Heart Failure Flashcards
What is cardiac output?
The volume of blood leaving EITHER side of the heart per minute (usually in the context of the left ventricle)
What is heart failure and what is this reliant on?
CO is inadequate in heart failure.
This is dependant on:
-Preload ( strech of that cardiomyocyte): Inadequate venous return can compromise SV
-Afterload ( force the ventricles have to contract against to eject blood) : Excessive resistance compromises ejection volume
-Contractility (intrinsic muscle strength): Inadequate contractility can compromise SV.
How to work out stroke volume?
How to work out ejection fraction?how to work cardiac output?
Stroke volume= End diastolic volume (EDV) - End systolic volume (ESV)
Stroke volume/ End-diastolic volume x 100 = Ejection fraction.
Cardiac output= stroke volume x heart rate
what can lead to a low SV?
Low Preload low venous return
High Afterload high peripheral resistance
Low Contractility ionic imbalance
How to measure ejection fraction?
Using a transthoracic echocardiogram.
- ultrasound of the chest
Define heart failure.
Syndrome that arises when the heart is unable to maintain an appropriate blood pressure without support. - P. Harris
Definition of heart failure in man - a clinical syndrome caused by an abnormality of he heart and recognised by a characteristic pattern of haemodynamic, renal, neural and hormonal responses.
- Inability of the heart to keep up with demand
- Inadequate perfusion of organs (e.g. brain, liver, kidneys)
- Congestion in lungs and legs
- Collection of signs and symptoms
What other organ normally fails as a result of heart failure?
Kidneys - they receive around 35-40% of cardiac output
State some causes of heart failure.
Arrhythmia Valve disease Pericardial disease Congenital heart disease Cardiomyopathy
What happens to the structure of the heart following myocardial infarction?
Part of the heart muscle will be weaker due to the formation of fibrous tissue, which leads to infarct expansion. The heart muscle will remodel and dilate in an attempt to maintain normal pumping activity.
What is cardiomyopathy? What are the main types?
Heart disease in the absence of a known cause. The muscle becomes enlarged, thickened and/or stiffened.
Dilated, Hypertrophic, Restrictive and Arrhythmic Right Ventricular Cardiomyopathy.
State some causes of dilated cardiomyopathy.
Congenital causes Idiopathic Infectious causes - HIV, rickettsia Toxins/Poisons - ethanol and cocaine Chemotherapeutic agents, antiviral agents
What is restrictive cardiomyopathy? State some causes.
The heart is unable to relax easily so the relaxation is very slow and there is diastolic dysfunction.
Causes: infiltrative disease e.g. sarcoidosis and amyloidosis
Storage disease - haemochromatosis and haemosiderosis
What is the commonest cause of death in heart failure?
Opportunistic arrhythmia
What is the hormonal response to heart failure?
Increased sympathetic firing - increase in noradrenaline and adrenaline (because your body thinks that it is bleeding to death)
RAS system is switched on - try to retain more sodium and water
Vasoconstrictors are produced by endothelial cells (e.g. endothelin-1)
What drugs are given to counteract these effect?
ACE inhibitors - block the RAS system
Beta blockers - MOST EFFECTIVE - they block the sympathetic drive
Aldosterone receptor antagonists (aldosterone receptors are high in heart failure)