LV dysfunction and heart failure 2 Flashcards
When is RAAS and the SNS stimulated?
When cardiac output drops, either due to:
blood loss
heart failure
Whats the renin-angiotensin-aldosterone system?
Angiotensinogen->RENIN-> Angiotensin 1-> ACE-> Angiotensin 2-> salt retention thru aldosterone release & vasoconstriction
angiotensin 2 is synergistic with the SNS- promotes the release of noradrenaline from nerve endings
What does the sympathetic nervous system do?
Releases noradrenaline-> vasoconstriction (leading to peripheral resistance) and increased cardiac output
also synergistic with RAAS- promotes the release of renin
How do changes in RAAS and the SNS benefit us when we lose blood?
tachycardia- increased CO
positive inotropic effect- increased CO
vasoconstriction- increased blood pressure- maintain flow
sodium and water retention- increased circulatory volume
How do changes in RAAS and the SNS make it worse when we have heart failure?
Tachycardia- increased workload and oxygen demand
positive inotropic effect- “ “
vasoconstriction- increase afterload
sodium and water retention- increased preload and oedema
chronic adrenergic stimulation- myocyte toxicity and arrhythmia
What are the main types of treatment for heart failure?
Diuretics vasodilators aldosterone antagonists ACE inhibitors ARB- angiotensin 2 receptor blocker beta blocker- interferes with SNS and thus noradrenaline production
What effects do ACE inhibitors have and when are they used? Examples of ACE inhibitors
Reduce mortality significantly -hypertension -heart failure -diabetic nephropathy ramipril, enalapril, perindopril, trandolapril
What are ACE inhibitors adverse effects?
Related to angiotensin 2- hypotension acute renal failure hyperkalemia teratogenic effects in pregnant women related to kinins- cough- dry and persistent rash anaphylactic reactions
Why do ACE inhibitors increase kinin levels?
ACE catalyzes the conversion of bradykinin to inactive peptides
inhibiting ACE means you potentiate the effects of bradykinin
What effects do beta blockers have and when are they used? Examples of beta blockers
reduce mortality (carvedilol, bisoprolol and metaprolol)
can also improve the chances of developing HF or having an event & being hospitalized
angina
heart failure
arrhythmias
hypertension
propanolol, atenolol, nadolol
How are beta blockers selective?
Either beta 1 selective or non selective (both beta 1 and 2)
increase the dose of the drug- becomes non selective
selectivity is relative rather than absolute
Why is the term cardioselective beta 1 incorrect?
up to 40% of the receptors in the heart are beta 2 receptors
thus cardioselective technically means beta 1 and 2
What are beta blockers main adverse effects?
central NS effects:
fatigue, headache, sleep disturbance, nightmares, depression
vascular effects:
bradycardia, hypotension, cold peripheries, erectile dysfunction, worsening of asthma or COPD, PVD-claudication or Raynauds
How can beta blockers cause heart failure?
When the heart is failing- SNS is doing its best to stimulate the heart and keep it going- if you use a standard dose of beta blocker (IN ACUTE HEART FAILURE)-> blocks these effects and causes a drop is pressure which is bad
can kill people with acute heart failure
thus it is only used in chronic heart failure and in very small doses
How does sacubitril and valsartan affect heart failure?
Combination therapy- known as entresto
sacubitril= neprilysin inhibitor- potentiate the effects of cardiac natriuretic peptides
valsartan= angiotensin 2 inhibitor- ARB