Pathophysiology Of Heart Failure Flashcards
What is the equation for cardiac output?
CO = Stroke volume x Heart rate
What is cardiac output?
The volume of blood expelled per ventricle per minute
What is stroke volume?
The volume of blood ejected by a single ventricle in a single beat
What is the total (total volume of blood available) called available at the end of diastole?
End Diastolic Volume
What is ejection fraction?
The amount of blood ejected by ventricle in a single heart beat as a fraction of total volume available (EDV)
What determines stroke volume?
Pre load
Myocardial contractility
After load
What is pre load?
The stretch on the ventricle just before contraction
What is afterload?
Total peripheral resistance
How does preload release to stroke volume?
The larger the volume in the ventricle at the end diastole (EDV) the more the ventricles stretch
The more stretch = higher stroke vol = higher CO = CARDIAC MYOCYTES CONTRACT HARDER (up until a certain point)
What is the term which describes the increased strength of contraction of the heart?
+ve inotropy
What balances the increased sympathetic activity of the heart (+ve inotropy) as stroke volume increases?
After load increases (as BP increases)
What is after load?
The pressure against the ventricle is ejecting blood
Generally what is the definition of heart failure?
The inability of the heart to meet the demands of the body (cant deliver enough 02 for example)
What is the clinical description of heart failure?
The clinical syndrome of reduced cardiac output, tissue hypoperfusion, increased pulmonary pressures and tissue congestion
What are the 2 ways which lead to reduced CO?
Impaired ventricular filling
Impaired emptying of the heart
What is tissue congestion?
When tissue fluid accumulates in the tissues (oedema)
What is the most common cause of heart failure?
Ischaemic heart disease = lack of blood supply to heart
What can cause heart failure?
Ischaemic heart disease
Hypertension
Valvular disease
Cardiomyopathies (hypertrophic)
Arrhythmias
How can sepsis and thyrotoxicosis cause heart failure?
The body has an extremely high metabolic demand. The cardiac output of the heart cant meet this demand
VERY RARE
How does ischaemic heart damage leading to remodelling affect the heart
Loss of myocytes + fibrosis:
Changes the ventricles ability to function, its size or its shape
This can affect the ventricles ability to fill or eject blood
What is the general problem if heart failure is an issue with ejection?
A contractile problem
What can make it so the heart cant pump with enough force?
Muscle walls thin and fibrosed
Chanmber space enlarged
Abnormal/uncoordinated myocardial contraction
When heart failure is caused be a filling problem how can ventricular volume/capacity for blood be reduced?
Ventricular chambers too stiff/not relaxed enough
Ventricular wall too thick
SPACE AVAILABLE IN VENTRICLE IS REDUCED (EDV/PRE LOAD IS REDUCED)
How can we measure wether heart failure is due to an ejection problem or a filling problem?
Measure Ejection Fraction
What is the equation for ejection fraction?
Stroke volume/EDV
Given as a percentage
How do you measure ejection fraction?
Echocardiogram
What is a normal healthy ejection fraction?
50% or more
What is the classification of HEart Failure with a reduced ejection fracture = ejection problem?
HFrEF
Ejection fracture < 40%
What is the classification of HEart Failure with a Normal ejection fracture = filling problem?
HFpEF
EF greater than or equal to 50%
What is HFrEF?
Heart failure with reduced ejection fracture indicating ejection problem
EF < 40%
What is HFpEF?
Heart failure with preserved Ejeection Fraction
Indicates filling problem
EF > 50%
Which ventricle i most commonly involved in heart failure?
Left
If one ventricle fails it eventually leads to both failing, what is it called when both ventricles fail?
Biventricular (congestive heart failure)
What are the key manifestations of both types of heart failure?
Dyspnoea
Fatigue
Tissue fluid retention (pulmonary and/or peripheral oedema)
What is dyspnoea?
Difficulty breathing
What causes the fatigue in heart failure?
Tissue hypoperfusion
What is left ventricular systolic dysfunction?
When there is an ejection problem involving the left ventricle
If left ventricular systolic dysfunction caused heart failure, what would the ejection fraction be?
EF < 40%
In Left Ventricular Systolic Heart failure, what happens to the cardiac output as the end diastolic volume/preload increases?
Small increase early on however it eventually worsens/decreases the cardiac output due to the impaired contractility of the cardiac myocytes
Why can left ventricular systolic heart failure cause pulmonary congestion/pulmonary oedema?
Left ventricle not emptying properly so EDV/preload increases inside it
This leads to increased pressure in the atria too
This leads to increased pressure in the pulmonary vessels leading into the LA
Increased pressure in these veins forces more tissue fluid out
Why is neuro-hormonal activation as a result of reduced cardiac output in heart failure a bad thing?
It exacerbates the heart failure
Increases the peripheral resistance and circulating blood volume which increases the blood pressure
What responses become stimulated in the neuro-hormonal response to heart failure?
Baroreceptors (neural stimulation)
RAAS (Renal perfusion/hormonal activation)
When cardiac output and BP is low in HF, what response does the baroreceptors stimulate?
Inc sympathetic drive:
-Inc Heart Rate
-Inc Peripheral resistance (vasoconstriction)
Afterload INCREASED
When cardiac output and BP is low in HF, what response does the poor renal perfusion/RAAS stimulate to increase Pre load?
Aldosterone stimulates more Na+ and water retention increasing blood volume
When cardiac output and BP is low in HF, what response does the poor renal perfusion/RAAS stimulate to increase after load?
Angiotensin II leads to vasoconstriction
What negative effects does the neuro-hormonal corrective mechanisms have in heart failure?
Further increase pressure in ventricles
Increased amounts of tissue fluid due to increased pressures in pulmonary or systemic circulation
Long term activation of sympathetic NS may lead to heart no longer being able to respond to adrenaline
What are the 3 clinical presentations of Heart Failure?
Dyspnoea
Fatigue
Tissue fluid retention (pulmonary and//or peripheral oedema)
What type of oedema tends to mainly occur with left ventricular heart failure?
Pulmonary oedema
Why can left ventricular heart failure result in pulmonary oedema?
Pressure in LV inc
Pressure in LA inc
Pressure in venule end of Pulmnary circulation increases
Hydrostatic pressure at venule end of pulmonary capillary beds inc greater than oncotic pressure
What sound would be hear when listening to Pulmonary oedema??
Crackling/crepitations
What can some peripheral oedema occur with left ventricular hypertrophy (mainly pulmonary oedema)?
Water retained due to RAAS and it pools in legs
What is Orthopnoea?
Dyspnoea which worsens on lying flat
What is Paroxysmal nocturnal dyspnoea?
Waking up suddenly in the night gasping for breath
Why would right ventricular heart failure cause Peripheral oedema (legs)?
Pressure in RV inc
Pressure in RA inc
Causes central venous pressure to increases
Jugular venous pressure increases
Increased hydrostatic pressure at venule end of systemic capillary beds
Inc tissue fluid
Gravity pulls tissue fluid down
What type of heart failure causes raised Jugular Venous Pressure?
Right Ventricular Heart failure
What commonly causes right ventricular heart failure?
Left ventricular heart failure usually leads to it
What is the definition of Congestive Heart Failure?
When both ventricles failure (biventricular heart failure)
What drugs can be given to reduce workload of the heart in heart failure?
Beta blockers (slow HR) Bisoprolol, Atenolol
Diuretics (reduce afterload/circulating blood) Furosemide
ACE inhibitors (vasodilator reduce afterload) Ramipril or enalapril
GTN spray (reduce pre load by vasodilation, reducing venous pressure going to heart)
What is the mechanism of action of GTN spray?
Gets broken down into Nitric Oxide which is a potent vasodilator
Vasodilates veins reducing preload
Vasodilates coronary arteries increasing blood supply to the heart
Leads to relaxation of smooth muscle in blood vessels
