Cardiovascular: Session 9 Flashcards
What is the definition of 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.
What is the primary cause of systolic heart failure?
Ischaemic heart disease
What are some other causes of systolic heart failure?
- Hypertension
- Dilated cardiomyopathy
- Valvular heart disease/Congenital
- Restrictive Cardiomyopathhy
- Hypertrophic Cardiomyopathy
- Pericardial disease
- High-Output heart failure
- Arrhythmias
What is the ejection fraction of the heart?
50% plus
What are some factors that influence cardiac output?
- Heart rate
- Venous capacity
- Myocardial contractility
- Aortic & Peripheral Impedance (after load)
What are the causes of left ventricular systolic dysfunction?
- Increase left ventricular capacity
- Reduced left ventricular cardiac output
- Thinning of the myocardial wall
- Mitral valve regurgitation
- Neuro-hormonal activation - e.g adrenaline surge
- Cardiac arrhythmias
What are some structural changes in the heart that lead to heart failure?
- Loss of muscle
- Uncoordinated or abnormal myocardial contraction
- Changes to the extra cellular matrix (increase in collagen, slippage of myocardial fibre orientation)
- Changes of cellular structure and function
How does the sympathetic nervous system attempt to correct cardiac output in heart failure patients?
There is an early compensatory mechanism to improve Cardiac output through the baroreceptor-mediated response. this is through
- Improvement of cardiac contractility
- Arterial and venous vasoconstriction
- Tachycardia
In the long term, how does the the sympathetic nervous system lead to heart failure?
- Beta adrenergic receptors are down regulated
- Chronic high levels of
- Noradrenaline leads to cardiac myocyte hypertrophy, myocyte apoptosis and necrosis via alpha receptors.It also induces up-regulation of the RAAS .
- Reduction in heart rate variability which can lead to greater risk of arrhythmia
What effect does angiotensin 2 have on the angiotensin 1?
- Increase in Water retention
- Vasoconstriction
What effect does angiotensin 2 have on the angiotensin 2 receptor?
-Increase in nitric oxide
What is the effect of nitric oxide on blood vessels?
Vasodilation
What causes an increase in nitric oxide?
- Bradykinin acting on the bradykinin 2 receptor
- Angiotensin 2 action on the angiotensin 2 receptor
What in the RAAS system has a deleterious effect that leads to pathology?
Angiotensin 2 acting on the angiotensin 1 receptor.
How is the RAAS system commonly activated in heart failure?
- Reduced renal bood flow
- Sympathtic Nervous System induction of renin from macula dense
What is the effect of elevated angiotensin 2?
- Potent vasoconstrictor
- Promotes left ventricular hypertrophy and myocyte dysfunction
- Promotes aldosterone release
- Promotes Na+/H2O retention
What is oedema?
Oedema is excessive volume of fluid within the tissues. One of its causes is heart failure. It is due to changes in capillary dynamics.
What is net filtration pressure?
Hydrostatic pressure - Osmotic pressure
How does hydrostatic pressure go up?
Increase in pressure due to increase in circulation volume increase the amount of hydrostatic pressure so you get increased oedema.
What can heart failure changes in vascular endothelium?
It can alter the vascular tone
What is the effect of alteration in vascular endothelium on skeletal muscle?
There is a change in the skeletal muscle due to reduced skeletal muscle blood flow. This leads to reduction in skeletal muscle mass so all muscle is affected including the limbs and respiratory (diaphragm). The abnormalities of structure and function contribute to fatigue and exercise tolerance.
What is the effect of sever heart failure on the renal system?
Renal blood flow falls leading to reduced glomerular filtration rate. This leads to subsequent rise in urea and creatinine.
What blood test can be done to test the function of the kidney in heart failure ?
-Test the urea levels
What exacerbates the renal system damage in severe heart failure?
Treatment by inhibition of the actions of angiotensin 2
