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1. UNIT 1 : UNDERSTANDING
HYPERTENSION

2. Objectives
By the end of this module participants should be able to:
1. Define hypertension
2. Describe the epidemiology and impact of hypertension
3. Describe Blood Pressure physiology
4. Describe factors that affect peripheral vascular resistance
5. Discuss the factors that affect cardiac output
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3. Case Study 1
At an international Cardiology conference held in UK
four delegates had the following preconference BP
measurements made at the gate of conference venue:
•James , 50 year old, British, BP= 170/95 mmHg
•Ibrahim, 38 year old, Iranian, BP 130/100 mmHg
•Adamu, 65 year old, Ethiopian, BP 160/80 mmHg
•Carlos, 56 year old, Brazilian, BP 130/85 mmHg
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4. Case Study 1
Answers:
1. Which delegate has hypertension?
None ,any raised BP is not hypertension , it should be confirmed on repeated
measurements to say it is hypertension.
2. Which delegate has normal blood pressure?
None, optimal(“normal”) Blood pressure is below 120/80mmHG.
3. In which delegate is the likelihood of complications higher?
Complications is higher with Adamu due to older age and black race.
4. Which delegate lives in high prevalent area of hypertension in the world?
Adamu lives in higher prevalence area, Sub-Saharan Africa has the highest
prevalence.
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5. Hypertension
Definition:Persistently elevated, systolic and/or
diastolic blood pressure of 140/90 mmHg or more
in subjects aged 18 years and above.
Systolic blood pressure is the pressure exerted when
the heart contracts.
Diastolic blood pressure is the pressure exerted
when the heart muscle relaxes.
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6. Epidemiology
Overall, approximately 22% of the world's adults are
estimated to have hypertension.
Sub Saharan Africa has the highest prevalence(40%).
In SSA Patients are younger, have more aggressive HTN,
present late and with complications.
Most studies done in Ethiopia show prevalence of raised
BP of 20-30 % (included more urban)
The recently conducted national NCD STEPS survey
which involved more than 10,000 participants from all
regions showed (unpublished data) that prevalence of
raised BP to be 16% (men 15.7%, women16.5%)
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7. Percentage of respondents with raised blood
pressure, or currently taking medication for raised
blood pressure, by sex, Ethiopia NCD STEPS, 2015
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8. Impact of hypertension
Of the 17 million global CVD deaths in 2010,
hypertension was responsible for the 9.4 million deaths
Hypertension is the main driver of Cardio Vascular
Disease killing twice as many women aged 60 and above
in Lower and Middle Income Countries compared to
developed countries.
It accounts for loss of 57 million disability adjusted life
years (DALYS).
For every increase in 20 mmHg systolic or 10 mmHg
diastolic blood pressure the lifetime risk of heart
disease DOUBLES.
Hypertensive Heart Disease(HHD) is the second most
common CVD in major referral hospitals of Ethiopia.
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9. Blood Pressure Physiology
Blood Pressure is the amount of force exerted on vessel wall
by blood per unit area at a given point in time.
It is the product of Cardiac output(CO) and Total peripheral
resistance (TPR).
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10. Physiology of blood pressure
Cardiac output is the amount of blood the heart pumps
through the circulatory system in one minute.
Peripheral vascular resistance is the degree of resistance
opposing ejection of blood by the heart . It is determined by
the diameter and stiffness of the arteries.
Blood pressure is determined by the amount of blood the
heart pumps and the amount of resistance to blood flow in
the arteries.
The more blood the heart pumps and the narrower the
arteries, the higher the blood pressure.
Consequently high blood pressure requires the heart to
work harder than normal to circulate blood through the
blood vessels.
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11. Blood Pressure Determinants
Blood Pressure
Cardiac Output
Stroke Volume
Preload
(Venous return)
Myocardial
Contractility
After load
(Forward resistance to
ejection of blood by the
heart)
Heart Rate
Total Peripheral
Resistance
Figure 2 : Interrelationships of the various determinants of
Blood Pressure .

12. Factors affecting blood pressure:
Peripheral Vascular Resistance
Vascular resistance is mainly determined by the structure
(anatomic) and functional changes in muscular small
arteries and arterioles.
 There are factors that reduce vascular diameter
(constrictors) and those that enlarge it (dilators)
Examples of vascular endogenous constrictors include
angiotensin II, catecholamines (Adrenaline and
noradrenaline), endothelin.
Examples of vascular Dilators: include Prostaglandins, and
Beta-adrenergic receptor activators, calcium channel
blockers
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13. Factors affecting blood pressure:
Cardiac output
Cardiac output is affected by the following factors:
• Heart Rate: the number of times the heart beats per minute
• Stroke volume ( amount of blood pumped out in one heart
beat) - depends on the following:
oPreload : the amount of blood returning to the heart)
oMyocardial Contractility: Force of contraction which is
increased by the sympathetic nervous system.
oAfterload : the resistance to ejection of blood by heart
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14. Blood Pressure Regulation
Blood pressure is regulated by a negative feedback mechanism.
The main regulatory systems in the body which maintain normal blood
pressure are:
1. Autonomic Nervous system :
Responsible for rapid control of BP .
With drop in blood pressure sympathetic outflow will increase with the final
effect of raising blood pressure by increasing heart rate, myocardial contractility
and increasing peripheral vasoconstriction.
Change in blood pressure is sensed by baroreceptors in carotid sinus, aortic
sinus and heart muscles.
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15. Autonomic Nervous System (Neuronal ) control
System
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16. Blood Pressure Regulation…..
2. Renin-Angiotensin-Aldosterone system:
 Is slow but the effect is prolonged .
With drop in blood pressure the system is
activated resulting in conservation of
intravascualr volume by decreasing GFR and
urinary sodium excretion.
The change in blood pressure is sensed by
special cells in the kidney.
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17. Regulation of Blood Pressure
Renin- Angiotensin- Aldosterone System Control
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18. Pathogenesis of Hypertension
The exact pathogenesis of hypertension is not clearly
understood in the majority of cases.
It is believed that the different environmental and
genetic factors interact at different levels of blood
pressure regulation to result in persistent elevation of
blood pressure.
Therefore majority of hypertension is not curable but
various drug treatment modalities can reduce blood
pressure by acting on either cardiac output or total
peripheral resistance .
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19. Proposed interaction between cardiac out put and
peripheral resistance in the pathogenesis of
essential hypertension

20. End of Unit 1