Heart Failure Flashcards
What is heart failure?
a complex of symptoms - shortness of breath (dyspnoea), fatigue and congestion
due to the heart’s inability to empty of blood or fill properly leading to inadequate perfusion or tissues during exertion and retention of fluid
What are the symptoms of heart failure?
dizziness, fainting tiredness, fatigue coughing shortness of breath (dyspnoea) pulmonary oedema peripheral oedema ascites - swelling in the abdomen
What are the diagnostic measurements for heart failure?
measure BNP (brain-type natriuretic peptide) or NT-proBNP (N-terminal pro brain-type natriuretic peptides) levels
echocardiography
What are the different classes of heart failure in the New York Heart Association Classification?
Class I - no limitation on physical activity, ordinary physical activity does not cause fatigue
Class II - slight limitation on physical activity, comfortable at rest, ordinary physical activity causes fatigue
Class III - marked limitation of physical activity, comfortable at rest, less than ordinary activity leads to symptoms
Class IV - unable to carry out any physical activity without discomfort, symptoms are present are rest, increased discomfort with any physical activity
What is ejection fraction?
a measurement, expressed as a percentage, of how much blood the left ventricle pumps out with each contraction
heart failure with reduced ejection fraction is that of less than 45%
What are the causes of heart failure?
coronary artery disease - blood supply to the heart is compromised
decrease in myocardial mass - long term loss of coronary blood flow leads to cell/tissue death (infarct)
valve dysfunction
- stiffens = doesn’t allow blood out
- inflamed = doesn’t close properly and blood back flows
cardiomyopathy - loss of the ability to pump due to thick/stiff/stretched ventricles
drugs
increased output
increased arterial resistance
What are the consequences of heart failure?
reduced ejection fraction = is less than 45%
stroke volume is less responsive to filling pressure
end diastolic volume increases
ventricular dilatation
beta-1 mediated responses attenuated (reduced)
What are the compensatory mechanisms of heart failure?
increased afterload - pressure the heart must eject blood against
increased residual volume - blood left in the left ventricle
increased preload due to overfilling - caused by
increased blood volume, reduced venous compliance
heart dilatation - ventricle is stretched , hypertrophy - thickening
pulmonary/systemic congestion - oedema
increased metabolism - increased oxygen demand
What are the aims of treatment?
decrease cardiac work - reduce pressure exerted on the heart
improve stroke volume by reducing after load - results in increased oxygen to the heart
improve mechanical efficiency decrease pulmonary congestion - reduces symptoms increase contractility (force and rate) - increases oxygen supply
What are the pharmacological treatments for heart failure?
angiotensin converting enzyme inhibitors (ACEi) angiotensin receptor blockers (ARBs) aldosterone antagonists beta blockers calcium channel antagonists - amlodipine only diuretics digoxin - symptomatic treatment only phosphodiesterase inhibitors
What are diuretics?
reduce circulating volume by increasing fluid excretion
thiazides
- act on Na/Cl co-transport in the distal convoluted tubule
= bendroflumethiazide, hydrochlorothiazide
loop diuretics
- act on Na/K/2Cl co-transport in the loop of hence
= furosemide, bumetanide
What is the function of diuretics?
inhibit sodium reabsorption in the kidney
- reducing the osmotic gradient reduces water reabsorption
decreases circulating volume
- decreases oedema and ventricular distension (stretching of ventricles)
What are the advantages and disadvantages of diuretics?
advantages
- relieve symptoms = congestion, oedema
- relieve atrial and ventricular diastolic pressure
disadvantages
- do not improve left ventricular dysfunction
- hypokalaemia = arrhythmia
- hyperglycaemia = diabetes
- hyperuricaemia = gout
incontinence - frequent and urgent peeing
What are aldosterone antagonists?
spironolactone
- acts via its active metabolite = canrenone
blocks aldosterone receptors on distal convoluted tubule and collecting duct
- inhibits sodium reabsorption via the Na/K exchanger
What are the side effects of aldosterone antagonists?
gynaecosmastia testicular atrophy menstrual irregularities hyperkalaemia - prevents hypokalaemia caused by other drugs
