Pathophysiology of heart failure Flashcards
Main causes of heart failure =
Ischemic heart disease Hypertension Dilated Cardiomyopathy Congenital Valvular etc.
New descriptions of HF
Acute
Chronic
Pre-load =
Venous return.
Filling pressure =
the pressure in the ventircles just before it starts to contract
What does increased preload do (Starlings’ law)
Stretches myocardial fibres and myocardial contraction increases/is restored
After load =
Outflow resistance/peripheral resistance.
What causes outflow resistance?
Pulmonary and systemic resistance
Volume of blood ejected
If preload/end diastolic volume increases, what does this do to after load?
Increases after load
What is increased in HF, SNS or PNS
SNS - originally to provide inotrophic support, chronically increases neurohormonal activation and myocyte apoptosis
What can happen to LV during remodelling
Hypertrophy
Intersistial fibrosis
Loss of myocytes
Acute heart failure =
Rapid onset of symptoms and signs of HF
Examples of acute HF presenation:
Pulmonary oedema
Anasarca
Cardiogenic shock
Starlings law in relation to HF
As muscle failures, need to increase preload to get ventricles to work.
What occurs in left ventricular pump failure to increase the BP
- fall in Bp - increased sympathetic - vasoconstriction - increase afterload
- fall in renal perfusion - RAAS - retention - increased preload
Clinical features of pulmonary oedema:
Tachypnoea Orthopnoea Crackles Use of accessory muscles Pink frothy sputum
O2 sat in pulmonary oedema
<90%
What can be seen of CXR in pulomonary oedema due to heart failure =
Enlarged heart (>50%) Kerley B lines (straight horizontal lines)
Normal pressure in lungs
Colloid = hydrostatic. Small amount of fluid leaves and is drained
Formation of pulmonary oedema
Blood backs up into pulmonary capillaires - increased hydrostatic pressure - more fluid into interstitial space.
What is anasarca?
Generalied oedema
What sided HF does anasarca occur in?
Right
Features of anasarca:
Peripheral oedema
Acities
Pleural effusions
Anasarca develops over
Days - weeks
What might a patient with anasarca notice?
Gradual weight gain
What causes anasarca?
Fall in CO - fall in renal perfusion - increased ADH and aldosterone - Na+ and H2O retention
3 features of chronic heart failure =
a. symptoms of HF
b. evidence of cardiac dysfunction (imaging, ECG)
c. response to treatment
4 models of progression of chronic heart failure =
- Haemodynamic
- Neurohormonal
- Peripheral
- Metabolic
Haemodynamic model:
Pump failure results in reduced BP and renal perfusion Increased sympathetic and RAAS Vasoconstriction and Na+/H2O Increased afterload and preload Worsens
Neurohormonal:
Increased ANP, BNP Increased ADH Increased Endothelin Increased RAAS Adrenergic activation
Endothelin function
Vasoconstriction
Natriuretic peptides function
Vasodilation
Increased Na+/H2O excretion
Inhibit renin, ACE
What hormones can cause fibrosis within the heart?
Aldosterone
ANP =
Atrial natriuretic peptide
BNP =
B-type naturietic peptide
What is always raised in HF?
BNP
In HF there is a switch from what to what (peripheral model)
Type 1 slow twitch to type 2 fast twitch skeletal muscle
Increased ventilation increases exercise =
Ergoreflex
In HF there is a shift between (catabolism/anabolism) to (catabolism/anabolism)
Anabolism to catabolism
Metabolic model:
Increased cost/energy cost
Resistance to anabolic hormones
