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ECG Flashcards

1
Q

Electrodes

A

material in contact with skin connected to cables

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2
Q

Cables/ Wires

A

Connected to electrodes

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3
Q

Leads

A

Perspective of electrical activity of the heart

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4
Q

Vector

A

quantity that has both magnitude and direction

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5
Q

Isoelectric line?

A

represents no net change in voltage. i.e. vectors are perpendicular to the lead.

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6
Q

Width of deflection=

A

duration of the event

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7
Q

Upward deflections are towards

A

the cathode (+)

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8
Q

Each wave is composed of both

A

both the up- and downstrokes

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9
Q

Downward deflections are towards

A

the anode (-)

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10
Q

Steepness of line denotes the

A

‘velocity’ of action potential

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11
Q

P wave=

A

The electrical signal that stimulates contraction of the atria (atrial systole)

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12
Q

QRS =

A

The electrical signal that stimulates contraction of the ventricles (ventricular systole)
No atrial repolarisation possible because QRS hides it

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13
Q

T wave=

A

The electrical signal that signifies relaxation of the ventricles

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14
Q

Conduction system parts

A 
SA node
Atrial myocardium
AV node
Bundle of His
Endocardium
Myocardium
Epicardium
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15
Q

Why is lead II most important?

A

the negative electrode is on the right arm and positive electrode= right leg which is how the heart is lined up so deflections are most prominent here

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16
Q

Conduction system mapped to ECG
(know drawing of normal wave+ relate to each part)
(slide 11, lecture 13)

A
  1. SAN= P wave
    Autorhythmic myocytes
    Atrial depolarisation
    Not big or fast= wide dome shaped
    In diagram, red arrow pointing more towards positive which is why there is a positive wave
  2. AVN
    AVN depolarisation
    Isoelectric ECG- flat line
    Slow signal transduction
    Protective
  3. Bundle of His
    Rapid conduction- purkinje cells- cells are organised lengthways
    Insulated- small bit of the flat line continued
  4. Bundle branches
    Septal depolarisation
    Small negative deflection
    Small and fast, just to a small bit of muscle
  5. Purkinje fibres (1)
    Ventricular depolarisation
    Massive depolarisation, lots of cells+ muscle, towards +ve
    Impulse works its way up myocardium walls, up the sides on both but because its more prominent on LV= that side dominates
    At this point its in full systole, has ejected blood
  6. Purkinje fibres (2)
    Late ventricular depolarisation
  7. Fully depolarised ventricles
    Isoelectric ECG- flat line
  8. Repolarisation= T wave
    Ventricular repolarisation, heading towards –ve electrode (-ve+ -ve= +ve) so positive deflection, not a rapid event so its wide
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17
Q

12 leads

View of heart+ coronary artery its referring to

A 
1st columb:
Lateral, LCx (Left circumflex)
Inferior, RCA (Right coronary artery)
Inferior, RCA
2nd column:
n/a, n/a
Lateral, LCx
Inferior, RCA
3rd column:
Septal, LAD (Left Anterior Descending Artery)
Septal, LAD
Anterior, RCA
4th column:
Anterior, RCA
Lateral, LCx
Lateral, LCx
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18
Q

ECG one big square width+ depth meaning?

A

One width= 0.2s (each small square= 0.04s)

One depth= 0.5mV (each small square= 0.1mV)

19
Q

Lead 1=?
Lead 2=?
Lead 3=?

Electrode placement?

A

Lead 1= RA to LA (-ve to +ve) (one L)
Lead 2= RA to LL (-ve to +ve) (two Ls)
Lead 3= LL to LA (+ve to -ve) (3 Ls)

First electrode of each pair= always -ve (first electrode= higher up/ to the left)

V1= Right sternal border, in the 4th intercostal space
V2= Left sternal border in the 4th intercostal space
V3= Halfway between V2 and V4 (put after V4)
V4= Mid-clavicular line In the 5th intercostal space
V5= Anterior axillary line at the level of V4
V6= Mid-axillary line at the level of V4
20
Q

12 leads table
(slide 14, lecture 13)
Location, Polarity, Plane, Cathode (+ve), Anode (-ve), View

A

Polarity= how many physical points are there in the line (most of them aren’t from one electrode to another)

21
Q

PR interval

A

Measure from P to Q actually (sometimes you can’t see it)

22
Q

How to find heart rate on ECG

A

60/ RR interval

Divide 300 by number of big squares

23
Q

How to find QRS axis

A

Can’t be worked out just from one lead
If you get another lead that has another 90 degree view from the first lead you can calculate it (e.g. Lead II and aVL)
1. Find net deflection of highest and lowest part of ECG (count from highest point to 0 then 0 to lowest point and subtract down from up)
2. Therefore in Lead II direction, draw arrow of net value
3. Do the same as 1 for second lead (aVL in this case) and from the end of the arrow of the first lead, draw the arrow of the value parallell to direction of second lead (90 degrees)
4. This means that the cardiac axis (one cardiac vector) is the sum of those two arrows
5. Find the angle in the triangle by trigonometry
6. Figure out angle from the line that combines the lines you’ve drawn to the 0 line (in this case its 60- angle)

24
Q

Types of arrhythmias

A 
Supraventircular = problems that originate above AV node
Junctional=  junction between atria+ ventricles= AV node/ could be in bundle branches
Ventricular= ventricular muscle itself
25
Types of abnomalities of the heart
Conduction abnormalities Structural abnormalities, e.g. LV hypetrophy= muscle grows concentrically into ventricle= axis deviation Perfusion abnormalities, e.g. narrowing/ blockage of arteries= ischamic tissue
26
Parts of heart | slide 5, lecture 14
-
27
Things to look for in an ECG
1) Rate+ Rhythm (RR) 2) P wave+ PR interval- shows how long the signal takes to go through Atrial myocardium + AV node (supposed to be slower) 3) QRS duration 4) QRS axis (trigonometry) 5) ST segment- focus on height
28
Sinus rhythm | Rate=?
Each P-wave is followed by a QRS wave (1:1) | Rate is regular (even R-R intervals) and normal (83 bpm)
29
Types of ECG abnormalities | Know general shapes from lecture
``` Supraventricular abnormalities: Sinus bradycardia Sinus tachycardia Sinus arrhythmia Atrial fibrillation Atrial flutter ``` ``` Junctional arrhythmias: First degree heart block Second degree heart block (Mobitz I) Second degree heart block (Mobitz II) Third degree heart block ``` ``` Ventricular arrhythmias: Ventricular tachycardia Ventricular fibrillation ST elevation ST depression ```
30
Sinus bradycardia Rate? Causes?
Each P-wave is followed by a QRS wave (1:1) Rate is regular (even but long R-R intervals) and slow (56 bpm) Can be healthy, caused by medication or vagal stimulation
31
Sinus tachycardia Rate? Cause?
Each P-wave is followed by a QRS wave (1:1) Rate is regular (even but short R-R intervals) and fast (107 bpm) Often a physiological response (i.e. secondary)
32
How to tell if heart is left-axis deviated or right axis deviated?
Look at QRS complex on Leads I and III If Lead I is positive, Lead III is negative (both moving in opposite directions)= LEFT axis deviated If Lead I is negative, Lead III is positive (both moving towards each other= RIGHT axis deviated
33
Sinus arrhythmia | Rate?
Each P-wave is followed by a QRS wave Rate is irregular (variable R-R intervals) and normal-ish (65-100 bpm) R-R interval varies with breathing cycle
34
``` Atrial fibrillation Baseline? Rhythm? Rate? Increase what risk? Why can you still live with it? ```
Oscillating baseline – atria contracting asynchronously Rhythm can be irregular and rate may be slow Turbulent flow pattern increases clot risk Atria not essential for cardiac cycle
35
Atrial flutter Baseline? Atria: Ventricular beats?
Regular saw-tooth pattern in baseline (II, III, aVF) Atrial to ventricular beats at a 2:1 ratio, 3:1 ratio or higher Saw-tooth not always visible in all leads
36
First degree heart block- can usually see in rhythm strip Interval caused by? Rhythm? Sign of?
Prolonged PR segment/interval caused by slower AV conduction Regular rhythm: 1:1 ratio of P-waves to QRS complexes Most benign heart block, but a progressive disease of ageing
37
Second degree heart block (Mobitz I) -can usually see in rhythm strip Regularity? Cause? Also called?
Gradual prolongation of the PR interval until beat skipped Most P-waves followed by QRS; but some P-waves are not Regularly irregular: caused by a diseased AV node (4th signal not conducted through AV node) Also called Wenckebach
38
Second degree heart block (Mobitz II) Regularity? Danger?
P-waves are regular, but only some are followed by QRS No P-R prolongation but doesn't come through sometimes Regularly irregular: successes to failures (e.g. 2:1) Can rapidly deteriorate into third degree heart block
39
Third degree heart block
P-waves are regular, QRS are regular, but no relationship (atria and ventricles have no relationship) P waves can be hidden within bigger vectors (e.g. P waves 'move left' because less frequent that QRS) A truly non-sinus rhythm SA, AV and myocardium all have their own autonomic rates (decrease as you go through) but because SA is quickest it usually controls the rest but this doesn't happen here– back-up pacemaker in action
40
Ventricular tachycardia Rate? High risk of?
P-waves hidden – dissociated atrial rhythm Rate is regular and fast (100-200 bpm) Ventricular vectors= regular At high risk of deteriorating into fibrillation (cardiac arrest) but shockable rhythm – defibrillators widely available Ventricles= beating faster than they can fill
41
Ventricular fibrillation Heart rate? High risk of?
Heart rate irregular and 250 bpm and above Heart unable to generate an output- brain doesn't get blood Not every wave looks the same At high risk of deteriorating into fibrillation (cardiac arrest) Shockable rhythm – defibrillators widely available
42
ST elevation Rhythm? Rate? Caused by?
P waves visible and always followed by QRS Rhythm is regular and rate is normal (85 bpm) ST-segment is elevated >2mm above the isoelectric line Caused by infarction (tissue death caused by hypoperfusion) Therefore >2mm elevation= infarction
43
ST depression Rhythm? Rate? Caused by?
P waves visible and always followed by QRS Rhythm is regular and rate is normal (95 bpm) ST-segment is depressed >2mm below the isoelectric line Caused by myocardial ischaemia (coronary insufficiency)- Coronary arteries cant provide myocardium with enough oxygen

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