Heart failure Flashcards
Explain the difference between a disorder, a disease and a syndrome
Disorder - your body is not functioning properly
Disease - A disease means that your body is not functioning normally, and science understands the specific process that led to that state. Everybody with the same disease undergoes the same basic process. There may be variations, but the underlying process is the same.
Syndrome - A collection of symptoms, but there is no guarantee that two patients with the same symptoms will have the same underlying pathology
Define heart failure
- A disoder of the heart that impairs it’s ability to deliver oxygen to the perihary and support physiological processes
What are the 3 main causes of heart failure?
Coronoary artery disease
Cardiomyopathy (structural changes in the muscle of the heart)
Hypertension
Heart failure can be a result of systolic or diastolic dysfunction.
Systolic dysfunction results from what?
Diastolic dysfunction results from what?
Systolic: Inability of heart muscle to contract properly
Diastolic: the inability of the heart to relax and fill properly
When the failing heart can longer pump blood properly, there are various hemodynamic burdens placed in the heart as a result. State the most important
- Increase in end-diastolic ventricular volume
- increased end diastolic pressures
- Elevated venous pressure
In heart failure, blood ends up backing up into which organ?
The lungs
Good to way to look at heart failure is loking at the Stroke volume (how much blood is ejected from the ventricle, as a percentage of the total volume of blood that was in the ventricle (as not all blood will get ejected). The percetage of blood that is ejected (Stroke Volume/Total blood in ventricle before contraction) = Ejection fraction.
What is a normal range of Ejection fraction?
What is an ejection fraction of less than 50% suggestive of?
50-70%
Systolic heart failure
Diastolic heart failure is when the heart is squeezing fine but not filling enough blood.
In this case the ejection fraction is NORMAL. Explain what is happening with regards to the stroke volume and the preload?
The stroke volume is lower, so is the total volume since in diastolic heart failure the ventricle is not filling properly. Therefore you would expect a normal ejection fraction
What are some of the main causes of heart failure?
Coronary heart disease
Hypertension
Mycocardial infarction
In heart Failure, is the main hemodynamic factor that is affected?
Cardiac output
Discuss the 2 main neurohumeral compensatory mechanisms that are employed in heart failure.
- Activation of the symapthetic nervous system
- Noradrenaline is released by autonomic nerves which act on BETA 1 receptors, therefore increasing heart rate
- Activation of the renin angiotensin system stimulating water and salt retention, therefore increasing blood volume and therefore mainitaning arterial pressure
Increased preload in heart failure results in what changes to the structure of the heart. What changes occur and what is this called?
Heart stretches to accomodate increased volume - Cardiac Dilation, allows the heart to contract more forcefully in response to the increased amount of blood since the fibres are now LONGER
ALthough the stretching initially helps stroke volume, overstretching will do what to the stroke volume?
Reduce it
Aside from cardiac dilation, what other structural change in the heart can occur?
Hypertrophy
Describe briefly the difference between dilation and hypertrophy?
- Hypertrophy is increase in muscle thickness
- Dilation is increase in fibre length but not thickness
State the clinical signs of heart failure
- Pulmonary oedema (accumulation of fluid in alveoli) - this makes sense given the increased build up fluid as a result in reduced stroke volume, pulmonary blood pressure will be increased - meaning more fluid will leak out
- Raised jugular venous pressure due to fluid build up in right side of heart
- Peripheral oedema - more fluid is pushed out as a result of increased venous pressure, and therefore remains there
INCREASED VERNOUS PRESSURE MAKES SENSE - AS LESS BLOOD IS BEING PUMPED OUT INTO THE ARTERIAL CIRCUIT
Explain why you would expect to see perihpheral oedema in heart failure patients
- Venous blood pressue is going to be up
- Hydrostatic pressure is significantly increased, meaning a lot of fluid will be pushed out, but not the same amount will be pushed back in, leading to fluid build up
This diagram summaries the major responses to heart failure
Explain how ACE inhibitors ar used to treat heart failure. GIve examples of such drugs
- Inhibit the enzyme ACE which is produced in the lungs, preventing the conversion of angiotensin 1 to angiotensin 2
- Angiotensin 2 has vasconstrictive properties, so this effect is blocked by ACE inhibitors thereby reducing TPR
- Also prevents activation of Renin-Antgiotensin-Aldosterone system, therefore ACE inhibitors prevent the system increasing blood pressure
Captopril, Enalapril, Lisinopril
Explain how beta blockers can be used to treat heart failure. Give examples of such drugs
These drugs would typically be used in dyastolic heart failure - basically the idea is that you would slow the heart rate down allowing it more to time to relax and FILL
- Prevents Sympathetic activity that would normally increase heat rate
- Also reduces sympathetic activity to adrenal gland - thereby reducing renin prodution (renin is produced by juxtaglomerual cells in the kidney)
Atenolol (Beta 1 selective), Propanolol (beta 1 and 2)
Explain how mieralocorticoid receptor antagonists can be used to treat heart failure. Give examples
- Normally, Aldosterone stimulates reabsorption of Sodium AND WATER, promotes excretion of potassium of hydrogen ions
- The mineralocorticoid receptor antagoists prevents all of this, therefore, reducing water reabsorpion and sodium, therefore reducing blood volume.
Spironalactone
See normal functions below
