Treating Heart Failure

Question 1

What are the aims of treatment in heart failure?

Answer 1

Relieve symptoms of fluid overload

Decrease cardiovascular risk factors

Question 2

How do you reduce fluid overload in heart failiure?

Answer 2

Prescribe a loop diuretic such as furosemide

Question 3

What is the risk of using furosemide?

Answer 3

Can cause hypokalaemia

Question 4

What is the mechanism of action of furosemide?

Answer 4

Inhibits NKCC transporters in ascending limb of loop of henle

Question 5

What is a common drug interaction of ACE inhibitors that is potentially dangerous?

Answer 5

When used with potassium sparing diuretics can produce hyperkalaemia.

Question 6

Which diuretic is prescribed if the patient is at risk of becoming hypokalaemic?

Answer 6

Potassium sparing diuretic such as spironolactone.

Question 7

ACE inhibitors are commonly prescribed at the same time as diuretics are given in heart failure. What is their mechanism of action?

Answer 7

Reduction of angiotensin II synthesis so produce arterial and venous dilation which decreases ventricular EDV.

Question 8

What is a common side effect of ACE inhibitors?

Answer 8

Dry cough.

Question 9

What is a common contraindication for ACE inhibitors? Why?

Answer 9

Renal failure- ACE inhibitors cause vasodilation of the efferent arteriole so GFR decreases.

Question 10

Why do ACE inhibitors cause hyperkalaemia?

Answer 10

Potassium losing effects of aldosterone are blocked

Question 11

What other major classs of drug is indicated in heart failure in addition to ACE inhibitors and diuretics?

Answer 11

Beta blockers

Question 12

What is the mechanism of action of beta blockers in heart failure?

Answer 12

Reduced workload of heart
Reduced cardiac hypertrophy and fibrosis
Anti arrhythmic effects

Question 13

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?

Answer 13

Digoxin

Question 14

What is the mechanism of action of digoxin in atrial fibrillation associated heart failure?

Answer 14

Digoxin has a positive inotropic effect which is used as a supplement to diuretic and ACE inhibitor therapy.

Question 15

How would a patient with digoxin toxicity present?

Answer 15

Gastrointestinal upset
Hyperkalaemia
Life threatening dysarrythmias including automaticity and AV nodal blockade.

Question 16

What other drugs can be tried in heart failure for those that cannot tolerate an ACE i?

Answer 16

Hydralazine, isosorbide dinitrate

In addition to diuretic provides balanced arterial and venous dilation

Question 17

What is the mechanism of action of beta blockers in ischaemic heart disease?

Answer 17

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.

Question 18

What are the pharmacokinetics of beta blockers?

Answer 18

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.

Question 19

What are the side effects of beta blockers?

Answer 19

Excessive bradycardia
Bronchospasm in people with asthma
Hypoglycaemia
CNS effects- sleep disturbance, vivid dreams and hallucinations
Blood lipid levels- raise TG and lower HDL.

Question 20

What is a dangerous drug interaction of beta blockers?

Answer 20

With CCBs such as verapimil/ dilitiazem as they both reduce force of cardiac contraction and slow heart rate.