ECG analysis Flashcards
How to calculate rate
If regular:
300/no. of large squares
If irregular:
no. of QRS complexes within 30 large squares x 10
Rythmn
Sinus - every P wave followed by QRS
AF - no P waves and irregularly irregular QRS
Atrial flutter: saw-toothed baseline
Nodal rhythm: regular QRS but no P waves
Axis
II most +ve = normal axis
AVL most +ve = Left axis deviation
AVF most +ve = right axis deviation
Systematic analysis of ECG
- Rate
- Rhythm
- Axis
- P waves and PR interval
- QRS
- ST segment
- T waves
P waves
Atrial depolarisation
- Absent: AF, SAN block, nodal rhythm
- Dissociated: complete heart block
• Bifid P waves = LA hypertrophy
- HTN, Aortic stenosis, Mitral regurgitation or stenosis
• Peaked P waves= RA hypertrophy
- pulmonary HTN, COPD
QRS
Ventricular initiation depolarisation
• Wide QRS >120ms - more than 3 small squares
- Conduction defect
- WPW
- Broad complex tachycardia
• Pathological Q wave
- Full Thickness MI
- RVH: Dominant R wave in V1 + deep S wave in V6
- LVH
- R wave in tall V6
- R wave in V5/V6 + S wave in V1
PR interval
PR interval (3-5 small sq) Start of P wave to start of QRS
• Long: heart block
•Short
- Accessory conduction: e.g. WPW
- Nodal rhythm
Long QT
QTc - Start of QRS to end of T wave
> 420ms
ST Segments
Elevated
• STEMI
• Pericarditis: saddle-shaped
• Aneurysm: ventricular
Depressed
• NSTEMI
• Unstable angina
T-waves
- Peaked in ↑K+
* Flattened in ↓K+
U waves
Hypokalaemia
1st Degree Heart Block
Constantly extended PR interval with no absent QRS complexes
PR > 200ms (more than 1 large sq)
2nd Degree Heart Block
- Wenckebach /Mobitz I
Progressive lengthening of
PR interval
Absence of QRS complex
Next conducted beat has
shorter PR interval
2nd Degree Heart Block
- Mobitz II
Constant PR
Occasional absent QRS
- block is usually in bundle
branches of Purkinje fibres
2nd Degree Heart Block
- 2:1 Block
Two P waves per QRS
Normal consistent PR
intervals
3rd Degree Heart Block
P waves and QRS are dissociated
RBBB
Broad complex QRS Bunny ear V1 Slurred S wave Causes: • Infarct – Inferior MI • Normal variant • Congenital – ASD, VSD, Fallot’s • Hypertrophy – RVH (PE, Cor Pulmonale)
Left BBB
Broad complex QRS
-ve V1
+ve at V6
Left axis deviation
Causes: • Fibrosis • LVH – AS, HTN • Infarct – Inf. MI •Coronary HD
Bifascicular Block
RBBB + axis deviation
Trifascicular Block
RBBB + axis deviation + 1st
degree AV block
Bradycardia
Less than 50bpm
TAchycardia
More than 100 bpm
Atrial escape
Missed P wave as SAN fails to depolarise
Normal QRS
Atrial Flutter
Saw-toothed baseline as
atria contract at 300bpm
2:1 - 150bpm
