Hypertension pathophysiology

Hypertension, commonly known as high blood pressure, is a condition in which the force of the blood against the artery walls is consistently too high. Blood pressure is measured in millimeters of mercury (mm Hg) and consists of two numbers: systolic pressure (the pressure when the heart beats) and diastolic pressure (the pressure when the heart rests between beats). A normal blood pressure reading is usually around 120/80 mm Hg. Hypertension is typically defined as blood pressure consistently at or above 130/80 mm Hg.

Photo by National Cancer Institute on Unsplash

Pathophysiology of Hypertension

The pathophysiology of hypertension is complex and involves multiple mechanisms, including:

1. Genetic Factors: Family history and genetic predisposition play a significant role in the development of hypertension.

2. Environmental Factors: Diet (high salt intake), lack of physical activity, obesity, and stress are significant contributors.

3. Renal Mechanisms: The kidneys play a crucial role in regulating blood pressure by controlling fluid balance and sodium levels. Dysregulation can lead to hypertension.

4. Sympathetic Nervous System: Overactivity of the sympathetic nervous system can lead to increased heart rate and vasoconstriction, raising blood pressure.

5. Renin-Angiotensin-Aldosterone System (RAAS): This hormonal system regulates blood pressure and fluid balance. Overactivation can cause vasoconstriction and sodium retention, contributing to hypertension.

6. Vascular Mechanisms: Endothelial dysfunction and increased arterial stiffness can increase vascular resistance and blood pressure.

7. Hormonal Factors: Hormones such as aldosterone and antidiuretic hormone (ADH) can influence blood pressure by affecting fluid retention and vascular tone.

Rational Use of Drugs in the Treatment of Hypertension

The primary goal in the treatment of hypertension is to reduce blood pressure to a safe level to prevent complications such as heart disease, stroke, and kidney damage. The choice of medication depends on various factors, including the severity of hypertension, the presence of comorbid conditions, and patient-specific factors. Common classes of antihypertensive drugs include:

1. Diuretics: Help the kidneys remove excess sodium and water, reducing blood volume and blood pressure. Examples include thiazide diuretics (hydrochlorothiazide) and loop diuretics (furosemide).

2. ACE Inhibitors (ACEIs): Block the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. This leads to vasodilation and reduced blood pressure. Examples include enalapril and lisinopril.

3. Angiotensin II Receptor Blockers (ARBs): Block the action of angiotensin II, leading to vasodilation and decreased blood pressure. Examples include losartan and valsartan.

4. Calcium Channel Blockers (CCBs): Inhibit the entry of calcium into vascular smooth muscle and cardiac cells, causing vasodilation and reduced heart rate. Examples include amlodipine and verapamil.

5. Beta-Blockers: Decrease heart rate and cardiac output by blocking the effects of adrenaline on the beta receptors. Examples include metoprolol and atenolol.

6. Alpha-Blockers: Reduce vascular resistance by blocking alpha-adrenergic receptors in the blood vessels. Examples include prazosin and doxazosin.

7. Aldosterone Antagonists: Block the effects of aldosterone, leading to reduced sodium retention and lower blood pressure. Examples include spironolactone and eplerenone.

8. Renin Inhibitors: Directly inhibit renin, an enzyme involved in the production of angiotensin II. An example is aliskiren.

Combination Therapy

In many cases, combination therapy with two or more antihypertensive drugs from different classes may be required to achieve optimal blood pressure control. This approach can also minimize the adverse effects associated with higher doses of a single drug.

Lifestyle Modifications

In addition to pharmacotherapy, lifestyle modifications are crucial in managing hypertension. These include dietary changes (reducing salt intake, increasing potassium intake), regular physical activity, weight loss, moderation of alcohol intake, and smoking cessation.

Overall, the management of hypertension involves a comprehensive approach, integrating pharmacological treatment with lifestyle modifications to achieve and maintain blood pressure control, thereby reducing the risk of cardiovascular complications.