Abnormal ECG Flashcards
What should you look for in the case of a Premature Atrial Contraction
While technically not abnormal, a Premature Atrial Contraction will have:
Regular looking ECG pattern except the R-R interval will be shorter than normal for one beat
What should you look for in the case of a Premature Ventricular Contraction
While technically not abnormal, a Premature Ventricular Contraction will have:
- Shorter R-R Interval
- No P wave before QRS
- Wide, oddly shaped QRS complex
- Abnormal T wave
- Compensatory pause after the contraction occurs
What is Supraventrciular Tachycardia and what would see on an ECG?
Supraventricular Tachycardia is when atrial muscle has taken over the pacemaker role from the SA node and the heart rate is greater than 100 bpm.
You would see a sinus rhythm but the P wave may appear abnormal.
It is difficult to distinguish sinus tachycardia and Supraventricular Tachycardia.
If the heart rate is quick enough, the AV node may no longer conduct the AP resulting in no QRS complex after each P wave.
What is Ventricular Tachycardia and what would you see on an ECG?
Ventricular Tachycardia is when ventricular muscle has taken over the pacemaker role from the SA node and the heart rate is greater than 100 bpm.
You would see:
- P waves may not be visible, but if they are they won’t be at all associated with the QRS/T wave
- Wide and bizarrely shaped QRS complexes
- Abnormal T waves
What is a Re-entry Event?
A re-entry event is when a depolarization travels through the heart but does not stop and continues to be conducted around the heart over and over
What is a flutter?
A flutter occurs when a re-entry event occurs in a reasonably consistent pattern, causing a high-rate, weaker than normal contraction that is somewhat reproducible. Atrial flutter is stable and not life-threatening. Ventricular flutter is unstable due to the size of the muscle mass and will eventually form into ventricular fibrillation (which is life-threatening).
What is a fibrillation?
A fibrillation occurs when a re-entry event occurs and does not have a consistent pattern of travel; rather it is chaotic. This causes abolishes the hearts ability to pump blood despite the occurrence of depolarization.
Atrial Fibrillation is survivable, ventricular fibrillation is life-threatening.
What does Atrial Fibrillation look like on an ECG?
No P wave
Chaotic “noise” between beats on baseline
QRS complexes are “irregularly irregular” due to random timing of impulses getting to AV node
What does Ventricular fibrillation look like on an ECG?
It appears as chaotic waves repeating at a high rate
What does an SA node block look like on an ECG?
Flat line
What is a First Degree AV Block and what does it look like on an ECG?
First degree AV block is when conduction of depolarization from the SA node to AV node is slowed down.
This causes an increased PR interval to be seen on an ECG
Normal PR interval is 0.12 to 0.2 seconds.
What is a Mobitz II Second Degree AV Block and what does it look like on an ECG?
Injury to AV node causes occasional (but regular) blocks in AV conduction.
This causes occasional (but regular) loss of QRS complexes after P waves.
Can occur in different ratios (P wave: QRS):
3:2, 3:1, 2:1
What is a Mobitz I Second Degree AV Block and what does it look like on an ECG?
Injury to AV node causes a progressive increase in duration of AV conduction until the refractory period prevents conduction, blocking depolarization into the ventricles.
This causes the PR interval to progressively increase from beat to beat until a QRS complex cannot be produced.
What is Third Degree AV Block and what does it look like on an ECG?
Severe injury to AV node prevents any conduction through it, a total block occurs.
Bundle of His takes over for ventricular contraction pacemaker.
If the bundle of his or any other potential pacemaker tissues cannot function, then this is life threatening as the ventricles cannot be depolarized and thus cannot pump blood
In the event where the bundle of his takes over, the ECG will show the P wave and QRS complex are completely dissociated and act independently of one another.
