9- Heart Failure Flashcards
Define heart failure
A state in which the heart fails to maintain an adequate circulation for the needs of the body despite adequate filling pressure
What are the main causes of heart failure?
Ischaemic heart disease Hypertension Congenital/ valvular disease Arrhythmia Dilated cardiomyopathy (pregnancy/alcohol/bacteria)
Explain the classification of heart failure
Class I- no symptomatic limitation
II - normal physical activity results in symptoms
III - less than normal physical activity results in symptoms, marked limitation of physical activity
IV- unable to do any physical activity without symptoms, symptoms at rest
Explain heart failure in terms of starlings law
The heart cannot produce the same amount of force for a given level of filling (stretch of fibres)
What happens to the heart in left ventricular systolic dysfunction?
Increased left ventricular capacity
Reduced LV output
Myocardial wall thins due to fibrosis/necrosis and matrix proteinases destroying collagen
Mitral valve incompetence as LV dilates
Weakened heart adversely affected by adrenaline surges
Cardiac arrhythmias
What structural changes can lead to heart failure?
Bundle branch blocks: change in contractility
Extracelluar matrix protein changes, increased collagen III
Cellular structure/function changes (myocyte hypertrophy, sER dysfunction)
Describe the two main pathways to heart failure
High BP, LV hypertrophy, increased afterload, global thinning of wall
MI, remodelling, scar tissue forms and thins area of infarct
Both increase LV size and capacity, reducing cardiac output
What does the sympathetic nervous system do in heart failure and what effect does this have?
Up-regulates RAAS - leading to fluid retention and LV hypertrophy
Vasoconstriction - increases wall stress, LV hypertrophy and decreased contractility
Increases heart rate and contractility - increases myocardial demand for oxygen leading to decreased contractility
Beta adrenergic receptors down regulated
Noradrenaline induces hypertrophy/necrosis via alpha receptors
How is RAAS activated in heart failure?
Reduced renal blood flow
Sympathetic stimulation releasing renin from macula densa
What are the effects of increased angiotensin II?
Vasoconstriction
Aldosterone release, leading to Na and H2O retention, which increases blood volume, increasing afterload, LV hypertrophy
Organ damage
What receptor does Angiotensin II bind to?
AT1 receptor
What effect does angiotensin II have on the brain?
Atherosclerosis
Vasoconstriction
Leading to stroke
What effect does,angiotensin II have on vasculature?
Vascular hypertrophy
Endothelial dysfunction
Leading to hypertension
What effect does angiotensin II have on the heart?
LV hypertrophy Fibrosis Remodelling Apoptosis Leading to heart failure and MI
What effect does angiotensin II have on the kidneys?
Decreased glomular filtration rate
Increased proteinuria
Increased aldosterone release
Renal failure
