Cardio renal L9 Flashcards
how might angina feel to a patient
This describes the severe, suffocating chest pain that is characteristic of an attack of angina
where is angina often refered to
s ‘referred’ to the left shoulder and upper arm and sometimes the teeth8.
wen does blood perfuse the myocardium?
The coronary circulation thus is unusual, because during systole, the myocardium receives little blood (and so oxygen) supply, but blood does perfuse the myocardium during diastole.
why does symapthetic stimulation predispose angina suffereds to pain?
- Increases heart rate, reducing the proportion of the time the heart is in diastole and thus capable of being perfused.
- Increases force of contraction (and thus oxygen demand).
- Deceases cardiac efficiency (more oxygen used to perform the same mount of work).
angina is normally primarily a result of…
Normally primarily as a result of occlusion of coronary arteries by fatty deposits and secondarily by subsequent pathological changes to the arteries
T or F
Anything that predisposes the heart to work reduces its capacity for perfusion and can result in angina
T
which is normal and which is angina?
for people who suffer from angina - may there be no more capacity - aka the arterioles are already amximally dilarted?
yep - so when demand increases - the heart cannot supply
During exercise there may be no additional capacity for dilatation and so the myocardium becomes ischaemic leading to …
During exercise there may be no additional capacity for dilatation and so the myocardium becomes ischaemic leading to the characteristic anginal pain
People with ischaemic heart disease develop ….. what to help them cope?
People with ischaemic heart disease develop collateral blood vessels to help the myocardium to cope
Individuals with ischaemic heart disease develop collateral blood vessels as a response to the poor perfusion. This phenomenon is known as ______.
Individuals with ischaemic heart disease develop collateral blood vessels as a response to the poor perfusion. This phenomenon is known as angiogenesis.
give some classes of druges used to treat angina?
- Nitrovasodilators
- ß-adrenoceptor blockers
- Ca2+-channel blockers
- If-blocker
- Inhibition of the late Na+ current
*
describe how nitrovasodilators can treat angina?
- include glyceryl trinitrate9, isosorbide mononitrate and amyl nitrite
- they are converted to NO in vascular smooth muscle cells
- cause venous dilitation - reducing central venous filling pressure - and preload
- also operate on the collaterals in chronic angina patients - mainly in ischaemic areas, not affecting dilitation in well perfused areas
Glyceryl trinitrate- how is it administereed?
Glyceryl trinitrate is poorly absorbed from the stomach and so it is taken sublingually (where it is absorbed directly into the systemic circulation)
nitrovasodilators:
They include glyceryl trinitrate, isosorbide mononitrate and amyl nitrite.
The first two of these are commonly used to treat ……
The third is a ….
They include glyceryl trinitrate9, isosorbide mononitrate and amyl nitrite. The first two of these are commonly used to treat angina, the former especially in acute attacks. The third is a non-therapeutic recreational drug
describe coronary steal?
Other vasodilator drugs, such as dipyridamole (which stimulates adenosine receptors) open all vessels (not only in ischaemic, but also in well oxygenated tissues) and diverts the blood away from the ischaemic region. This phenomenon is known as ‘coronary steal’.
describe how Beta blockers are used to treat angina
- ß-blockers like bisoprolol and atenolol (ß1 antagonists) reduce the effects of sympathetic stimulation that normally occur in the heart
- decrease BP - decreasing afterload
- Coronary blood vessels also have ß2 receptors (which normally cause vasodilatation) and also á1 receptors that produce vasoconstriction.
- Normally the á response is overwhelmed by the ß2 response, but non- specific ß-antagonists inhibit this, and unmask the á1-mediated constriction.
- In heart failure (which frequently occurs concurrently with angina) it is necessary to maintain sympathetic stimulation to produce an adequate cardiac output.
- Hence Beta blockers arent always great for heart failure - as sympathetic stimulation is required to maintain adequate CO
describe how Ca2+-channel blockers are used to treat angina
- dihydropyridines - block Ca2+ entry to smooth muscle
- causes vasodilation
- decreasing BP
- decreasing afterload
*
most commonly used dihydropyridine for treating angina?
Amlodipine
why do dihydropyridines work on vascular smooth muscle in preference to cardiac Ca2+ channels?
The answer lies in the low resting potential (-50 to -60 mV) of vascular smooth muscle.
This means that more channels remain inactivated than in cardiac muscle (with a resting potential of -80 to -90 mV) and dihydropyridines bind to the inactivated form of the channel.
how are funny current blockers used to treat angina?
- eg: ivabradine
- blocking If reduces pacemaker activity
- slows heart rate
- improves perfusion of the myocardium
- helps people with stable angina
- It is normally only used when ß-blockers or Ca2+-channel blockers are inappropriate - eg heart failure
what is stable angina?
best drug ?
angina due to exercise
these patients often have avery high heart rates
ivabradine may be appropriate
where in the heart is ivabradine selective to>
Because of the location of the HCN channels upon which ivabradine acts, its effects are selective to the sinus node and ivabradine has no effect on intra- cardiac conduction, myocardial contractility or ventricular repolarisation
describe how Inhibition of the late Na+ current can help in the treatment of angina
- drug eg: ranolazine
- inhibits the late phase of the Na current in cardiac myocytes
- in ischaemic myocardium - late Na current leads to climbing calcium levels (thorhg NaCa exchanger)
- leads to impaired relaxation
- poor cardio perfusion
- Blocking late INa means Ca2+ overload and diastolic wall stress are reduced, leading to improved coronary blood flow.
