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Cardiovascular System > ECG: PRO > Flashcards

ECG: PRO Flashcards

1
Q

What are you likely to see on an ECG in someone with atrial fibrillation? What causes this?

A

Caused by chaotic activity in the atria; resulting in an inability for the atria to contract and a missing P wave. Instead, they quiver; generating a wavy baseline on an ECG.

Since the SA node is not active, the chaotic atrial activity is acting as the pacemaker, but the AV node cannot conduct every AP into the ventricles.

The Purkinje fibres work fine, so the QRS complex itself will be normal, but the pulse will be irregular since the AV node is being bombarded by 100s of random signals.

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2
Q

What are 3 features on an ECG that can be seen during an MI?

A
  1. ST-elevation (dying tissue, the T wave may have inverted)
  2. pathological Q waves > 2mm deep
  3. Inverted T waves
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3
Q

What does the tombstone sign on an ECG indicate?

A

ST-elevation, the patient is having an MI until proven otherwise

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4
Q

What can indicate a previous MI on an ECG?

A

A longer/wider Q wave

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5
Q

Why would a T wave invert?

A

A dead ventricle may repolarise the wrong way, inverting the T wave

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6
Q

What typically causes a R axis deviation?

What does this mean?

A

R ventricular hypertrophy and pulmonary conditions

The direction of depolarisation is distorted to the right

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7
Q

What is a L axis deviation?

What usually causes this?

A 
The direction of depolarisation distorted to the left
Conduction defects (not increased mass in L ventricle)
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8
Q

What are the features of right bundle branch block an ECG? Which leads should you look at?

A
  1. Bunny ears: V1, maybe V2 and 3
  2. slurred S wave in lateral leads: 1, aVL and V6
  3. QRS duration>120 ms
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9
Q

What defines ST elevation?

A

S starts 2 small squares above the isoelectric baseline in 2 consecutive chest leads

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10
Q

What does a ‘tented’ T wave indicate? When is it normal to see an inverted T wave?

A

Tented means very big; means there is a high K+ causing a bigger repolarization.

Inverted T wave can be normal in V1

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11
Q

How would the R wave appear in leads 1,2,3 in a R axis deviation?

A

Lead 1: R is negative
Lead 2: R is positive but smaller
Lead 3: R is large and positive

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12
Q

How would the R wave appear in leads 1,2,3 in a L axis deviation?

A

Lead 1: R is abnormally positive
Lead 2: R is less positive
Lead 3: R is negative

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13
Q

What is a common symptom of 2nd-degree heart block?

A

Syncope

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14
Q

What is characteristic of Mobitz 1 Wenckebach?

A

The P-R interval gets continually longer until the AV node cannot conduct electricity and the QRS complex disappears. Therefore there is a reduced heart rate.
“Wencke-wencke-wencke-bach (drop)”

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15
Q

What is characteristic of Mobitz 2?

A

No PR prolongation but the blocked QRS complexes are random; therefore, there is an erratic relationship between the P and R waves

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16
Q

What kind of heart rate is typically associated with heart block?

A

Bradycardia

17
Q

What is characteristic of a 3rd-degree heart block? Why is this?

A

The AV node has completely lost its ability to conduct electricity into the ventricles, so there is no relationship between the P and R waves. In order to keep the heart beating, the ventricle can generate slow APs through a ventricular pacemaker; overall producing a very slow heartbeat.

The QRS will be broad, because conduction through the myocardium is much slower than conduction through the Purkinje fibres.

18
Q

What is characteristic of a 1st-degree heart block?

A

AV node conduction is slower than normal, so although each P wave generates a QRS there is a delay between them (prolonged PR interval).
Therefore PR is consistent but prolonged >200ms (over 5 little squares apart)
The heart rate will be regular, but slower.

19
Q

What is the definition of 2nd-degree heart block and what are the 2 types called?

A

Some, but not all, of the P waves conduct a QRS complex.
Mobitz 1: wenckebach
Mobitz 2

20
Q

What causes atrial flutter and how does this appear on an ECG?

What is one diagnostic criterion?

A

Atrial flutter occurs when there is a single re-entry circuit in the atria that is rapidly firing causing many atrial contractions, as the SA node is not active. This generates a ‘sawtooth’ pattern of multiple P waves on an ECG.

The AV node is unable to conduct every P wave. Since Purkinje fibres are normal, when an AV node does conduct electrical activity down the septum it generates a normal/narrow QRS complex, and the rhythm is usually regular since the fluttering of the atria is also regular.
E.g; there may be 4 P waves for every 1 R wave, so the conduction is 4:1

Diagnostic criteria: p waves are 250-300 bpm

21
Q

Why can’t an AV node conduct every P wave?

A

If there are too many P waves, they may hit the AV node during its refractory period and are, therefore, blocked

22
Q

How does a ventricular tachycardia appear on an ECG?

What symptoms might the patient experience?

A

In ventricular tachycardia, the heartbeats are originating in the muscle wall of the ventricle and >100 bpm. Since diastole has been shortened, the heart fills less and the SV reduces. Since the ventricles are also being depolarised abnormally, the FOC is reduced which also lowers the SV = overall a decreased CO occurs.

On ECG:
Wide QRS; Basically no AV node conduction
HR>100
Since the P waves are not being conducted into the ventricles, there is an absence of a PR interval (although there still are P waves as the atria can still contract).

Since the CO is falling, the patient will likely be hypotensive and may experience dizziness, faintness, SOB, syncope or very sweaty.

23
Q

What are some common causes of ventricular tachycardia?

A

Coronary disease, previous heart attacks, heart failure and heart valvular disease

24
Q

What causes ventricular fibrillation? How does this appear on an ECG and how would you treat it?

A

Caused by abnormal firings of electrical signals in the ventricles, this causes the heart to stop beating.

Therefore, there are NO QRS complexes and no P waves can be seen, and the entire ECG is a wavy chaotic baseline. Since there is no pulse, the heart goes into cardiac arrest and the body quickly loses perfusion.
This means the patient will quickly go unconscious and require CPR, IV meds and defibrillation.

25
Q

What does supraventricular tachycardia mean?

A

Any tachycardia that is NOT ventricular tachycardia

26
Q

What causes a bundle branch block?

A

When someone has had an MI some of the myocardium is dead. Therefore, that side’s bundle of HIS cannot conduct electricity as it should, and there is delayed conduction between the atria and that side.

This means the QRS complex will be broad as conduction on the dead side must pass through normal myocardium which is much slower.

27
Q

What defines a sinus bradycardia? When is this common?

A

A heartbeat initiated by the sinus node and is beating <60 bpm. P waves, PR interval, QRS complex are all normal and rhythm is regular

Common in athletes and during sleep

28
Q

What defines sinus tachycardia?

When is this normal?

A

A heart rhythm initiated by the sinus node and is beating >100 bpm. On the ECG: a steeper and shorter S may be noticed. The rhythm is regular, and the P waves, PR interval and QRS complex are all normal.

Sinus tachycardia is the normal response to exercise and anxiety

29
Q

What are some causes of R bundle branch blocks?

A

Congenital, MI, hypertension, PE

30
Q

What are 3 criteria on an ECG for a L bundle branch block?

A
  1. QRS >120 ms
  2. Downwardly deflected R wave in V1 (it is upwards in a R bundle branch block)
  3. Absent Q wave in leads 1, V5 and V6
31
Q

How could you determine whether a L or R axis deviation is present with your thumbs????

A

Look at Leads 1 and aVF, your L thumb goes with lead 1 and your right thumb with aVF. Point your thumb in the direction that the R wave is going:

Normal: Both thumbs point up
L axis deviation: Thumbs pointing away from each other, “Left is for leaving”
R axis deviation: thumbs point towards each other: “R is for reaching”
(If both thumbs point down, the axis is indeterminate)

32
Q

What is the step by step process you would analyze an ECG?

RRAP PRQQTT

A

Is there electrical activity?

  1. Rate
  2. Rhythm
  3. Axis: look at leads 1 and aVF R wave (both thumbs up?)
  4. Is there a P wave?
  5. PR segment? Should be 120-200 ms
  6. QRS complex: wide or narrow
  7. QT interval? Should be 400-440 ms
  8. T wave
33
Q

What does the PR interval measure? How long should it be?

A

AV conduction time; 3-5 little squares

34
Q

What does the QT interval measure?

A

The time of ventricular activity; including depolarisation and repolarisation

35
Q

What does it mean if QRS is broad?

A

Conduction through the ventricular myocardium is very slow (should be 80-100 ms, broad would be >=120)
(either a defect in HIS and/or Purkinje or myocyte-myocyte depolarisation)

Cardiovascular System (18 decks)

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