Pathophysiology of Heart Failure

Question 1

What is the pathophysiological definition of heart failure?

Answer 1

Abnormality of cardiac structure or function leading to failure of the heart to deliver oxygen at a rate commensurate with the requirements of the metabolizing tissues

Question 2

What type of cardiac dysfunctions can underlay heart failure?

Answer 2

CAD
Valvular heart disease - endocarditis, rheumatic
High-output cardiac failure - anaemia, thyrotoxicosis, liver cirrhosis, pagets. pregnancy
Arrhythmias and Conduction - tachy/brady, tamponade

Question 3

What are the 2 classifications of heart failure?

Answer 3

HFrEF
Heart Failure with Reduced Ejection Fraction
HFpEF
Heart Failure with Preserved Ejection Fraction

Question 4

What conditions need to be present for each type of heart failure? Assume both have signs and symptoms typical of heart failure.

Answer 4

HFrEF
Reduced LVEF
HFpEF
Normal/mildly reduced LVEF + LV not dilated
relevant structural heart disease

Question 5

What is the equation for ejection fraction?

Answer 5

EF(%) = SV/EDV

Question 6

What does HFrEF affect?

Answer 6

Affects contraction of the heart muscle

Myocardial injury or overload (inc preload/afterload)

Question 7

Why does ventricular remodelling happen?

Answer 7

Designed to preserve SV (Cardiac Output reserve)
Myocardial Injury or chronic volume overload (pre-load) = ventricular dilation
Chronic pressure overload = hypertrophy
Often both co-exist

Question 8

Why do you get oedema in heart failure?

Answer 8

Hydrostatic pressure changes:
capillary filtration increases more than absorption in the venous compartment
Fluid is retained in interstitial space
plasma protein is reduced (reduced oncotic force) as in severe hepatic venous congestions

Question 9

What are the compensatory mechanisms for heart failure? (There are 3! Name the organs involved)

Answer 9

Baroreceptor response (brain) -> SNS activation -> Inc HR and contractility
RAAS activation/Decreased GFR (kidneys) -> Fluid retention -> Inc preload -> Inc CO
Inc ventricular wall tension (heart) -> myocyte growth -> Hypertrophy

Question 10

How can you treat acute decompensated HF?

Answer 10

ABCDE✝
O2 via  re-breath bag
GTN (spray / infusion)
Diuretics
Continuous Positive Airway Pressure (cPAP)
Inotropes
Rarely transplant