ECG Flashcards
what do ECGs allow us to identify?
conductional abnormalities, structural abnormalities, perfusion abnormalities
What is happening if the deflection from the isoelectric line is in a downward direction?
theres a charge travelling towards the negative electrode (anode)
what is happening if the deflection from the isoelectric line is in an upward direction?
the wave of excitation is moving toward the cathode (positive electrode)
What is happening if there is no deflection from the isoelectric line?
no net change in voltage, the vectors are perpendicular to lead
What happens during the P wave of an ECG?
atrial excitation phase, the electrical signal stimulates the contraction of the atria (atrial systole)
What happens during the QRS complex of an ECG?
contraction of ventricles, electrical signal stimulating ventricular contraction (ventricular systole)
What happens during the T wave of an ECG?
repolarisation of the ventricles, electrical signal that signifies the relaxation of ventricles
What are the six cardiac vectors?
SAN, AVN, bundle of his, bundle branches, purkinje fibres 1, purkinje fibres 2,
What is the SAN vector?
Shows Autorythmic myocytes and atrial depolarisation
What is the AVN vector?
Shows AVN depolarisation, isoelectric ECG, slows signal transduction , is protective and important for mechanics of heart
What is the Bundle of His vector?
Is insulated and has rapid conduction
What is the bundle branches vector?
Shows septal depolarisation, start of QRS complex
What is the Purkinje fibres 1 vector?
Shows ventricular depolarisation, is the R wave
What is the Purkinje fibres 2 vector?
Shows late ventricular depolarisation, is the S wave
What is the fully repolarised vector?
Comes after QRS complex, is isoelectric
What is the repolarisation vector?
The T wave
How are leads arranged in an ECG?
Rule of L’s:
Lead 1 = right arm to Left arm
Lead 2 = right arm to Left Leg
Lead 3 = Left arm to Left Leg
How is each lead read in an ECG?
Drawn as a triangle, read from left to right, and top to bottom, 1st electrode in each pair is the anode
What is the chest electrode arrangement?
V1 = right sternal border, 4th intercostal space
V2= left sternal border, 4th intercostal space
V3 = Halfway between V2 and V4
V4 = mid-clavicular line, 5th intercostal space
V5 = Anterior axillary line at level of V4
V6 = Mid-axillary line, level of V4
What are the 8 things we can calculate from an ECG?
R-R interval, P wave duration, P-R interval, QRS duration, QT interval, T wave duration, HR, QRS axis
Each small square on an ECG represents how long?
0.04 seconds (big square = 0.2 seconds)
What do we need to be able to calculate the cardiac axis?
2 perpendicular leads
Which leads are perpendicular to each other?
aVF perpendicular to lead 1. aVL perpendicular to lead 2, aVR perpendicular to lead 3
What checks are made before an ECG report is conducted?
Is it the correct recording, review the signal quality and leads, verify the voltage and paper speed, review the patient background if available
Outline the steps of the ECG reporting procedure
1.Rate and rythmn
2. P wave and PR interval: duration, are all P waves followed by R
3. QRS duration: how long signal taking to get through myocardium
4. QRS axis
5. ST segment
6. QT interval
7. T wave
Double check findings
What is seen on the ECG of someone with Sinus rythmn?
Each P wave followed by a QRS wave. Rate is regular (even R-R intervals) and normal (60-90bpm)
What is seen on the ECG of someone with sinus bradycardia
Each P wave followed by QRS. Rate is regular and slow (<60bpm)
What is seen on the ECG of someone with sinus tachycardia?
Each P wave followed by QRS. Rate is regular and fast (>100bpm)
What is seen on the ECG of someone with sinus arrhythmia?
Each P wave followed by QRS. Rate is irregular (variable R-R intervals) and normal-ish (65-105bpm). R-R interval varies with breathing cycle
Why does the R-R interval of a patient with sinus arrhythmia vary with the breathing cycle?
Turns up or down PNS which slows down HR
What is seen on the ECG of someone with atrial fibrillation?
An oscillating baseline as atria contracting asynchronously. Rhythm can be irregular and rate may be slow.
The turbulent flow pattern seen on the ECG of a patient with atrial fibrillation increases the risk of what?
Blood clots
What is seen on the ECG of someone with atrial flutter?
Regular sawtooth pattern baseline. Atrial to ventricular beats at 2:1 ratio, 3:1 ratio or higher. Sawtooth not always visible in all leads
What is seen on the ECG of someone with first degree heart block?
Prolonged PR segment caused by slower AV conduction. Regular rhythm
What is seen on the ECG of someone with second degree heart block - Mobitz 1?
Gradual prolongation of the PR interval until beat skipped. Most P-waves followed by QRS but some are not. Is ‘regularly irregular’ (caused by a diseased AV node
What is seen on the ECG of someone with second degree heart block - Mobitz 2?
P-waves are regular but only some are followed by QRS complexes, no P-R prolongation.
What is seen on the ECG of someone with third degree heart block?
P-waves are regular, QRS are regular but no relationship between them, P waves can be hidden within bigger vectors
What is seen on the ECG of someone with ventricular tachycardia?
P-waves are hidden, rate is regular and fast
Ventricular tachycardia puts the patient at high risk of what?
Deteriorating into fibrillation (cardiac arrest)
What is seen on the ECG of someone with ventricular fibrillation?
Irregular heart rate and speed of 250bpm and above, heart unable to generate output
What two cardiac abnormalities show a shockable rythmn?
Ventricular tachycardia and ventricular arrhythmia
What is seen on the ECG of a patient with ST elevation?
P waves visible and always followed by a QRS, rythmn is regular and rate is normal, ST segment elevated
What causes the upwards movement associated with an ST elevation on an ECG?
Infarction
What is seen on the ECG of someone with ST depression?
P waves visible and always followed by QRS. Rythmn is regular and rate is normal, ST segment is depressed below isoelectric line
What causes ST depression?
Ischaemia
