Basic ECG Flashcards
Which are the septal leads?
- facing: v1, v2
- no reciprocal
Which are the anterior leads?
- facing: v3, v4
- no reciprocal
Which are the anteroseptal leads?
- facing: v1, v2, v3, v4
- no reciprocal
Which are the lateral leads?
- facing: I, aVL, V5, V6
- reciprocal: II, III, aVF
Which are the anterolateral leads?
- facing: I, aVL, V3, V4, V5, V6
- reciprocal: II, III, aVF
Which are the inferior leads?
- facing: II, III, aVF
- opposite: I, aVL
Which are the posterior leads?
- facing: none
- opposite: v1, v2, v3, v4
What does a positive lead I and negative aVF suggest?
left axis deviation
What does a negative lead I and positive aVF suggest?
right axis deviation
What does a negative lead I and negative aVF suggest?
extreme axis deviation
How does a normal P wave look like?
- P wave positive in leads II, III, AVF
- P wave duration <0.12s
- P wave height <2.5mm
What is normal q wave duration?
Duration <0.04s (1 small sq)
What does a normal qrs complex look like?
- Duration <0.12s (3 small sq)
- Normal R wave progression from V1 to V4 (should get more positive)
What is the normal PR interval?
0.12-0.20s (3-5 small squares)
What is the normal QT Interval?
0.38-0.42s (9.5 - 10.5 small squares) or grossly
What does the P wave represent?
atrial depolarisation originating in the sinoatrial node (SA node)
What does the PR interval represent?
depolarization originating in the SA node and traveling through the atria, the AV node, and the His-Purkinje system
What does the QRS complex represent?
ventricular depolarisation
What does the ST segment represent?
the segment between ventricular depolarization and repolarization
What does T wave represent?
ventricular repolarization
What does the QT interval represent?
total time of ventricular depolarisation and repolarisation
What are the causes of right atrial enlargement?
Caused by pulmonary HTN
- Chronic lung disease (Cor Pulmonale)
- Pulmonary embolism
- Tricuspid Stenosis
- Tricuspid Regurgitation
How does right atrial enlargement appear on ECG?
- Axis deviation of P wave to right
- Amplitude of 1st part of P wave increases (>2.5mm)
- P wave width no change (because 2nd part of P wave is left atrial in origin, hides prolonged depolarization of right atrium)
What are the causes of left atrial enlargement?
If in isolation, classically seen with MS
If in association with LVH
- Systemic HTN
- Aortic stenosis
- Mitral regurgitation
- Hypertrophic Cardiomyopathy
How does left atrial enlargement appear on ECG?
- No significant axis deviation (because left atrium is normally already electrically dominant)
- 2nd part of P wave increase in amplitude (i.e. >1mm below isoelectric line in V1; not visible in lead II)
- Increase in duration of P wave
What are the causes of right ventricular enlargement?
- Chronic lung disease (cor pulmonale)
- Pulmonary embolism
- Pulmonary stenosis
- Pulmonary hypertension
- Congenital heart disease (e.g. ToF)
What are the ecg changes seen in right ventricular enlargement?
Right axis deviation (>100)
- Lead I more –ve than +ve
Poor R wave progression
- V1: R wave larger than S wave
- V6: S wave larger than R wave
+/- RV Strain Pattern (Downward sloping ST Depression + T wave inversion)
What are the causes of left ventricular enlargement?
- Hypertension (most common cause)
- Aortic stenosis
- Aortic regurgitation
- Mitral regurgitation
- Coarctation of the aorta
What are the ecg changes seen in left ventricular enlargement?
kolov-Lyon criteria: R wave amplitude (V5 or 6) + S wave amplitude (V1 or 2) is >35mm (>7 large squares)
Left axis deviation (not as useful in Dx)
+/- LV Strain Pattern (Downward sloping ST Depression + T wave inversion)
In which leads can T wave inversion be physiological?
May be inverted in III, aVR, V1 & V2 without being abnormal
