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)
Other than troponin I and T, what other hormone is elevated in heart failure?
Atrial Natriuretic Peptide
What is a clear sign of heart failure in a chest X-ray?
Massively increased cardio: thoracic ratio
The widest part of the heart should be no more than 50% the width of the thorax
What is the system used to classify heart failure patients based on functional capacity?
New York Heart Association Classification (PPQ!)
1 = barely any symptoms
4 = can’t get out of chair or in bed
What are the different syndromes of heart failure and what symptoms are they associated with?
Pitting Oedema
Fluid accumulation leads to pitting effect when pushed
Raised JVP
Increased right-sided heart pressure backs up blood to jugular vein, causing it to bulge
Ascites
Fluid accumulation in PERITONEAL cavity
What do you give immediately if someone has pulmonary oedema?
Diuretics - to get rid of the fluid (increase urinary output)
State some common drugs used in heart failure.
ACE inhibitors Beta blockers Aldosterone antagonist - spironolactone Digoxin (for atrial fibrilation) Devices (cardiac resynchronisation, implanted cardioverter defibrillator)
What is the mechanism for left and right heart failure?
Left heart failure:
Insufficient contractility Blood backs up in lungs causing PULMONARY CONGESTION
Respiratory Symptoms: Breathlessness, Coughing, Wheezing
Dizziness
Cyanosis
Right heart failure:
PULMONARY HYPERTENSION High afterload
Increased afterload of the pulmonary circulation (pulmonary hypertension), this increases afterload on the right ventricle which has to pump with a greater pressure to contract.
-Ventricles need to work harder, leads to cardiomyocytes cell death and so right hear failure
Often secondary to left heart failure.
what is the difference between chronic HF and acute HF?
Chronic HF:
Slow onset.
Infection, pulmonary embolism, myocardial infarction or surgery.
Acute HF.
Rapid onset.
Symptoms similar to chronic HF, except the timing of onset is quicker and worsening is much more severe.
What is the difference between HF with reduced and preserved ejection fraction?
Reduced:~ 32%
- HF with reduced EF (HFrEF)
- Abnormal systolic function, i.e. ventricle is unable to pump blood into the aorta, this could be due to dilated cardiomyopathy, or valve stenosis
- Impaired contraction of the ventricles = increase in HR results in decreased cardiac output
- Typically, weakness is caused by damage or destruction of the ventricular myocytes
- Weaker ejection leads to higher diastolic pressures
- causes left ventricular end systolic volume to increase, as more blood left.
- Stroke volume decreases
- ejection fraction decreases
Preserved:50%
- HF with preserved EF (HFpEF)
- Abnormal diastolic function
- Normal contraction of the ventricle
- Increased stiffness of ventricle, impaired relaxation or impaired filling, lower preload
- Because EDV is inherently reduced, the stroke volume is also reduced so ejection function is preserved.
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Anatomy of the heart22
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Cardiovascular mechanics I26
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Cardiovascular mechanic II32
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Blood vessels21
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Electrical properties of the heart24
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Cardiovascular control 218
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Microcirculation25
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Blood vessel order, function & specialisation of cells in the cardiovascular system42
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The Sympathetic Nervous System and the Renin Angiotensin System40
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ECG basic14
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Identifying some basic disturbances of rhythm51
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Hypertension26
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Basic Haemostasis48
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Clinical Haemostasis and Thrombosis28
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Vascular Endothelium16
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Heart Failure39
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Atherosclerosis - Basics and Roles of Inflammatory Cells38
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Coronary Heart Disease, Angina, MI and Embolism25
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Patient cases12
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Calculating ECG3
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CBM self tests24
