Pathophysiology of Heart Failure

Question 1

Cardiac output varies in response to both physiological and pathological factors: (4)

Answer 1

Preload
Afterload
Contractility
Heart Rate

Question 2

WHat is Preload (filling pressure)

Answer 2

The left ventricle end-diastolic volume that stretches the ventricle to its greates dimensions.
High Preload = High CO

Question 3

What is the Afterload?

Answer 3

The pressure against which the heart must work to eject blood during systole (contraction of ventricle)
High afterload = Low CO

Question 4

How does contractility effect the CO?

Answer 4

This is the ability of the Myocardium to contract. If the contractility increases, the CO increases

Question 5

How does the Heart rate affect CO?

Answer 5

CO = HR x SV
So if Heart rate increases, the CO increases.
SV = stroke volume (volume pumped from the venticle per beat)

Question 6

What is responsible for heart failure?

Answer 6

Abnormalities in the Cardiac function causing failure of the heart to pump blood at a rate which meets metabolic demand of tissues.

Question 7

The symptoms of Heart Failure (HF).

Answer 7

SYmptoms are different for every one and will arise at different times per infividual.

• Excercise intolerance,
• Breathlessness
• Fatigue
• Oedema

Question 8

What is Acute Heart Failure

Answer 8

Sudden circulatory collapse due to either

• Haemorrhagic shock (lose >20% of blood volume)
• Cardiogenic shock during Acute Myocardial Ifarction

Question 9

Chronic Heart Failure:

How much of population have this and how much die?

Answer 9

1.5% of whole population

30-40% die within 12 months of diagnosis.

Question 10

What is likely to be the cause of Chronic HF?

Answer 10

There is usually some form of Cardiomyopathy which is a disease directly affecting the heart.

Question 11

What are the causes of Inherited Cardiomyopathy (CM)?

Answer 11

• congenital hypertrophic CM (where part of the heart thickens)
• Arrhythmic Right Ventricle CM

Question 12

What are the causes of Aquired CM?

Answer 12

• Ischaemic CM post Myocardial Infarction
• Overload of pressure due to hypertension
• Valvular disease (often due to pressure)
• Infection or Inflammation (myocarditis)
• Alcoholic CM (direct effect of ethanol)

Question 13

What is the progression of CM

Answer 13

Gradual reduciton in cardiac function results in symptoms:
Reduced myocardial contractility and reduced CO, causing FATIGUE
Reduced tissue perfusion as blood is sent to vital organs causing WEAKNESS
REduced Venous Return.
Volume Expansion - Retaining water in the kidney LESS URINE
LV failure - pulmonary oedema COUGHING and difficulty breathing
RV failure
WEIGHT LOSS, MUSCLE WASTING, ANOREXIA

Question 14

What does any Heart Failure likely to be due?

Answer 14

Due to SYSTOLIC dysfunction which is often accompanied by Diastolic dysfunction

Question 15

What side is most prevelantly associated with Heart Failure?

Answer 15

Left-sided failure is most prevelant, and is the greatest cause of Right-sided failure

Question 16

What is Biventricular HF?

Answer 16

Left and right Ventricles

Question 17

WHat is Systolic HF?

Answer 17

Reduced ventricular Contractility

Question 18

What is Diastolic HF?

Answer 18

Reduced ventricular Filling

Question 19

What is Compensated HF?

Answer 19

Stable, controlled symptoms

Question 20

What is Decompensated HF?

Answer 20

Acute, with more symptoms and respiratory deistress.

Question 21

What is reduction in Cardiac Output?

Answer 21

A neurohormonal reflex.

Question 22

What does a fall in CO that presents in HF cause?

Answer 22

A physiological response to try to maintain perfusion to vital organs, and is a response similar to that of a big hemorrhage.

Question 23

What does the Sympathetic NS do in response to reduced CO? (The neurohormonal response)

Answer 23

It is a Baroreceptor reflex that fires from the baroreceptors, Noradrenaline is released to increase the heart rate, to cause venous smooth muscle contraction, vasoconstriction, and increased Myocardium contraction in an effort to increase CO

Question 24

What is the other system activated by decreased CO?

the neurohormonal response

Answer 24

The renin-angiotensin system: this causes increased renin secretion from the juxoglomerular cells of the kidney leading to increased Angiotensin II production, and therefore more Aldosterone form the adrenal cortex and ADH from the pituitary to increase water reabsrption , increaseing blood Volume

Question 25

What is the problem with the body’s attempt to increase CO?

Answer 25

It causes further pathology

Question 26

What will cause remodelling of the heart?

Answer 26

A primary disease, in this case Heart Failure will cause remodelling

Question 27

What is remodelling of the heart?

Answer 27

Thinning or thickening of the cardial wall causing a decrease in CO.

Question 28

What is the spiral that tries to increase CO, but causes further pathology?

Answer 28

The remodelling due to primary disease (HF) causes a decrease in CO,
A neurohormonal response is activated- the sympathetic NS and the Renin-Angiotensin System. These result in an increase in blood volume and vasoconstriciton to try to increase CO.
These result in an increased Preload and afterload causing Ventricular Dilation (stretched and thinned ventricle), meaning that the cardiac workload increases, which then decreases the CO. So it is a cycle.

Question 29

What are the counter-regulating Vasodilators released and why?

Answer 29

These are released to try to counter the increase in Vasoconstriction (by the Sympathetic NS and the renin angiotensin system). Examples are Adrenomedullin and Nitric Oxide. The levels of these give the extent of the disease and also a diagnosis
High levels of counter-regulating vasodilators mean severe disease