17 Pathophysiology of Heart Failure Flashcards
Define heart failure.
Inability of heart to meet demands (blood volume w./ oxygen/ glucose - allows body to function) of body (clinical syndrome of reduced cardiac output, tissue hypoperfusion, increased pulmonary pressures and tissue congestion)
How do we measure ejection fraction?
Echocardiogram
How do we measure ‘Ejection Fraction’?
SV/EDV
What parts of the heart malfunction/ get impaired to cause heart failure?
1, One-way valves 2, Functioning muscle 3, Chamber size
What’s the most common cause of heart failure?
IHD (myocardial dysfunction via fibrosis)
Apart from IHD, what other causes of heart failure are there?
- Hypertension (increased overload in ventricles+accelerated atherosclerosis) 2. Aortic stenosis (increased afterload in ventricles) 3. Cardiomyopathies eg hypertrophy 4. Arrhythmias 5. Valvular/myocardial structural disease 6. Pericardial diseases (rarely)7. sepsis/severe anaemia, thyrotoxicosis(high CO)
How do we measure CO? (vol expelled per ventricle per min)
CO=SV x HR (SV= volume ejected by ventricle in single beat)
What is the ‘ejected fraction’?
SV/EDV
What factors influence SV? (3)
1-Pre-load 2-Myocardial contractility 3-After-load
=What is Frank-Starling’s law? What is it due do?
More ventricular distension during diastole=greater vol ejected during diastole Due to: intrinsic property of cardiac myocytes
What may cause the Frank Starling curve to shift?
Increased sympathetic activity Greater CO for given pressure
What cause SV to be reduced (eg in heart failure)? (3)
- Reduced pre-load (EDV) - impaired filling 2.Reduced myocardial contractility 3. Increased afterload- increased pressure which ventricle must contract against eg aortic stenosis/severe hypertension
=What are the 2 overarching causes of heart failure?
1) FILLING PROBLEM-Diastolic- ventricular vol reduced (EDV) as chambers=too stiff/not relaxing enough/walls hypertrophied
2) CONTRACTILITY PROBLEM-Systolic- can’t pump with enough force as= muscle walls thin/fibrosed, chambers enlarged (overstretched), abnormal/uncoordianted myocardial contraction
How is heart failure classified according to ‘Ejection Fraction’?
1.HFrEF (reduced Ejection Fraction) contractility issue 2.HFpEF(preserved Ejection Fraction)filling problem
Out of HFrEF and HFpEF what is the most common type of heart failure?
HFpEF
What is the normal Ejection Fraction for a healthy heart?
>50% (reduce if <40%)
=How is Ejection Fraction measured?
Echocardiogram
How can a heart be failing even if EF is maintained?
EF is a fraction so still less CO relative to normal healthy heart
How is heart failure classified according to ventricles involved?
Left, Right, Biventricular
What is another name for biventricular heart failure?
Congestive heart failure
In which side of the heart is heart failure is most common?
Left (usually causes right ventricular heart failure)
To which main 2 conditions is right ventricular heart failure usually secondary to?
- LV heart failure 2. Chronic lung disease
=How does Frank-Starling’s curve appear in heart failure? Why?
Reduced CO for given ventricular filling- eventually curve dips as are worsening CO
Why do the mechanisms in the body that respond to a drop in CO cause further deterioration in an unhealthy heart?
Increased cardiac demand- further reduction in SV
What are the 2 neurohormonal mechanisms that respond to a drop in CO?
1)Baroreceptors- carotid sinus- increase sympathetic drive, HR. peripheral resistance-increased afterload 2)Decrease renal perfusion- Activate RAAS pathway- Angiotensin II–> Increase circulating vol, stimulate ADH, vasoconstriction, enhance sympathetic actvity- increase preload and afterload
What are the symptoms of heart failure?
=Fatigue, lethargy =Breathlessness =Leg swelling
What are the signs of Heart Failure?
Oedema : Pulmonary tissues, Peripheral tissues (pitting)(esp lower limbs)
=How does tissue fluid form?
Gradient between hydrostatic and oncotic pressure.
=Explain why someone with heart failure might get oedema.
Increased capillary hydrostatic pressure. Fluid less favourable returns to capillary at venule end. Due to HIGH VENOUS PRESSURE- increased hydrostatic pressure
=What is pulmonary oedema due to heart failure indicative of?
Left sided heart failure
=What is pitting oedema in peripheral tissues indicative of?
Right sided heart failure
=What symptoms would be seen in left ventricular heart failure compared to right ventricular heart failure?
:
=What simple measurement reflects pressures in the right side of the heart?
Jugular Venous Pressure (JVP) - would be raise in right ventricular heart failure
