Hypertension (High Blood Pressure) – Types, Causes, and Effects

3 Types of Hypertension:

1. Primary (Essential) Hypertension:
   • Most common (90-95% of cases).
   • Cause is unknown (idiopathic).
   • Defined as consistent blood pressure >140/90 mm Hg in adults.
   • Usually asymptomatic, detected via routine blood pressure measurements.
   • Mechanism: Excessive vasoconstriction, leading to increased systemic resistance and high blood pressure.
2. Secondary Hypertension:
   • Caused by identifiable conditions (e.g., kidney disease, endocrine disorders).
     • Kidney disease:
       • Overproduction of renin leads to excessive vasoconstriction and fluid retention.
     • Endocrine disorders:
       • Excess epinephrine and norepinephrine from tumors (e.g., pheochromocytoma) promote systemic vasoconstriction.
       • These signals increase blood pressure by increasing vascular tone and blood volume.
3. Malignant Hypertension:
   • Severe, resistant to treatment, rapidly progressive.
   • Often associated with organ damage.

Pathophysiology & Cycle:

• Vasoconstriction:
  • Main cause of increased resistance and hypertension.
  • Damages endothelial tissue: promotes sclerosis and loss of elasticity.
• Kidney response:
  • Reduced blood flow causes kidneys to secrete renin.
  • Initiates renin-angiotensin-aldosterone system (RAAS).
  • Angiotensin II: Vasoconstricts, raising resistance.
  • Aldosterone and ADH: Increase salt and water retention, increasing blood volume and BP.
  • This forms a vicious cycle increasing hypertension.

Effects of Chronic Hypertension:

• Damage to arterial walls, sclerosis, and loss of elastic fibers.
• Increased risk of aneurysm (bulging and thinning of vessel walls).
• First signs: Often appear in retinal blood vessels, as seen in eye exams.
• Retinal changes:
  • Aneurysms, cotton-wool spots (lipid deposits).
  • Hemorrhages from ruptured fragile vessels.
  • Impaired vision due to nerve damage and ischemia.

Systemic Effects:

• Tissues like the brain and kidneys are highly sensitive to ischemia.
• Vessel damage can lead to organ dysfunction, necrosis, or stroke.
• Vision loss from retinal vessel damage is common and irreversible.

Pathophysiology:

• Elevated vasoconstriction results in high systemic resistance.
• Kidney response:
  • Detects poor blood flow: secretes renin.
  • Renin activates angiotensinogen to angiotensin I, which converts to angiotensin II (potent vasoconstrictor).
  • Aldosterone and ADH are released:
    • Increase salt and water retention, expanding blood volume.
  • Increased plasma volume and vasoconstriction raise blood pressure further.
• Vicious cycle:
  • Higher pressure causes vascular damage, leading to atherosclerosis and aneurysm formation.
  • Damaged vessels (brain, retina, kidneys) become leaky, leading to edema, hypertension, and organ damage.

Common Effects of Hypertension (on Eyes, Kidneys, Heart):

• Eyes:
  • Causes retinopathy, with hypertensive changes visible in the retina.
  • Features include aneurysms, bleeding, and nerve rupture.
• Kidneys:
  • Hypertension causes damage to capillaries and nephrons.
  • Reduced blood flow leads to renal ischemia, impairing kidney function.
• Heart:
  • Increased workload leads to angina and potential myocardial infarction.
  • Accelerates atherosclerosis and can cause left-sided heart failure.

Signs and Symptoms:

• Cerebral effects:
  • Intracranial pressure rise causes headache, visual disturbances, brain ischemia, and hemorrhages.
  • Retinal changes: hyperperfusion damages retinal veins, causing papilledema, hemorrhages, and vision loss.
• Brain: Potential encephalopathy and cerebral edema.
• Heart: Increased workload leads to left-sided congestive heart failure.
• Kidneys: Damage to renal vessels can cause renal failure.

Relationship Between Diabetes and Hypertension:

• Diabetes mellitus:
  • High blood sugar damages blood vessel walls.
  • Damaged vessels become narrowed and constricted.
  • This vascular damage can lead to hypertension.
• Risks for diabetics:
  • Elevated risk of developing hypertension and atherosclerosis.
  • Leads to damage in vital organs such as kidneys and eyes.

Consequences of Uncontrolled Hypertension:

• Aneurysm formation, stroke, organ ischemia, and heart failure.
• Vicious cycle: Elevated blood pressure damages vessels, which leads to more hypertension, worsening organ damage.

Summary:

Chronic hypertension results from increased vasoconstriction, causing pressure damage and tissue ischemia, especially in the retina, brain, and kidney. It predisposes to aneurysm formation, organ infarction, and microvascular damage, emphasizing the importance of early detection and management to prevent life-threatening complications.

Secondary hypertension mainly results from kidney or endocrine disorders. It involves a self-perpetuating cycle of vasoconstriction, fluid retention, and vascular damage, affecting brain, eyes, heart, and kidneys. Early detection and management are critical to prevent severe organ damage, hemorrhages, and life-threatening complications.

Hypertension linked to diabetes damages blood vessels, accelerating atherosclerosis and increasing the risk of aneurysm formation, especially in the aorta. Aneurysms are often silent until rupture, which is life-threatening. Early diagnosis, lifestyle management, and surgical repair are vital to prevent catastrophic outcomes.