Electrocardiography And Rhythm Disorders Flashcards
What are the 3 classes of abnormalities in the heart?
Conduction abnormalities
Structural abnormalities
Perfusion abnormalities
What are the advantages of ECGs?
Relatively cheap and easy to undertake
Reproducible between people and centres
Quick turnaround on results and reports
What is meant by a vector?
A quantity that has both magnitude and direction
What does an isoelectric line for a lead represent, with reference to relative vector position to lead?
No net change in voltage
Vectors are perpendicular to lead
What does an upwards deflection mean about the position of the vector relative to the lead?
Travelling towards positive electrode
What does a downwards deflection mean about the position of the vector relative to the lead?
Travelling towards negative electrode
What does the steepness and width of the line denote?
Steepness - Velocity of an action potential
Width - Duration of an event
What does the P wave show?
Electrical signal that stimulates contraction of the atria
What does the QRS complex show?
Electrical signal that stimulates contraction of the ventricles (ventricular systole)
What does the T wave show?
The electrical signal that signifies relaxation of the ventricles (ventricular repolarisation)
What part of an ECG wave reflects atrioventricular node activity?
What part of an ECG wave reflects Bundle of His activity?
What part of an ECG wave reflects bundle branches activity?
What part of an ECG wave reflects Purkinje fibres activity?
What part of an ECG shows fully depolarised ventricles?
In the image below, add where the leads I, II, III, aVR, aVL, aVF would go?
Where do the leads V1-6 go?
V1 - Right sternal border in the 4th intercostal space
V2 - Left sternal border in the 4th intercostal space
V3 - Halfway between V2 and V4
V4 - Mid-clavicular line in the 5th intercostal space
V5 - Anterior axillary line at the level of V4
V6 - Mid-axillary line at the level of V4
Which leads represent the Left Circumflex Artery?
Lead I
Lead aVL
Lead V5
Lead V6
(Lateral leads)
Which leads represent the Right Coronary Artery?
Lead II
Lead III
Lead aVF
(Inferior leads)
Which leads represent the Left Anterior Descending Artery?
Lead V1
Lead V2
Lead V3
Lead V4
(Anteroseptal leads)
What plane are the limb leads in?
Coronal
What plane are the chest leads in?
Horizontal
How do you calculate the heart rate from an ECG?
300/(No. of big squares in R-R interval)
A P-R interval below what is abnormal?
3 small squares
Note : A normal PR interval is 0.12-0.2s = 3 to 5 small squares!
What are the average rates for different intervals/rates on an ECG?
Outline the ECG reporting procedure
What is the heart rate interval in normal sinus rhythm generally?
60-100bpm
What is sinus rhythm characterised by?
Each P-wave is followed by a QRS complex (1:1)
Rate is regular
What is the heart rate interval in sinus bradycardia generally?
Under 60bpm
Can sinus bradycardia be healthy and what is it caused by?
Yes
Medication or vagal stimulation
Can sinus tachycardia be healthy?
Yes often a secondary physiological response
What defines sinus arrhythmia?
Rate is irregular - variable R-R intervals
R-R interval varies with breathing cycle
Is heart rate normal in sinus arrhythmia?
Relatively normal
65-100 bpm
How would you describe the ECG in atrial fibrillation?
Oscillating baseline - atria contracting asynchronously
Would the rhythm and rate be affected in atrial fibrillation?
Rhythm can be irregular
Rate may be slow
Why does atrial fibrillation increase clot risk?
Turbulent blood flow
In atrial flutter, how would you describe the ECG?
Regular saw-tooth pattern in baseline (II, III, aVF)
What is the ratio of atrial to ventricular beats in atrial flutter?
2:1 or 3:1 or higher
Is Saw-tooth pattern visible in all leads?
Not always
How would you describe the ECG changes in first degree heart block?
Prolonged P-R segment/interval caused by slower AV conduction however regular rhythm (1:1 P wave to QRS)
Is first degree heart block a progressive disease of ageing?
Yes
What are the ECG changes in second degree heart block Mobitz I?
Gradual prolongation of PR interval until beat skipped
Most P-waves followed by QRS complex but some are not
Regularly irregular
What is second degree heart block caused by?
Diseased AV node
How would you describe the changes in second degree heart block Mobitz II?
P waves are regular but only some are followed by QRS
No P-R prolongation
Regularly irregular: successes to failures (2:1) or random
Can rapidly deteriorate into third degree heart block
What are the changes in ECG caused by third degree (complete) heart block?
P waves are regular, QRS are regular but no relationship
P waves can be hidden within bigger vectors
Is there sinus rhythm in third degree heart block?
Non-sinus rhythm - back-up pacemaker required
In ventricular tachycardia, how would you describe the ECG?
P-waves are hidden - dissociated atrial rhythm
Rate is regular and fast (100-200 bpm)
What is dangerous about ventricular tachycardia?
High risk of deteriorating into fibrillation (cardiac arrest)
Shockable rhythm - defibrillators widely available
In ventricular fibrillation, how would you describe the changes in the ECG?
Heart rate irregular and 250 bpm and above
Heart unable to generate an output
Does ventricular fibrillation have a shockable rhythm?
Yes - defibrillators widely available
How would you describe the ECG changes in ST elevation?
P waves visible and always followed by QRS (1:1)
Rhythm is regular and rate is normal (85 bpm)
ST segment elevated >2mm above the isoelectric line
What causes ST elevation?
Infarction - tissue death caused by hypoperfusion
How would you describe the changes in ECG during ST depression?
P waves visible and always followed by QRS
Rhythm is regular and rate is normal (95 bpm)
ST segment is depressed >2mm below the isoelectric line
What causes the ST depression?
Myocardial ischaemia (coronary insufficiency)
