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ECG- Dr. Najeeb > Cardiac Arrhythmias > Flashcards

Cardiac Arrhythmias Flashcards

1
Q

What are the requirements to call heart rhythm normal?

A

1) The HR should be between 60-100
2) Every cardiac impulse should originate from the SA node
3) Every cardiac impulse should propogate through the normal conduction pathway
4) It should also have normal velocity as it passes through the conduction system

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2
Q

What is simple cardiac tachy- Arrhythmia?

A

It is an abnormal Heart rhythm with a rate between 100-150

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3
Q

What is paroxysmal tachyarhythmea?

A

It is an abnormal heart rhythm with an HR between 150-250 BPM

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4
Q

What is the difference between atrial and ventricular flutter?

A

They both have an HR between 250-350 BPM. But originates in atria and ventricles

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5
Q

What is the difference between atrial and ventricular fibrillation?

A

The electrical activity is over 350 BPM , but occurs in different chambers

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6
Q

What are mild bradyarrhythmias?

A

These are brady-arrhythmias with an HR between 40-60

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7
Q

What are moderate brady- arrhythmias?

A

These are brady-arrhythmias with a HR between 20-40

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8
Q

What are severe brady- arrhythmias?

A

These are brady-arrhythmias with HR <20

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9
Q

What are sinus arrhythmias ?

A

Any abnormal rhythm that has a sinus origin, we call it sinus arrhythmia

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10
Q

What are atrial arrhythmias?

A

These are arrhythmias originating from the atrial syncsytium other than the SA node.

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11
Q

What are junctional arrhythmias?

A

These are abnormal rhythms originating from the atrioventricular junction or AV node.

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12
Q

What are ventricular arrhythmias?

A

These are abnormal rhythms originating from the ventricular syncytium.

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13
Q

What are supraclavicular tachi- arrhythmias?

A

Supraventricular tachy-Arrhythmias consist of sinus, atrial and nodal or junctional tachi- arrhythmias

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14
Q

What is automaticity?

A

It is the ability of a tissue to undergo spontaneous depolarization

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15
Q

Explain the mechanism of spontaneous AP generation in SA node?

A

During SA nodal AP generation the resting membrane potential tips to threshold potential due to the presence of leaky sodium channels, which results in the opening of voltage gated calcium channels leading to the generation of SA nodal AP the repolarization occurs due to the subsequent cloer of voltage gated calcium channels and opening of voltage gated potassium channels.

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16
Q

How does epinephrine and norepinephrine augment the automaticity of the SA node and induce sinus tachicardia ?

A

They bind to the beta-1 receptors and thereby initiate phosphorylation of additional calcium through G- protein coupled mechanisms leading to more influx of calcium and more rapid action potential generation.

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17
Q

What is the mechanism of ventricular triggered automaticity associated tachyarhythmea?

A

This occurs when abnormally high cation loading occurs in ventricular cells due to myocardial ischemia or injury, the ventricular membrane potential don’t reach the resting membrane potential after the normal AP as a result the fluctuating membrane potential may reach threshold potential inducing early after depolarization or delayed after depolarization which are manifested as triggered ventricular tachiarhythmias.

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18
Q

Mechanism of tachi-arrhythmias by reentry?

A

It is a circular movement of AP around an ischemic focus in the ventricle leading to tachyarhythmea.

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19
Q

What is the neurotransmitter involved in vagal inhibition of SA node?

A

Acetylcholine

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20
Q

How does acetylcholine down regulates SA nodal excitation?

A

Acetylcholine binds to muscarinic receptors and increases the inward potassium current and decreases the pacemaker current and slow inward calcium current

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21
Q

What causes physiological sinus arrhythmia?

A

During inspiration the vagus nerve is inhibited and so the vagal inhibition of SA node which incurs a slight increase in SA nodal AP frequency and consequently the ventricular rate goes up. During expiration the opposite happens. The phenomenon is called physiological sinus arrhythmia

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22
Q

Physiological sinus arrhythmia is not seen in patients with heart transplant and diabetic automatic neuropathy. Why?

A

In both of these cases the vagal control of sinus node is void and therefore there is no sinus physiological respiratory arrhythmia.

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23
Q

What is the ECG characteristic of respiratory sinus arrhythmia?

A

The RR interval shortens during inspiration and lengthens during expiration.

24
Q

Heart rate in obstructive jaundice?

A

Bradycardia

25
Q

What is the mechanism of bradycardia in obstructive jaundice and intrahepatic cholestasis of pregnancy?

A

It is caused by the increased bilirubin levels in the blood which has direct inhibitory effect on SA node by decreasing inward calcium and sodium currents and increasing outward potassium current.

26
Q

What is the ECG pattern in sick sinus syndrome?

A

It is tachycardia - bradycardia combination or vice versa.

27
Q

What are the types of sinus arrhythmias ?

A

1) sinus bradycardia
2) sinus tachicardia
3) respiratory sinus arrhythmia
4) sick sinus syndrome

28
Q

What are the types of atrial tachiarhythmias?

A

1) atrial tachycardia
2) atrial flutter
3) atrial fibrillation

29
Q

What is the heart rate in atrial tachycardia?

A

120-250 beats per minute

30
Q

ECG pattern in atrial tachycardia?

A

It is marked by Atrioventricular dissociation. In ECG it manifest as multiple well defined P waves followed by a QRS Complex.

31
Q

ECG pattern in atrial flutter?

A

Sawtooth like P waves called flutter waves followed by QRS Complexes. They are generated by intra Atrial high speed reentry phenomenon.

32
Q

ECG pattern in atrial fibrillation?

A

In atrial fibrillation due to the presence of multiple ectopic foci with multiple vector orientations there will be some fluctuations in the isoelctric baseline preceding the QRS Complex or absence of any true P wave before qrs Complex

33
Q

How does atrial fibrillation precipitate ventricular fibrillation?

A

If the multiple atrial depolarization vectors that occurs in atrial fibrillation hyper excites the AV node and pass to the ventricles simultaneously it can trigger ventricular fibrillation.

34
Q

How to prevent ventricular fibrillation precipitated by atrial fibrillation?

A

By either stopping the atrial fibrillation or by slowing down the AV nodal conduction.

35
Q

What are the drugs that can be used to slow Down the AV nodal conduction in atrial fibrillation?

A

Calcium channel blockers, beta blockers, digitalis due to its vagal tone increasing effect.

36
Q

Why does AV nodal conduction depends on slow calcium channels?

A

The AV nodal resting membrane potential is -60 mV at this voltage the fast sodium channels are permanently closed.

37
Q

How does caffeine enhance Av nodal conduction?

A

Caffeine is a dromotropic and inotropic agent therefore it enhances the calcium dependent conduction through the AV node and by the means of catecholamines surge.

38
Q

Caffeine is metabolized by the liver into ___ by the CYP450 enzyme system?

A

Theophylline

39
Q

What are the junctional or nodal arrhythmias?

A

Junctional bradycardias and tachicardias.

40
Q

Junctional tachycardias cause and ECG pattern?

A

AV nodal conduction fastens due to calcium channel mediated conduction augmentation. ECG findings will be shortening of PR segment and interval.
The normal PR interval= 120-200 Ms.

41
Q

Junctional tachyarhythmeas presenting with short PR interval are called?

A

Pre- excitation syndromes

42
Q

What are the types of pre-exitation syndromes?

A

Lown- Ganong - Levin syndrome and WPW syndrome

43
Q

What is the ECG characteristic of Lown- Ganong- Levin syndrome?

A

PR interval<120 Ms. + Narrow complex QRS Complex.

44
Q

What is the clinical presentation of Lown- Ganong-Levin syndrome?

A

Palpitations and supraventricular tachycardia.

45
Q

What is the pathophysiology of Lown-Ganong-Levin syndrome?

A

It is due to an abnormally faster conduction through the AV nodal intrensic fast conduction pathways or through the extra AV nodal atrioventricular conduction fiber bundle known as Brechenmacher fibers or through the James bundle which is part of the normal AV node.

46
Q

What is WPW syndrome?

A

It is a pre excitation syndrome that occurs due to the direct activation of ventricles by the atria through Kent bundle instead of through the normal AV nodal bundle of hiss system.

47
Q

ECG presentation of WPW syndrome?

A

Short PR interval <120 Ms + delta wave+ ST segment and T wave abnormalities reflecting repolarization abnormalities

48
Q

What are junctional blocks / nodal blocks/ heart blocks ?

A

These are unusual delays in SA nodal impulse conduction through the AV node.

49
Q

ECG pattern in first degree hear block?

A

Prolongation of PR segment and interval due to prolongation of AV nodal conduction delay.

50
Q

Second degree hear block or mobitz type 01 block or wenckebach phenomenon ecg characteristics ?

A

Progressive prolongation of PR segment followed by a skipped QRS Complex.
The longest PR interval will be before the skipped av nodal conduction and the shortest will be the succeeding one.

51
Q

Mechanism of mobitz type 1 or wenckebach phenomenon type 01?

A

Malfunctioning AV nodes progressively fatigue and fail to conduct one cardiac impulse.

52
Q

What are the P: QRS frequency patterns of wenckebach phenomenon?

A

3:2, 4:3, 5:4.

53
Q

What are the three tracts that carry SA nodal impulse?

A

Wenckebach bundle: the median bundle that connects the SA node to AV node
Thorel’s bundle: the posterior internodal pathway that connects the SA node to AV node
The anterior internodal pathway
The Bachmann’s bundle to the left atrium

54
Q

ECG pattern in mobitz’s type 2 or second degree heart block?

A

Some of the P waves are not followed by QRS Complex without PR segment prolongation.

55
Q

ECG pattern in complete heart block or third degree heart block?

A

It is due to failure of AV nodal conduction and manifested with different atrial and ventricular rates called AV dissociation.

56
Q

What are second degree 2:1, 3:2, 4:3,and 5:4 heart blocks?

A

This has a pattern of P: QRS 2 Ps followed by 1 QRS, 3 Ps followed by two QRS etc.

57
Q

What is the source of the delta wave in WPW syndrome?

A

It is the septal depolarization by the bundle of Kent before it depolarize the bundle of Hiss- Purkinje system

ECG- Dr. Najeeb (2 decks)

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