Cardiac Failure

Question 1

What determines cardiac output?

Answer 1

preload, heart rate, contractility, afterload

Question 2

What is preload?

Answer 2

The blood that comes in to the heart from venous return - end diastolic volume

Question 3

What is afterload?

Answer 3

The resistance that the heart has to pump against

Question 4

Why does an increased preload give an increased force of contraction?

Answer 4

Because the increased volume stretches the muscles and allows them to contract more - necessary to match cardiac output and venous return

Question 5

What is Starling’s Law?

Answer 5

Increased LVEDV gives increased cardiac output

Question 6

How can you measure RVEDP?

Answer 6

JVP

Question 7

How can you measure LVEDP?

Answer 7

pulmonary artery wedge pressure

Question 8

What is pulmonary artery wedge pressure?

Answer 8

Pressure in the pulmonary vein measured by occluding the pulmonary artery - measured using a Swan-Ganz catheter

Question 9

What are the starling forces?

Answer 9

The balance of hydrostatic and osmotic pressure across the capillary. Means that the fluid will leak out at the arterial end and leak in at the venous end.

Question 10

What causes oedema?

Answer 10

An increase in venous pressure - leads to an imbalance in the starling forces and fluid can’t enter the capillaries at the venous end

Question 11

What are other causes of oedema?

Answer 11

decreased osmotic pressure due to renal or liver failure, blocked lymphatics or increased capillary permeability due to infection or inflammation

Question 12

What causes pulmonary congestion?

Answer 12

A LVEDP that is over 20-30mmHg

Question 13

What is cardiac failure?

Answer 13

When the cardiac output is less than the body needs

Question 14

What causes cardiac failure?

Answer 14

Either decreased cardiac output or increased body needs

Question 15

What is the response to cardiac failure?

Answer 15

Increase LVEDP to maintain cardiac output by retaining fluid

Question 16

What is the mechanism of cardiac failure?

Answer 16

• loss of myocardial muscle
  
  • • ischaemic heart disease
    • cardiomyopathy
  • pressure overload
  • • aortic stenosis
    • hypetension
  • volume overload
  • • valve regurgitation
    • shunts

Question 17

What are the pathological causes of cardiac failure?

Answer 17

ischaemic heart disease, valvular heart disease, hypertensive heart disease, congenital heart disease, cor pulmonale, pericardial disease

Question 18

What are the clinical features of left heart failure?

Answer 18

short of breath, fatigue, tachycardia, crackles

Question 19

What are the clinical features of right heart failure?

Answer 19

oedema

Question 20

Why is water retention a response of cardiac failure?

Answer 20

Because of decreased blood supply to the kidney activating the renin-angiotensin-aldosterone system. This leads to greater pressure on the heart.

Question 21

What is the result of sympathetic nerve activation in cardiac failure?

Answer 21

Causes increased contractility but in the long term also causes arrhythmias, vasoconstriction and has a toxic effect on myocardium

Question 22

What are the mechanisms for right heart failure?

Answer 22

global heart disease, specific right heart disease or left heart failure

Question 23

How does left heart failure lead to right heart failure?

Answer 23

Left heart failure leads to pulmonary congestion which leads to hypoxia which leads to pulmonary vasoconstriction which leads to pulmonary arterial hypertension which leads to right heart failure

Question 24

What is the treatment for cardiac failure?

Answer 24

• reduce fluid and vasodilate
  
  • • diuretics, aldosterone antagonists, ACE inhibitors, angiotensin receptor antagonists
  • increase contractility
  • • digoxin
  • block effects of NA
  • • beta blockers
  • treat underlying causes