ECG Flashcards
What are the interpretation steps?
- Rate
- Rhythm
- Cardiac axis
- P waves
- P-R interval
- QRS complex
- ST segment
- T waves
- QT interval
Describe P waves
- Atrial depolarisation
- Height: <2small squares (increased in right atrial enlargement e.g. caused by pulmonary HTN)
- Absent in AF
- Chaotic baseline - fibrillation waves
- Bifid = P mitrale (left atrial enlargement - mitral stenosis)
- Peaked = P pulmonale (right atrial enlargement - lung disease)
Describe the P-R interval
- P wave to Q wave
- Normal = 120-200ms (3-5 small squares)
- Time taken for conduction between atria and ventricles
- Prolonged = >0.2 secs (>5 small squares), suggests presence of AV block
- Shortened = delta wave, associated with Wolff Parkinson White Syndrome
What is Mobitz type 1 (2nd degree heart block)?
Mobitz type 1: progressive prolongation of PR interval until atrial impulse is not conducted and QRS complex is dropped
What is Mobitz type 2 heart block?
Consistent PR interval duration with intermittently dropped QRS complexes due to a failure of conduction - usually 3:1 or 4:1.
What is complete heart block (3rd degree)?
No electrical communication between atria and ventricles due to complete failure of conduction.
Describe QRS complex
- Narrow <0.12 secs (<3 small squares)
- Broad >0.12 secs - abnormal depolarisation sequence e.g. ventricular ectopic, bundle branch block
- Height - small <5mm in limb leads or <10mm in chest leads - tall imply ventricular hypertrophy
- Dominant R wave in V1/2 (right ventricular hypertrophy, posterior MI)
Describe the ST segment
- ST elevation >1mm (1 small square) in 2 or more contiguous limb leads or >2mm in 2 or more chest leads
- ST depression >0.5mm in >2 contiguous leads indicates myocardial ischaemia
What would hyperkalaemia show on an ECG?
- Small or absent P waves
- Tall tented T waves
- Broad bizarre QRS complexes
- Long PR interval
- Sinus wave pattern
- Short QT interval
What would hypokalaemia show on an ECG?
- U waves
- Small or absent T waves (occasionally inversion)
- Prolong PR interval
- ST depression
- Long QT
What is first degree heart block?
Regular prolongation of the PR interval (>5 small squares and regular)
What are the ECG lead changes by infarct territory?
- V1-4 - anteroseptal (LAD)
- V4-5, lead I and AVL - anterolateral (LAD or left circumflex artery)
- II, III + AVF - inferior (right coronary artery)
- AVR - medial
- I, aVL +/- V5-6 (left circumflex)
- Dominant R wave V1-2, horizontal ST depression V1-3 - posterior (left circumflex or right coronary)
What is the significance of the AVR lead?
All the leads are negative
What is the normal trend from V1-6 leads?
- V1 > 6 - R wave is growing, negative at beginning to positive
- V3/4 - R and S are equal usually
- V1 > 3 - S wave growing
- V4 > 6 - S wave not really there
What are the different types of rhythm and what do they classically look like on an ECG?
- AF = no clear P waves and irregular QRS
- Atrial flutter = saw-tooth baseline 75-150bpm
- SVT = narrow complex tachycardia with abnormal or no discernible P waves
- VF, VT = broad complex tachycardia with no P waves
- 2nd degree/complete heart block = P waves present but without constant PR interval
