Interpretation of ECG Flashcards
how is a regular rate on an ECG calculated?
300/number of big squares per R-R interval
what is a normal rate?
60-100 bpm
what is a sinus rhythm?
- normal P waves
- normal QRS complexes
- one P wave per QRS complex
- regular rhythm
how is atrial fibrillation seen on an ECG trace?
- no discernable P waves
- irregular QRS complexes
how is arterial flutter seen on an ECG trace?
- p waves seen at a rate of 300 per minute
- p waves have a saw toothed appearance
what is Junctional tachycardia? how is junctional tachycardia seen on ECG?
- impulses arriving from AV node
- normal QRS complexes yet absent P waves
what is ventricular tachycardia?
- after 2 sinus beats rate increases to 150 bpm
- QRS complexes become broad and T waves are difficult to identify
what is a P wave? What is its normal form on an ECG?
- time for atrial depolarisation
- less than 0.25 mv should be upright in 2,3 and aVF
what is P-mitrale?
- bifid P wave
- L atrial hypertrophy
what is P pulmonale?
- peaked P wave greater than 0.25 mv
- R atrial hypertrophy
what is the PR interval? what is the normal range?
- time between atrial and ventricular depolarisation
- 0.12 s-0.2 s
what does an abnormal length PR interval mean?
prolonged interval implies delayed AV conduction hence a 1st degree heart block
what is QRS complex? what is the normal range?
- time for ventricular depolarisation
- normally is less than or equal to 0.12s
what is normal Q wave?
less than 0.04s and less than 2mm in depth
what is an abnormal QRS complex? What is it indicative of?
- greater than 0.12s
- ventricular conduction defects- left or right Bundle Branch Block
what does it mean if the voltage of the QRS complex is less than 5mv?
- hypothyroidism
- COAD
- Myocarditis
- precarditis and pericardial effusion
how is L ventricular hypertrophy seen on an ECG?
R wave in V5 greater than 25mv
how is R ventricular hypertrophy seen on ECG trace?
dominant R wave in V1 or deep S wave in V6
what features define a significant Q wave?
- interval greater than 0.04s
- depth greater than 2mv
what does an abnormal Q wave in lead 3 indicate?
Pulmonary embolism
what is QT interval?
- measured from start of Q to end of T
- ventricular depolarisation then repolarisation
how is corrected QT calculated?
QTc= QT/ square route of RR interval
what is normal range for the QT interval?
0.38-0.42 s
why is the corrected QT interval used?
any change in heart rate alters QT interval and the heart rate is not constant
what can cause prolonged QT interval?
-acute myocardial ischaemia
-myocarditis
-bradycardia
-head injury
-hypothermia
-urea and electrolyte imbalance
congenital
-drugs
what is the the ST segment?
time from end of ventricular depolarisation to start of ventricular repolarisation
what is a normal ST segment?
isoelectric
what does ST elevation indicate? what defines ST elevation?
- 1mm in 2 adjacent limb leads
- infarction
what does depression of ST segment indicate?
ischaemia
what are T waves representative of?
ventricular repolarisation
where are T waves most likely to be inverted?
aVR and V1
where is it abnormal for T waves to be inverted? What is this indicative of?
- lead 1 or 2 and V4-V6
- ischaemia or infarction
what effects does digoxin have on T waves?
- T wave inversion
- St segment slopping depression
what 3 changes happen to ECG trace in Acute MI?
- T wave peaking followed by T wave depression
- ST segment elevation
- appearance of new Q waves
how is an anterior infract identified on an ECG?
- sinus rhythm
- Q waves in leads V2-V4
- inverted T waves leads V4-V6
how is an anterolateral infarct seen in an ECG?
- sinus rhythm
- Q waves in leads 1, 2 aVL
- raised ST segments V2-V6
how is an inferior infract seen on an ECG?
- sinus rhythm
- Q waves leads 3 and aVF
- depressed ST segment in aVL and V6
how is a posterior infarct identified from an ECG?
V1- ST segment depression and tall R wave
How can a pulmonary embolism be identified from an ECG?
- large S wave in lead 1
- deep Q wave in lead 3
- inverted T wave in lead 3
what are the features of hyperkalaemia on an ECG?
- Tall, tented T wave
- widened QRS
what are the ECG features of hypokalaemia?
- small T wave
- prominant U wave
what is the features on an ECG of hypercalcaemia?
short QT interval
what are the 2 features on an ECG identifying hypocalcaemia?
- long QT interval
- small T waves
