Ischaemic Heart Disease and MI Flashcards
When are fibrinolytic drugs used
For prophylaxis and after a myocardial infarction.
When are fibrinolytic effective to reduce mortality
If they are given immediately (less than 12 hours) after MI or stroke.
What do fibrinolytic drugs do
They act to accelerate conversion of plasminogen to plasmin which degrades fibrin in a thrombus.
What are two examples of fibrinolytic drugs
Tissue plasminogen activator (tPA) and streptokinase.
What is produced naturally by the body with fibrinolytic properties
Tissue plasminogen activator (tPA).
What is the risk associated with using fibrinolytic drugs
Bleeding
How many times a year can fibrinolytic drugs be used
Once
What reverses bleeding
Tranexamic acid
What surgical approaches are used for ischaemic heart disease
- Balloon angioplasty
- Senting
Why are there now more people living with heart failure
Because we are better equipped to deal with it now so not as many die straight away from it.
What is the Frank-Starling mechanism
If there is increased blood volume, there will be increased stretch of the myocardium and increased force with which to pump blood out.
By what mechanism does the heart work
By stretch and recoil. The greater the stretch, the greater the degree of recoil up to a certain point.
What happens to preload when more blood returns to the heart
Preload increases.
What is venous return
The amount of blood entering the ventricle during diastole
What does venous return determine
Preload
What does increased preload result in
Increased stroke volume and increased cardiac output.
What factors determine the end diastolic volume and therefore preload
- Venous tone and capacitance controlled by the sympathetic nervous system
- Plasma volume controlled by sodium and water secretion from the kidney.
What increases preload
The sympathetic nervous system constricting smooth muscle of blood vessels and the RAAS increasing blood volume.
What is afterload
The force against which the heart has to pump
What is afterload determined by
The tone in resistance arterioles.
What increases afterload
Increased resistance in the arterioles.
In which conditions is preload increased
- Hypervolemia
- Regurgitation of cardiac valves
- Heart failure
In which conditions is afterload increased
- Hypertension
- Vasoconstriction
Why is preload often larger in heart failure
Because the kidneys are not being effectively perfused and this results in a decreased ability to get rid of fluid.
Where is blood pressure detected in the kidneys
The juxtaglomerular cells near the afferent arteriole
What happens when low blood pressure is detected by the juxtaglomerular cells of the kidney
Renin is secreted into the plasma.
What does renin do
Renin cleaves angiotensin to produce angiotensin I which is then converted to angiotensin II.
Which enzyme converts angiotensin I to angiotensin II
Angiotensin converting enzyme (ACE).
What is the action of angiotensin II
It is a vasoconstrictor so increases blood pressure and afterload. It also stimulates the release of aldosterone and ADH.
Where is aldosterone secreted from
The adrenal cortex.
What is the role of aldosterone
It increase reabsorption of sodium ions in the kidney tubules back into the blood.
What do sympathetic nerves do to the heart
Act at beat 1 adrenoceptors to increase heart rate, conduction and contractility.
What do sympathetic nerves do at arterioles
Act on alpha adrenoceptors to bring about vasoconstriction and increase afterload.
What do sympathetic nerves do at the veins
Act on alpha receptors to bring about vasoconstriction and increase preload.
What do parasympathetic nerves do to the heart
Act at M2 (muscarinic/cholinergic) receptors to reduce heart rate, conduction and contractility.
What do sympathetic nerves do at the kidney
Act on beta-1 adrenoceptors to bring about activation of the renin-angiotensin system.
What are the symptoms of heart failure
- Breathlessness
- Muscle weakness
- Peripheral oedema
- Cardiac arrhythmias
- Poor tissue perfusion and organ failure.
What are the causes of heart failure
- Myocardial infarction
- Pressure overload
- Volume overload
- Cardiomyopathy
- Myocarditis
What is digoxin used to treat
Heart failure
What is digoxin
A cardiac glycoside
What do cardiac glycosides do
Increase the force of contraction due to increased calcium within the cell - it is a positive inotrope.
Other than digoxin, what is an example of another inotrope used to increase contractility
Dobutamine
What type of drug is dobutamine
A beta 1 adrenoceptor agonist.
Which drugs are used to break the cycle of heart failure and unload the heart
- Diuretics
- Inhibitors of the RAAS system - renin inhibitor, ACE inhibitor, angiotensin I receptor agonist, mineralcorticoid receptor agonists
- Beta blockers
- Other vasodilators.
What structural changes can occur in heart failure
- Fibroblasts laying down collagen leading to stiffness of vessels
- Hypertrophy
What is the aim at the kidney for treating heart failure
To increase sodium and water loss and therefore reduce blood volume and preload.
What are two examples of loop diuretics
- Frusemide
- Bumetamide
What do loop diuretics do
Loop diuretics impair NA+/K+ and Cl- reabsorption in the ascending loop of Henle.
What is an example of a mineralcorticoid receptor antagonist
Spironalactone
What do mineralocorticoid receptor antagonists like spironolactone do
Block the effects of aldosterone on Na/K reabsorption to increase fluid loss.
What do ACE inhibitors do
Inhibits angiotensin converting enzyme so angiotensin I is not converted to vasoconstrictor angiotensin II.
Give two examples of ACE inhibitors
- Enalapril
- Lisinopril
What do angiotensin receptor antagonists do
Prevent the binding of angiotensin II to its receptor to prevent the initiation of vasoconstriction.
Give two examples of angiotensin receptor antagonists
- Losartan
- Valsartan
Give two examples of beta 1 selective beta adrenoceptor antagonists
- Atenolol
- Metoprolol
What is the action of beta 1 selective adrenoceptor blockers
Reduce the sympathetic drive to the heart to reduce heart rate and block renin release from the kidney to decrease vasoconstriction so afterload and blood volume so preload.
What is an example of a nitrovasodilator
Isosorbide mononitrate
What is hydralazine
A vasodilator
In what situations ate nitrates and hydralazine used
When there is acute heart failure or in patients with chronic heart failure who do not respond to other drugs.
What happens to the heart wall in the progression of heart failure
it will become thicker and stiffer due to fibrosis and hypertrophy.
