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Y1 - CVS > Arrythmias And Actions Of Drugs On The CVS > Flashcards

Arrythmias And Actions Of Drugs On The CVS Flashcards

1
Q

What is Bradycardia?

A

Slow heart rate
Less than 60bpm

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2
Q

What is atrial flutter?

A

When atria beat faster but regularly compared to the ventricles (like 4 atria contractions per 1 ventricular contraction)

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3
Q

What is atrial fibrillation?

A

When atrial electrical contraction/activity is chaotically irregular

Irregularly irregular

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4
Q

What is Tachycardia?

A

Fast heart rate
Over 100bpm

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5
Q

What are the 2 types of Tachycardia?

A

Ventricular tachycardia
Supraventricular tachycardia

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6
Q

What is ventricular fibrillation?

A

Irregularly irregular contractions/electrical activity of the ventricles

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7
Q

What is the definition of an arrhythmia?

A

Any deviation from the normal rhythm of the heart

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8
Q

What are the 2 types of arrhythmias?

A

Tachyarrythmias
Bradyarrythmias

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9
Q

What are some of the different causes of Tachyarrythmias?

A

Ectopic pacemaker activity
Early after depolarisations
Atrial flutter/atrial fibrillation
Re-entry loop

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10
Q

How does Ectopic pacemaker activity cause a Tachyarrythmia/tachycardia?

A

Damaged area of myocardium becomes depolarised and spontaneously active (rapidly depolarises)

Ischaemic damage can cause a region which depolarises faster than the SAN to form

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11
Q

How can early after depolarisations cause Tachycardia/tachyarrythmia?

A

Triggered activity (abnormal depolarisations following an action potential) cause more AP to be fired than should be

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12
Q

What type of tachycardia can Atrial flutter/atrial fibrillation cause?

A

Supraventricular tachycardia

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13
Q

How do re-entry loops cause tachycardia?

A

Either a conduction delay
or
Accessory pathway

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14
Q

What are the 2 causes of Bradyarrythmias?

A

Sinus bradycardia
Conduction block

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15
Q

What is sick sinus syndrome?

A

Cause of sinus bradycardia
Where the SAN doesn’t depolarise quickly enough

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16
Q

What type of drugs can cause sinus bradycardia?

A

Beta blockers
Somme Ca2+ channel blockers

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17
Q

How do Conduction blocks occur causing bradycardia?

A

Problems at AVN or bundle of his causing slow conduction
Slow conduction due to factors like Beta blockers and some Ca2+ channel blockers

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18
Q

The prolonged duration of what increases the chances of Early After Depolarisations (EAD)?

What interval on an ECG indicates a longer AP?

A

Action potentials

Longer QT interval = longer AP

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19
Q

What condition of the blood can increase chances of EADs and why?

A

Hyperkalaemia

Takes longer for ventricles to repolarise due to less steep gradient of K+
This prolongs the action potential making it more likely for EADs

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20
Q

What type of tachycardia is likely to develop when AP/QT interval is longer?

A

Ventricular tachycardia

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21
Q

What are Delayed after-depolarisations? (Triggered activity)

A

An action potential that occurs after repolarisation

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22
Q

What makes Delayed after-depolarisations more likely to happen?

A

High Intracellular [Ca2+]

Possibly involves Na+/Ca2+ exchanger

If threshold reached AP triggered

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23
Q

What is the re-entrant mechanism for generating arrhythmias?

A

A unidirectional conduction block (incomplete conduction damage)
Allows for conduction to only flow one way through or decreases speed of conduction, meaning there isn’t a point where impulses cancel out
Produces constant loop to be set up (excitation travels the wrong way)

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24
Q

What is AV Nodal Re-entry?

A

Fast and slow pathways in the AVN create a re-entry loop

Causes ventricles to contract early (Supraventricular tachycardia)

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25
What causes Ventricular Pre-excitation?
Accessory pathway for electrical impulses between atria and ventricles creating a re-entry loop
26
What is a condition which has an accessory pathway between atria and ventricles?
Wolff-Parkinson-White syndrome
27
How can the re-entrant mechanism cause atrial fibrillation?
Several re-entry loops form in atria
28
What are the 4 basic classes of anti-arrhythmic drugs?
I. Block VOltage gated sodium channels II. Antagonists of B-adrenoreceptors III. Drugs that block K+ channels IV. Drugs that block Ca2+ channels
29
What is an example of a drug which blocks Voltage gated Na+ channels? (Class I)
Local anaesthetic lidocaine
30
What type of arrhythmia is Lidocaine used to treat?
Ventricular Tachycardia
31
How is Lidocaine administered to treat Ventrcular Tachycardia?
Intravenously
32
What state are the VGSCs in when Lidocaine blocks it and why is this useful?
Only blocks Open or Inactivated channels so preferentially blocks damaged depolarised tissues
33
How does Lidocaine treat ventricular tachycardia?
Blocks the damaged areas of myocardium’s Voltage gated Na+ channels preventing these areas from firing automatically
34
What is another name for drugs that are B-adrenoreceptor antagonists?
Beta blockers
35
What are the names of some Class II B-adrenoreceptor antagonists (Beta blockers)?
Propranolol Bisoprolol Atenolol
36
How do Beta blockers act to prevent Supraventricular tachycardia?
Act on B1 receptors in heart Slows down the funny current from reaching threshold in the SAN (HCN channels) Slows conduction at AVN by reducing VG Ca2+ activity in the AP upstroke
37
Why are Beta blockers often used following MI?
MI leads to increased sympathetic activity of the heart So Beta blockers often given to reduce this activity preventing ventricular arrhythmias It makes the heart not work so hard decreasing its O2 demand minimising further ischaemic damage
38
Which stage of the action potential does Class III K+ channel blockers affect?
Repolarisation
39
What affect do Class III antiarrhythmics have on the heart? (Amiodarone)
Lengthens the Absolute refractory period HOWEVER Prolongs the action potential (prolong QT interval) so can be PRO-arrhythmic
40
What is a Class III anti-arrhythmic that blocks K+ that is the exception which is used and why?
Amiodarone Has other affect like Beta blocking as well as blocking K+ channels Treats Wolff-Parkinson-White syndrome
41
What are the 2 types of Ca2+ channel blockers?
Non Dihydropyridine Ca2+ channel blockers Dihydropyridine Ca2+ channel blockers
42
What is the type of Ca2+ channel blocker which acts as an anti-arrhythmic drug affecting heart rate and rhythm?
Non Dihydropyridine Ca2+ channel blockers Like a Phenylaklyamine like Verapamil
43
What are some examples of Ca2+ channel blockers that act as Class IV anti-arrhythmics?
Phenylalkylamine = Verapamil Benzothiazapine = Diltiazem
44
How do Ca2+ channel blockers affect the heart?
Decreased influx of Ca2+ into cells Decreases speed of upstroke of AP at SAN Decreases AVN Conduction (both above have -Ve chronotropic effect) Decreases force of contraction (-Ve inotropic effect)
45
What do Dihydropyridine Ca2+ channels work on if they don't prevent arrhythmias?
Vascular smooth muscle
46
What type of receptor is the Alpha 1 adrenoreceptor?
G protein coupled receptor
47
How does adenosine act to treat arrhythmia?
Acts on A1 receptors at AVN Enhances K+ conductance causing hyperpolarisation Temporarily stops the heart allowing the APs to re align
48
What is an example of an ACE-inhibitor?
Perindopril Enalapril Lisonopril Ramipril
49
How does the ACE inhibitor Perindopril act to treat hypertension and Heart failure?
Prevents conversion of Angiotensin I to Angiotensin II Prevents Angiotensin II s effects of increasing Na+ and water reabsorber and its acton as a Vasoconstrictor
50
What is the goal of ACE inhibitors in treating heart failure and how do they acheive this?
Reduce how hard the heart has to work Decrease vasomotor done (dec BP) reducing afterload Decrease fluid retention (dec blodo vol) reducing preload
51
What is afterload?
Pressure the heart must work against to eject blood during systole
52
Why might someone not be able to tolerate ACE-inhibitors?
Can cause a dry cough
53
What can be given to patients who cant tolerate ACE inhibitors? (Have a dry cough, why do they have this?)
Angiotensin II receptor blockers Losartan Due to Bradykinin accumulating as a result of inhibiting ACE being inhibited
54
How do Diuretics treat heart failure and hypertension ?
Reduce Na+ and water retention Helps reduce pulmonary and peripheral oedema
55
What is the name of a drug that can treat congestive heart failure which is a loop diuretic?
Furosemide
56
How do the Dihydropyridine Ca2+ channel blockers help reduce workload of the heart?
Act on vascular smooth muscle Decreases peripheral resistance Decreases arterial BP Which reduces the afterload
57
What are some Dihydropyridine Ca2+ channel blockers (act on vascular sm)?
Amlopidine Nicardipine
58
What 2 types of drugs are positive inotropes? (Increase contractility of the heart)
Cardiac glycosides B-adrenergic agonists
59
What do both Cardiac glycosides and the B-adrenergic agonist Dobutamine do?
Block Na+/K+ ATPase leading to stronger contractions
60
What is an example of a cardiac glycoside?
Digoxin
61
How does the cardiac glycoside digoxin act to increase strength of heart contraction?
[Na+] in cell inc due to Na+/K+ ATPase being blocked by Digoxin Means activity of Na+/Ca2+ exchanger decreases since gradient of Na+ decreases so [Ca2+] in cell INCREASES More Ca2+ in cell = STRONGER contraction
62
Why are cardiac glycosides not normally used to treat heart failure?
Only normally improve symptoms but not long term outcome because the heart is being made to work harder
63
What affect do cardiac glycosides have on the heart?
Increased vagal activity on heart Slows AV conduction Slows heart rate
64
When are cardiac glycosides like Digoxin used as a form of treatment for heart failure?
Only when the heart failure is accompanied by arrhythmia since into an anti-arrhythmetic
65
How does the B-adrenoreceptor agonist Dobutamine act on the heart?
Stimulates B1 receptors at SAN and AVN and on myocytes in ventricles Can be used to help restart heart
66
What receptors does the Beta blocker Propranolol act on?
Non selective so on B1 and B2
67
What affect does Propranolol have on the body?
-Ve chronotropic affect on heart (B1) -Ve Isotropic affect on heart (B1) Bronchoconstriction can happen (B2)
68
Bisoprolol is often used when a patient is asthmatic when the heart is too fast, why is this the case?
Its cardio selective so only affects B1 receptors Means that bronchoconstriciton is less likely
69
What is an example of an alpha adrenoreceptor antagonist and what receptor does it work on?
Prazosin (doxazosin too) On A1 receptor
70
What is Prazosins mechanism of action as an A1 adrenoreceptor antagonist?
Inhibits Noradrenalines action on the A1 receptors of vascular smooth muscle causing VASODILATION
71
What is Angina?
When O2 supply to the heart does meet its requirements so some ischaemia of the heart occurs causing pain
72
When do you normally feel the pain with stable angina?
Upon exercise/exertion due to increase O2 demand of heart
73
How do organic nitrates cause venous dilation?
Organic nitrate forms NO2- This is reduced to NO (nitric oxide)
74
What blood vessels do organic nitrates/NO (nitric oxide act on?
Powerful vasodilator of veins Likely due to less endogenous nitric oxide in veins
75
On a basic level how does Nitric oxide cause vasodilation of veins?
Reduces Intracellular [Ca2+] causing the vascular sm to relax
76
How does the action of nitric oxide causing vasodilation of veins help treat angina?
Lowers central venous pressure Reduces the PRELOAD since less blood returns to the heart (heart fills less so doesn’t contract as hard) This lowers the hearts demand for Oxygen Has minimal action on coronary collateral arteries improving O2 supply to heart
77
What are the 2 general principles to treating angina?
Reduce workload of heart Improve blood supply to the heart
78
How can the workload of the heart be decreased to treat angina?
Organic nitrates (venodilation) B-adrenoreceptor blockers (propranolol or bisoprolol) Ca2+ Channel antagonists (Amlopidine, nicardipine, verapamil and Diltiazem)
79
How can the blood supply to the heart be increased to treat angina?
Ca2+ channel antagonists (Minor affects of organic nitrates)
80
What heart conditions increase risk of thrombus formation?
Atrial fibrillation Acute myocardial infarction Mechanical prosthetic heart valves
81
What are the anticoagulants that prevent venous thromboembolism?
Heparin (inhibits thrombin) Warfarin (inhibits action of vitamin K)
82
What are 2 anti platelet drugs and when are they typically given?
Aspirin Clopidogrel Following acute MI or people with high risk of MI
83
What is the definition of a supra-ventricular tachycardia?
Tachycardia which arises as a result of problems in the atria or AV node
84
What is the definition of ventricular tachycardia?
Tachycardia which arises as a result of problems in the bundle of His, Purkinje fibres or the ventricular myocytes
85
What is the key difference between early after depolarisations and delayed after depolarisations?
EAD when an action potential is fired during repolarisation (Hyperkalaemia cause) DAD when an action potential is fired after repolarisation (High Intracellular Ca2+ cause)

Y1 - CVS (21 decks)

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