Hypertension Flashcards
What factors combine to determine blood pressure?
Cardiac Output
Resistance to Bloodflow
What dictates the level of resistance to bloodflow?
- The diameter of the lumen in the blood vessel
- The viscosity of the blood
- (also atherosclerosis obviously)
What is Cardiac Output?
Stroke Volume * Heart Rate
What is the normal range for cardiac output?
4 to 8 liters per minute
How is blood pressure measured?
What a sphygmomanometer; records systolic and diastolic pressure
What is the ideal blood pressure range? Systolic/Diastolic
90/60 to 120/80mmHg at rest
What is hypertension defined as in terms of blood pressure?
- 140/90mmHg or higher at rest
Why is there an ideal blood pressure range?
Blood pressure needs to be high enough to allow the blood to reach all our organs and tissues at a sufficient rate, but not so high that it damages our blood vessels
How is blood pressure regulated in the short term?
Baroreceptors in the aortal arch and the carotid sinus detect pressure change, feeding back to the autonomic nervous system, which then either increases or reduces heart rate/cardaic contractility via sympathetic/parasympathetic fibres to increase or decrease blood pressure, respectively.
What system dictates long term regulation of blood pressure?
The Renin-Angiotensin System (RAAS) in the Kidney
Where is renin secreted from, and in response to what?
A peptide hormone released from the juxtaglomerular apparatus of the kidney in response to sympathetic stimulation, decreased kidney blood flow, and reduced sodium chloride delivery to the distal convoluted tubule. (All due to decreased blood pressure)
What is the role of Renin in the RAAS for long term blood pressure regulation?
Facilitates the conversion of angiotensinogen to angiotensin I.
What is ACE (Enzyme)?
Angiotensin converting enzyme:
- Converts angiotensin I to active angiotensin II
- Breaks down Bradykinin (potent vasodilator)
What is the role of Angiotensin II II in the RAAS system?
It causes vasoconstriction, increasing peripheral resistance, and causes aldosterone release, which increases sodium resorption and thus water retention, increasing blood volume and thus blood pressure
Where is Angiotensin 1 produced?
Liver
What is the mechanism when too high blood pressure is detected?
There isn’t one, other than reducing renin secretion
What do the systolic and diastolic values mean for blood pressure?
Systolic is highest it will get (during contraction) and Diastolic is lowest it will get (between contraction)
Why is Mean Arterial Pressure a potentially better metric than looking at Systolic or Diastolic blood pressure?
You can be high in one and not the other, so you may have undetected hypertension if you only use the Sys/Dias metric because you wont fit the measure of hypertension
How is Mean Arterial Pressure calculated?
MAP = DP + 1/3SP
How is hypertension influenced by age?
Older you are the higher the prevalence
What are the two main types of hypertension?
Primary/Essential Hypertension
Secondary Hypertension
What is Primary/Essential/Idiopathic hypertension?
No known cause, about 9% of cases are this
What is secondary hypertension?
The product of something else like kidney disease, diet, hormonal imbalance, obesity, etc.
What are the risk factors for hypertension?
- Genetic predisposition
- Excessive sodium intake
- Obesity
- Sedentary lifestyle
- Stress
- Excessive Alcohol Consumption
- Age
- Oral Contraceptive
What is natriuresis?
Excretion of sodium in the urine
What is the Guyton Hypothesis?
Sustained hypertension can occur only when the relationship between arterial pressure and natriuresis is abnormal
How does obesity impact hypertension?
- Increased cardiac output
- Increased sympathetic renal nerve traffic increasing sodium retention, due to high leptin
- Increased RAAS activation due to increased adipose tissue secretion of angiotensinogen
- Hyperinsulinemia. Insulin also causes sodium resorption
what is the prevalence of hypertension in the UK?
- 10% of adult population recieving treatment for hypertension
- Approx 15% of adults have untreated hypertension
How does chronic stress increase risk of hypertension?
-Frequently or constantly increased secretion of catecholamines (like adrenaline and cortisol) lead to increased HR, Cardiac Output and Blood Pressure.
How does excessive alcohol consumption lead to hypertension?
Alcohol consumption acutely raises blood pressure, and excessive habitual alcohol intake chronically raises blood pressure, but the mechanisms are unclear.
what is Double Product?
A value used to describe the amount of work the heart is having to do, calculated by:
HR * Systolic BP
What physiological changes occur to the heart in response to chronic hypertension?
Cardiac Hypertrophy/Pronounced thickening of the cardiac walls but with no change in chamber size
What occurs to blood vessels in chronic hypertension?
Excessive shear and direct stress, making damage more likely, which provides more gaps for LDL to fit under, to cause atherosclerosis
Apart from CHD, what else does hypertension increase the risk of?
Stroke and Intermittent Claudication
What are the most common pharmacological treatments for blood pressure?
- Beta Blockers
- Alpha Blockers
- Calcium Channel Blockers
- Diuretics
- ACE Inhibitors
- Angiotensin II Receptor Blockers
How do Beta Blockers work? (Beta-Adrenergic Blocking Agents)
Reduces Heart rate by blocking the effects of adrenaline/epinephrine
How do Alpha Blockers work? (Alpha-Adrenergic Blocking Agents)
Reduces vascular tone/vasoconstriction by blocking the effects of noradrenaline/norepinephrine
What are the most common non-pharmacological treatments of hypertension?
- Diet (Weight loss and controlled salt intake)
- Relaxation/Stress Reduction
- Exercise
How does training status impact the relationship between menopause and blood pressure?
-Blood pressure did not change pre-post menopause for trained women, but it increased in sedentary women
How does regular exercise chronically reduce blood pressure?
Unclear, but proposed:
- Increased lumen size
- Decreased adiposity and body mass (indirect)
- Increased Insulin sensitivity
- Decreased Stress
- Decreased Arterial Stiffness
How does exercise acutely reduce blood pressure?
- Reduced norepinephrine
- Reduced sympathetic activity leading to reduced angiotensin II
What evidence exists to suggest an optimal exercise intensity for lowering blood pressure?
Hagberd et al 1989 found that 50% VO2max exercise was superior to 70% VO2max for reducing blood pressure. Otherwise the best intensity is not clear.
What impact does existing blood pressure have on the impact of exercise on blood pressure? Give evidence
Cornelissen and Fagard found that exercise reduced blood pressure in hypertensive individuals more than normotensive individuals, but the decrease was found in both.
What impact does isometric exercise have on blood pressure? Give evidence
Smart et al 2019 found consistent effective response of isometric exercise on decreasing blood pressure
