Heart failure

Question 1

What events lead to heart failure?

Answer 1

Cardiac growth and remodelling due to reflex mechanisms that aim to maintain CO, e.g. increased SNS
Increase HR and contractility
Atrial and venous constriction
Increased catecholamines
Increased renin release, as renal perfusion decreases.

Question 2

Compare cardiac remodelling is systolic and diastolic hypertension.

Answer 2

Systolic- dilated

Diastolic - hypertrophy

Question 3

How is heart failure treated?

Answer 3

Lifestyle changes
Drugs reducing cardiac workload
Drugs increasing cardiac contractility

Question 4

What are examples of K+ sparing diuretics?

Answer 4

Aldosterone agonists - spironolactone, eplerenone
Na+ channel blockers - amiloride

Act as distal tubule/collecting duct

Question 5

What is the mechanism of action aldosterone agonists, e.g. spironolactone, eplerenone?

Answer 5

Act at the distal tubule/collecting duct as diuretics, oppose cardiac remodelling.

Question 6

How can hypokalaemia be prevented in use of K+ sparing diuretics?

Answer 6

Use K+ sparing diuretics with thiazide or loop diuretics

Question 7

What is the benefit of non-selective over selective beta blockers?

Answer 7

Alpha receptor antagonist reduces afterload

Question 8

When are beta-blockers used in heart failure?

Answer 8

Adjunct to conventional therapy when the patient is stable, starting with low doses and slowly increasing

Question 9

What are the side effects and clinical considerations of beta blockers?

Answer 9

Cold extremities with antagonised beta2 receptors, provocation of asthma, heart failure if unstable, mask glycaemic episodes in diabetes as stop tremors

Question 10

List the positive ionotropic agents that are used in HF.

Answer 10

Cardiac glycosides - digoxin

Beta1 adrenoceptor agonists

Question 11

What is the mechanism of action of digoxin?

Answer 11

Inhibits Na/K ATPase, increasing inracellular NA, activating Na+/Ca2+ exchanger, increasing myocardial intracellular Ca2+

Question 12

What is the therapeutic effect of digoxin?

Answer 12

Increased myocardial contractility and reduced O2 use, increases CO

Question 13

When is digoxin most effective?

Answer 13

Cardiomyopathies, some dysrhythmias

Less effective in CHF secondary to hypertension.

Question 14

What is the major concern in use of digoxin?

Answer 14

Narrow safety margin, 75% absorption, long 1/2-life of 30-40 hours (mainly excreted by kidneys)

Question 15

How long does it take to reach the steady state for digoxin?

Answer 15

A week

Question 16

List the ADRs of digoxin.

Answer 16

CVS: dysrrhythmia
GIT: anorexia, nausea, vomiting, diarrhoea
Nervous system: stimulates vagal and vomiting centres, visual disturbance, disorientation, agitation, hallucination

Question 17

Why is the use of beta1 adrenoceptor agonists, such as dobutamine, limited?

Answer 17

Desensitisation while there is already down-regulation of beta1 adrenoceptors in CHF
Can trigger dysrhythmias

Question 18

What are the peripheral vasodilators used in HF?

Answer 18

Nitrovasodilators
Hydralazine
Milrinone

Question 19

What is the mechanism of action of nitrovasodilators?

Answer 19

Organic nitrates that donates NO to smooth muscle, e.g. isosorbide dinirate, GTN, sodium nitroprusside

Question 20

What are side effects of hydralazine?

Answer 20

Hypotension, flushing, head ache, tachycardia

Question 21

What is the mechanism of action of milrinone?

Answer 21

Ionotropic and vasodilator activity

Phosphodiesterase inhibition increases cAMP in cardiac and vascular smooth muscle.