Lecture 27: Overview of HTN epidemiology and consequences Flashcards
What is hypertension?
A disorder of regulation of Systemic Vascular Resistance
A syndrome that encompasses a large group of disorders
-systemic arterial pressure is regulated at a sustained abnormally increased level
Abnormal fibrosis (deposition of collagen) in tissues
End product of heredity, environment and behavior
What are the two groups of HTN?
- Primary (essential) hypertension
- resistance hypertension
- compliance hypertension (stiff pipes)
- Secondary hypertension
What is the vicious cycle of HTN?
Increases systolic pressure (LV hypertrophy and fibrosis of myocardium)
Elastic arteries are subjected to increased stress due to increased systolic pressure
Increased stress = atherosclerosis and aneurysms more SVR
Arterioles then go obliterative destructive process, particularly in kidney
Renal failure = further increase in systolic BP
What are the clinical consequences of HTN?
- cardiac dysfunction secondary to progressive LV hypertrophy and myocardial fibrosis
- Accelerated disease of large and small systemic arteries
- leads to MI, stroke and aneurysms
- Renal dysfunction secondary to progressive renal destruction due to disease of arteries from HTN
What happens to SBP and DBP with age?
SBP increases but DBP decreases (since you have less compliance and therefore less blood that is stored in the elastic arteries to maintain diastolic BP)
Thus pulse pressure increases
What are the two definitions of HTN?
- epedimiological definition
2 morbidity based definition
Hard to define HTN because BPO varies with gender, age and race
What are the challenges for the epidemiologic definition of HTN?
Continuum of BP values in the population
Disorder is so prevalent that HTN may appear to be normal
Tendency for BP to increase with age
What are the challenges of the morbidity based definition?
Continuum of frequency of morbidity with BP
But Lower is usually better
What is the physiological significance of hypertension?
i. Left ventricle: generates higher pressure, leads to higher wall stress, left ventricular hypertrophy, fibrosis of myocardium
ii. The arterial system: must contain the increased pressure, increases wall stress, aneurysms, atherosclerosis, destruction of systemic arterioles
iii. The kidney: destruction of the kidney due to arteriolar destruction, decrease ability to excrete sodium
Leads to MI, stroke and aneurysms
What’s the correlation between coronary heart disease and systolic/diastolic pressure?
Higher the pressure = higher risk of coronary heart disease
Why is HTN the silent killer?
You have no symptoms until you have end organ failure
What is the etiology of hypertension?
- secondary (caused by one of the arterial pressure regulatory mechanisms)
- kideny, adrenal, CNS disease or drug intake
- primary (no identifiable cause)
What is BP determined by?
BP = CO x SVR
What are the mechanisms that should prevent the development of hypertension?
- baroreceptor reflex
- pressure-natriuresis
- RAA system
When these mechanisms go wrong, you get hypertension
How can HTN override the baroreceptor reflex?
If you have sustained HTN, the baroreceptor is reset and will not signal afferent nerves to decrease systolic BP