Treating Heart Failure Flashcards
What are the aims of treatment in heart failure?
Relieve symptoms of fluid overload
Decrease cardiovascular risk factors
How do you reduce fluid overload in heart failiure?
Prescribe a loop diuretic such as furosemide
What is the risk of using furosemide?
Can cause hypokalaemia
What is the mechanism of action of furosemide?
Inhibits NKCC transporters in ascending limb of loop of henle
What is a common drug interaction of ACE inhibitors that is potentially dangerous?
When used with potassium sparing diuretics can produce hyperkalaemia.
Which diuretic is prescribed if the patient is at risk of becoming hypokalaemic?
Potassium sparing diuretic such as spironolactone.
ACE inhibitors are commonly prescribed at the same time as diuretics are given in heart failure. What is their mechanism of action?
Reduction of angiotensin II synthesis so produce arterial and venous dilation which decreases ventricular EDV.
What is a common side effect of ACE inhibitors?
Dry cough.
What is a common contraindication for ACE inhibitors? Why?
Renal failure- ACE inhibitors cause vasodilation of the efferent arteriole so GFR decreases.
Why do ACE inhibitors cause hyperkalaemia?
Potassium losing effects of aldosterone are blocked
What other major classs of drug is indicated in heart failure in addition to ACE inhibitors and diuretics?
Beta blockers
What is the mechanism of action of beta blockers in heart failure?
Reduced workload of heart
Reduced cardiac hypertrophy and fibrosis
Anti arrhythmic effects
A 75 year old man was treated 3 months ago for an anterioseptal MI. He has since developed shortness of breath and exercise intolerability. He also complains of feeling breathless when lying down which sometimes wakes him from sleep. His past medical history includes atrial fibrillation. What drug is indicated to treat this condition?
Digoxin
What is the mechanism of action of digoxin in atrial fibrillation associated heart failure?
Digoxin has a positive inotropic effect which is used as a supplement to diuretic and ACE inhibitor therapy.
How would a patient with digoxin toxicity present?
Gastrointestinal upset
Hyperkalaemia
Life threatening dysarrythmias including automaticity and AV nodal blockade.
What other drugs can be tried in heart failure for those that cannot tolerate an ACE i?
Hydralazine, isosorbide dinitrate
In addition to diuretic provides balanced arterial and venous dilation
What is the mechanism of action of beta blockers in ischaemic heart disease?
Competitive antagonists of catecholamina at B adrenoreceptors.
They decrease heart rate
Reduce force of contraction
Lower blood pressure.
Slower heart rate legnthens diastole and gives more time for coronary perfusion which improves myocardial oxygen supply.
What are the pharmacokinetics of beta blockers?
Highly lipophilic beta blockers such as pranolol and metoprolol are well absorbed from gut and undergo extensive first pass metabolism in liver. This varies among individuals. Titration of drug is therefore required to achieve maximal effect.
Hydrophilic beta blockers such as atenolol are less well absorbed in the gut and have a narrower dose range, but longer half life.
What are the side effects of beta blockers?
Excessive bradycardia
Bronchospasm in people with asthma
Hypoglycaemia
CNS effects- sleep disturbance, vivid dreams and hallucinations
Blood lipid levels- raise TG and lower HDL.
What is a dangerous drug interaction of beta blockers?
With CCBs such as verapimil/ dilitiazem as they both reduce force of cardiac contraction and slow heart rate.
