Block A Lecture 1 - Hypertension Flashcards
What is systemic circulation?
When blood is pumped from the left ventricle into the Aorta, to the body, and is then pumped back into the heart via veins such as the vena cava
(Slide 3)
What is pulmonary circulation?
When blood is pumped from the right ventricle to the pulmonary artery and into the lungs before being pumped from the lungs back to the heart via the pulmonary vein
(Slide 3)
What is bronchial circulation?
It is complementary to pulmonary circulation and supplies lung cells with oxygen and nutrients
(Slide 3)
Compare the structures of veins and arteries.
Arteries have small lumen and a thick wall whereas veins have large lumen and a thin wall, while also having a valve in them
(Slide 4)
What do valves present in veins do?
They prevent the backflow of blood
(Slide 4)
Why do veins have valves but arteries don’t?
As veins are responsible for carrying blood against gravity, especially in the lower body
(Slide 4)
What is blood pressure created as a result of?
The force of blood pushing against the walls of blood vessels (arteries) as it is pumped by the heart
(Slide 6)
What 2 factors does blood pressure depend on?
Peripheral Vascular Resistance (PVP) * Cardiac Output (CO) = BP
Note: Heart Rate (HR) * Stroke Volume = CO
(Slide 6)
How does peripheral vascular resistance affect blood pressure?
As PVR is the diameter of arteries / arterioles which determines resistance to flow, if dilated, there’s a low resistance to flow, a low PVR and therefore low blood pressure.
(Slide 7)
What are 4 factors which affect arterial BP?
Answers Include:
Stroke volume
Heart Rate
Peripheral Resistance
Elastic Vessels
Blood Volume
Ventricular Ejection
(Slide 7)
What are some examples of systems / mediators / receptors which affect blood pressure?
Autonomic nervous System (immediate)
Renin-angiotensin System (not immediate)
Local Mediators released from vascular endothelium (such as NO)
Sympathetic nervous system (β1-adrenoceptors increase CO, α1-adrenoceptors cause vasoconstriction, causing increased BP, or stimulation of them causing venoconstriction, increasing CO and BP)
(Slide 8)
What are 2 types of endothelium-derived factors?
Endothelium-Derived Relaxing Factors (EDRFs) and Endothelium-Derived Contracting Factors (EDCFs)
(Slide 11)
What do EDRFs and EDCFs do?
They modulate vascular smooth muscle and therefore vessel diameter
(Slide 11)
What are 3 examples of EDRFs?
Nitric Oxide (NO)
Prostacyclin (PGI2)
Hyperpolarizing Factor (EDHF)
(Slide 11)
What are 2 examples of EDCFs?
Endothelin (ET-1)
Thromboxane (TXA2)
(Slide 11)
Why do arteries have thick muscular walls, which contain elastic fibres?
To help them carry blood at high blood pressures
(Slide 12)
What can hypertension increase the risk of?
Heart, brain, kidney or other disease
(Slide 16)
What is etiology?
The study of the causes or origins of diseases or medical conditions
(Slide 17)
What is the etiology of hypertension?
It’s complicated as hypertension is the result of many factors which interact to raise blood pressure
(Slide 17)
What is systolic pressure (SP)?
The maximal arterial pressure reached during peak ventricular ejection
(Slide 18)
What is diastolic pressure (DP)?
The minimal arterial pressure just before ventricular ejection begins
(Slide 18)
What is pulse pressure (PP)?
The difference between SP and DP
(Slide 18)
What is mean arterial pressure (MAP)?
The average pressure in the cardiac cycle
(Slide 18)
How is blood pressure measured using a sphygmomanometer (cuff on arm thingy)?
At first, cuff pressure blocks blood flow, and then pulse can be heard when systolic pressure exceeds cuff pressure. Then pulse cannot be heard when diastolic pressure exceeds cuff pressure.
Pressure is released from the cuff while listening via a stethoscope, as blood pressure returns to arm
(Slide 19)
What is a normal BP range?
< 130 systolic and <85 diastolic for normal
or
130-19 systolic &/or 85-89 diastolic for high normal
(Slide 20)
What are the systolic and diastolic ranges for grade 1 and 2 hypertension?
140-159 systolic &/or 90-99 diastolic for grade 1
160 or more systolic &/or 100 or more diastolic for grade 2
(Slide 20)
How is systemic hypertension usually diagnosed?
It is usually asymptomatic and is often diagnosed when patient presents with a different condition
(Slide 21)
What is pulmonary hypertension?
It’s commonly found in COPD patients where the pulmonary vasculature (the network of blood vessels which pump blood from the heart to the lungs) has been affected leading to increased vascular resistance. Results in shortness of breath and sometimes chest pain.
(Slide 21)
What does a sustained increase in pulmonary vascular resistance lead to?
Progressive right heart failure (the right side of the heart can’t pump blood to the lungs)
(Slide 21)
What are 5 examples of primary risk factors for hypertension?
Answers Include:
High salt consumption
Lack of Exercise
Excessive use of alcohol
Tobacco
Obesity
Diabetes
Age / Sex
Lipid Disorders
(Slide 22)
What are 3 examples of secondary risk factors (factors initiated by another disease) for hypertension?
Aortic coarctation (narrowing of the aorta)
Renal Disease
Mineralocorticoid excess
Thyroid disease
Eclampsia (complication of pregnancy - causes seizures)
Cancer treatment
(Slide 22)
What are 5 examples of the effects of hypertension?
Progressive structural changes in vasculature
Acceleration of atherosclerosis (narrowing of blood vessels)
Stroke, aneurysms, vascular dementia (dementia which occurs when blood flow to the brain is disrupted)
Left ventricular hypertrophy (when the left heart muscle thickens and enlarges)
Kidney failure
(Slide 23)
What are 4 differences between a healthy artery and a remodelled artery as a result of hypertension?
Answers include:
Proliferation of fibroblasts and infiltration of immune cells in adventitial layer
Vascular smooth muscle cells (VSMCs) proliferation and migration in media
Double elastic lamina develops due to increased muscularisation
Proliferation of apoptosis-resistant endothelial cells
Narrowing / occlusion (blocking) of vessel lumen
(Slide 24)
What are 4 examples of classes of antihypertensive drugs and how do they reduce blood pressure?
Answers Include:
Vasodilators (reduce vascular resistance)
Sympathetic inhibitors (reduce cardiac output)
RAAS inhibitors (decrease venous return)
Diuretics (decrease blood volume)
Calcium Channel Blockers
(Slides 27 and 31)
What are 2 types of sympathetic inhibitors which can be used to decrease hypertension, and how do they work?
β-blockers (such as atenolol or propranolol) - they decrease CO and can reduce renin production leading to a reduction in Angiotensin II. Can also indirectly cause vasodilation of peripheral arteries
α-blockers (such as prazosin) - block post-synaptic α1 adrenoceptors which leads to dilation of arteriolar resistant vessels and lower peripheral resistance. They also dilate venous capacitance vessel, which reduces venous return and CO.
(Slide 29)
What are 2 examples of RAAS acting drugs which reduce blood pressure and how do they do so?
ACE inhibitors (such as captopril) - reduce angiotensin II levels
Angiotensin II receptor antagonists (ARBs) - e.g (such as losartan and valsartan) - selectively block AT1 receptors which mediate the vasoconstrictive, cardiac / vascular hypertrophy effects of angiotensin II
(Slide 30)
How do diuretics reduce blood pressure?
They act at varying sites in the kidney to increase sodium and water depletion which leads to a hypotensive effect
(Slide 30)
How do calcium channel blockers (CCBs) reduce blood pressure?
Calcium channel blockers (diltiazem, verapamil, amlodipine) block calcium entry into vascular smooth muscle cells (VSMCs) and / or cardiac muscle cells, promoting relaxation of the muscle and vasodilation
(Slide 31)
During what scenario are vasodilators used to reduce blood pressure?
During a “hypertensive emergency” - as they provide rapid and controlled blood pressure reduction
(Slide 31)
What are the current treatment guidelines for grade 1 and 2 hypertension?
Grade 1 - Immediate drug treatment in high-risk patients or those with CVD, CKD, DM or HMOD
Grade 2 - immediate drug treatment in all patients.
Step 1 - ACE inhibitors in patients over under 55 or calcium channel inhibitors (patients over 55 and all black people of African or Caribbean descent) (thiazide-like diuretics can be used in people with oedema)
Step 2 - Both of the above
Step 3 - Both of the above + a thiazide-like diuretic
Step 4 - (Resistant hypertension) all 3 of above plus a further diuretic (such as low dose spironolactone or higher doses of thiazide like diuretic or an α or β blocker)
(Slide 32)
