pthophysiolec6
TRANSCRIPT
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Pathophysiology
Challenge 2010propound
Lecture Notes
Lecture Title : CVS disorders
Prof name : Dr.Mostafa Shihebat
Done by : Pharmacy students
Corrected by : Dentistry students
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:(Ischemia)CVS disordersToday's lecture about
Anatomical and Physiological Introduction:-
Heart arteries are mainly 2 arises from the ascending
aorta (which is the largest art. In human) and supply the
oxygenated blood to the myocardium :
1- Left Coronary art. Divides into :
-anterior interventricular branch.
-circumflex branch.2- Right Coronary art. Divides into :
- posterior interventricular branch.
-marginal branch( left and right).
Drainage of veins through the Coronary sinus ( a
vascular sinus which's thin-walled that has no
smooth muscle ) which enters the blood in theright atrium.
( Note : that these art. or this system of art.
sovascularity of the heartreferred to as the
thatswhy we explained them to get the idea about
how ischemia occurs).
Normal coronary blood flow:
The resting coronary blood flow= 225
ml/min (relaxed situation e.g sleeping )
In strenuous exercise = increase three to
four folds. ( sometimes up to 7 folds)
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Now the question is when perfusion occurs
during the systole or the diastole?
Systolic pressure created from thecontraction of the left ventricle(phase of
contraction) .
Diastolic pressure created from the recoil
of the aorta (phase of relaxtion) .
During systole: arteries( thesubendocardial arteries) of the heart will
ofperfusionso most of thebe compressed
.diastoleoccurs duringheart
As you see in the following diaghram:
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Systole BF is 100 ml/minute.
Diastole BF is 300 ml/minute.
Which controls the coronary blood flow and all
arteries of the body in general ?
Need or increased demand in order to increase the
blood supply.
Otherwise ( if there's imbalance between the supply
aassumedand the demand) it's going to be
Ischemia.which is called(defect )disorder
Blood flow is controlled mainly by :-
Metabolic (activities) regulation : if it increased then
bf will increase.(Blood flow through coronary system
is regulated almost entirely by local arterialvasodilatation in response to cardiac muscle need for
nutrients which leads to increased contraction so
Increase in rate of coronary blood flow) .
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Nervous regulation : sympathetic stimulation
increase the heart rate and contractility so it will
increase the cardiac output which means increased
coronary blood flow.
Now let us start with pathophysiology:-
:Ischemia
There are two important subjects placedunder or related to ischemia generally :
-Ischemia.
-Necrosis.
Now what do we mean by Ischemia?
Lack of oxygen due to inadequate perfusion of the
myocardium, which causes imbalance between
oxygen supply and demand.
Specificly : when there's a constriction , narrowing
or subdivision(partial occlusion) in the arteries
which supply the heart(coronary arteries ).
The other part is necrosis(myocardial infarction ):
When there's complete occlusion of the blood
vessel ( not partial).
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Then the myocytes beyond the occlusion will die
and it might be fatal (this leads to a state of
necrosis) .
Ischemia equation :
e.g u need 10 liter and
blood supply only 8 ltrs ( this leads to ischemia).
-causes of myocardial ischemia :
The most common cause is Coronary atherosclerosis(
which means blockage of arteries ):
Thickening or narrowing of the wall of the arteries
due to accumulation of fatty material such as
cholesterol ( most common in old people ).
Epicardial coronary arteries are the major site.
Major risk factors that causes atherosclerosis(precipitating factors) :
Increase in LDL( low density lipoprotein) .Decrease in HDL( high density lipoprotein) .Cigarette smoking.Hypertension.
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DM (Diabetes mellitus).*Additional note : low density lipoprotein means bad cholesterol and HDL means good
cholesterol.
all of us know that smoking ,hypertension..etc are
common causes , but what the mechanism?
Because all these things leads to destruction or injury to
the endothelial (has to be smooth) layer of the arteries
which leads to aggregation of clotting factors ( platelets)
due to the fragility of its surface ( no luminar flow) .
This mechanism similar when we got injured or had an
external cut this leads to rough (fragile) surface and
aggregation of clotting factors.
*remember that blood vessels consists of 3 layers : tunica interna(endothelial) , tunica
media ,tunica externa .
*there are 2 type of blood flow : luminar flow( steady or smooth state ) and turbulentflow.
Normal function of vascular endothelium :
-Local control of vascular tone.
-Maintenance of an anticoagulant surface.-Defense against inflammatory cells.
Loss of these defensesleads to:
-Inappropriate constriction.
-Luminal clot formation.-Abnormal interactions with blood monocytes &
platelets.
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- Now the occlusion caused either by Thrombosis or
Embolism, but what the difference ?
The thrombosis is local formed clot , but in the embolismthe clot could be transferred to other sites (from artery to
another artery) & may follow deep venous thrombosis.
The Dr started to talk about angina(to know that it differs
from local spasm) it occurs in people who has neither
embolism , thrombosis nor any problem but they develop
signs and symptoms that resemble the angina ( whenthey get angry, sad or stressed.) they could feel a pain
in their chest ( thorax) this case is due to spasm of the
coronary arteries ( angina-like symptoms) that occurred
because of the deffientcy of blood perfusion (low or less)
due toover sympathetic stimulation .
And if the patient brought to ER and had an examinationit would be a normal ECG without angina.
Partial occlusion
(ischemia) may develop
to complete
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The Location of the obstruction Influence the quantity of
myocardial ischemia ,Determines the severity of the
clinical manifestations which means that if the occlusion
where in major artery then the effect will be major ( the
heart will be affected so much , massive destruction of
cells leads to massive dead myocytes) but if the artery is
small the complication will be less( why? Because there's
a less amount of dead cells).
Collateral circulation:
Before that there's a question : if where young man
had a myocardial infarction he would die but an old
or middle- aged man wouldn't?
Due to Collateral circulation that only formed in
old people and athletes .
Which means that an area(the same one) supplied
by many arteries ( network of blood vessels) it is
Complete occlusion
(necrosis) death of
the area supplied by
the artery
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not opened in young people (except athletes) but
opens when we get older.
*in athletes because they have a high demand(cardiomegaly ).
If heart rate less than 60 it's a disorder which is
called brady cardi but in athletes not ( their heart
size is larger = cardiomegady) normal to had HR
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-Fatty acid cant be oxidized.-Glucose is broken down to lactate.-Reduced intracellular PH and ATP stores.
3) Cell membrane function:
-Leakage of potassium and uptake of sodium by
myocytes.4) Electrical function:-ECG changes:Repolarization abnormalities.Transient ST segment depression.-Electrical instability:
Ventricular tachycardia and fibrillation.
Later on when we discuss arrythimia we will know
that one of its important causes is ischemia and
massive myocardial infarction ( it may lead to
ventricular fibrillation which is fatal).
-angina
there are 2 types :
-unstable angina : which is misdiagnosed between
unstable angina and acute MI(myocardial infarction
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)both of them are Acute coronary syndrome(symptoms:
retrosternal severe chest pain near to the left hand).
We can differentiate between them by ecg ,we have todo blood tests, ckmp, troponine (will be +ve for MI
patients andve for unstable angina patients) next lecture
we will discuss it in detail .
-stable angina:chronic artery disease,
Characteristics:Heaviness,Pressure, Squeezing,
Smothering and Choking pain.
Causes:
-CAD ( coronary artery disease).- Aortic valve disease.
- Hypertrophic cardiomyopathy.
History:
A man > 50 years.
A woman > 60 years.
Pain with physical & emotional
exertion.
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Last to 5-10 min (relieved by vasodilators).
But how does the pain occurs or start? Radiating pain to the
left shoulder, both arms, back, interscapular region, root of the
neck, jaw and teeth but you need to know that any other
symptoms that are not related to the heart in diagnosing angina
or MI ( e.g abdominal pain) otherwise if you didn't you might
kill the patient because you will forget or misdiagnose that he
has angina and you will give him another treatment for other
disease ( that you thought) .
Both types have the same cause(narrowing andconstriction of the coronary artery) but the stable is
relieved by Vasodilators(nitro-peceline sublingual,
nitrates,-adrenergic
blockers,Calcium,antagonist,Antiplatelet drugs.) occurs
mainly after doing exercises specially when the demand
become more than the supply which leads to a severe
chest pain but signs and symptoms will be subsided by
Vasodilators .
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But in unstable pain will not be subsided by
Vasodilators.
*tread-mill or stress test : to know if that your heart doing well ( 220- the
age) e.g ( your age is 20 then 220-20=200 this means that your HR after
doing exercise should reach 200 without feeling any chest pain otherwise
there would be a disorder .
Why are these patient given analgesics (morphine or opium) or
we call them painkillers?
Because heart pain is very severe (painful).
THE END