Lesson 22: Topic 18 - High Systolic BP Flashcards
what is the most important homeostatically regulated thing in our body that is always trying to be maintained?
mean arterial pressure
what are the consequences of high systolic blood pressure?
- aneurysm
- myocardial infarction
what is an aneurysm?
a rupture of wall of aorta
what is an aneurysm caused by?
high blood pressure that damages the artery itself
when the aorta is stretched out, what is it referred to as?
aorta with large abdominal aneurysm
aorta with large abdominal aneurysm is caused by?
having sustained pressure over time and every time you stretch our the aorta, the stretch could be permanent
what is an aortic dissection?
there is a rupture through the wall of the aorta that is a weak point and all of a sudden there is a pressure there that is going to push blood into the walls of the aorta which will weaken the structure
are aneurysms common in young?
no, unless there is a genetic predisposition like Marfan Syndrome
an abdominal aorta aneurysm is more common in what age group and what sex?
greater than 60 years and is more likely in males than females
what are a few things that become more common as you get around the 60 years of age mark?
- atherosclerotic plaque formation inside the arteries
- elastic properties of arteries (stretch becomes less elastic)
- causes aneurysms to be more common with age
what causes aneurysms to be more common in males than females?
caused by hypertension which is can be caused by smoking and drinking which are more common in men than women
what is another name for marfan syndrome?
spiderman syndrome
what is marfan syndrome cellularly?
a mutation in the extracellular matrix protein “fibrillin-1”
what is fibrillin-1?
the protein that attached elastic and non-elastic tissue to a structural membrane. it is the connective tissue between elastic and non-elastic tissue and anchors it to the basement membrane
patients of marfan syndrome appear how?
tall, thin, and arm span exceeds their height
- severe: caved in chest
the skin of patients of marfan syndrome appears how?
their skin can be stretched far with poor recoil
- this is because it is not anchored to the basement membrane
an aorta with normal fibrillin, what does the elastin fibre look like?
eastin fibre is well organized in a lasagna formation
an aorta with mutated fibrillin, what does the elastin fibre look like?
elastin fibres are disorganized leading to high risk of aortic aneurysm
true or false: height exceeds arm span in marfan syndrome
false. arm span exceeds height in marfan syndrome
what is the problem that causes the myocardial infarction?
the cardiac workload is too high to meet the oxygen demand
- work from heart does not get oxygen supplywhich leads to cardiac death
to maintain cardiac output when aortic pressure is elevated during hypertension, what must contract harder?
the left ventricle
- this increases oxygen demand by the cardiac muscle cells
when MAP increases during hypertension, stroke volume decreases IMMEDIATELY. why?
because aortic valve only opens when left ventricular pressure is higher than aortic pressure. so because aortic pressure is now higher due to hypertension, ejection of blood is shorter in time because the LVP is going to be higher than aortic for a shorter amount of time
- isovolumetric ventricular contraction time is going to be prolonged
- aortic valve opens later and closes sooner
ESSENTIALLY:
- higher aortic pressure means that a higher LVP is required to open the aortic value which means less blood is ejected in one cardiac cycle which leads to less stroke volume
MAP = “afterload”
what is afterload?
refers to the pressure that is distal to the ventricle that the heart must work against for blood flow to occur
- essentially pressure gradient
ejection of the hearts chambers only occurs when?
left ventricular pressure is greater than aortic pressure
the dichotic notch is the start of?
isovolumetric ventricular contraction and then aortic valve closes
during ventricular ejection of a normal aortic pressure, what is stroke volume?
typically 75mL
during ventricular ejection of a pre-compensation to high aortic pressure, what is stroke volume?
very reduced
- goes down to 40mL when its supposed to be 75mL
what causes decreased stroke volume during pre-compensation to high aortic pressure?
shorter ventricular ejection duration
what happens with someones oxygen levels when stroke volume decreases under hypertension?
oxygen deficit happens
because of oxygen deficit due to stroke volume decreasing under hypertension, how does the body compensate for this?
left ventricle contracts strong, to develop higher left ventricular pressure which will cause LVP to be greater than AP for longer so that more blood can be ejected.
- activate afferents, go to ANS to increase SNS activity to increase stroke volume to cause LVP to be greater
- brings ejection up to 70mL
- duration of systole is prolonger and diastole is shortened which causes consequences
what is the problem with high aortic pressure with compensation?
the more intense contraction requires more energy and oxygen
what does the “with compensation” and “pre-compensation” mean?
the body compensating or not compensating for the high aortic pressure
what are the immediate consequences of increased MAP to the heart?
- decreased stroke volume
causes - decreases coronary blood flow (less blood flow to the heart from coronary arteries)
and - decreases oxygen delivery
leading to
oxygen deprivation to cardiac myocytes (cardiac muscle cells)
what are the compensation consequences of increased MAP to the heart?
- increased LV contractility (stroke volume maintained)
causes - increased oxygen demand
- decreased coronary blood flow due to longer systole vs diastole
leading to
oxygen deprivation to cardiac myocytes (cardiac muscle cells)
coronary arteries branch where?
superficially on the heart and then penetrate through into the heart with arterioles and capillaries
how does cardiac myocytes receive oxygen and nutrients?
through the coronary artery network, NOT by direct diffusion of substances from the chamber of the heart
what is cardiac ischemia?
cell death in the hearts muscles due to not enough oxygenated blood supply
there is different levels of cardiac ischemia depending on?
where the obstruction (plaque formation in the coronary arteries) is occuring
why does prolonged systole and a shortened diastole lead to impaired blood supply to the heart?
we have a drop in left coronary artery blood flow during systole
- high ventricular pressures during systole compress the arteries, reducing coronary blood flow temporarily. so when we have a prolonged systole, the blood flow to the heart is reduced because the coronary arteries are being contracted. diastole is when blood flow is restored to the heart so when its shorter, there is less blood flow
why do we have a drop in left coronary artery blood flow during systole?
- it drops to 0
- this is because the heart is contracting. as it contracts, the pressure being generated is going to squeeze onto those arterioles and capillaries and block blood supply into the cardiac muscle cell
coronary artery blood flow dropping during systole is more extreme where?
endocardial region, the inner layer because it has the finest capillaries so they are most likely to be susceptible to compression and they are the layer closest to the left ventricle
how does high aortic pressure with compensation lead to a myocardial infarction?
prolonged systole and shortened diastole –> decreased blood flow –> decreased oxygen to myocytes which could lead to decreased ATP in mitochondria –> myocytes cannot repolarize or relax (eg. ST segment plateau) –> myocardial infarction
what does atherosclerosis do?
blocks blood delivery to the heart
that is a thrombus?
an atherosclerotic plaque when it is immobile
- it is just stuck to the side of the blood vessel wall
when a blood clot, thrombus or atherosclerotic plaque moves, what is it called?
embolus
what is a thrombo-embolism?
an embolism that completely clogs an artery
- impedes blood supply
what is the “perfect storm”?
atherosclerosis and hypertension both leading to heart failure as we get older once exertion of increased O2 is in demand because we are doing a difficult activity like shoveling the snow
- all three of these then leads to an insufficient blood supply to myocytes (especially during systole) which leads to a myocardial infarction which leads to EITHER death(depends where it is) or a cardiomyocyte dysfunction which leads to congestive heart failure
what is congestive heart failure?
when the heart is too weak to pump blood efficiently in the body. Congestive refers to fluid accumulation
