Pharmacology of drugs used to treat heart failure Flashcards
when is heart failure with reduced ejection fraction initiated (1,2,3,4 answers LAQ of why do heart failure treatment drugs work)
initiated when an index event causes the pumping capacity of the heart to be impaired
what does reduced pumping capacity of the heart result in (2)
results in compensatory activation of the sympathetic nervous system and the renin angiotensin aldosterone system
- neurohormonal activation
what does neurohormonal activation lead to (3)
results in a series of coordinated responses that collectively work to restore cardiovascular homeostasis in the short term
what does sustained neurohormonal activation lead to (4)
drives the progression of HFrEF through the deleterious effects exerted on the circulation and myocardium
what forms the basis of modern therapy for HFrEF
Antagonism of neurohormonal systems
what effects does heart failure have on the sympathetic nervous system
- decreased Baroreceptor responsiveness
- myocyte hypertrophy
- increased arrhythmias
- impaired diastolic and systolic function
- reduced renal blood flow
- increased renin release
- increased tubular reabsorption of Na+
- increased activation of RAAS
- decreased response to natriuretic peptides
- vascular hypertrophy
what is the equation for cardiac output
cardiac output= Stroke volume x heart rate
describe the sympathetic response to reduced cardiac output in the neurohormonal model
- Heart is damaged which activates sympathetic system
- releases adrenaline which acts on B1 receptors
- increase frequency and force of contractability
- increases work load so heart is using more energy
- causes vasoconstriction of arterioles and this increases after load and pre load
- Increases In intercellular calcium and cAMP
- not effective in HF
describe the RAAS response to reduced cardiac output
- reduced cardiac output
- reduces renal blood flow
- activates RAS and angiotensin II
- activates aldosterone and leads to Na+ and H2o retention
- increases arterioconstruction
- Ang II works on AT1 receptors and increases afterload and preload and drives remodelling of heart
- increases cardiac workload
- NOT beneficial in the long term
describe the natriuretic peptide response to low cardiac output
- reduced cardiac output
- increased natriuretic peptides
- leads to veno dilation and arteriodilation
- decreases remodelling
- decreases blood pressure
- reduces cardiac workload
- Increased stretch of the heart
- ANP is increased
- Natriuretic Peptides don’t have much effect
- when RAAS and sympathetic system are over activated, reduces the effect of natriuretic peptides
what is the equation for blood pressure
blood pressure= total peripheral resistance x cardiac output
what are the problems with prolonged compensation
- starlings law- overstretch leads to loss of function
- desensitisation of beta receptors
- increased angiotensin secretion leads to increased afterload which can drive remodelling of heart
- abnormally high levels of NA/A causes increases in heart rate (catecholamines) leading to arrhythmias
- myocardial hypertrophy
- makes heart stiffer
- muscle growth can decrease chamber size
- muscle growth can occur faster than blood vessel supply
what is the 1st line treatment of heart failure
- offer diuretics for congestive symptoms and fluid retention
- for heart failure with preserved ejection fraction, manage comorbidities and offer personalised exercise based cardiac rehabilitation programme
- for heart failure with reduced ejection fraction, offer ACE inhibitor or beta blocker
what are the most effective diuretics for heart failure
loop diuretics
- furosemide, bumetanide
what is the role of diuretics
- provide symptomatic relief
- decrease Na+ retention and increase H2O loss
- decrease preload and afterload
what can be used to overcome resistance in diuretics
metalozone (thiazide like diuretic) can be used in combo with loop diuretics
what are the side effects of loop diuretics
- dehydration/hypotension
- loss of ions
- hyperuricaemia and gout
what is the mechanism of action of loop diuretics
- blocks sodium potassium chloride cotransporter
- increases Na+ excretion
- increases K+ excretion
- increases Cl- excretion
- reduce sodium chloride reabsorption in the thick ascending limb of the loop of Henle