Pathophysiology of Heart Failure Flashcards
What is the definition of Heart Failure?
Inability of the cardiovascular system to deliver sufficient cardiac outpout to supply tissues with adequete O2 and nutrients for their requirements
What compensatory mechanisms are activated to return SABP to normal?
Arterial vasoconstriction (re-distribute blood flow from non-essential tissues to brain and heart):
Sympathetic nervous system
Renin-angiotensin system
Vasopressin release
Endoththelin release
Increase venous return and cardiac filling pressures, increase force of contraction and heart rate
CO= SV x HR
SNS activation: A and beta receptors stimulated: increase in VR HR and contractility
Renin-angiotensin system activation: vasocontriction, NaCl+water retention
Vasopressin secretion:
Enhance water retention to complement NaCl retention
Endothelin system- venoconstriction- aldosterone secretion-NaCl and water retention
How to calculate SABP?
SABP=CO x TPR
SABP= Systemic arterial blood pressure
CO- Cardiac output
TPR- Total peripheral resistance
Why compensatory mechanism are appropriate for haemorrhage but detrimental if chronically activated?
Lead to salt and water retention (volume overload and congestion)
Toxic to heart muscle:
- Require an increase in work of failing myocardium (law of laplace)
- Lead tofibrosis of myocardium
- Cardiac muscle hypertrophy occurs out-frows blood supply
- Gene expression in cardiac muscle cells changes to more fetal phenotype
- Down-regulation and uncoupling of beta-receptors
Blood vessels change occur which are detrimental:
-Vessel walls stiffen, become less compliant
- Endothelial cell dysfunstion occurs
- Receptor expression changes
What are the counter-regulatory mechanisms activated in chronic heart failure to counteract maladaptive responses?
Inhibit salt and water retention
Reduce vascular tone
Reduce the force of contraction of heart muscle
Have anti-fibrotic and anti-proliferative effects on cardiac and vascular smooth muscle
What are the counter-regulatory mechanisms in chronic heart failure?
Natriuretic factors:
ANP & BNP (produced by atria and ventricles)
Endogenous digitalis-like factors
Endothelium-dependent vasodilators:
Reduce vascular tone
Anti-proliferative effects on vascular smooth muscle and cardiac muscle (Nitric oxide and PGI₂)
What is the functional abnormality/species affected and definitve treatment when Valves: a) endocardiosis, b) stenosis are affected
a) endocardiosis: Leaky mitral valve, Dog (small breeds), Valve replacement/repair
b) stenosis: Stenotic aortic or plumonic valve, Dogs(boxers), Baloon dilutions
What is the functional abnormality/species affected and definitve treatment when Heart muscles: a) Dilated cardiomyopathy, b) Hypertrophic Cardiomyopathy
a) Dilated cardiomyopathy: Poor systolic function, Dogs-giant and large breeds, Cardiac muscle assist/heart transplant or increase force of contraction
b) Hypertrophic Cardiomyopathy: Poor siastolic function, Cats, No treatment
What is the functional abnormality/species affected and definitve treatment when electrical/conducting tissue is affected?
Cardiac arrythmias, Often associated with other diseases can be congenital abnormalities in conduction systems, Surgical ablation of abnormal conduction pathways OR treat with anti-dysrhythmic drugs
What is the functional abnormality/species affected and definitve treatment when Pericardium is affected?
Cardiac tamponade (heart unable to fill), Dogs(st Bernard), Surgical drainage of pericardium fluid
What you need to do if there is no way to treat?
Inhibit the compensatory mechanisms leading to sodium chloride and water retention, vasoconstriction, muscle hypertrophy and fibrosis
Boost the counter-regulatory systems which are naturally trying to counteract these compensatory mechanisms.
