Heart failure Flashcards
Heart failure
A state where the heart is unable to maintain cardiac output to meet the demands of the body.
This results from any structural or functional abnormality that impairs:
Ejection of blood from the ventricle
Filling of ventricle with blood
Diastolic vs systolic heart failure
A structural or functional abnormality of the heart that impairs:
The ventricles to eject blood out- Systolic
Shows high end systolic volume
The filling of blood in ventricles- Diastolic
Shows low end diastolic volume
Heart rate and cardiac output
An increase in HR generally increases CO due to the equation: CO= HR x SV
BUT: when HR is too high, this decreases preload, which will decrease SV.
Excessively high HR can decrease CO.
Preload:
-Factors that affect it
Stretching of cardiomyocytes are the end of diastole, before systole.
Factors that affect preload:
Central venous pressure-
increased pressure= increased preload.
Rate of venous return- higher rate= increase preload
Blood volume- preload increases
Vasoconstriction- increases preload
Afterload:
- Factors that affect afterload
The resistance against the blood ejected by the ventricles.
Factors that affect afterload:
Pressure in Aorta and pulmonary artery- increase in pressure, increases afterload.
Hypertension- Higher blood pressure= higher afterload
Vasoconstriction- increase TPR, which increase blood pressure= increased afterload.
Systolic heart failure:
- Include causes
A type of low output heart failure.
Results from the loss of contractile function in the cardiomyocytes. This can be due to:
Ischaemic injury (MI)
Volume overload- eccentric hypertrophy
Pressure overload- concentric hypertrophy
Diastolic heart failure
- Include causes
A type of low output heart failure.
The heart chambers are unable to relax during diastole, preventing them from filling and expanding.
Causes:
Significant L.ventricular hypertrophy
Infiltrative disorders- deposits in the heart that causes ventricular walls to stiffen.
Constrictive pericarditis
Restrictive cardiomyopathy.
Dilated cardiomyopathies
- Include causes
Disease of the cardiomyocytes which causes the left ventricle to become enlarged and weakened
Causes: 50% hereditary Pregnancy Drug toxicity- like chemotherapy (herceptin), alcohol dependence, systemic disease. Myocarditis- viral
Hereditary hypertrophic cardiomyopathy
- Include causes
Condition where the heart is unable to pump blood out efficiently due to thickened ventricular wall.
This condition can be inherited due to mutation of a gene that codes for the sarcomere.
Restrictive cardiomyopathy
- Include causes
Rare cause of cardiomyopathy where heart contraction is normal, but it cannot relax properly to allow ventricles to fill.
Causes:
Build up of scar tissue
Build up of abnormal proteins- amyloid main cause in UK.
Compensatory mechanisms in heart failure.
Vasoconstriction- increases venous return and preload.
This generates greater force of contraction in cardiomyocytes.
Structural change of cardiomyocytes:
Hypertrophy
Neurohormonal system:
Noradrenaline released- increase HR, vasoconstriction and contractility.
Atrail natriuretic peptide (ANP)- increases renal Na+ secretion, which lowers blood volume, thus blood pressure.
RAAS activation
Pressure overload
- Causes and problems with this
Pressure exerted on cardiomyocytes exceed the force generated via contraction.
This leads to concentric left ventricular hypertrophy- cardiomyocytes grow in size to try and meet demand in pressure.
Causes:
Hypertension
Aortic stenosis
Problem:
Reduction in chamber diameter, increases afterload and decreases preload.
Volume overload
-Include causes
Dilation of the cardiac chamber due to excessive blood.
Cardiomyocytes alter their structure:
New sarcomeres
Increased length and width
Causes:
Valvular regurgitation.
Left sided heart failure
- Include causes
In inability for the left side of the heart to eject blood efficiently.
Blood backs up from the left atrium to pulmonary circulation.
Causes:
Ischaemic heart disease
Hypertension
Valvular heart disease
Myocardial disease.
Effects of left ventricular failure on the lungs.
- Include symptoms
If the blood is unable to be pumped out of the left ventricle, blood backs up in the pulmonary veins.
This leads to pulmonary congestion and oedema- heavy, wet lungs.
Symptoms:
Dyspnoea
Orthopnoea
Paroxysmal nocturnal dyspnoea
Effects of left ventricular failure on the kidneys.
Back up of blood in the left ventricles leads to decreased CO.
Less blood flow to kidneys.
This triggers the kidneys to activate the RAAS.
Kidneys absorb more salt, thus water, increasing blood volume, thus blood pressure.
