Essential Hypertension Overview Quiz

Pathology of Hypertension

• Hypertension is a condition of high blood pressure.
• Clinically significant hypertension is diagnosed when diastolic pressure surpasses 80 mmHg or systolic pressure exceeds 120 mmHg.

Outline

• Normal blood pressure homeostasis is a complex process.
• Pathogenic mechanisms underpin hypertension.
• Hypertension-associated changes occur in blood vessels.
• The etiology of secondary hypertension warrants investigation.

HTN, Classification

• Secondary hypertension (10%): This type of high blood pressure results from an identifiable underlying cause. Examples of underlying causes:
  • Adrenal diseases (e.g., primary aldosteronism, Cushing syndrome, pheochromocytoma)
  • Renal diseases, such as renal artery stenosis.
  • Idiopathic (essential) hypertension (90%): In these cases, the underlying cause remains unknown.

Secondary Hypertension

• Renal causes of secondary hypertension: Acute glomerulonephritis, Chronic renal disease, Polycystic disease, Renal artery stenosis, Renal vasculitis, Renin-producing tumors
• Endocrine causes of secondary hypertension: Adrenocortical hyperfunction (Cushing syndrome, primary aldosteronism, congenital adrenal hyperplasia, licorice ingestion), Exogenous hormones (glucocorticoids, estrogen, sympathomimetics, tyramine-containing foods), Pheochromocytoma, Acromegaly, Hyperthyroidism (thyrotoxicosis), Pregnancy-induced hypertension (preeclampsia)
• Cardiovascular causes: Coarctation of the aorta, Polyarteritis nodosa, Increased intravascular volume, Increased cardiac output, Rigidity of the aorta
• Neurologic causes: Psychogenic, Increased intracranial pressure, Sleep apnea, Acute stress, including surgery

Hypertension Complications

• Hypertension raises the risk for various complications, including:
  • Atherosclerosis
  • Cardiac hypertrophy
  • Heart failure (hypertensive heart disease)
  • Multi-infarct dementia
  • Aortic dissection
  • Renal failure
• Severe hypertension, sometimes, can remain clinically silent for a long duration.

Malignant Hypertension

• About 5% of hypertensive persons experience a rapid rise in blood pressure. If untreated, this can lead to death within 1 to 2 years. Characteristics include:
  • Severe pressure elevations (systolic pressure > 200 mm Hg, diastolic pressure > 120 mm Hg)
  • Renal failure
  • Retinal hemorrhages and exudates

Blood Pressure Regulation

• Blood pressure is influenced by several factors:
  • Blood volume
  • Cardiac output
  • Peripheral resistance
  • Local factors (autoregulation, pH, hypoxia)

Cardiac Output

• Cardiac output is a function of
  • Stroke volume
  • Heart rate
• Sodium homeostasis is key to regulating filling pressure, a crucial component of stroke volume

Peripheral Resistance

• Peripheral resistance is controlled primarily at the level of the arterioles via neural and hormonal input.
  • A balance exists between vasoconstrictors (e.g., angiotensin II, catecholamines, endothelin) and vasodilators (e.g., kinins, prostaglandins, NO).
• Autoregulation of resistance vessels helps maintain blood flow.
• Tissue pH and hypoxia also contribute to regulating blood pressure.

Renin

• Renin, a proteolytic enzyme, is produced by juxtaglomerular cells in the kidneys.
• Renin's release is triggered by low blood pressure, elevated catecholamines, and low sodium levels.
• Renin activates the RAAS (renin-angiotensin-aldosterone system).

Renin - RAAS System

• Renin cleaves angiotensinogen to angiotensin I.
• Angiotensin I is converted to angiotensin II by ACE.
• Angiotensin II's roles include:
  • Inducing vascular contraction
  • Stimulating aldosterone secretion
  • Increasing tubular sodium resorption

Adrenal Glands

• Aldosterone plays a critical role in regulating blood pressure by increasing sodium reabsorption in the distal convoluted tubules.
• This process leads to increased blood volume and ultimately, elevated blood pressure.

Other Factors

• Kidneys also release factors (prostaglandins, NO) that counteract the vasoconstrictive effects of angiotensin.

Myocardial Natriuretic Peptides

• Myocardial natriuretic peptide (ANP) is released in response to elevated blood volume, contributing to sodium excretion and diuresis. ANP also causes systemic vasodilation.

Key Concepts, Blood Pressure Regulation

• Hypertension's causes and regulation involve multiple complex factors at play.

Mechanisms of Secondary Hypertension

• Renovascular hypertension: Renal artery stenosis interferes with normal glomerular flow. Resulting in renin release, and a cascade of events leading to blood pressure elevation, and increased vascular tone.
• Primary hyperaldosteronism: Autonomous secretion of aldosterone by adrenal glands directly results in hypertension and the suppression of the renin-angiotensin system.
• Single-gene disorders: Some genetic mutations interfere with aldosterone metabolism and blood pressure regulation

Primary Hyperaldosteronism

• Conditions with chronic excess aldosterone secretion leads to hypertension and suppression of the renin-angiotensin system.
  • Bilateral idiopathic hyperaldosteronism
  • Adrenocortical neoplasm
  • Familial hyperaldosteronism
• Secondary to other conditions: decreased renal perfusion (e.g., renal artery stenosis), arterial hypovolemia, or pregnancy.

Essential Hypertension, Mechanisms

• Genetic and environmental factors interact.
• Numerous complex elements are implicated in essential hypertension's etiology.

Essential Hypertension, Genetic Factors

• There is evidence that genetics play a role in hypertension.

Essential Hypertension, Insufficient Renal Sodium Excretion

• Insufficient renal sodium excretion is implicated in essential hypertension's pathogenesis. Normal arterial pressure also leads to insufficient sodium excretion. This influences blood volume, cardiac output, and peripheral vasoconstriction.
• At higher blood pressures, kidneys adjust to the new steady state of balance.

Essential Hypertension, Vasoconstrictive Influences

• Factors leading to vasoconstriction and structural changes in vessel walls elevate peripheral resistance, and contribute to essential hypertension.

Essential Hypertension, Environmental Factors

• Environmental factors implicated in hypertension include:
  • Stress
  • Obesity
  • Smoking
  • Physical inactivity
  • Heavy salt consumption

Vascular Pathology in Hypertension

• Hypertension causes degenerative changes in arteries and can lead to:
• Aortic dissection
• Cerebrovascular hemorrhage

Hypertension-related small vessel disease

• Three forms are associated with hypertension:
  • Hyaline arteriolosclerosis
  • Hyperplastic arteriolosclerosis
  • Pulmonary hypertension

Vascular Pathology in Hypertension, Hyaline Arteriolosclerosis

• Characterized by homogeneous pink hyaline thickening and narrowing of arteriolar lumens.
• Implicated causes are plasma protein leakage, increased synthesis of extracellular matrix by vascular smooth muscle cells.
• Elderly also exhibit this type of pathology less severely. Chronic hypertension contributes to this arterial damage.

Hyaline Arteriolosclerosis

• Arteriolar walls thicken due to protein deposition, leading to lumen narrowing.

Vascular Pathology in Hypertension, Hyperplastic Arteriolosclerosis

• Thickening of arteriolar walls forms concentric laminated layers.
• Seen in severe hypertension, often accompanied by fibrinoid deposits.

Hyperplastic Arteriolosclerosis

• Onion-skinning of arteriolar walls and lumen obliteration, caused by proliferation of smooth muscle cells.

Pulmonary Hypertension

• Fibrosis of the intima.
• Hypertension involves affected pulmonary vessels, thickened and showing fibrotic intimal thickening of their walls.
• Common causes include left heart failure, congenital valve disorders, and lung conditions.

Hypertension, Key Concepts

• Hypertension is a significant health problem impacting many adults.
• This condition is a major risk factor for many diseases, including heart disease, heart failure, and renal failure.
• The underlying causes and mechanisms of essential hypertension are complex and multifactorial.
• The interaction of genetic and environmental factors is key.

Hypertension, Key Concepts

• Sustained hypertension involves participation of the kidney.
• In hypertension, increased blood volume, and greater peripheral resistance, both contribute to the elevated blood pressure.
• Histological changes (thickened arterial walls, hyaline deposits) are associated with hypertension in various degrees.

Test your knowledge on essential hypertension with this quiz that covers significant initiating events, genetic contributions, and the role of environmental factors. Explore complications, kidney function impacts, and the nature of small vessel disease related to hypertension.