3.4 Pathophysiology of Heart Failure Flashcards
List some common causes of systolic and diastolic dysfunction
- Myocardial infarction
- Arrhythmia
- Coronary Artery Disease
- Cardiomyopathy
- Hypertension
- Valvular pathology
Why can diastolic heart failure lead to an increased ejection fraction?
Because it decreases end diastolic volume, which is inversely proportional to stroke volume
What is heart failure called on both sides?
Biventricular heart failure
Mechanism: how can hypertension lead to left sided systolic heart failure?
- Increased peripheral resistance
- Left ventricular hypertrophy
- Increased myocardial oxygen demand
- Coronary arteries are compressed
- Not enough oxygen, myocardium cannot function optimally
- Left sided heart failure
Is systolic or diastolic heart failure more common in left-sided heart failure?
Systolic
Explain how left ventricular hypertrophy can lead to left sided diastolic heart failure
- Increased muscle size
- Decreased room for filling of ventricle
- Diastolic heart failure
What is a major, major sign of heart failure, and how can it manifest itself clinically?
Major, major sign: pulmonary oedema
Manifests:
- Dyspnoea
- Orthopnea
- Paroxysmal nocturnal dyspnoea
How can left sided heart failure lead to right sided heart failure?
- Left sided heart failure
- Blood is not circulating as efficiently
- Blood is backed up in the lungs
- Increased pressure in pulmonary artery
- Right ventricle fails to pump hard enough
How can a left-to-right shunt lead to systolic and diastolic right sided heart failure?
- Blood shunted to right side (high to low pressure)
- Increased fluid volume in right side of heart
- Right sided hypertrophy
- Decreased filling space (diastolic)
- Ischaemia due to increased demand (systolic)
Define heart failure
Structural and/or functional abnormality of the heart that results in elevated intracardiac pressures and/or inadequate cardiac output at rest and/or during exercise
LVEF for HFrEF
<= 40%
LVEF for HFpEF
> = 50%
Criteria for HFpEF other than (EF)
- LV diastolic dysfunction
and/or - Evidence of raised LV filling pressures
Describe the neurohumoral mechanism that is activated in response to reduced stroke volume from the heart
- Sympathetic activation (chronotopic; increased heart rate + inotropic; increased contractility)
- Renal hypoperfusion + sympathetic activation activates the RAS
- Increased blood volume increases CO (via RAS system), and increased arterial pressure due to vasoconstriction
What is a potential negative side effect of prolonged RAAS activation?
Cardiac fibrosis
List the two kinds of natriuretic peptides released from the heart, and state which chambers they are released from
Atrial Natriuretic Peptide (Atria)
Brain Natriuretic Peptide (BNP)
What are the effects of natriuretic peptides, and when are they released?
- Cause loss of sodium through urine, leading to decreased blood pressure
- Released in response to volume overload in heart
Describe early pathological remodelling of the heart following an ischaemic event (<72hr). Specify the histological changes.
- Wall thinning
- Chamber dilation
- Increased wall stress
Histological changes:
- Formation of a fibrous scar in myocardium
Describe late pathological remodelling of the heart following an ischaemic event (>72hr). Specify the histological changes.
- Increased SNS and RAAS due to decreased cardiac output
- Leads to myocardial hypertrophy and fibrosis
Histological changes:
- Myocyte hypertrophy
- Increased interstitial collagen
Briefly explain how heart failure can be progressive
- Left ventricular remodelling in response to damage
- Maladaptive alterations lead to increased energy demand and ECM degradation, further increasing remodelling and perpetuating a decline in cardiac function
Normal LVEF
60%+
Normal LVEF
60%+
Normal LVEF
60%+
Approximately what percentage of heart failure patients have HFpEF?
50%
List three signs that can be used to diagnose HFpEF
- Increase in BNP
- CV imaging showing impaired diastolic function
- Raises LV filling pressures during catheterisation
How can increased pre-diastolic pressure within the ventricles lead to decreased stroke volume?
- Ventricular filling stops when the pressure in the ventricles exceeds the pressure in the atria
- If the pressure in the ventricles is higher, this occurs sooner, meaning there is less time for blood to enter ventricles
- Therefore, less blood is pumped out with each beat, even if ejection fraction is maintained (like in HFpEF)
What are some primary risk factors for HfpEF?
- Age
- Hypertension
- Obesity
- Atrial fibrilation
- Type 2 diabetes
Basic mechanism of HFpEF
- Stiffening of LV due to risk factors, but systolic function preserved
- Increased pressure in LV
- Increase LA pressure, as more blood remains in LA
- Remodelling of LA
- Diastolic dysfunction
How can LV heart failure cause peripheral oedema?
- LV function decreases
- Pressure backs up in pulmonary circulation (orthopnea/dyspnoea), and eventually backs up into right side of heart, inhibiting venous return
- Fluid remains in the peripheral circulation, where it extravasates and causes oedema
How can congestive cardiac failure cause nocturia?
- In heart failure, renal perfusion decreases
- In the supine position, renal perfusion improves, leading to increased urine production and thus nocturia
How does an echocardiogram assist in the diagnosis of heart failure?
It provides a representation of chamber size and structure, and the relative movement of valves, enabling heart function to be assessed.
