3.4 Pathophysiology of Heart Failure

Question 1

List some common causes of systolic and diastolic dysfunction

Answer 1

• Myocardial infarction
• Arrhythmia
• Coronary Artery Disease
• Cardiomyopathy
• Hypertension
• Valvular pathology

Question 2

Why can diastolic heart failure lead to an increased ejection fraction?

Answer 2

Because it decreases end diastolic volume, which is inversely proportional to stroke volume

Question 3

What is heart failure called on both sides?

Answer 3

Biventricular heart failure

Question 4

Mechanism: how can hypertension lead to left sided systolic heart failure?

Answer 4

• 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

Question 5

Is systolic or diastolic heart failure more common in left-sided heart failure?

Answer 5

Systolic

Question 6

Explain how left ventricular hypertrophy can lead to left sided diastolic heart failure

Answer 6

• Increased muscle size
• Decreased room for filling of ventricle
• Diastolic heart failure

Question 7

What is a major, major sign of heart failure, and how can it manifest itself clinically?

Answer 7

Major, major sign: pulmonary oedema
Manifests:
- Dyspnoea
- Orthopnea
- Paroxysmal nocturnal dyspnoea

Question 8

How can left sided heart failure lead to right sided heart failure?

Answer 8

• 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

Question 9

How can a left-to-right shunt lead to systolic and diastolic right sided heart failure?

Answer 9

• 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)

Question 10

Define heart failure

Answer 10

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

Question 11

LVEF for HFrEF

Answer 11

<= 40%

Question 12

LVEF for HFpEF

Answer 12

> = 50%

Question 13

Criteria for HFpEF other than (EF)

Answer 13

• LV diastolic dysfunction
  and/or
• Evidence of raised LV filling pressures

Question 14

Describe the neurohumoral mechanism that is activated in response to reduced stroke volume from the heart

Answer 14

• 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

Question 15

What is a potential negative side effect of prolonged RAAS activation?

Answer 15

Cardiac fibrosis

Question 16

List the two kinds of natriuretic peptides released from the heart, and state which chambers they are released from

Answer 16

Atrial Natriuretic Peptide (Atria)
Brain Natriuretic Peptide (BNP)

Question 17

What are the effects of natriuretic peptides, and when are they released?

Answer 17

• Cause loss of sodium through urine, leading to decreased blood pressure
• Released in response to volume overload in heart

Question 18

Describe early pathological remodelling of the heart following an ischaemic event (<72hr). Specify the histological changes.

Answer 18

• Wall thinning
• Chamber dilation
• Increased wall stress

Histological changes:
- Formation of a fibrous scar in myocardium

Question 19

Describe late pathological remodelling of the heart following an ischaemic event (>72hr). Specify the histological changes.

Answer 19

• Increased SNS and RAAS due to decreased cardiac output
• Leads to myocardial hypertrophy and fibrosis

Histological changes:
- Myocyte hypertrophy
- Increased interstitial collagen

Question 20

Briefly explain how heart failure can be progressive

Answer 20

• 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

Question 21

Normal LVEF

Answer 21

60%+

Question 22

Normal LVEF

Answer 22

60%+

Question 23

Normal LVEF

Answer 23

60%+

Question 24

Approximately what percentage of heart failure patients have HFpEF?

Answer 24

50%

Question 25

List three signs that can be used to diagnose HFpEF

Answer 25

- Increase in BNP - CV imaging showing impaired diastolic function - Raises LV filling pressures during catheterisation

Question 26

How can increased pre-diastolic pressure within the ventricles lead to decreased stroke volume?

Answer 26

- 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)

Question 27

What are some primary risk factors for HfpEF?

Answer 27

- Age - Hypertension - Obesity - Atrial fibrilation - Type 2 diabetes

Question 28

Basic mechanism of HFpEF

Answer 28

- 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

Question 29

How can LV heart failure cause peripheral oedema?

Answer 29

- 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

Question 30

How can congestive cardiac failure cause nocturia?

Answer 30

- In heart failure, renal perfusion decreases - In the supine position, renal perfusion improves, leading to increased urine production and thus nocturia

Question 31

How does an echocardiogram assist in the diagnosis of heart failure?

Answer 31

It provides a representation of chamber size and structure, and the relative movement of valves, enabling heart function to be assessed.