Lecture 13 Flashcards
Characteristics of Hypertension
Increased cardiac output
Increased sympathetic nerve activity
Increase in angiotensin II and aldosterone levels
Impairment of renal-pressure natriuresis mechanism
Inadequate secretion of salt and water
Primary Hypertension (Essential Hypertension)
Hypertension of unknown origin; represents 90-95% of hypertension; caused by:
Weight gain, resulting in - increased cardiac output, increased sympathetic nerve activity, increased angiotensin II and aldosterone levels, and impaired renal-pressure natriuresis mechanism
Sedentary life style
Secondary Hypertension
Hypertension second to some other cause, such as:
Tumor affecting renin-secreting juxtaglomerular cells, renal artery constriction, coarctation of the aorta, preeclampsia, neurogenic hypertension, genetic causes
Factors Contributing to Hypertension
Genetic factors, other single-gene disorders that alter sodium reabsorption by the kidneys, genetic variants in the renin-angiotensin system, stress, obesity, smoking, physical inactivity, heavy consumption of salt
Factors that Decrease Peripheral Resistance (Vessel Dilation) leading to Decreased Blood Pressure
Increased production of nitric oxide
Increased release of prostacyclin
Increased release of kinins
Increase in atrionatriuretic peptide (ANP)
Decreased neural factors (beta-adrenergic)
Factors that Decrease Cardiac Output leading to Decreased Blood Pressure
Decreased blood volume
Decreased heart rate
Decreased contractility
Factors that Increase Cardiac Output leading to Increased Blood Pressure
Increased heart rate
Increased contraction
Increased blood volume (due to aldosterone)
Factors that Increase Peripheral Resistance leading to Increased Blood Pressure
Increased angiotensin II
Increased catecholamines
Increased thromboxane
Increased neural factors (alpha-adrenergic)
Renal Causes of Hypertension
Chronic renal disease Renal artery stenosis Renin-producing tumors Acute glomerulonephritis Polycystic disease Renal vasculitis
Endocrine Causes of Hypertension
Cushing syndrome (adrenocortical hyperfunction), exogenous hormones (glucocorticoids, estrogen), pheochromocytoma, acromegaly, hypothyroidism (myxedema), hyperthyroidism (thyrotoxicosis), pregnancy induced
Cardiovascular Causes of Hypertension
Coarctation of the aorta, polyarteritis nodosa, increased intravascular volume, rigidity of the aorta, increased cardiac output
Neurologic Causes of Hypertension
Psychogenic, increased intracranial pressure, sleep apnea, acute stress
Lethal Effects of Chronic Hypertension
Early heart failure and coronary artery disease, cerebral infarct, kidney failure
Atherosclerosis
Type of arteriosclerosis; major characteristic of atherosclerosis is the presence of lesions within the intima of the vessel wall that protrude into the vessel lumen
Non-Modifiable Risk Factors for Atherosclerosis
Age (risk increases between ages of 40-60; death rates from ischemic heart disease increase with each decade); gender (uncommon in premenopausal women without other risk factors; increases after menopause and eventually exceeds that of men); Genetics (some mendelian disorders associated with atherosclerosis but mostly multifactorial)
Modifiable Risk Factors for Atherosclerosis
Hyperlipidemia/Hypercholesterolemia (major risk factor, correlated with high levels of LDL as opposed to HDL); Hypertension (increases risk of IHD by 60%, most important cause of left ventricular hypertrophy); Cigarette smoking, Diabetes
LDL vs HDL
LDL carries cholesterol to peripheral tissues
HDL carries cholesterol to liver
Hyperhomocystinemia
Inborn error of metabolism; associated with premature vascular disease
Enodthelial Dysfunction/Injury
Results in intimal thickening and may lead to formation of atheroma in presence of hyperlipidemia
Factors Related to Endothelial Dysfunction
Hypertension, hyperlipidemia, cigarette smoke, homocysteine, infectious agents, hemodynamic disturbances, hypercholesterolemia
Smooth Muscle Proliferation
Intimal smooth muscle cell proliferation and extracellular matrix deposition converts a fatty streak into a mature atheroma
Atheroma
Consists of a cap of smooth muscle cells, macrophages, foam cells (converted macrophages), and other extracellular components, overlying a necrotic center composed of cell debris, cholesterol, foam cells, and calcium
Common Arterial Sites for Atherosclerosis
Lower abdominal aorta, coronary arteries, popliteal arteries, internal carotid arteries, Circle of Willis
Short Term Control of Arterial Pressure
Via sympathetic nervous system effects on total peripheral vascular resistance and capacitance and cardiac pumping ability
Long Term Control of Arterial Pressure
Via multiple nervous and hormonal controls and via local controls in kidney that regulate salt and water excretion
Pressure Diuresis
Arterial pressure increases which leads to an increase in urine output
Pressure Natriuresis
Arterial pressure increases which leads to an increase in sodium output
Chronic Hypertension
One’s mean arterial pressure is greater than the upper range of the accepted normal measure
Normal BP
90 mm Hg (110/70)
Hypertensive BP
110 mm Hg (135/90)
Severe Hypertensive BP
150-170 mm Hg (250/130)
Lethal Effects of Chronic Hypertension
Early heart failure, coronary heart disease, heart attack, cerebral infarct, destruction of areas of kidney which leads to kidney failure which leads to uremia which leads to death
