Pathophysiology of cardiac disease and congestive heart failure

Question 1

Congestive heart failure is also known as?

Answer 1

Backwards heart failure

Question 2

What is backwards HF associated with?

Answer 2

Elevated filling pressures and extravasation of fluid (e.g. pulmonary oedema in L-CHF).

Question 3

Define preload and how does this affect stroke volume?

Answer 3

Venous return to the heart – stretches sarcomeres – more returned the higher the SV

Question 4

Define afterload

Answer 4

Force of ejection from the heart (of the ventricles) – arterial resistance/pressure

Question 5

Describe how preload influences cardiac output by the Frank Starling mechanism

Answer 5

Increased the endo diastolic ventricular volume
Sarcomere lengths are increased
Stroke volume of the heart is increased

Question 6

What are the major consequences of CHF?

Answer 6

• Oedema and Effusions
• Peripheral vasoconstriction
• Tachycardia / Arrhythmias
• Remodelling and fibrosis of the myocardium

Question 7

How does an increased afterload affect CO?

Answer 7

Increased afterload causes a decreased SV making it harder for the heart to pump

Question 8

Define heart failure

Answer 8

A clinical syndrome caused by heart diseases resulting in systolic and / or diastolic function severe enough to overwhelm the normal compensatory mechanisms

Question 9

What are the consequences of forwards HF?

Answer 9

Poor cardiac output and reduced peripheral perfusion

Question 10

What are the consequences of backwards/congestive HF?

Answer 10

Elevated filling pressures, resulting in oedema and effusions

Question 11

What is the role of neuro-hormonal activation in the consequences of CHF?

Answer 11

Baroreceptors – increase sympathetic drive in response to a decrease in BP
Sodium and water retention is trying to increase preload but can lead to oedema and effusions if too much

Question 12

What is endothelin?

Answer 12

potent vasoconstrictor and causes myocardial remodelling and fibrosis

Question 13

What are the 3 immediate consequences of an increased sympathetic drive in response to decreased blood pressue?

Answer 13

• Increased HR (contractility)
• Vasoconstriction
• Renin release (RAAS)

Question 14

What is the function of cardiac beta-1 adreno-receptors?

Answer 14

Increased HR - tachycardia
- The aim is to increase cardiac output (CO = SV x HR), but this is detrimental in the
long term, as it increases myocardial oxygen consumption and reduces coronary
perfusion.

Question 15

What is the function of cardiac alpha-1 adreno-receptors?

Answer 15

Lie on vascular smooth muscle cells and cause vasoconstriction –> increases BP –> increases venous return (preload)

Question 16

What is the role of angiotensin II within cardiac myocytes?

Answer 16

Results in hypertrophy and fibrosis (cardiac remodelling)

Question 17

What is the function of vasopressin (ADH)?

Answer 17

Results in water retention

Excessive Sodium and water retention results in Oedema and Effusions.

Question 18

In heart failure what is released during atrial stretch?

Answer 18

Atrial natriuretic peptide (ANP)

Question 19

In heart failure what is released due to increased left ventricle pressues?

Answer 19

Brain natriuretic peptide (BNP)

Question 20

What is used to diagnostically test for HF?

Answer 20

ANP and BNP can be assayed to demonstrate the presence of heart failure, but have a short half-life.
Dogs with CHF have sig. higher levels than normal dogs.

Question 21

In patients with oedema and effusions what is the aim of treatment?

Answer 21

To increase preload - venous return to the heart

Question 22

Give examples of mediators of peripheral vasoconstriction

Answer 22

• Alpha-1 receptors in the peripheral NS
• Angiotensin II
• Reduced bradykinin levels
• Vasopressin
• Endothelin

Question 23

How does Angiotensin II affect filtration pressure in the kidney?

Answer 23

• Angiotensin II causes greater EA constriction than AA.

- This increases glomerular capillary pressure (filtration pressure).

Question 24

What is the overall function of ACE inhibitors?

Answer 24

Counteract adverse effects of angiotensin II

Question 25

Which drug can be used to stop aldosterone escape (increased aldosterone levels despite adequate ACE inhibition)?

Answer 25

Spironolactone

Question 26

Compensatory hypertrophy due to volume overload is an example of ... hypertrophy?

Answer 26

Eccentric

Question 27

What is volume overload of the heart?

Answer 27

One or more chambers of the heart “see” an increased volume of blood. This leads to chamber dilation and usually compensatory hypertrophy

Question 28

In which situations would eccentric hypertrophy be seen?

Answer 28

- Mitral regurgitation - Ventral septal defects - Patent ductus arteriosus - Tricuspid regurgitation

Question 29

What is pressure overload of the heart?

Answer 29

There is increased impedance or increased resistance to outflow of blood from a particular heart chamber (usually a ventricle). Relative wall thickness increases (walls thick; chamber may be small).

Question 30

Pressure overload results in ... hypertrophy?

Answer 30

Concentric

Question 31

Examples of pressure overload conditions on the left and right ventricles are:

Answer 31

- Aortic stenosis - Systemic hypertension - Pulmonic stenosis - Pulmonary hypertension

Question 32

A pressure overload will lead to increased wall stress, how is this compensated for?

Answer 32

By increasing wall thickness (which lowers the chamber radius)

Question 33

What is the difference in adaptive and maladaptive modelling

Answer 33

``` Adaptive = initially compensatory Maladaptive = long term compensatory, more harmful than helpful ```

Question 34

Myocardial remodelling is associated with?

Answer 34

Fibrosis Increased wall stress Myocardial ischaemia