Heart Failure Flashcards
What is heart failure?
Failure to deliver adequate blood to the body
Failure as a pump
Insufficient oxygen and metabolic supply to the tissues
What are the causes of heart failure?
- Ischaemic damage (chronic)
- Excessive cardiac workload (hypertension or valve disease)
-> stiffening of valves - changes morphology of the heart
What is the equation for cardiac output?
Heart rate (bpm) x stroke volume (L/b)
What often causes the problems in heart failure?
Stroke volume - less ejected blood
What is cardiac index?
Cardiac index (L/min/m2) = cardiac output/body surface area
What is the pathophysiology of heart failure?
Pump failure
Fall in blood pressure
Reflex compensatory mechanisms
1. Retention of salt and water -> increased blood volume (renin-angiotensin-aldosterone system)
2. Reflex tachycardia and vasoconstriction (baroreceptor reflex)
= increase cardiac workload which exacerbates the heart failure
What happens when the right hand pump fails?
- Right hand fails
- Build up in venous side
- Vessels distend
- Oedema (hydrostatic pressure)
- Swollen ankles, enlargement of liver
What happens when left hand pump fails?
- Left hand fails
- Increased pulmonary pressure
- Pulmonary oedema
- Insufficient oxygen exchange
- Breathlessness
Why measure CVP?
Establish the pressure in the right atrium Establish blood volume deficits Evaluate circulatory failure Act as a guide in fluid replacement Reflect response to treatment
How do you measure pulmonary pressure?
The Swanz-Ganz Catheter
What does the Swanz-Ganz catheter do?
Measure pulmonary artery and diastolic pressure or pulmonary wedge pressure
What does measuring pulmonary pressure reflect?
Left atrial pressure (left ventricular diastolic filling pressure)
Treatment of heart failure
What can be administered to decrease the workload?
ACE Inhibitors
Diuretics
Beta-Blockers
Treatment of heart failure
What can be administered to increase the force of contraction?
Cardiac glycosides
To treat heart failure, what 2 ways can you treat it?
Decrease workload
Increase force of contraction
A new heart failure diagnosis is made- how do you treat it at first?
ACE Inhibitor and titrate upwards
What happens if the first treatment doesn’t work?
If ACE inhibitor not tolerated, consider angiotensin II antagonist (ARB)
Why would the first treatment not be tolerated?
Severe cough for example
What would be the second treatment option?
Add beta-blockers and titrate upwards
What if patient was still moderately- severely symptomatic after the second treatment?
Administer spironolactone (diuretic)
Why would you administer diuretic to a patient with heart failure?
To control congestive symptoms and fluid retention
When would you give digoxin?
If patient still symptomatic with diuretic, ACE inhibitor and beta blocker
What do you do when the patient has all the available medication and is still symptomatic?
Seek specialist advice
What do ACE inhibitors do?
Inhibit the synthesis of angiotensin II by blocking angiotensin enzyme
What is angiotensin II?
Vasoconstrictor
When is angiotensin II released?
In renin-angiotensin-system
What does angiotensin enzyme do?
Convert angiotensin I -> angiotensin II
What is the result of inhibiting angiotensin II synthesis?
Decreased peripheral resistance and reduction in blood pressure
What examples of ACE inhibitors are there? (name 3)
Enalapril, Lisinopril, Ramipril
How does the renin-angiotensin system work?
- Kidney releases renin
- Renin acts on the pathway of angiotensinogen -
> angiotensin I - Angtiotensin I is converted to angiotensin II via angtiotensin converting enzyme
- Angtiotensin II is converted to aldosterone
- Aldosterone leads to sodium and water retention
- Angtiotensin II leads to vasoconstriction
- Vasoconstriction and sodium and water retention lead to the increase in BP
- Vasoconstriction also leads to increased afterload
- Increased afterload and blood pressure lead to heart failure
- Heart failure leads to low blood pressure
- low blood pressure acts on the kidney which acts on the kidney
Why are there angiotensin receptors in the medulla?
To prevent aldosterone release
What is lorsartan?
Angiotensin II receptor antagonist
Why would you use lorsartan?
Alternative to ACE inhibitors that may give a dry persistent cough
How do ACE inhibitors cause a cough?
Bradykinin is converted to inactive metabolites. ACE inhibitors block this conversion which leads to a build up of bradykinin. This build up causes a cough
What are ARBs?
Angiotensin receptor blockers
What do ARBs do?
Block Angtiotensin I -> Angiotensin II.
Do ARBs cause a cough? Why?
No - specific to angiotensin I. ACEs aren’t which is why they act on Bradykinin
What are direct renin inhibitors used for and why?
Angiotensin II can be produced by other pathways so block renin
Also, when Angiotensin II is blocked, renin builds up, so need to inhibit it
What is an example of a direct renin inhibitor?
Aliskaren
What are diuretics used for?
Reduce blood pressure and fluid overload
What 3 kinds of diuretics are available?
Thiazaides
Loop diuretics
Potassium-sparing diuretics
What is an drug example of a Thiazaide?
E.g. bendroflumethiazide
What do thiaziaides do?
Decrease blood volume and inhibits sodium reabsorption in distal tubule
How do thazaides decrease blood volume?
Inhibit sodium reabsorption in distal tubule
What is an example of a loop diuretic?
Furosemide
What do loop diuretics do?
Decrease blood volume
How do loop diuretics decrease blood volume?
Inhibit sodium reabsorption from loop of Henle
Whats more potent - Thiazaides or loop diuretics?
Loop diuretics
What kind of heart failure do loop diuretics treat?
Severe heart failure
What is a side effect of loop diuretics? How?
Encourages potassium excretion - can cause hypokalaemia
What two kinds of potassium-sparing diuretics are there?
Aldosterone receptor antagonists
Sodium channel blockers
What is an example of an aldosterone receptor antagonist?
Spironolactone
What heart failure is spironolactone used to treat?
Severe heart failure
What is an example of a sodium channel blocker?
amiloride
triametrene
What do beta-blockers do?
Block sympathetic stimulation of the heart to reduce contractility
What treatment are beta-blockers used alongside?
ACE inhibitors and diuretics
3 examples of beta blockers
Carvedilol, bisoprolol, metoprolol
Are cardiac glycosides an inotrophic drug or a chronotrophic drug?
Inotrophic
What are cardiac glycosides used for?
Increase force of contraction
What two types of digitalis are there?
Digoxin - White fox glove
Digitoxin - Purple foxglove
What is the mechanism of action of cardiac glycosides?
Competitively bind to K+ site of Na+/K+ ATP-ase pump in myocytes- inhibiting it
Inhibition leads to Na+ build up on the inside of the cell
High Na+ concentration inside the cell leads to reduces Ca2+ and Na+ exchange:
Ca2+ is meant to be pumped out, Na+ pumped in - already Na+ build up so slows this
Increases intracellular Ca2+ levels
More Ca2+ available in cell for muscle contraction
Na+/K+ ATP-ase pump - Which of Na+ and K+ is on the inside of the cell, and the outside?
K+ - Outside
Na+ - Inside
give 2 examples of cardiac glycosides
digoxin
digitoxin
