ECGs Flashcards
Name the rhythm
Junctional Tachycardia
How fast does ECG paper run as standard?
Outline time intervals for each square.
Comes out a 25mm/s
Horizontal
One small box 0.04s
One large box 0.20s
therefore 5 boxes = 1 s
Describe the shap, duration and PR interval of a normal P-wave
The normal P-Wave
Shape: Smooth and rounded
Duration: 0.08 - 0.10 seconds
PR interval 0.12 - 0.20 seconds
Describe the componets of a normal QRS
Normal QRS
Q-Wave: the first negative deflection in the QRS not preceded by an R-wave
R-wave: First positive deflection in the QRS complext
S-wave: First negative deflection in the QRS complex after an R wave
Note a QS wave is a QRS complex that consists entirely of a single, large negative deflection
Describe the duration of a normal QRS complex
Normal QRS
Duration: 0.06 - 0.12 in adults (<0.08 in children)
Measured from Q onset to the J-point
Describe the normal T wave and is duration
Normal T wave
The onset of the T wave is identified by the first deviation after the ST segment
Normal duration is 0.10 - 0.25 seconds
QT interval is important
The normal T wave should be in the same direction as the QRS complex
Describe the PR interval and its significance
PR Interval
The PR interval is measured from the onset of the P wave and concludes with the onset of the QRS complex
Normal duration is 0.12 - 0.20 s (dependent on HR)
A QRS should follow every P wave
A normal PR interval indicates the SA node signal is procceding normally through the electrical conduction system (ie AV node, bundle of His) normally and without delay
Define the PR interval
PR interval
A PR interval represents the time of progression of the electrical impulse from the SA node (or etopic pacemaker) through the entire electrical conduction system of the heart to the ventricular myocardium.
It begins with the onset of the P wave and ends with the onset of the QRS complex
Define a long and short PR interval
PR Interval
Short < 0.12s
Long >0.20s
Define the QT interval
QT Interval
A QT interval represents the time between onset of depolarisation and the termination of repolarisation of the ventricles
It is meausured from the first wave of the QRS complex to the point where the T wave returns to the isoelectric line
Describe the J point
The J point is the the junction between the termination of the QRS complex and the beginning of the ST segment
Define the ST Segment
The ST segment is the flat, isoelectric section of the ECG between the end of the S wave (the J point) and the beginning of the T wave.
It represents the interval between ventricular depolarization and repolarization.
The most important cause of ST segment abnormality (elevation or depression) is myocardial ischaemia or infarction.
Normaly
Define the PR Segment
PR Segment
The PR segment is the flat, usually isoelectric segment between the end of the P wave and the start of the QRS complex.
Describe Sinus Rhythm
Sinus Rhythm
- Rhythm is regular
- (QRS) Rate is 60-100 bpm
- P-wave is upright with normal rounded morphology
- P-R interval is 0.12-0.20 sec
- QRS width is 0.06-0.12 s
- A QRS complex follows every P-wave
- A P-wave precedes ever QRS complex
- A T-wave follows every QRS complex
Describe Sinus Tachycardia
Sinus Tachycardia
- Rhythm is regular
- (QRS) Rate is >100 bpm
- P-wave is upright with normal rounded morphology
- P-R interval is 0.12-0.20 sec
- QRS width is 0.06-0.12 s
- A QRS complex follows every P-wave
- A P-wave precedes ever QRS complex
- A T-wave follows every QRS complex
Accelerated Junctional Rhythm
Narrow complex rhythm; QRS duration < 120ms (unless pre-existing bundle branch block or rate-related aberrant conduction).
Ventricular rate usually 60 – 100 bpm.
Retrograde P waves may be present and can appear before, during or after the QRS complex.
Retrograde P waves are usually inverted in the inferior leads (II, III, aVF), upright in aVR + V1.
AV dissociation may be present with the ventricular rate usually greater than the atrial rate.
There may be associated ECG features of digoxin effect or digoxin toxicity.
Note:
Junctional Escape Rhythm: 40-60 bpm
Accelerated Junctional Rhythm: 60-100 bpm
Junctional Tachycardia: > 100 bpm
Junctional Bradycardia: <40 bpm
Name this rhythm
Premature Atrial Complex (PAC)
An abnormal (non-sinus) P wave is followed by a QRS complex.
The P wave typically has a different morphology and axis to the sinus P waves.
The abnormal P wave may be hidden in the preceding T wave, producing a “peaked” or “camel hump” appearance — if this is not appreciated the PAC may be mistaken for a PJC.
PACS arising close to the AV node (“low atrial” ectopics) activate the atria retrogradely, producing an inverted P wave with a relatively short PR interval ≥ 120 ms (PR interval < 120 ms is classified as a PJC).
PACs that reach the SA node may depolarise it, causing the SA node to “reset” — this results in a longer-than-normal interval before the next sinus beat arrives (“post-extrasystolic pause”). Unlike with PVCs, this pause is not equal to double the preceding RR interval (i.e. not a “full compensatory pause”).
Similarly, PACs arriving very early in the cycle may not be conducted to the ventricles at all. In this case, you will see an abnormal P wave that is not followed by a QRS complex (“blocked PAC”). It is usually followed by a compensatory pause as the sinus node resets.
Name this rythm
Premature Junctional Complex
A complex originating from an etopic pacemaker in the AV junction. Occurs before the next ecpected beat and causes a compensatory pause. Occurs without a preceding P wave.
PJC QRS will match those of other beats
Name this rhythm
Premature ventricular Compex
Ectopic beat orginating in the ventricles
Wide QRS >0.12ms
No p waves
Full compensatory pause
Name this rhythm
SVT (AVNRT)
The term supraventricular tachycardia (SVT), whilst often used synonymously with AV nodal re-entry tachycardia (AVNRT), can be used to refer to any tachydysrhythmia arising from above the level of the Bundle of His.
Rate 150-250 (140-280)
Normal to narrow QRS
P waves usually absent
