L.10 Heart Failure

Question 1

Digoxin

Answer 1

• positive inotropic drugs
• cardiac glycosides
• derived from Digitalis, is very toxic
• inhibits Na+/K+ ATPase and parasympathetic effect
• inhibiting parasympathetic effect leads to slower AV conduction which is useful in atrial fibrillation
• Na2+/K+ works in tandem with Na+/Ca2+
• Na+/Ca2+ antiporter pumps sodium INTO the cell and calcium OUT of the cell
• Na2+/K+ antiporter pumps sodium OUT of the cell
• Digoxin blocks Na2+/K+ antiporter which leads to the accumulation of sodium in the cell.
• Reduced action of Na+/Ca2+ will lead to increased calcium in the intracellular space
• Calcium activates ryanodine receptors to release large amounts of calcium from the sarcoplasmic reticulum to trigger muscle contraction
• final result: increase in muscle contractility

Question 2

furosemide

Answer 2

• loop diuretics
• blocks Na2+/K+/2Cl- symporter which increases Ca2+ excretion in thick ascending loop of nephron
• decreases sodium reabsorption, decreases water reabsorption and increases water excretion
• reduces blood volume
• reduces preload and afterload -> reduces the work the heart does
• leads to hypokalemia

Question 3

captopril

Answer 3

• angiotensin antagonist
• ACE inhibitors
• reduces preload, afterload and remodeling by inhibiting action of angiotensin II

Question 4

losartan

Answer 4

• angiotensin antagonist
• AT1 receptor antagonist -> competitive inhibitors to AT1 receptors
• reduces preload, afterload and remodeling by inhibiting action of angiotensin II

Question 5

metoprolol

Answer 5

• beta blocker
• prolongs life in chronic heart failure
• unknown mechanism BUT said that it is involved in decreasing renin secretion

Question 6

dobutamide

Answer 6

• beta receptor agonist
• beta 1 selective for severe heart failure
• increase cardiac force, reduces afterload and increases CO

Question 7

theophylline

Answer 7

• phosphodiester inhibitor
• acute decomposition in heart failure due to decreased afterload
• prevents the breakdown of cAMP by phosphodiesterase -> increase in cAMP leads to increase in contractility

Question 8

nitroglycerin

Answer 8

• vasodilator
• acute decomposition of heart failure
• reduce afterload and preload