CVS S11 - Heart failure

Question 1

What is the definition of the clinical state of heart failure?

Answer 1

State in which the heart fails to maintain an adequate circulation for the needs of the body despite an adequate filling pressure

Question 2

What is starling’s law?

Answer 2

Force developed in a myocardial fibre depends on the degree to which the fibre is stretched or the heart is filled

Question 3

How does heart failure effect starling’s law?

Answer 3

Heart can no longer produce the same force of contraction and therefore cardiac output for a given level of filling/stretch

In severe heart failure, at high venous pressures the CO decreases

Question 4

What are the different classifications of heart failure?

Answer 4

Compensated and un-compensated

Systolic dysfunction and diastolic dysfunction

Right and left sided heart failure

Question 5

How do systolic and diastolic dysfunction differ?

Answer 5

Diastolic is due to decreased relaxation of the ventricles and ventricular filling

Systolic is due to decreased pumping of the heart

Question 6

What are the main causes of heart failure?

Answer 6

IHD, arrhythmias, hypertension, valvular disease, pericardial disease

Question 7

What are the features of systolic dysfunction?

Answer 7

• Increased LV capacity and decreased LV cardiac output
• Thinning of the myocardial wall
• Mitral valve incompetence
• Neuro-hormonal activation
• Cardiac arrhythmias

Question 8

How does systolic dysfunction cause mitral valve incompetence?

Answer 8

Dilatation of the left ventricle causes valve leaflets to no longer come into contact

Question 9

Outline the differences between the structural changes that occur in ventricular remodelling after acute MI and in diastolic and systolic heart failure

Answer 9

Acute MI- initial necrosis of myocardial tissue, thinning follows in one area

D/S HF- hypertrophy in diastolic, symmetrical thinning in systolic

Question 10

What are the primary causes of systolic dysfunction?

Answer 10

Increased after-load or decreased contractility

Question 11

What causes diastolic dysfunction?

Answer 11

Most commonly left ventricular hypertrophy/ fibrosis

Question 12

What are the features of diastolic dysfunction?

Answer 12

Reduced LV compliance, impaired myocardial relaxation and diastolic filling result in a lower CO which triggers neuro-hormonal activation

Question 13

What is congestive heart failure?

Answer 13

Failure of both the right and left sides of the heart

Question 14

How does the formation of oedema differ in right and left heart failure?

Answer 14

Right- due to increased pulmonary resistance creating pulmonary hypertension, this leads to increased RV afterload causing increased venous pressure and congestion in the tissues, rise in capillary hydrostatic pressure causes peripheral oedema

Left- left ventricles fails to pump blood out of the heart, causes blood to build up in left side of heart and leads to pulmonary venous congestion, blood thereby accumulates in the lungs and results in pulmonary oedema

Question 15

Outline how fibrosis of the lungs results in heart failure

Answer 15

Deceased efficiency of gas exchange results in chronic pulmonary vasoconstriction

This causes an increase in pulmonary resistance leading to pulmonary hypertension

This increases afterload on the RV stimulating RV hypertrophy and eventual RH failure

Question 16

How are neuro-hormonal mechanisms activated in heart failure?

Answer 16

Decrease in blood pressure due to decreased cardiac output activates the sympathetic nervous system and renin release from the kidneys

Question 17

What receptors mediate the sympathetic nervous system’s response?

Answer 17

Baroreceptors

Question 18

How does the sympathetic nervous system initially compensate for heart failure?

Answer 18

Improves cardiac output by increasing contractility, arterial and venous vasoconstriction and tachycardia

Question 19

How does the Renin-Angiotensin Aldosterone System work?

Answer 19

Renin secreted from the kidneys stimulates the conversion of angiotensinogen to angiotensin I

Angiotensin I is then converted to angiotensin II by the angiotensin converting enzyme

Angiotensin II stimulates the release of aldosterone from the cortex of the adrenal glands

Question 20

How is the RAAS involved in heart failure?

Answer 20

• Renin released in response to low BP which results in aldosterone release
• Aldosterone increases Na+ reabsorption and water retention thereby increases blood volume
• Angiotensin II also acts as a vasoconstrictor to increase TPR
• This combined effect is to increase blood pressure

Question 21

Where would a heart rhythm causing atrial fibrillation occur?

Answer 21

Supraventricular ectopic pacemaker cells

Question 22

Why would the pacemaker not be in the ventricles?

Answer 22

Ventricular pacemaker cells produce slow heart rate

Question 23

How can mitral stenosis results in atrial arrhythmias such as atrial fibrillation?

Answer 23

Mitral stenosis increases left atrial pressure resulting in left atrial dilatation which predisposes to arrhythmias due to the stretching of the myocardium