ECG Flashcards
What indicates left axis deviation on an ECG?
Lead 1 is positive and avF is negative
What indicates right axis deviation on an ECG?
Lead 1 is negative and avF is positive
What would a normal axis show on an ECG?
Both lead 1 and avF would be positive
What would the ECG axis be if both lead 1 and avF are negative?
Indeterminate
How can the heart rate be calculated when rhythm is regular?
300/the number of large boxes between the top of each QRS complex.
How can the heart rate be calculated when rhythm is irregular?
Count the number of QRS complexes in the rhythm strip x 6
i.e. 14 QRS complexes x 6 = 84 bpm
Normal duration of PR interval?
Normally 0.12-0.2s
Normal length of QRS complex?
Usually less than 0.1s
Heart rate in atrial fibrillation?
300bpm
Rhythm of atrial fibrillation?
Irregularly irregular rhythm
P waves are present in atrial fibrillation. True/false?
False P waves are absent
What is the characteristic P wave pattern in atrial flutter?
“Saw tooth” pattern
QRS complexes are normal in atrial fibrillation. True/false?
False
Narrow QRS complexes typically present in atrial fibrillation.
Normal QRS complexes in atrial flutter.
What is the typical appearance for ventricular fibrillation?
Bizarre irregular waveform
No recognisable QRS complexes
Random frequency and amplitude
Unco-ordinated electrical activity
What is the main difference between monomorphic and polymorphic ventricular tachycardia?
In polymorphic VT, the QRS complex amplitude varies whereas in monomoprhic VT, it remains the same.
What are the 2 main features of torsades de pointes?
A specific polymorphic VT associated with a long QT interval.
QRS complexes appear to twist around the isoelectric line.
Characteristic feature of 1st degree heart block?
PR interval greater than 0.2s (5 small squares) - not usually serious and can be found in healthy patients.
Characteristic feature of 2nd degree heart block - Mobitz type 1?
Progressive lengthening of the PR interval, eventually resulting in a dropped beat (P wave with no QRS).
Characteristic feature of 2nd degree heart block - Mobitz type 2?
Each P wave is associated with a QRS complex until there is 1 atrial conduction (atrial depolarisation) or P wave that is not followed by a QRS complex.
Tends to happen in a specific pattern i.e. every 3 waves.
Characteristic feature of 3rd degree heart block?
No relation between P wave and QRS complexes but both are present.
Characteristic feature of Wolff-Parkinson-White syndrome?
Sloping QRS complex (delta wave) - pre-excitation
What are the 2 main AV nodes?
Left bundle branch
Right bundle branch
How to distinguish between RBBB and LBBB (use WiLLiaM MoRRoW)?
Look at the QRS morphology in V1 and V6.
If the QRS looks like W in V1 and M in V6 it is LBBB. (WiLLiaM)
If the QRS looks like M in V1 and W in V6 it is RBBB. (MoRRoW)
If both leads V1 and V6 don’t have these then can assume normal
LBBB is ALWAYS pathological. True/false?
True
RBBB on the other hand can be physiological e.g. if young and growing
When QRS complexes are narrow, where is the origin of the tachycardia typically and what is an example?
Above the AV node
Example: supraventricular tachycardia
When QRS complexes are wide, where is the origin of the tachycardia typically and what is an example?
Below the AV node
Example: VT (ventricular tachycardia)
Ventricular tachycardia is a medical emergency. True/false?
True
VT until proven otherwise. Associated with cardiac arrest.
First line treatment for SVT?
Vagal manoeuvres are a first-line (first choice) treatment for supraventricular tachycardia (SVT) (fast heart rate) because they’re a low-risk, low-cost way to slow down a heart rate that’s too fast.
What is carotid sinus massage?
Gentle pressure is applied to the carotid sinus, a small area located on either side of the neck where the carotid artery splits into two branches.
This technique is used to slow down the heart rate and can help diagnose or treat certain types of abnormal heart rhythms, such as supraventricular tachycardia (SVT).
What is the valsalva manoeuvre?
A breathing technique that involves a person trying to exhale forcefully with a closed mouth and nose.
Can be used to stop episodes of supraventricular tachycardia (SVT) by stimulating the vagus nerve, which helps slow down the heart rate.
What is adenosine used for?
Adenosine is primarily used to treat and diagnose certain types of supraventricular tachycardias (SVTs), which are abnormal fast heart rhythms originating above the ventricles.
Why is adenosine ineffective for VT?
It is not effective for arrhythmias that originate in the ventricles (ventricular tachycardia)
Adenosine primarily affects the atrioventricular (AV) node, slowing conduction through this node and interrupting re-entrant circuits that involve it.
VT originates in the ventricles, below the AV node, so adenosine’s effects on the AV node do not influence the ventricular tissue directly where VT occurs.
Why is it risky to give adenosine for wide-complex tachycardias i.e. ventricular tachycardia?
In cases of wide-complex tachycardia where the diagnosis is uncertain, using adenosine can be risky because it may cause adverse effects without treating the arrhythmia if it turns out to be VT.
Adenosine is reserved for use in SVT. True/false?
True
First line treatment for VT in haemodynamically unstable patients (i.e. low blood pressure, chest pain, altered mental status, signs of shock)?
Immediate Synchronized Cardioversion - delivers a shock timed with the QRS complex to restore normal rhythm safely.
Treatments for VT in haemodynamically stable patients ?
anti-arrhythmic medications:
Amiodarone: Often the first-line drug due to its efficacy in converting VT to sinus rhythm and preventing recurrence.
Lidocaine: Another option, particularly in cases related to acute myocardial ischemia.
Procainamide: Sometimes used as an alternative, especially in cases of monomorphic VT.
Treatment options for patients with recurrent VT or high risk of recurrence?
ICDs - can detect and terminate VT episodes with pacing or shocks.
Catheter ablation - Ablation targets the areas of the heart responsible for the abnormal rhythms.
Beta-blockers - Used in patients with underlying structural heart disease or after myocardial infarction to prevent VT.
Addressing underlying causes - identifying and treating reversible causes like electrolyte imbalances, ischemia, or drug toxicity.
Which one SVT or VT has narrow QRS complexes and typically originates above the AV node?
SVT (supraventricular tachycardia)
What areas of the heart do the chest leads look at?
V1 Septal view of the heart
V2 Septal view of the heart
V3 Anterior view of the heart
V4 Anterior view of the heart
V5 Lateral view of the heart
V6 Lateral view of the heart
Remember: SSAALL
