Pathophysiology of Heart Failure

Question 1

What is heart failure?

Answer 1

the inability of the heart to pump blood out therefore reduced stroke volume hence reduced cardiac output

Question 2

what are starlings forces?

Answer 2

forces that determine whether fluid will move in to or out of the capillary.

Question 3

what direction does hydrostatic pressure force fluid?

Answer 3

out of the capillary

Question 4

where is hydrostatic pressure the highest, arteriole or venuole end?

Answer 4

arteriole

Question 5

what is oncotic pressure?

Answer 5

osmotic pressure doe to protein, albumin

Question 6

what direction does oncotic pressure force fluid?

Answer 6

into the capillary from extracellular tissue fluid

Question 7

what is oedma?

Answer 7

when there is an inbalance in the hydrostatic and oncotic pressure so the hydrostatic pressure is higher forcing fluid out of the capillary

Question 8

what is the capillary filtration coefficient ?

Answer 8

a value denoting the permeability of the capillary. The higher the permeability, the higher the coefficient

Question 9

how do we calculate net pressure?

Answer 9

hydrostatic pressure gradient + colloid osmotic (oncotic) pressure gradient

Question 10

what is the net flow of fluid through the capillary?

Answer 10

3L a day

Question 11

where does the 3L of fluid that leaves the capillary go?

Answer 11

it enters the lymphatic system and is returned to the venule end

Question 12

what are the classifications of heart failure?

Answer 12

1. Acute or Chronic
2. Left or Right sided failure
3. biventricular failure

Question 13

what can be used to detect a reduction in ejection fraction of the heart?

Answer 13

an echocardiogram

Question 14

what are clinical features of heart failure (i.e. symptoms)

Answer 14

1. reduced ejection fraction (reduced fraction of blood pumped out in comparison to volume of blood in the ventricles)
2. hypotension (causing tiredness and dizziness)
3. reduced urine flow
4. cold peripheries - less blood to fingers and toes
5. breathlessness (co of oedema (especially in lungs)
6. atrial fibrilation (due to pressure on atrium causing electrical disturbances)

Question 15

why do patients have reduced urine flow with heart failure?

Answer 15

• because there will be less flow of blood to the kidneys hence less blood filtered to produce urine.
• also, fluid is lost at the capillary end so less fluid in systemic circulation for urine

Question 16

what are the 4 categories for factors causing heart failure?

Answer 16

1. impaired contractility
2. pressure overload
3. left ventricular diastolic dysfunction
4. obstruction of left ventricular filling

Question 17

what diseases cause a pressure overload to cause heart failure?

Answer 17

1. aortic stenosis

2. uncontrolled hypertension

Question 18

how does aortic stenosis cause heart failure?

Answer 18

narrowing of the aorta hence causing increased aortic pressure therefore it becomes more difficult to move blood through the aorta

Question 19

how does uncontrolled hypertension cause heart failure?

Answer 19

when the ventricles have to overcome high pressure hence increasing workload on the ventricular muscles therefore resulting in heart failure

Question 20

what diseases cause impaired contractility to cause heart failure?

Answer 20

1. myocardial infarction
2. transient myocardial ischemia
3. chronic volume overload (mitral and aortic regurgitation)
4. dilated cardiomyopathy

Question 21

what is dilated cardiomyopathy?

Answer 21

a muscle disorder causing a lack of contraction hence heart failure

Question 22

what is chronic volume overload?

Answer 22

two types: mitral and aortic regurgitation.

• mitral: backflow of blood from high pressure pulmonary artery into right ventricles
• aortic: backflow of blood from high pressure aorta into left ventricles

Question 23

what diseases cause left ventricular diastolic dysfunction to cause heart failure?

Answer 23

1. left ventricular hypertrophy
2. hypertrophic cardiomyopathy
3. restrictive cardiomyopathy
4. transient myocardial ischemia

Question 24

what diseases cause obstruction of left ventricular filling to cause heart failure?

Answer 24

1. mitral stenosis

2. pericardial constriction or tamponade

Question 25

what causes a rise in atrial pressure?

Answer 25

a rise in end-diastolic volume coupled with increased myocardial hypertrophy

Question 26

when the contractility of the ventricles reduces (heart failure), what happens?

Answer 26

• less ventricular emptying
• causing an increase in end-diastolic volume
• so the fall in stroke volume is less than it would have otherwise been
• more left ventricular filling leads to pulmonary congestion

Question 27

what is activated when stroke volume and cardiac output is reduced?

Answer 27

1. sympathetic reflexes
2. Renin-angiotensin system
3. ADH release

Question 28

what drugs are used to treat heart failure?

Answer 28

1. diuretics
2. positive inotropes
3. vasodilators
4. beta adrenorector antagonists

Question 29

give examples of positive inotropes?

Answer 29

• adrenoreceptor agonists

- cardiac glycosides

Question 30

give examples of vasodilators?

Answer 30

1. RAAS antagonists (ACEI)
2. Nitrates
3. Alpha adrenoreceptor antagonists

Question 31

Explain how drugs work to treat heart failure?

Answer 31

1. Failing heart with reduced stroke volume and left ventricular end diastolic pressure causes pulmonary congestion
2. diuretics reduce pulmonary congestion without increasing stroke volume
3. excessive diuresis or venous dilation may cause fall in stroke volume hence hypotension
4. end diastolic pressure of left ventricles reduced by ionotropic therapy causing arterial dilation
5. this represents the potential of combining vasodilators and ionotropic therapy