What is heart failure?
A state that develops when the heart fails to maintain an adequate cardiac output to meet the demands of the body
What causes heart failure?
Results from any structural or functional abnormality that impairs the ability of the ventricle to eject blood (systolic HF) or fill with blood (diastolic HF)
At rest in a typical adult what is normal cardiac output?
70mls/kg/min
List 3 factors which affect stroke volume
Contractility
Preload
Afterload
How does an increase in heart rate affect the cardiac output?
Causes an increase
In which phase does filling of the heart occur?
Diastole
In which phase does contraction of the heart occur?
Systole
What does excessive high heart rate cause?
Excessively high HR results in a decrease in the amount of time allowed for the ventricles to fill in diastole which causes SV and, thus CO to fall
Define contractility
The intrinsic ability of the myocardium to contract
What is preload?
The volume of blood or stretching of cardiomyocytes at the end of diastole prior to the next contraction
What is afterload?
The resistance/end load against which the ventricle contracts to eject blood
When does preload increase?
When there is an increase in blood volume and vasoconstriction
What decreases preload?
Blood volume loss and vasodilatation
What does the frank starling law state?
An increase in volume of blood filling the heart stretches the heart muscle fibres causing greater contractile forces which, in turn, increases the stroke volume
Is true only up to a certain point… at some stage the fibres become over-stretched and the force of contraction is reduced
What does vasodilatation do to afterload?
Decreases
What does hypertension and vasoconstriction do to afterload?
Increases
What happens to cardiac output as afterload increases?
Decreases
State the 2 types of low output heart failure
Systolic heart failure
Diastolic heart failure
What is high output heart failure?
Occurs in the context of other medical conditions which increase demands on cardiac output, causing a clinical picture of HF
The heart itself is functioning normally but cannot keep up with the unusually high demand for blood to one or more organs in the body
What can cause high output heart failure?
Thyrotoxicosis, profound anaemia, pregnancy, paget’s disease, acromegaly, sepsis
What is systolic heart failure?
Where the heart has become weak
Progressive deterioration myocardial contractile function
List 3 causes of systolic heart failure
Ischemic injury
Volume overload
Pressure overload
What is diastolic heart failure?
Inability of the heart chamber to relax, expand and fill sufficiently during diastole to accommodate an adequate blood volume
List the causes of diastolic heart failure
Significant left ventricular hypertrophy (LVH) e.g HCM
Infiltrative disorders
Constrictive pericarditis
Restrictive cardiomyopathy
State some other causes of heart failure
Coronary Heart Disease Hypertensive Heart Disease Valvular Heart Disease Myocardial Disease/ Cardiomyopathies Congenital Heart Disease
Define cardiomyopathy
Diffuse disease of the heart muscle leading to functional impairment
List the 3 types of cardiomyopathy
Dilated cardiomyopathy
Hypertrophic cardiomyopathy
Restrictive cardiomyopathy
Describe the pathophysiology of heart failure
Pump failure leads to reduced SV and CO. Compensatory mechanisms kick in to maintain arterial pressure and perfusion of vital organs
List some compensatory mechanisms of heart failure and state what they do
The Frank Starling mechanism: vasoconstriction, increased venous return to the heart, increased preload, heart muscle fibres stretch, enhanced contractility
Myocardial structural change: Augmented muscle mass (hypertrophy) with or without cardiac chamber dilatation
Activation of neurohormonal system:
Release of Noradrenaline – increases heart rate and myocardial contractility. Causes vasoconstriction
Release of ANP/BNP
Activation of renin-angiotensin – aldosterone system
What is the problem with compensatory mechanisms of heart failure?
They may worsen the heart failure
What can pressure overload cause?
Concentric left ventricular hypertrophy
Augmented muscle may reduce the cavity diameter
Cross sectional areas of the myocytes are increased
What can volume overload cause?
Chamber dilatation with increased ventricular pressure
Deposition of new sarcomeres
Increased cell length and width
Muscle mass and wall thickness are increased in proportion to chamber diameter
Describe some clinical types of heart failure
Left sided, right sided and biventricular failure
Acute and chronic heart failure
Compensated and decompensated heart failure
Describe left sided heart failure
Blood backs up progressively from the left atrium to the pulmonary circulation
What are the causes of left sided heart failure?
Ischaemic heart disease
Hypertension
Valvular heart disease
Myocardial disease
How does left ventricular failure affect the lungs?
Pressure in the pulmonary veins is transmitted retrogradely to the capillaries and arteries
This leads to pulmonary congestion and oedema
What problems are caused by heavy/wet lungs from left ventricular failure?
Orthopnoea
Paroxysmal nocturnal dyspnoea
Dyspnoea
How does left ventricular failure affect the kidneys?
Decreased cardiac output
Reduction in renal perfusion
Activation of renin - angiotensin – aldosterone system
Retention of salt and water with consequent expansion of interstitial fluid and blood volumes
How does left ventricular failure affect the brain?
Hypoxic encephalopathy Irritability Loss of attention Restlessness Stupor and coma
Describe right sided heart failure and its causes
Right sided HF due to significant pulmonary hypertension due to increased resistance within the pulmonary circulation
Usually as a result of respiratory disease e.g. COPD or pulmonary emboli
Other causes:
Valvular heart disease
Congenital heart disease
What causes biventricular failure (Congestive cardiac failure)?
Either due to the same pathological process on each side of the heart
OR
A consequence of left heart failure leading to volume overload of the pulmonary circulation and eventually the right ventricle causing right ventricular failure
List the main clinical presentations of heart failure
Dyspnoea Orthopnoea, paroxysmal nocturnal dyspnoea Oedema Hepatic congestion Ascites Fatigue Weakness
Describe the new york classification of heart failure
Class I: No limitation of physical activity
Class II: Slight limitation of ordinary activity
Class III: Marked limitation, even during less-than-ordinary activity
Class IV: Severe limitation with symptoms at rest
List the symptoms of acute pulmonary oedmea
Acute Breathlessness Pallor Cyanosis Sweating Rapid Pulse Hypoxia Crackles in Lungs
List the current drug treatments for heart failure
Diuretics SA node blockades Beta blockers Aldosterone antagonists ARNI ACE inhibitors
Give an example of a loop diuretic
FRUSEMIDE
How do loop diuretics work?
Inhibit Na+ re-absorption from the proximal tubule
K+ loss from distal tubule
If used incorrectly what can loop diuretics cause?
Electrolyte abnormalities
Hypovolaemia and diminished renal perfusion
Give an example of a mineralocorticoid receptor antagonist
Spironolactone
How do mineralocorticoid receptor antagonists work?
Acts on distal tubule
Promotes Na+ excretion and K+ re-absorption
Reduces hypertrophy and fibrosis
How do ACE inhibitors work?
Act on activated renin - angiotensin system
Given orally in small doses with slow titration
Block production of angiotensin:
Vasodilatation
BP lowering
Reduce cardiac work
Give an example of an ACE inhibitor
Ramipril
Give an example of a beta blocker
Bisoprolol
How do beta blockers work?
Block the action of adrenaline and noradrenaline on adrenergic beta receptors
Slow HR, reduce BP
What does digoxin do?
Action:
Increases myocardial contractility
Slows conduction at the AV node (use in AF)
Excreted by kidney - Toxicity important
When is digoxin given?
Acute HF especially in AF
Chronic HF in selected cases
State the immediate treatment of acute pulmonary oedema
High flow oxygen
IV Morphine
IV Nitrates
IV Frusemide