Drugs that Modify Cardiac Rate and Force

Question 1

3 types of b-adrenoceptor agonists (catecholamines) that act on the heart

Answer 1

Dobuamine
adrenaline
noradrenaline

Question 2

effect of the catecholamines(B agonists) on the heart

Answer 2

increased force, rate and CO and Oxygen consumption

decreased cardiac efficiency (oxygen consumption is increased more than cardiac work)

Question 3

what is an adverse effect of using B1 agonsits

Answer 3

cause arrhthymias

Question 4

what mixed (a/B) agonist is given IV and used to treat Cardiac arrests in advanced life support

Answer 4

Adrenaline

Question 5

why is adrenaline used in short term in emergencies

Answer 5

short half life 2 mins due to uptake/metabolism

Question 6

effect of adrenaline on cardiac arrest patients’ hearts

Answer 6

positive inotropic and positive chronotropic effect (stimulates SAN) actions B1

Question 7

effect of adrenaline on cardiac arrest patients’ blood flow

Answer 7

redistributes blood flow to the heart (constricts blood vessels in skin, mucosa and abdomen (a1)

Question 8

3 ways adrenaline helps cardiac patients

Answer 8

stimulates SAN increase in HR and force
redistributes blood flow to heart
dilates coronary arteries improving blood flow to heart

Question 9

what receptor is present in coronary arteries

Answer 9

B2

Question 10

what drug is given IM to patients in anaphylactic shock

Answer 10

adrenaline

Question 11

what drug is given in acute heart failure that is potentially reversible (after surgery, cardigenetic, septic shock) in high dependence via IV infusion

Answer 11

Dobutamine

Question 12

what is the half life of dobutamine

Answer 12

short (2 mins)

Question 13

what type of agonist is dobutamine

Answer 13

selective for B1

Question 14

what is the effect of dobutamine on the heart

Answer 14

increases force of contraction little effect in increasing HR

Question 15

is dobutamine used in short or long term

Answer 15

only short term use

Question 16

what do B-adrenoceptor antagonists ability to block receptors depends on

Answer 16

the degree to which sympathetic nervous system is activated

they do nothing when the sympathetic NS is inactive

Question 17

give an example of a nonselective blocker of b-adrenoceptor

Answer 17

Propranolol

blocks both B1 and B2

Question 18

give 3 examples of selective b-adrenoceptor blockers that block the receptor competitively

Answer 18

Atenolol
Bisoprolol
Metoprolol

Question 19

what are non-selective partial agonists of B-adrenoceptors and give an example

Answer 19

they weakly activate receptor itself but will bock the effect of a full agonist eg. adrenaline but it itself will increase HR slightly eg. alprenolol

Question 20

what is the effect of non-selective propranolol at rest

Answer 20

little effect on rate, force, CO, MABP

Question 21

non-selective partial agonised activity will increase/decrease Heart rate at rest but will increase/decrease heart rate during exercise

Answer 21

increase rate in rest

decrease rate in exercise

Question 22

what effect will non-selective propranolol have on the heart during exercise and stress

Answer 22

rate, force and CO will be significantly reduced (reduction in max exercise tolerance)

Question 23

what is used to treat atrial fibrillation and supraventicular tachycardia

Answer 23

b-blockers

delay conduction through AVN and help restore sinus rhythm

Question 24

what is used to treat arrhythmias (excessive symapthetic activity = tachycardia or spontaneous activation of latent cardiac pacemaker outside nodal tissue)

Answer 24

b-blockers decrease excessive sympathetic drive and help restore normal sinus rhythm

Question 25

what is the first line treatment of Angina

Answer 25

B-adrenoceptor antagonists | alternative to Ca entry blockers

Question 26

what is used to treat heart failure

Answer 26

low dose B-blockers (this is paradoxical) proven to improve morbidity and mortality by reducing sympathetic drive reducing increased risk of arrhythmias developing

Question 27

name a B-blocker + a1 antagonist that causes vasodilation which reduces total peripheral resistance so heart doesn’t need to pump as forcefully given to (compensated) heart failure patients

Answer 27

Carvedilol

Question 28

how should carvedilol be given

Answer 28

start low increasing slow to prevent worsening patients condtion

Question 29

when is b-blocker the 1st line treatment of hypertension

Answer 29

only if co-morbities like angina

Question 30

why are B-blockers given to patients with arrhytmias

Answer 30

block abnormal electrical activity leaving the atria and passing to ventricles to restore normal sinus rhythm

Question 31

what are the adverse effects of B-blockers

Answer 31

``` bronchospasm not compensated heart failure (worsening effect) hypoglycaemia fatigue cold extremities ```

Question 32

why can B-blockers not be given to asthmatics

Answer 32

block ASM B2adrenoceptors causing bronchospasm

Question 33

why do patients on b-blockers feel fatigue

Answer 33

CO (B1) and skeletal muscle perfusion (B2) in exercise are regulated by B-adrenoceptors

Question 34

how can b-blockers induce hypoglycaemia (worsen blood sugar in diabetics)

Answer 34

B2 adrenoceptor controls release of glucose from the liver therefore there will be too much glucose output from the liver if B2 is blocked

Question 35

why do patients on B-blockers have cold extermities

Answer 35

loss of B2 adrenoceptor mediated Vasodilation in cutaneous vessles

Question 36

what is a non-selective competitive antagonist of muscarinic Ach receptor on the heart

Answer 36

Atropine

Question 37

what is the effect of atropine

Answer 37

increases HR (at all but low doses)

Question 38

effect of low dose atropine on heart

Answer 38

decreases HR

Question 39

effect of high dose atropine on heart

Answer 39

increase HR

Question 40

why is the effect of atropine more pronounced on a trained athlete

Answer 40

trained athletes have cardiac muscle hypertrophy so increased SV (due to increased vagal tone)

Question 41

what is the effect of atropine on arterial BP

Answer 41

none | resistance vessels lack parasympathetic innervation

Question 42

what is the 1st line treatment of sever bradycardia in MI

Answer 42

Atropine

Question 43

what is used to reverse cardiac arrest by blocking the effect of the parasympathetic effect on the heart

Answer 43

Atropine

Question 44

when using atropine reverse cardiac arrest should a low r high dose be given

Answer 44

HIGH dose low dose will make things worse 300-600 mg monitoring required

Question 45

what is an alternative to atropine to reverse cardiac arrest

Answer 45

glycopryrronium

Question 46

what is used to treat anti cholinesterase poisoning to reduce excessive parasympathetic activity

Answer 46

atropine

Question 47

what is a cardiac glycoside used to increase heart contractility

Answer 47

Digoxin

Question 48

what is digoxin used to treat

Answer 48

heart failure when CO is insufficient to provide adequate tissue perfusion ventricular function curve is depressed

Question 49

what 2 drugs have a positive inotropic effect

Answer 49

digoxin | dobutamine

Question 50

what effect does digoxin have on a ventricular function curve

Answer 50

upward and leftward shift so SV increases at any given EDP

Question 51

how does Digoxin increase contractility

Answer 51

by inhibiting sarcolemma ATPase blocking Na/K ATPase increasing intracellular Na

Question 52

what does Ca removal from the cell to the ECF depend on

Answer 52

Na/K ATPase by secondary active transport as the Na/Ca exchanger causes Na influx and Ca efflux Na coming in via Na/Ca exchanger moves out via Na/K ATP tase

Question 53

how does digoxin directly increase contractility

Answer 53

you block Na/K ATPase there is increased Ca in SR as Na build up prevents Ca moving out so more Ca in SR which can be relased during Ca induced Ca release

Question 54

why is digoxin dangerous

Answer 54

competes with K for Na/K ATPase, effects can be dangerously enhanced by low plasma K (hypokalaemia) also very narrow therapeutic window

Question 55

what is the direct effect of digoxin

Answer 55

increases vagal activity: increases parasympathetic drive/vagal activity: to slow SAN discharge, Slow AVN conduction and increase refractory period

Question 56

what is the direct effect of digoxin

Answer 56

shortens AP + refractory period in arterial and ventricular myocytes

Question 57

what happens if there is a toxic concentration of digoxin

Answer 57

membrane depolarisation + oscillatory afterpotentials due to Ca overload = tachycardia -> atrial fibrillation + potential death

Question 58

when is digoxin used to treat heart failure

Answer 58

added to treatment in last resort in patients who haven't responded to diuretics and ACE inhibitors

Question 59

why is digoxin given to patients with heart failure AND atrial fibrillation

Answer 59

increases AVN refractory period so helps prevent spreading arrhythmias to ventricles

Question 60

what are the adverse effects of digoxin

Answer 60

heart block (excessive depression of AVN conduction) nausea/vomiting diarrhoea disturb colour vision

Question 61

what is levosimendan

Answer 61

a calcium sensitiser that is an inotropic drug which binds to troponin C in myocytes sensitising it to Ca forms cross bridges

Question 62

how does the calcium sensitiser levosimendan act as a vasodilator

Answer 62

opens K channes in vascular smooth muscle = hyper polarisation and less excitable

Question 63

what drug is used to treat acute decompensated heart failure via IV

Answer 63

Levosimendan (calcium sensitiser)

Question 64

give 2 examples of inotropic drugs that reduce peripheral resistance

Answer 64

amrinone and milrinone

Question 65

how do amrinone and milrinone act as inodilators

Answer 65

inhibit PDE in cardiac smooth muscle cells and increase cAMP to reduce resistance in short term to improve life quality

Question 66

what inodilator that increases cardiac contractility can trea acute heart failure by IV administration

Answer 66

amrinone and milrinone

Question 67

why can amrinone and milrinene only be use in short term

Answer 67

shorten life by causing arrhythmias