ECG basics Flashcards
What three types of abnormalities are detected by an ECG?
Conduction abnormalities
Structural abnormalities
Perfusion abnormalities
What are the three main advantages of conducting an ECG?
Relatively cheap and easy to undertake
Reproducible between people and centres
Quick turnaround on results/report.
What is the definition of a vector?
A vector is a quantity that has both magnitude and direction
What does a downwards deflection represent in an ECG?
Downwards deflections are towards the anode
What does an upward deflection represent in an ECG?
Towards the cathode
What does the width of a a deflection denote in an ECG?
Denotes the duration of the event
What does the steepness of an ECG line denote?
The velocity of an action potential.
What does an isoelectric ECG line represent?
Represents no net change in voltage (vectors are perpendicular to the lead).
What does the p wave represent?
Electrical signal that stimulates contraction of the atria (atrial systole).
Autorythmic myocytes
Atrial depolarisation
What does the QRS complex represent?
The electrical signal that stimulates contraction of the ventricles (ventricular systole)
What does the T wave represent?
An electrical signal that signifies relaxation of the ventricles (ventricular repolarisation).
What does the PR segment represent?
AVN depolarisation (Isoelectric ECG) There is slow signal transduction
Protective
Describe the speed of electrical transmission through the Bundle of His?
Rapid conduction (insulated)
What type of depolarisation occurs within the bundle branches?
Septal depolarisation
What does the Q wave represents?
Septal depolarisation
Which fibres are responsible for ventricular depolarisation?
Purkinje fibres
Which ECG structure represents the fully depolarised ventricles?
ST-segment
Where does lead 1 go from and to?
From the right arm to the left arm
Where does lead 2 go to?
From the right arm to the left leg
Where does lead two go from and to?
From the right arm to the left leg
What is the direction of depolarisation (negative to positive) in lead 1?
Right to left (anode to cathode)
Where is V1 placed?
Right sternal border in the fourth intercostal space
Where is V2 placed?
Left sternal border in the fourth intercostal space.
Where is V3 placed?
Halfway between v2 and v4
Where is V4 placed?
In the 5th intercostal space at the mid clavicular line
Where is V5 placed?
Anterior axillary line at the level of V4
Where is V6 placed?
Mid axillary line at the level of V4.
Which electrode is placed in the fourth intercostal space at the mid clavicular line?
V4
Which coronary artery is associated with lead 1?
Left circumflex artery
Which coronary artery is associated with lead 2?
Right coronary artery
Which coronary artery is associated with lead 3?
Right coronary artery
Which coronary artery is associated with aVL?
Left circumflex artery
Which coronary artery is associated with AvF?
Right coronary artery
Which coronary artery is associated with V1?
Left anterior descending artery
Which coronary artery is associated with V2?
Left anterior descending artery
Which artery is associated with V3?
Right coronary artery
Which coronary artery is associated with V4?
Right coronary artery
Which coronary artery is associated with v5?
left circumflex artery
Which coronary artery is associated with v6?
Left circumflex artery
Which ECG leads are associated with the lateral view of the heart?
Lead 1
aVL
V5 and V6
Which coronary artery is associated with leads of the lateral view of the heart?
left circumflex artery
Which ECG leads are associated with the anterior view of the heart?
V4
V3
Which coronary artery is associated with the anterior view of the heart?
Right coronary artery
Which ECG leads are associated with the inferior view of the heart?
Lead 2 and lead 3
AvF
Which coronary artery is associated with the inferior view of the heart?
Right coronary artery
Which ECG leads are associated with the septal view of the heart?
V1
V2
Which coronary artery is associated with the septal view of the heart?
Left anterior descending artery
Which leads are bipolar?
leads 1-3
Which leads are located on the limb?
Lead 1-3
AVR
AVL
AVF
Where is the cathode (+) located lead 1?
Left arm
What are the pairs of perpendicular leads?
Lead 1 and AVF
Lead 2 and AVL
Lead 3 and AVR
What is the first step of ECG reporting?
Check rate and rhythm (RR)
What is the second step of ECG recording (after checking the rate)?
Check p-wave and PR interval
What is the third stage of ECG recording (after checking the p-wave and pr interval)?
QRS duration
What is step 4 of ECG reporting?
QRS axis (using perpendicular leads and net deflections)
What is step 5 of ECG reporting?
Check ST segment
What is step 6 of ECG reporting after checking the ST segment?
Check the QT interval
what is the final step of ECG reporting?
T wave
What is sinus rhythmn?
Each p-wave is followed by a QRS complex (1:1).
Rate is regular (R-R intervals even), and normal
What is sinus bradycardia?
Each p wave is followed by a QRS complex (1:1).
Rate is regular (even R-R intervals) and slow (56bpm)
Can be caused by vagal stimulation or muscular heart (reduced heart rate to maintain same cardiac output).
What is sinus tachycardia?
Each p-wave is followed by a QRS complex (1:1).
Rate is regular (even R-R intervals), and fast (107bpm)>
Often physiological
What is sinus arrhytmia?
Each p-wave is followed by a QRS wave
Rate is irregular (variable R-R intervals), and normal (65-100bpm).
R-R intervals varies with breathing cycle
Which type of cardiac abnormality is associated with a varying R-R interval with breathing cycles?
Sinus arrhythmia
What is atrial fibrillation?
Oscillating baseline given the atria are contracting asynchronously.
The rhythm can be irregular and rate may be slow
Turbulent flow pattern increases clot risk
Which type of cardiac abnormality is associated with an increased risk of embolism?
Atrial fibrillation due to inadequate atrial contraction and pumping of blood.
What ECG pattern is commonly seen in atrial flutter?
There is a sawtooth pattern
What is atrial flutter?
Regular saw-tooth pattern in baseline (leads II, III, and AVF).
Atrial to ventricular beats (2:1 ratio or 3:1 ratio
There are p waves without succeeding QRS complexes.
What is the atria to ventricular beat ratio in individuals with atrial flutter?
2:1, 3:1 +
What is first degree heart block?
The PR segment is inappropriately long, there is impaired conduction through the atrioventricular node to the ventricles.
prolongation is caused by slower AV conduction, there is a regular rhythm 1:1 ratio of p-waves to QRS complexes.
Which form of heart block is associated with regular prolongation of the PR interval?
First degree heart block
What is a mobitz-I heart block?
There is progressive prolongation of the PR interval until a beat is dropped.
Majority of p-waves are followed by QRS complex.
Regularly irregular, caused by diseased AV node.
I.E 75 75 40 75 75 40
Which type of heart block is concerned with a progressive prolongation of the PR interval until there is a dropped beat?
Mobitz-I
What type of rhythm is exhibited by a Mobitz-I heart block?
Regularly irregular
What is a Mobitz-II heart block?
P-waves are regular, however only some are followed by QRS complex
There is NO PR prolongation.
Regularly irregular
Which heart block is associated with no PR prolongation, however partially absent QRS complexes?
Mobitz-II.
What is third degree heart block?
P-waves are regular, QRS are regular however there is no relationship
Truly non-sinus rhythmn, there is complete AV nodal failure.
What is ventricular tachycardia?
P-waves are hidden, given that there is dissociated atrial rhythm.
Rate is regular and fast (100-200bpm).
Shockable rhythm
What is ventricular fibrillation?
Heart is irregular and 250bpm and above
Unstable to generate cardiac output.
uncoordinated manner, the QRS complexes are irregular, thus there is no coordination of muscular contraction.
What causes ST elevation?
Caused by infarction (tissue death caused by hypoperfusion).
By what measurement is ST-elevation classified?
> 2mm above the isoelectric line
What causes ST depression?
Myocardial infarction (coronary insufficiency).