Cardiovascular pathophysiology W8 Flashcards
What is the Australian Classification of clinical hypertension
Sustained systolic >140mmHg
OR
Sustained diastolic >90mmHg
High blood pressure!
What are the risk factors that lead to hypertension
Combination of genetics and environmental factors
- Hereditary
- Diet: High intake of NaCl, cholesterol, fats
- Obesity
- Age
- Diabetes Mellitus
- Stress
- Smoking: Nicotine -> vasoconstriction & chemicals damage blood vessels -> narrowing of arteries
Describe the pharmacoloical treatments for hypertension
- ACE inhibitors (Angiotensin converting enzyme inhibitors)
- Angiotensin (2) receptor blockers
- Beta blockers
- Calcium channel blockers
- Diuretics
What is hypertension a risk factor for?
CVD - cardiovascular disease
(as well as stroke, kidney disease, heart failure, coronary heart disease, acellerated atherosclerosis)
Why is hypertension called ‘the silent killer’
Asymptomatic for 10-20 years
Creates greater after load -> myocardium hyperthropy -> weakened heart
Accelerates process of atherosclerosis
Affects cardiac output and perfusion to tissues
Why is afterload, and therefore cardiac output, effected with hypertension
If pressure in Aorta is 100 (hypertension) the minimum pressure the ventricle has to generate is 150, to generate that higher pressure you need a greater contraction and therefore more effort is required -> strain -> Valves get stiffer, muscle hyperthropy
= cardiac output drops and less blood to tissues
What are the two types of Hypertension
- Primary (90%)
No underlying cause
Lifestyle factors? - Physical activity and weight loss -> treatment - Secondary
Underlying cause ie. kidney disease
Are the hormones estrogen and testosterone good or bad in the prevention of hypertension
Estrogen = supple = protective
Testosterone = hardens arteries (less compliant) = risk
Post-menopausal = higher risk ie. loose protective factor
Men at older age = lower risk ie. loose risk factor
Why is obestity a risk factor for hypertension
Mechanical stress from high level of fat tissue (needs blood so heart works harder)
Atherosclerosis due to poor diet
Physical stress on vascular (fat) -> impedes venous return
Impaired kidney function
What is the action of aldosterone
Controls the level of Na+ (main extracellular cation - salt) –> Osmolarity of blood –> how much fluid you retain
What is the action of Angiotensin
POTENT VASOCONSTRICTOR
Briefly describe the control system for managing Na+ levels
Renin-Angiotensin-Aldosterone System (cascase)
- Kidneys (pressure sensors) get less blood -> release RENIN
- Liver pro-hormone (ANGIOTENSINOGIN) is converted to ANGIOTENSIN 1 by RENIN
- ACE in lungs convert ANGIOTENSIN 1 to ANGIOTENSIN 2
- ANGIOTENSIN 2 acts on B.V -> vasocontriction AND acts on to adrenal gland stimulating release of ALDOSTERONE
- ALDOSTERONE acts on kidneys causing more reabsorbtion of Na+ (ie. increased water reabsorbtion to) = higher blood volume = higher blood pressure
What are the three hormones involved in the control system for managing Na+ levels
-Aldosterone
-Angiotensin
-Renin
Describe the effects of Angiotensin 2
B.V -> vasocontriction
acts on to adrenal gland stimulating release of ALDOSTERONE A-> reabsorbtion of Na+ by kidneys = increased B.V
Describe the mechanism of action of ACE inhibitors (Captopril, perindopril ect.)
Blocks angiotensin converting enzyme (NO angiotensin 1 converted to angiotensin 2 in lungs)
= reduced constriction of arteries
&
= reduced Na+ and water retenion by kidneys (= lower blood volume)
What does ACE 2 do?
Breaks down angiotensin 2
ie. Constriction only lasts a little bit of time
What is the side effects of a ACE inhibitor
Promotes production of Bradykinin (inflammation)
= COUGH a lot
What is the mechanism of action for Angiotensin 2 receptor blockers
Inhibit action of angiotensin 2
= vasodilation of arteries
= reduces Na+ and water retention by kidneys = lower B.V
ACE inhibitors are the most common hypertensive drug as it is cheap and effective.
In what situations are Angiotensin 2 receptor blockers more commonly used?
More commonly used for heart failure, hypertrophy of the left ventricle, history of myocardial infarction or renal disease due to diabetes mellitus
What are the mechanism of action of calcium channel blocker (in general)
Calcium channel blockers block movement of calcium into cell and therefore reduce contraction likihood
What are the mechanism of action of calcium channel blocker - DIHYDROPYRIDINES Most common
Smooth muscle req. calcium to enter cell for contraction (Ca2+ binds to troponin - troponin removes tropomyosin - exposed myosin binding site for actin)
DIHYDROPYRIDINES effect smooth muscle in blood vessels - not the heart!
= no contraction = vasodilation
What are the mechanism of action calcium channel blocker - NON-DIHYDROPYRIDINES Less common
NON-DIHYDROPYRIDINES the heart!
Pacemaker AP depolarisation due to Ca2+ influx
Therefore block Ca2+ entry
= Less AP’s generated
= Reduced heart rate and force of contraction
What is the mechanism of action for Beta Blockers
Reduce the effect of noradrenaline
ie. Block site of action (Beta 1 receptors) ie. reduced Ca2+ influx
= Reduced HR and cardiac output
In which situations are Beta Blockers most commonly used
Myocardial infarction, angia, heart, failure, arrthymia
What is the difference between B1 and B2 receptors (adrenergic receptors)
B1 = Increases contraction - stimulatory action
- Adrenalines binds and incerases Ca2+ influx
- Mostly on the heart
B2 = dilates B.V’s - inhibitory action (no contraction)
- Mostly on B.V’s
general rule odd numbers stimulate
What is the mechanism of action for diuretics with regard to Hypertension
- Reduce water retention
- Reduce sodium retention
- Decreases blood volume
= reduced cardiac output = reduced BP
Ex. Loop diuretics - increases loss of Na+ (and water)
Usually used in combination with another drug
Which of the five antihypertensive drug classes cause vasodilation
Which of the five antihypertensive drug classes reduce cardiac output
Which of the five antihypertensive drug classes reduces blood volume
ACE inhibitors
Angiotensin 2 receptor blockers
Diuretics