heart failure Flashcards
What usually leads to impaired cardiac function?
Altered chamber size
Altered functioning muscle
Cardiac output (volume delivered per minute) =
SV x HR
What is the fraction that gets ejected from the heart? (eg the fraction of total volume available)
Ejection fraction
What is ejection fraction?
Fraction ejected from heart in a single beat from the total volume available (EDV)
How do you calculate ejection fraction?
Stroke volume / end diastolic volume (filled ventricle)N
Normal stroke volume and ventricular capactity
SV - 70-75ml
Ventricle capacity - 110-150 ml
Normal ejection fraction
> 50%
Usually 60-70% (2/3)
How is stroke volume increased? (made bigger)
Increasing preload (increases stretch on ventricle just before contraction) Increasing myocardial contractility Decreasing afterload (TPR)
How is an increase in demand met by the heart?
Increase HR
Increase stroke volume
How does preload increase stroke volume?
Increase EDV increases stretch on ventricles
More stretch during diastole = increase stroke volume in systole
= increase cardiac output
What is an intrinsic property of cardiac myocytes?
Greater they are stretched the greater their contractility (force of contraction)
…up to a point
Relationship between myocardial contractility and stroke volume
Contractility improves with greater stretch (greater EDV) and increased sympathetic activity
What else occurs during increased sympathetic activity that could affect cardiac output
Increased afterload (increased pressure that the heart is pumping against)
What is heart failure?
Its a Clinical syndrome of:
reduced cardiac output
tissue hypoperfusion
increased pulmonary pressures
tissue congestion
-arising from problems with ventricular filling and/or emptying
Most common cause of heart failure
Ischaemic heart disease
Other causes of heart failure
Hypertension
Valvular disease (eg aortic stenosis)
Cardiomyopathies (hypertrophic/dilated)
Arrhythmias
Rare causes heart failure
Increased demand of cardiac output (no problem with heart, body is just demanding too much)
eg:
sepsis
thyrotoxicosis
What is important in heart failure?
To identify underling cause as this shapes treatment options (eg repair valve etc)
What occurs from these conditions that results in heart failure?
Re-modelling of cardiac muscle - loss of myocytes and fibrosis
Changes ventricular function, size/shape
What does remodelling result in?
Impairment of ventricular filling (chamber size)
Impairment of ventricular ejection (emptying)
Impairment of filling
Ventricles become thick walled and stiff
Impairment of ejection
Muscle thin and weak
Cannot contract with enough force/uncoordinated
what type of heart failure is caused by ejection problem?
HFrEF (reduced ejection fraction)
Contractility (systolic) problem - cannot pump with enough force
Ventricles in HFrEF
Muscle walls thin and fibrosed
Chamber space enlarged
Abnormal/un-coordinated myocardial contraction
SPACE NOT REDUCED just POOR contraction
What type of heart failure is caused by filling problem?
HFpEF (preserved ejection fraction)
Filling (diastolic) problem
Ventricles in HFpEF
Ventricle volume/capacity for blood is reduced
Ventricle chambers too sniff/not relaxed
Thickened walls
SPACE AVAILABLE REDUCED, EDV reduced
How do we determine type of heart failure?
Measure ejection fraction (echocardiogram)
Ejection fraction in different heart failures
HFrEF - ejection fraction reduced LOWER than 40%
HFpEF - ejection fraction greater/equal to 50% (normal ejection)
HFrEF and HFpEF meaning
HFrEF - Heart failure with REDUCED ejection fraction (ejection problem)
HFpEF - Heart failure with PRESERVED ejection fraction (filling problem)
How can a heart be failing if EF is maintained?
Filling problem: EDV reduced from smaller chamber size
Fraction still maintained BUT stroke volume is SMALLER = decreased cardiac output
Ventricle most commonly involved in heart failure
Left
Failure of both ventricles
Biventricular (congestive) heart failure
What can cause isolated right ventricle failure (rare)
Chronic lung disease
What can failure of one ventricle lead to?
Failure of the other ventricle
Symptoms of HFrEF and HFpEF
Very similar:
Dyspnoea (breathlessness)
Fatigue (limiting exercise tolerance)
- due to hypoperfusion
Tissue fluid retention (pulmonary/peripheral oedema)
Why perform an echocardiogram for heart failure?
Confirm diagnosis (identify structural/functional issues)
Identify potential cause (valve problem)
Implicates prognosis and treatment
How does type of heart failure impact treatment?
HFrEF treatments have no effect on mortality/morbidity of patients with HFpEF
(only helps symptoms eg reduced oedema)
what is HFrEF known as in left ventricle?
Left ventricular systolic dysfunction
50% cases of heart failure
HFrEF of left ventricle (left ventricular systolic dysfunction)
What happens to FranK starling curve in left ventricular systolic dysfunction?
LV pre load (EDV) increase leads to little increase in CO (shallow gradient curve)
Eventually increase filling = worsening CO (curve dips)
Develop pulmonary congestion
What does reduced cardiac output trigger?
Neurohormonal activation to ‘correct’
How is reduced cardiac output sensed and neurohormonal activation activated?
Reduced blood pressure
- baroreceptors sense less stretch
- Decreased renal perfusion
Blood pressure =
cardiac output x TPR
Neuro part
Baroreceptors sense drop in BP (low CO)
Increase sympathetic drive = increased heart rate and peripheral resistance
= increased afterload
= increased cardiac work
MAKES WORSE
Hormonal activation
Decreased renal perfusion (from low BP) =
activation of renin-angiotensin-aldosterone system:
- increased volume (Na+ and water reabsorption kidney, ADH release)
- Vasoconstriction
What does RAAS do?
Increases volume = increase pre load Increases resistance (vasoconstriction) = increase afterload
= increase cardiac workload
What happens due to neurohormonal activation?
Increased afterload + increased circulating volume
Increase pressures within ventricle (failing to eject volume, low CO)
Increased tissue fluid in interstitium - lungs and peripheries mostly
Cardiotoxic effects from long term activation of sympathetic nervous system
How does pulmonary oedema occur?
Increase LV pressure (cannot eject volume sufficiently)
Increased pulmonary circulation pressure (venule end)
Increased hydrostatic pressure at venule end of capillary beds
No favourable gradient (hydrostatic and oncotic) for fluid to return to capillaries
Increased fluid volume in pulmonary interstitium
= pulmonary oedema (+/-peripheral oedema)
Which failure = pulmonary oedema
left sided ventricular heart failure
How does pulmonary oedema present?
Fluid in lungs on CXR Dyspnoea Basal pulmonary crackles (auscilation) Orthopnoea (dyspnoea worse at night) Paroxysmal nocturnal dyspnoea (waking suddenly at night gasping for air)
What happens in right ventricular heart failure? or left
Increased pressure RV
Increased systemic pressure (venule end)
Increased central venous pressure = increased jugular venous pressure
Increase hydrostatic pressure at venule end of systemic capillaries
Non favourable (hydrostatic and oncotic) gradient for return of fluid to capillaries
Tissue fluid accumulates in interstitial tissues (gravity dependent eg legs)
= peripheral oedema
Peripheral oedema signs
Pitting oedema (legs) (LV or RV heart failure can cause)
Raised jugular venous pressure (ONLY in RV failure)
what can be used to indicate RV pressure?
Jugular venous pressure (right jugular vein)
LV vs RV heart failure
Both:
Fatigue/lethargy
Breathlessness
LV:
pulmonary oedema and all symptoms +/- peripheral oedema
Cardiomegaly (displaced apex beat enlarged LV)
RV:
peripheral oedema
raised jugular venous pressure
tender, smooth and enlarged liver (congestion)
How can peripheral oedema occur in LV failure?
Activation of RAAS due to lack of perfusion of kidney
