P15: Treatment of Heart Failure Flashcards
What is (congestive) heart failure
A state in which the heart cannot provide sufficient cardiac output to satisfy the metabolic needs of the body.
Name as many symptoms of Congestive Heart Failure as you can
Shortness of breath upon motion Coughing Fluid retention Oedema in lower limbs and abdomen Increased nocturnal urination Tiredness Muscle Weakness Dizziness Irregular heartbeat May be asymptomatic
Define what happens in myocardial infarctions, coronary heart disease and cardiac arrest
- Myocardial Infarction - Death of a piece of heart tissue
- Coronary Heart Disease - failure of heart oxygen supply
- Cardiac Arrest - complete cessation of blood supply
AY BAWS CAN I HABE DE NOTE PLZ
Heat failure can cause similar symptoms to liver failure, kidney failure, obesity, thyroid disease and anaemia
What are the potential causes of heart failure
Any condition that reduces the efficiency of the myocardium through damage or overloading:
Myocardial infarction
Hypertension
Valve disease
Excessive Alcoholism
Infection
Amyloidosis - abnormal deposition of amyloid proteins in tissues
What can often be observed in the stroke volume and heart rate of people with heart failure
Reduced SV due to failure of systole and/or diastole
Increased HR due to increased SNS activity
What is the Frank Starling law of the heart
Stroke volume increases in response to an increase in the volume of blood filling the heart (EDV) when all other factors remain constant
What is the End Diastolic Volume
This is the amount of blood in the ventricle immediately before contraction
Describe the mechanism of the frank starling law
As a larger volume of blood flows into the ventricle, this stretches the walls of the heart, causing a greater expansion during diastole
This increases the force of the contraction and thus the quantity of blood that is pumped into the aorta during systole
Why does the mechanism of the frank starling law fail in congestive heart failure
Damage to cardiac muscle fibres
Ventricle wall overstretch, actin-myosin coupling becomes disorganised
The reduced CO from heart failure causes what physiological responses
- Decreased arterial BP, activating baroreceptors and causing peripheral vasoconstriction - improves BP but increases heart workload
- Increased pituitary ADH release, increased fluid retention, raises BP
- Reduced kidney perfusion stimulates the RAAS system, promotes sodium and water retention, vasoconstriction
AY BAWS CAN I HABE DE NOTE PLZ
Loads of circulating hormones released in response to decreased CO directly induce structural remodelling of the heart, causing cardiac hypertrophy, like catecholamines, renin, angiotensin and aldosterone
What is Stroke volume governed by
Preload
Afterload
Contractility
What is preload
the EDV at the beginning of systole
What is afterload
ventricular pressure at the end of systole (i thot it was the resistnace that systole has to push against)
What are overall aims of heart failure treatment
- Increase contractility of cardiac muscle
- Reduced preload/afterload
- Reduce water load (blood volume)
What are some examples of cardiac glycosides
Digoxin
Digitoxin
What is the mechanism and effect of cardiac glycosides
- Bind to K+ site of Na+/K+ antiporter
- Maintain Ca2+ entry
- Increase contractile strength without increasing O2 demand
AY BAWS - improves symptoms, doesnt prevent mortality
Name as many side effects of Digoxin (cardiac glycosides) as you can
- Increased AV conduction time (increased vagal activity)
- Increased incidence of ectopic pacemaker activity - increased autorhythmicity
- Increased Diuresis
- narrow therapeutic window
- patients with hypokalaemia are at increased risk of toxicity
- toxic effects of digoxin are managed by anti-digoxin antibodies
What type of drugs are used to prevent/treat oedema
diuretics
Where are oedemas most likely to happen
lungs and lower body
Name a thiazide diuretic and describe its mechanism
Hydrochlorothiazide
Acts on early DCT = increased Na+ and K+ excretion
Name a loop diuretic and describe its mechanism
Frusemide
Acts on ascending LOH = increased Na+ and K+ excretion
Name a potassium sparing diuretic and describe its mechanism
spironolactone
Acts on the DCT = increased Na+ excretion, important when using cardiac glycosides
What 2 approaches are used to reduce the preload/afterload
- Direct vasodilators
- Modulate the renin, angiotensin, aldosterone system
These reduce the arterial blood pressure and/or venous return
AY BAWS CAN I HABE DE NOTE PLZ
i think the RAAS system, which occurs along with reduced arterial BP, causes Na+ and water retention, which can cause the oedema formation in ppl with heart failure lol?
Name some ACE inhibitors
angiotensin converting enzyme
enalapril
captopril
Name some angiotensin 2 receptor antagonists
iosartan
candesartan
What are the overall effects of ATII
Increased ADH, aldosterone, SNS and vasoconstriction
What converts angiotensinogen to angiotensin 1
renin
why are the no useable renin inhibitors
too many side effects
How do ACE inhibitors affect symptoms and mortality and ventricular hypertrophy
- Improves symptoms
- Decreases mortality
- Reduces ventricular hypertrophy
What can be used instead of ACE inhibitors
ATII receptor antagonists
How do ACE inhibitors and ATII receptor antagonists decrease afterload
Antagonising the vasopressor effect of angiotensin, decreasing cardiac work
What is a downside to ACE inhibitors
Produces a persistent cough
What are ACE inhibitors often given alongside
Diuretics
Name an organic nitrate and describe their general mechanism
Isosorbide Dinitrate
Intracellular NO activates guanylate cyclase, increasing cGMP
Causes increased Ca2+ sequestration and smooth muscle relaxation
Venodilator, reduces preload
Name some problems with organic nitrates
Headaches
Flushing
Tachycardia
Tolerance
Name some other vasodilators
Hydralazine (mechanism unclear)
Minoxidil (K+ channel opener)
Arterial vasodilators, reduce afterload
When is isosorbide - hydralazine combo therapy used and why
Appears to be particularly beneficial in CHF patient of African or Caribbean origin
they respond less effectively to ACEI therapy
What type of drugs aims to improve cardiac contractility in heart failure
Cardiac glycosides
What type of drugs aim to reduce workload by reducing blood volume in heart failure
Diuretics
What type of drugs aim to reduce workload by reducing pre/afterload
ACE inhibitors and vasodilators
