Clinical epidemiology and Clinical epidemiology and consequences of having consequences of having high blood pressurehigh blood pressure

Ivo Ricardo de Seabra Rodrigues DiasIvo Ricardo de Seabra Rodrigues Dias

What is hypertension?

• Hypertension (HT), or high blood pressure, is a condition in which blood pressure is persistently elevated, that is, it maintains itself at high levels during a long period of time

• NOT to be confused with elevated blood pressure just after a stressful situation or exercise, for example

Hypertension (HT) facts I• Higher incidence of HT in Western

society• According to the Blood Pressure

Association, as blood pressure rises with age, about half of all people over the age of 75 and about one quarter of all middle-aged people have HT

• 41% of men and 33% of women in the UK suffer from HT; almost 80% of these men and 70% of these women are NOT GETTING TREATMENT

Hypertension (HT) facts II• Doctors call HT the silent killer because

it can exist with no obvious symptoms• Undiagnosed HT leads to potentially life-

threatening health problems• You’re most likely to develop HT after

age 30• In the absence of high blood pressure

symptoms, HT is diagnosed based on several blood pressure readings taken over a period of time

Blood pressure table for HT

110 and above180 and aboveStage 3 HT

100-109160-179Stage 2 HT

90-99140-159Stage 1 HT

85-89130-139High normal

Less than 85Less than 130Normal

Less than 80Less than 120Optimal

Diastolic BP (mmHG)

Systolic BP (mmHG)Category

Two main types of HT

• Essential HT – 95% of individuals with HT suffer from this form; it is of unknown origin

• Secondary HT – 5% of individuals with HT suffer from this; it is called secondary HT because it has at its origin usually a physical cause

Secondary HT I• Volume-loading HT – caused by excess

accumulation of extracellular fluid in the body– HT caused by Primary Aldosteronism

• caused by excess aldosterone or other types of steroids in the body; Primary Aldosteronism is a small tumor in one of the adrenal glands that causes the secretion of large quantities of aldosterone, which in turn increases the rate of salt and water reabsorption thereby increasing the extracellular fluid volume

Secondary HT II• Types of HT in which Angiotensin is involved– Hypertension caused by a Renin-Secretin Tumor or by Infusion of Angiotensin II• Sometimes a tumor of the renin-secretin juxtaglomerular cells occurs that secretes enormous amounts of renin, which, in turn, equals large amounts of angiotensin II

– “One-Kidney” Goldblatt HT• One kidney is removed and a constrictor is placed

on the renal artery of the remaining kidney; this triggers renin release

• Named after Dr. Goldblatt

Secondary HT III– “Two-Kidney” Goldblatt HT

• When the artery to one kidney is constricted while the artery to the other kidney is normal, the constricted kidney retains salt and water because of decreased renal arterial pressure and the normal kidney retains salt and water because of renin produced by the ischemic kidney; both kidneys become salt and water retainers

– HT caused by diseased kidneys that secrete renin chronically• Patchy areas of one or both kidneys are diseased

and become ischemic because of local vascular constrictions; similar to two-kidney Goldblatt HT

Secondary HT IV• Other types of HT caused by combinations of volume-loading and vasoconstriction– HT in the upper part of the body caused by coarctation of the aorta• When this occurs, blood flow to the lower body is

carried by multiple small collateral arteries in the body wall, with much vascular resistance between the upper aorta and the lower aorta thus having an arterial pressure in the upper part of the body that is about 55% higher than that in the lower body

Secondary HT V– HT in Toxemia of Pregnancy

• HT is one of the manifestations of the syndrome toxemia of pregnancy; it is believed there is a thickening of the kidney glomerular membranes, which reduces the rate of fluid filtration; to resume the normal filtration rate, the arterial pressure level must be increased

– Neurogenic HT• Acute HT can be caused by strong stimulation of

the sympathetic nervous system (ex. stress, anxiety); when the sympathetic system becomes excessively stimulated, peripheral vasoconstriction occurs everywhere in the body

Secondary HT VI• Malignant HT

– Occurs when a sudden and dangerously high rise in blood pressure occurs

– Symptoms: chest pain, blurred vision, headaches, numbness, seizures, sudden confusion

– This disorder can be life threatening, as multiple organs can be damaged by the sudden rise in pressure

– Usually strikes people with previous histories of HT, particularly secondary HT due to kidney diseases

Secondary HT VII• Pulmonary HT

– Often caused by heart and lung diseases but can occur due to HIV infection or intravenous drug use

– High blood pressure only in the arteries that enter the lungs while the rest of the body is at normal or even low blood pressure

• Portal HT– Caused by liver disease (ex. cirrhosis)– Creates varicose veins at the upper part of

the stomach, which can rupture

Essential HT I• Contributors to HT:

– Excessive weight– Lack of physical activity– Excessive salt intake– Diets high in fat and cholesterol– Alcohol consumption– Smoking– Stress– Genetics– Race (ex. African-Americans suffer more from HT

than white Americans)– Gender (males are more likely to develop HT)

Essential HT II• Many of the risk factors vary from individual

to individual (ex. some people thrive under stress levels that cripple others)

• Some characteristics of severe essential HT:1. The mean arterial pressure is increased 40% to 60%2. In the late, more severe stages, the renal blood flow is

decreased to about one half normal3. Resistance to blood flow through the kidneys is increased

twofold to fourfold4. Despite the decrease in renal blood flow, the glomerular

filtration rate is often near normal5. The cardiac output is about normal6. Total peripheral resistance is increased about 40% to 60%7. Kidneys will not excrete adequate amounts of salt and

water unless arterial pressure is high (reason for this is unknown)

Treatment for HT• Secondary HT can be treated by curing

the disease responsible for this type of HT

• Treatment of Essential HT varies from person to person

• For a mild case of HT, treatment might include stopping smoking, cutting down on alcohol, lose weight and/or exercise

• For more severe cases, a variety of medications are also used to combat HT

Consequences of HT• If left untreated, HT can result in:

– Shortened life expectancy (no more than a few years at severely high pressures)

– Excess workload on the heart leads to early heart failure and coronary heart disease

– Clogged arteries– The high pressure frequently ruptures a major blood

vessel in the brain, followed by death of major portions of the brain (cerebral infarct)

– High pressure almost always causes multiple hemorrhages in the kidneys, producing many areas of renal destructions and, eventually, kidney failure, uremia and death

• Blood pressure should be regularly checked

• Untreated HT can lead to fatal consequences

• To prevent or even treat HT, one must live a healthy lifestyle without stressful situations

• Two main types of HT: Essential HTand Secondary HT

References• NCERx (2005) About Hypertension, www

.about-hypertension.co.uk, [Accessed 2 March 2005]

• NCERx (2005) Hypertension Symptoms and Normal Blood Pressure, www.detecting-hypertension.co.uk, [Accessed 2 March 2005]

• Guyton, A.C. & Hall, J.E. (2000) Textbook of Medical Physiology 10th Edition, W.B. Saunders Company, pg. 199-206