CVS 11.1 - Heart Failure Flashcards
What is heart failure?
A state in which the heart fails to maintain an adequate circulation for the needs of the body despite an adequate filling pressure
How does ischaemic heart disease lead to heart failure?
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How does hypertension lead to heart failure?
- Causes LV hypertrophy which then dilates
- Chronic increased afterload = decreased ventricular compliance
- Increases oxygen demand of the myocardium
How does dilated cardiomyopathy lead to heart failure?
- LV becomes large and weakened
- ↓ pumping ability of hypertrophic part
- ↓ function
How does valvular heart disease lead to heart failure?
- Stenosis of blood in the atria = Doesn’t drain properly
- ↑ stretch of the myocardium
- Stretches enough to damage electrical conducting system
How does pericardial disease lead to heart failure?
- ↑ fluid between heart and pericardium
- ↑ intrapericardial pressure
- Causes ↑ SV so ↑ CO
Give an example of high output heart failure and describe how it can lead to heart failure
- Anaemia
- ↓ haemoglobin = ↑ work load of heart to compensate for ↓ O2
- Puts extra pressure on the mitral valve
How does heart failure progress?
- Class 1 = no symptoms, physical activity isn’t limited
- Class 2 = physical activity slightly limited resulting in symptoms (not at rest)
- Class 3 = Limited physical activity, less than normal resulting in symptoms (none at rest)
- Class 4 = Can’t exercise with symptoms, ↑ with activity and are present at rest
What is the value for cardiac output?
5 litres/minute
What is the value for stroke volume?
75ml/beat
What is the value of LV eSV?
~75ml
What is the value of LV eDV?
~150ml
What is ejection fraction?
The percentage of blood ejected from each ventricle per contraction (50%)
What is starling’s law? How does this relate to heart failure
- The force developed in a muscle fibre is dependent on the degree to which the fibre is stretched i.e. volume of blood
- HF = ↓ force for the same amount of volume
What is systolic dysfunction? How is it caused?
- Left ventricular ejection fraction becomes lower than 40% due impaired ventricular contraction
- Myocardial wall becomes thinner due to fibrosis/necrosis (↑ type 1-3 collagen) and matrix proteinases
What happens to cardiac output and LV capacity as a result of systolic dysfunction?
- LV capacity increases
- LV Cardiac Output decreases
What changes can occur to cause systolic dysfunction?
- Dilatation of the left ventricle
- Pulls cusps of the mitral valve apart = dysfunction
- ↑ risk of cardiac dysrrhythmias
What are the structural changes involved in heart failure?
- Globalised remodelling (dilatation) leading to localised thinning. Acute infarction = ↓ skeletal muscle blood flow so ↓ skeletal muscle mass
- Diastolic heart failure due to hypertrophy of left ventricle -> becomes smaller so can hold less volume and becomes stiff
What are the cellular changes involved in heart failure?
- Myocyte hypertrophy
- Irregular Ca2+ regulation
- ↑ Na+, angiotensin 2 and cytokines
- Release of troponin C
How does stimulation of the sympathetic nervous system lead to an increased cardiac output?
- Beta-1 activation in heart = +ve chronotropic effect (↑HR)
- Beta-1 activation in heart = +ve inotropic effect (↑ contractility)
- Alpha-1 activation in vascular smooth muscle = vasoconstriction of arteries so ↑ workload (↑ preload and afterload)
How can sympathetic stimulation become detrimental?
- Leads to downregulation of beta adrenoceptors
- Noradrenaline promotes formation of fibrosis and hypertrophy and promotes ↑RAAS
What is the function of angiotensin 2?
- Promotes LV hypertrophy and myocyte dysfunction
- Causes vasoconstriction
- Causes aldosteron release (Na+ and H2O retention in the kidneys = ↑BV)
How does bradykinin contribute to the cardiovascular system?
- Promotes natriuresis (Na+ excretion in the urine)
- Promotes vasodilation
- Stimulates prostaglandin production
- Stimulates NO production
What are natiuretic hormones?
- Polypeptide hormones (endocrine and paracrine) secreted by cardiac myocytes in response to ↑ stretch for powerful vasodilation
- Maintain blood pressure and extracellular blood volume
