Clinical epidemiology and consequences of having high blood pressure

1. Clinical epidemiology and consequences of having high blood pressure Ivo Ricardo de Seabra Rodrigues Dias

2. 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

3. 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

4. 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

5. Blood pressure table for HT

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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)

15. 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: • The mean arterial pressure is increased 40% to 60% • In the late, more severe stages, the renal blood flow is decreased to about one half normal • Resistance to blood flow through the kidneys is increased twofold to fourfold • Despite the decrease in renal blood flow, the glomerular filtration rate is often near normal • The cardiac output is about normal • Total peripheral resistance is increased about 40% to 60% • Kidneys will not excrete adequate amounts of salt and water unless arterial pressure is high (reason for this is unknown)

16. 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

17. 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

18. 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 HT and Secondary HT

19. 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