ECG Basics Flashcards
ECG: what is the J point?
Where the QRS complex becomes the ST segment.
ECG: what is the normal axis of the QRS complex?
-30° -> +90°
ECG: what does the P wave represent?
Atrial depolarisation.
ECG: how long should the PR interval be?
120 - 200ms.
ECG: what might a long PR interval indicate?
Heart block.
ECG: how long should the QT interval be?
0.35 - 0.45s.
ECG: what does the QRS complex represent?
Ventricular depolarisation.
ECG: what does the T wave represent?
Ventricular repolarisation.
ECG: where would you place lead 1?
From the right arm to the left arm with the positive electrode being at the left arm. At 0°.
ECG: where would you place lead 2?
From the right arm to the left leg with the positive electrode being at the left leg. At 60°.
ECG: where would you place lead 3?
From the left arm to the left leg with the positive electrode being at the left leg. At 120°.
ECG: where would you place lead avF?
From halfway between the left arm and right arm to the left leg with the positive electrode being at the left leg. At 90°.
ECG: where would you place lead avL?
From halfway between the right arm and left leg to the left arm with the positive electrode being at the left arm. At -30°.
ECG: where would you place lead avR?
From halfway between the left arm and left leg to the right arm with the positive electrode being at the right arm. At -150°.
Leads I, II and aVF are from what part of the heart?
Therefore, what artery is affected?
Inferior
Right coronary
(can remember this as aVf has an F like inFerior)
Leads V3 and V4 are from which part of the heart?
Therefore, which artery is affected?
Anterior.
LAD.
Leads V1 and V2 are from which part of the heart?
Septum
Leads I, V5, V6 and aVL are from which part of the heart?
Which artery is therefore implicated?
Lateral.
Left circumflex.
What is the dominant pacemaker of the heart?
The SA node. 60-100 beats/min.
How many seconds do the following represent on ECG paper?
a) small squares.
b) large squares.
a) 0.04s.
b) 0.2s.
How long should the QRS complex be?
Less than 110 ms.
In which leads would you expect the QRS complex to be upright in?
Leads 1 and 2.
In which lead are all waves negative?
aVR.
In which leads must the R wave grow?
From chest leads V1 to V4.
In which leads must the S wave grow?
From chest leads V1 to V3. It must also disappear in V6.
In which leads should T waves and P waves be upright?
Leads 1, 2, V2 -> V6.
What might tall pointed P waves on an ECG suggest?
Right atrial enlargement.
What might notched, ‘m shaped’ P waves on an ECG suggest?
Left atrial enlargement.
Give 3 signs of abnormal T waves.
- Symmetrical.
- Tall and peaked.
- Biphasic or inverted.
What happens to the QT interval when HR increases?
The QT interval decreases.
What part of the ECG does the plateau phase of the cardiac action potential coincide with?
QT interval.
What HR is considered sinus tachycardia?
>100bpm
Name some causes of sinus tachycardia
Anxiety, dehydration, recent exercise, sepsis, pneumonia etc etc
What lead(s) would you look in to assess sinus bradycardia/tachycardia?
any - rhythm strip is best
What HR is considered sinus bradycardia?
<60bpm
List some causes of left axis deviation
left anterior hemiblock
WPW syndrome
inferior MI
ventricular tachycardia
LVH
What is the most likely cause of right axis deviation? List any alternative causes
RVH is most likely
normal variant - tall thin people
lateral MI
WPW syndrome
dextrocardia or R/L arm lead switch
left posterior fascicular block
How would you detect left axis deviation?
Look for lead I and II “Leaving” each other - small lead I, negative lead II and III
What is a more likely cause of left axis deviation, conduction issues or LVH?
conduction issues
Describe what is seen:
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Complete heart block.
atrial rate is 60bpm
ventricular rate is 27bpm
slow ventricular escape rhythm
Describe what is seen:
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2:1 heart block
Describe what is seen:
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3:1 heart block
Describe what is seen:
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Mobitz II second degree heart block
Intermittent P waves without progressive lengthening of PR interval
Describe what is seen:
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Mobitz I second degree heart block
aka Weckebach phenomenon
progressive lengthening of PR interval until a QRS fails to conduct (dropped beat)
Describe what is seen:
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First degree heart block
PR >0.2s (5 small squares)
Describe what is seen:
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Right axis deviation
leads I and II reaching towards each other
Describe what is seen:
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Left axis deviation
Leads I and II are leaving each other
Describe what is seen:
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atrial fibrillation
irregularly irregular, absent P waves
Describe what is seen:
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Atrial fibrillation
irregularly irregular
absent P waves
Describe what is seen:
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Atrial flutter
“saw tooth P waves” at c300bpm
Describe what is seen:
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atrial tachycardia
narrow complex tachycardia at 120bpm
each QRS is preceded by an abnormal p wave
Describe what is seen:
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junctional tachycardia
narrow QRS
retrograde P waves before, during or after QRS
Describe what is seen:
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RBBB
broad QRS
M complex in V1-3
W complex in V6 (slurred S waves)
Describe what is seen
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LBBB
broad QRS
dominant S in V1 - W
broad R in lateral leads - M
Describe what is seen:
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ST elevation in I and aVL (high lateral leads)
reciprocal ST depression in III and aVF (inferior leads)
acute MI localised to superior part of lateral wall -
high lateral STEMI
occluded first branch of LAD
Describe what is seen
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ST elevation in inferior (II, III, aVF) leads and lateral (I, V5-V6) leads
ST depression in V1-V3 suggests associated posterior infarction
acute anterolateral STEMI with posterior extension
occlusion of proximal circumflex
Describe what is seen:
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ST elevation in leads II, III and aVF
Q-wave formation in III and aVF
reciprocal ST depression and T wave inversion in aVL
inferior STEMI
circumflex occlusion - ST elevation in lead II = lead III
Describe what is seen:
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marked ST elevation in leads II, III and aVF
reciprocal changes in aVL
inferior STEMI
RCA occlusion as ST elevation in lead III> lead II
What does this V2 lead trace suggest?
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posterior MI
horizontal ST depression
upright T wave
dominant R wave (R/S ratio >1)
Describe what is seen:
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ST elevation is maximal in anteroseptal leads (v1-V4)
Q waves present in septal leads (V1-2)
hyperacute (peaked) T waves in (V2-4)
hyperactute anteroseptal STEMI
Describe what is seen:
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ST elevation in V1-6 + I and aVL
minimal reciprocal depression in III and aVF
anterior STEMI
Describe what is seen:
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ventricular fibrillation
Describe what is seen:
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sinus rhythm
broad QRS with slurred upstroke - delta wave
dominant R wave in V1
Wolff-Parkinson-White
Describe what is seen
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Digoxin effect
“sagging” ST segements
hockey stick T waves
Describe what is seen:
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pericarditis
widespread concave ST elevation and PR depression throughout V2-V6 and I, II, aVL, aVF
reciprocal ST depression and PR elevation in aVR
What might ST elevation in leads 2, 3 and aVF suggest?
RCA blockage.
These leads show the activity of the inferior aspect of the heart and the RCA supplies the inferior aspect of the heart with blood.
Name a disease that might cause tall P waves.
Right atrial enlargement.
Name a disease that might cause broad notched P waves.
Left atrial enlargement.