heart failure Flashcards
what is the definition of heart failure?
- a state that developed when the heart fails to maintain an adequate cardiac output to meet the demands of the body
- results from any structural or functional abnormality that impairs the ability of the ventricle to eject blood or fill with blood
at rest what is the normal value of cardiac output?
70mls/kg/min
what is the equation for cardiac output?
heart rate x stroke volume
what does an increased heart rate generally lead to?
increased cardiac output
what generally happens to the heart during systole and diastole?
- heart contracts in systole
- heart relaxes in diastole
- ventricles fill in diastole
what does an excessively high heart rate result in?
a decrease in the amount of time allowed for the ventricles to fill in diastole which causes SV and therefore CO to fall
what is contractility?
the intrinsic ability of the myocardium to contract
what is preload?
the volume of blood 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
what affects preload?
the venous blood pressure and the rate of venous return to the heart which in turn is affected by venous tone and volume of circulating blood
what increases and decreases preload?
- increases with increasing blood volume and vasoconstriction
- decreases with blood volume loss and vasodilation
what does the Frank-Starling law do?
describes the relationship between preload and cardiac output
what does the Frank-Starling law state?
an increase in volume of blood filling the heart stretches and the heart muscle fibres causing greater contractile forces, which, in turn increases stroke volume
what is an issue with the Frank-Starling law?
it is only true up to a certain point as at some stage the fibres become overstretched and the force of contraction is reduced
what increases and decreases afterload?
- increases with hypertension and vasoconstriction
- decreases with vasodilation
what happens after afterload increases?
cardiac output decreases
what are 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 demand 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 of more organs in the body
what are the causes of high output heart failure?
- thyrotoxicosis
- profound anaemia
- pregnancy
- paget’s disease
- acromegaly
- sepsin
what is systolic heart failure?
progressive deterioration myocardial contractile function
what causes systolic heart failure?
- ischaemic 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
what causes diastolic heart failure?
- significant left ventricular hypertrophy
- infiltrative disorders
- constrictive pericarditis
- restrictive cardiomyopathy
what are the general causes of heart failure?
- coronary heart disease
- hypertensive heart disease
- valvular heart disease
- myocardial disease/cardiomyopathies
- congenital heart disease
what are cardiomyopathies?
diffuse disease of the heart muscle leading to functional impairment
what are the 3 different types of cardiomyopathies?
- dilated cardiomyopathy
- hypertrophic cardiomyopathy (hereditary)
- restrictive cardiomyopathy (rare)
what causes dilated cardiomyopathy?
- ETOH
- pregnancy
- systemic disease
- muscular dystrophies
- drug toxicity
what are the 3 compensatory mechanisms that kick in to maintain arterial pressure and perfusion of vital organs?
- The Frank-Starling mechanism
- myocardial structural change
- activation of neurohormonal system
what happens with the Frank-Starling compensatory mechanism?
- vasoconstriction
- increased venous return to the heart
- increased preload
- heart muscle fibres stretch
- enhanced contractility
what happens with the myocardial structural change compensatory mechanism?
augmented muscle mass with or without cardiac chamber dilatation
what happens with the activation of neurohormal system compensatory mechanism?
- release of noradrenaline: increases heart rate and myocardial contractility, causes vasoconstriction
- release ANP/BNP
- activation of renin-angiotensin: aldosterone system
what 3 side effects can the compensatory mechanisms cause on the body?
- vasoconstriction: increases resistance against which heart has to pump and therefore may decrease CO
- Na and water retention: increased fluid volume which increases preload, if too much stretch it leads to decrease contractile strength and CO
- excessive tachycardia: this leads to decreased diastolic filling time leading to decreased ventricular filling leading to decreased SV and CO
what are the clinical types of heart failure?
- left sided, right sided and biventricular
- acute and chronic
- compensated and decompensated
what happens with 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
what causes pulmonary congestion and oedema and left sided heart failure?
the pressure in the pulmonary veins is transmitted retrogradely to the capillaries and arteries
what effects to heavy wet lungs have on the body with left sided heart failure?
- breathlessness (dyspnoea) exaggerated of the normal breathlessness that follows exertion
- orthopnoea: breathlessness lying flat that is relieved by sitting or standing
- paroxysmal nocturnal dyspnoea: an extension of orthopnoea with attacks of extreme dyspnoea bordering on suffocation usually occurring at night
what happens to the kidneys with left ventricular failure?
- 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
what happens to the brain with left ventricular failure?
- hypoxic encephalopathy
- irritability
- loss of attention
- restlessness
- stupor and coma
what is normally a big cause of right sided heart failure?
usually as a consequence of left sided heart failure (congestive cardiac failure)
what is cor-pulmonale?
- right sided heart failure due to significant pulmonary hypertension due to increased resistance within the pulmonary circulation
- usually as a result of respiratory disease
what are the other causes of right sided heart failure?
- valvular heart disease
- congenital heart disease
what are the systemic effects on the liver and portal system of right heart failure?
- congestive hepatomegaly
- centrilobar necrosis when severe
- cardiac cirrhosis
what are the systemic effects on the spleen of right heart failure?
congestive splenomegaly
what are the systemic effects on the abdomen of right heart failure?
ascites: accumulation of transudate in peritoneal cavity
what are the systemic effects on the subcutaneous tissue of right heart failure?
- peripheral oedema of dependent portions of the body (especially ankle and pretibial oedema)
- sacral oedema
what are the systemic effects on the pleural and pericardial space of right heart failure?
effusions
what causes biventricular failure?
- 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 riskier
what is the clinical presentation of biventricular failure due to excess fluid accumulation?
- dyspnoea
- orthopnoea, paroxysmal nocturnal dyspnoea
- oedema
- hepatic congestion
- ascites
what is the clinical presentation of biventricular failure due to reaction in cardiac output?
- fatigue
- weakness
what are the New York heart association classifications of heart failure?
- class I: no limitation of physical activity
- class II: slight limitation or ordinary activity
- class III: marked limitation, even during less-than-ordinary activity
- class IV: severe limitation with symptoms at rest
what are the clinical signs of cardiac failure?
- cool, pale, cyanotic extremities
- tachycardia
- elevated JVP
- third heart sound (S3) - gallop rhythm
- displaced apex (LV enlargement)
- crackles or decreased breath sounds at bases on chest auscultation
- peripheral oedema
- ascites
- hepatomegaly
what are the clinical tests in heart failure?
- CXR
- ECG
- blood investigations
- echocardiogram/cardiac MRI or CT/CT-PET
- CTCA/coronary angiography
give the 2 examples of loop diuretics
- frusemide
- bumetanide
what do loop diuretics do?
- inhibit Na+ reabsorption from proximal tubule
- K+ loss from distal tubule
- can be given IV or orally
- potent can lead to: electrolyte abnormalities, hypovolaemia and diminished renal perfusions
give the 2 examples of minteralocorticoid receptor antagonists
- epelerenone
- spironolactone
how do mineralocorticoid receptor antagonists work?
- acts on distal tubule
- promotes Na+ extortion and K+ reabsorption
- reduces hypertrophy and fibrosis
- principle side effects: gynaecomastia, electrolyte and renal function abnormalities
give the 5 examples of ACE inhibitors
- ramipril
- perindopril
- enalapril
- captopril
- lisinopril
how do ACE inhibitors work?
- act on activated renin: angiotensin system
- given orally in small episodes with slow titration
- block production of angiotensin: vasodilation, BP lowering, reduce cardiac work
- principle side effects: cough, hypotension, renal impairment
give the 3 examples of beta blockers
- bisoprolol
- carvedilol
- metoprolol
how do beta blockers work?
- block the action of adrenaline and noradrenaline on adrenergic beta receptors
- slow HR, reduce BP
- given orally in small doses with slow titration
- (treat arrhythmias)
- principle side effects: bronchospasm, claudication
give the example of a SA node blockade
ivabradine
how do SA node blockades work?
- blocks the If channel with the SA node
- slow HR, no effect on BP
- given orally with dose titration
- principle side effects: visual aura, bradycardia
what is the action of digoxin?
- increased myocardial contractility
- slows condiction at the AV node (use in AF)
- excreted by the kidney: toxicity important
when is digoxin given?
- acute Hf especially in AF
- chronic HF in selected cases
give the example of ARNI
sacubitril valsartan
how does ARNI work?
- acts of activated renin: angiotensin system
- also blocks breakdown of ANP/BNP
- blocks production of angiotensin: vasodilation, BP lowering, reduce cardiac work
- promotes natriuresis: sodium excretion, vasodilation, reduce hypertrophy and fibrosis
- principle side effects: hypotension, renal impairment
what are the other therapies used to treat heart failure?
- cardiac resynchronisation therapy
- implantable cardioverter defibrillator
- dialysis and ultrafiltration
- ventricular assist decide
- intra-aortic balloon pump
- cardiac translation
- (stem cell therapy)
how many wires do pacemakers have?
2 wires but biventricular pacemakers have an additional 3rd lead designed to conduct signals directly into the left ventricle
how does biventricular pacing work?
- conduct pacing signals to specific regions of the heart
- combination of all 3 leads promote synchronised pumping of ventricles, increasing efficiency of each beat and pumping more blood on the whole
