness of Breath: Especially on exertion, may indicate heart failure or left ventricular hypertrophy.
• Dizziness: Can occur with severe hypertension or fluctuations in blood pressure.
• Visual Disturbances: Such as blurred vision, which can indicate hypertensive retinopathy.

Investigations

Diagnostic investigations for essential hypertension include:

• Urinalysis: To check for haematuria and assess kidney function.
• Urine Albumin:Creatinine Ratio: To assess for proteinuria, which can indicate kidney damage.
• Blood Tests: Including HbA1c, U&Es (urea and electrolytes), and lipid profile (cholesterol levels).
• Fundoscopy: To check for hypertensive retinopathy, indicating long-standing hypertension.
• 12-Lead ECG: To assess for left ventricular hypertrophy or other cardiac abnormalities.
• Q-Risk Assessment: To evaluate cardiovascular risk. If the risk is 10% or more, consider starting a statin.

Diagnosis

The diagnosis of essential hypertension is confirmed by measuring blood pressure and ruling out secondary causes:

• If clinic blood pressure is between 140/90 mmHg and 180/120 mmHg, arrange 24-hour ambulatory blood pressure monitoring (ABPM) or home blood pressure monitoring (HBPM) to confirm hypertension.
• Classify hypertension into stages based on the following:
  • Stage 1 Hypertension: Home BP ≥135/85 mmHg or ABPM ≥135/85 mmHg.
  • Stage 2 Hypertension: Home BP ≥150/95 mmHg or ABPM ≥150/95 mmHg.
  • Stage 3 Hypertension: Home BP ≥180/120 mmHg or ABPM ≥180/120 mmHg.
• Further investigations should be conducted to assess for end-organ damage or coexisting conditions.

Management

Management of essential hypertension involves lifestyle modifications and pharmacological treatment, following a stepped approach:

1. Lifestyle Modifications

• Encourage weight loss, regular physical activity, a healthy diet (such as the DASH diet), and reduced salt intake.
• Advise smoking cessation and moderation of alcohol consumption.

2. Pharmacological Management

Medications commonly used to manage hypertension include:

• ACE Inhibitors (ACEi): E.g., Ramipril. First-line for patients under 55 years old without diabetes, particularly in non-black populations.
• Angiotensin Receptor Blockers (ARBs): E.g., Losartan. Use if ACE inhibitors are not tolerated (e.g., due to cough).
• Calcium Channel Blockers (CCBs): E.g., Amlodipine. Preferred in patients over 55 years old or those of black African or African-Caribbean descent.
• Thiazide-like Diuretics: E.g., Indapamide. Used if CCBs are not tolerated or as part of combination therapy.
• Beta-blockers: E.g., Bisoprolol. Consider for patients with coexisting conditions such as heart failure or atrial fibrillation.
• Alpha-blockers: E.g., Doxazosin. Used in resistant hypertension or when other medications are not suitable.

3. Stepped Approach to Treatment

Follow the NICE guidelines for a stepped approach to managing hypertension:

• Step 1:
  • Offer an ACEi or ARB if under 55 years old and not of black African or African-Caribbean descent.
  • Offer a CCB if over 55 years old or of black African or African-Caribbean descent.
  • If a CCB is not tolerated, offer a thiazide-like diuretic (e.g., Indapamide).
• Step 2:
  • If BP is not controlled with an ACEi/ARB, add a CCB or thiazide-like diuretic.
  • If BP is not controlled with a CCB, add an ACEi/ARB or thiazide-like diuretic.
• Step 3:
  • If BP is not controlled with two drugs, use a combination of ACEi/ARB + CCB + thiazide-like diuretic.
• Step 4 (Resistant Hypertension):
  • If BP remains uncontrolled, consider adding a fourth antihypertensive, such as a low-dose spironolactone (if potassium is ≤4.5 mmol/L) or an alpha-blocker like doxazosin (if potassium is >4.5 mmol/L).
  • Review patient adherence and consider seeking specialist advice.

References

1. National Institute for Health and Care Excellence (NICE) (2024) Hypertension in adults: diagnosis and management. Available at: https://www.nice.org.uk/guidance/ng136 (Accessed: 26 August 2024).
2. British Hypertension Society (2024) Guidelines for the Management of Hypertension. Available at: https://bhs.org.uk (Accessed: 26 August 2024).
3. British National Formulary (BNF) (2024) Antihypertensive therapy. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).