Flashcards in Interpretation of ECG Deck (43):
how is a regular rate on an ECG calculated?
300/number of big squares per R-R interval
what is a normal rate?
what is a sinus rhythm?
-normal P waves
-normal QRS complexes
-one P wave per QRS complex
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?
-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?
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?
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
-urea and electrolyte imbalance
what is the the ST segment?
time from end of ventricular depolarisation to start of ventricular repolarisation
what is a normal ST segment?
what does ST elevation indicate? what defines ST elevation?
-1mm in 2 adjacent limb leads
what does depression of ST segment indicate?
what are T waves representative of?
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?
-Q waves in leads V2-V4
-inverted T waves leads V4-V6
how is an anterolateral infarct seen in an ECG?
-Q waves in leads 1, 2 aVL
-raised ST segments V2-V6
how is an inferior infract seen on an ECG?
-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
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