Cardiovascular Effects of Autonomic Antagonists

Question 1

What are the roles of muscarinic receptors in the heart?

Answer 1

1. reduce automaticity in SA node
2. reduce inotropy in atrial myocardium
3. increase refractoriness in AV node

minimal ventricular and his involvement

Question 2

What are the roles of muscarinic receptors in the vasculature?

Answer 2

vasodilation of systemic arterioles

minimal venous involvement

Question 3

Consequences of parasympathetic discharge on cardiac tissue?

Answer 3

1. reduced heart rate, reduced AV nodal conduction = profound bradycardia
2. reduced systemic arteriolar resistance via vasodilation leading to reduction in systemic arterial pressure

Question 4

_____ is the prototypical competitive antagonist for the muscarinic receptor’s ACh binding site.

Answer 4

atropine

Question 5

Why don’t we use scopolamine in cardiology?

Answer 5

scopolomine is a muscarinic antagonist but has strong central effect so it’s used in motion sickness vs in cardiac tx

Question 6

Effects of atropine

Answer 6

increase heart rate, reduce AV nodal refractoriness, reduce vasodilation

Question 7

Uses of atropine

Answer 7

prevent vagal reaction, restore AV conduction in disorders w/impaired AV nodal refractoriness like digitalis toxicity and inferior wall MI

Question 8

Do beta blockers tend to work via beta1 or beta2 receptors?

Answer 8

beta 1 –> decrease heart rate, increase refractoriness/reduce impulse conduction, reduce inotropy/metabolic rate, inhibit renin release

Question 9

What are the effects of alpha blockers?

Answer 9

1. arteriolar vasodilation via alpha1, alpha2
2. venodilation via alpha1
3. improve voiding function in pts with urinary bladder outlet obstruction (prazosin)

Question 10

Prototypical alpha1, alpha2 antagonist

Answer 10

prazosin –> alpha1 > alpha2

Question 11

Prototypical pure alpha1 blocker

Answer 11

doxazosin, terazosin

Question 12

Clinical uses of alpha blockers

Answer 12

1. to decrease peripheral vascular ressitance

2. third line tx of htn

Question 13

What limits the use of alpha blockers in the elderly?

Answer 13

adverse reaction of postural hypotension

Question 14

What the pharmacokinetic differences between pure alpha 1 blockers and dual blockers?

Answer 14

pure alpha1 blockers have slower onset and longer duration

Question 15

Why do we prefer beta1 selective blockers?

Answer 15

beta 2 blockers will cause bronchoconstriction

Question 16

What is ISA?

Answer 16

intrinsic sympathomimetic activity –> partial agonists that produce blockade by shielding receptors from more potent agonists

Question 17

Which beta blockers are lipophilic and what does this do?

Answer 17

propranolol, metoprolol –> readily absorbed by GI tract, metabolized by liver –> short half life

Question 18

Which beta blockers are hydrophilic and what does this do?

Answer 18

atenolol –> longer half life b/c longer absorption/metabolism –> kidney metabolism –> gotta be careful in people with kidney disease

Question 19

Which beta blockers have ISA?

Answer 19

acebutolol, pindolol at low doses –> act as beta blockers at higher doses

Question 20

Which is non selective? propranolol, metoprolol, atenolol, carvedilol

Answer 20

propranolol, carvedilol (alpha 1 blockade)

Question 21

Which is lipophilic? propranolol, metoprolol, atenolol, carvedilol

Answer 21

propranolol> metopropolol, carvedilol > atenolol

Question 22

Which is renal clearance? propranolol, metoprolol, atenolol, carvedilol

Answer 22

atenolol

Question 23

4 general cardiac conditions in which beta blockers are useful

Answer 23

1. heart failure
2. mi/angina
3. arrhythmias
4. htn

Question 24

Adverse effects of beta blockers

Answer 24

1. sinus bradycardia, sinus arrest, AV block
2. reduce LV contractility in symptomatic heart failure
3. bronchoconstriction
4. fatigue, mental deprex, nightmares, sexual dysfunction
5. limb ischemia in those with PVD, raynauds
6. withdrawal
7. increased TG, reduced HDL

Question 25

Why does sudden beta blocker removal cause withdrawal symptoms in patients with chronic beta blockade?

Answer 25

b/c you upregulate beta receptors when on beta blockers so sudden removal of the drug leads to overstimulation of beta receptors –> increased heart rate, etc.

Question 26

What is the treatment option of choice in patients with CHF?

Answer 26

carvedilol –> not just a beta blocker (reduces myocyte injury, hypertrophy, and activation of RAAS), but also alpha blocker ( reduces vasoconstriction, reduces sodium retention even more)

Question 27

What is the Bezold-Jarisch reflex?

Answer 27

The Bezold–Jarisch reflex is responsible for the sinus bradycardia that commonly occurs within the first 60 minutes following an acute myocardial infarction, and explains the occurrence of AV node block in the context of acute posterior or inferior myocardial infarction –> vagal nerve stimulation due to ischemia

Question 28

Beta blocker or no? MI with complete heart block

Answer 28

no –> contraindication (complete heart block) overrides indication (acute MI)

Question 29

How do beta blockers improve myocardial O2 supply?

Answer 29

reduce heart rate –> increase diastole –> improve subendocardial perfusion