SVT + VT Flashcards
What causes a delta wave?
Early depolarisation of the ventricles
What are re-entry tachycardias?
Wolff Parkinson White syndrome
AV re-entry tachycardias
SVT
What are the characteristics of re-entry tachycardias?
Narrow QRS
Possible P waves
Non specific ST depression
They are orthodromic
What are the characteristics of AV re-entry tachycardias?
Narrow complex tachycardia 160-250 bpm Delta waves present on ECG P waves present Inverted P wave in inferior leads and lead 1
What is the cause of antidromic AV re-entry tachycardia?
Re-entry circuit from the atria to ventricles
Antegrada conduction to the ventricles via an accessory pathway with retrograde conduction to the atria via the AV node
Rare as it is pure delta waves
What are the characteristics of antidromic AV re-entry tachycardias?
Wide complex tachycardia
Regular, sinus rhythm
Delta waves with QRS morphology with normal QRS complex
Inverted P waves
Which tachycardia is responsible for 2/3 narrow complex tachycardias?
AV re-entry tachycardia
Which gender is AV re-entry tachycardia more commoner in?
Women
What can be distressing for pts who suffer from AV re-entry tachycardia?
Recurrent palpitations
What are the ventricular rhythms?
Ventricular ectopics Bigeminy Idioventricular Ventricular tachycardia Monomorphic and polymorphic Torsades de pointes Ventricular fibrillation
What are the characteristics of ventricular arrhythmias?
No preceding P wave
Abnormal shape
Wide complex
Followed by a compensatory pause
What are the causes of ectopic beats?
Some are naturally occurring
IHD
Digoxin toxicity
LV dysfunction
What are the characteristics of ventricular ectopics / ventricular arrhythmias?
No P wave
Wide and bizarre QRS
Can look the same (unifocal) or different (multi focal)
Originates from a ventricular foci outside normal conduction pathways
What are the ventricular ectopic / ventricular arrhythmias rhythms?
Unifocal Multi focal Bigeminy Trigeminy Paris Couplet
What is VT classed as?
3 or more ventricular arrhythmias rhythms
Rate = >100 bpm
What is a pre excitation beat?
It’s when the impulse bypasses the normal conduction, via the bundle of Kent
Starts in the atrium into the ventricle
What are the causes of ventricular arrhythmias?
Electrolyte imbalance
Hypoxia/ischaemia
Acidosis
Invasive equipment
How do you treat ventricular arrhythmias?
Treat the cause
What are the characteristics of ventricular bigeminy?
Each sinus beat is followed by an ectopic beat
P waves can be seen in the T wave of the ectopic
What does idio-ventricular rhythm look like?
Slow VT
What is the cause of idio-ventricular rhythm?
Reperfusion of the myocardium post MI
How do you treat idio-ventricular rhythm?
It does not require treatment
What are the characteristics of idio-ventricular rhythm?
40-100 bpm Regular rhythm P waves not present PR interval not present QRS wide and abnormal T wave abnormal
What does an abnormal T wave mean?
Abnormal depolarisation = abnormal repolarisation
What are the characteristics of accelerated idioventricular rhythm?
Wide complex rhythm
Regular
P wave seen in T wave
What is accelerated idioventricular rhythm?
Reperfusion arrhythmia, usually seen in AMI
What should all wide complex tachycardias be treated as?
VT until proven otherwise
What are the characteristics of VT?
140-200 bpm
3+ consecutive ectopics
Wide (>2.5-3.5 small squares) and bizarre QRS
Where does ventricular tachycardia originate?
An ectopic pacemaker
What are the characteristics of broad complex tachycardia?
Broad complex
Tachycardia rate
P wave notches present
What are the 3 things needed on an ECG to diagnose VT?
- Evidence of AV dissociation (P wave in T wave)
- Fusion beats
- Capture beats
What is a fusion beat?
An impulse from 2 different foci meeting in the ventricle and depolarising simultaneously
Normally and SVT impulse and ventricular ectopic impulse
Similar to capture beat but merges with ventricular impulse
There is evidence of AV dissociation
What is a capture beat?
An SVT impulse conducting into the ventricle and then conducted normally in a normal QRS
Will be conducted in the middle of VT
Evidence of AV dissociation
What is the cause of monomorphic VT?
Myocardial ischaemia
What does VT look like on an ECG?
Regular rhythm
Chest leads are either all negative or all positive
No PR interval
AV dissociation of each complex slightly different
What is AV dissociation?
P wave in the T wave
What are the causes of polymorphic VT?
IHD (particularly MI) Impaired LV function Cardiomyopathies Long QT syndrome Electrolyte abnormalities Drugs Catecholamine sensitivity Can occur in normal hearts
What are the characteristics of polymorphic VT?
VT made up of multiple QRS morphologies Each beat = different shape Varying RR interval 150-300 bpm "Tornadoes de pointes"
What is Torsades do pointes?
A beat that starts with an R on T phenomenon
A ventricular premature beat that coincides with the T wave
What are the causes of Torsades de pointes?
AV block Hypokaleamia Hypomagnesia Drug induced long QT Drugs: amiodarone, sotolol, tricyclic antidepressant Congenital long QT syndrome IHD Myoedema
What are the characteristics of ventricular fibrillation?
Rate can't be detected Irregular rhythm P waves not present QRS not present Waves are abnormal and chaotic Can't determine onset or end of fibrillation waves Amplitude varies 3mm = coarse fibrillation
What causes the abnormal waves of VF?
Haphazard depolarisation of small individual groups of muscle
What are the causes of VF?
Digitails Quinidine Procainamide Hypoxia Acidosis Electrolyte imbalance
What does ventricular fibrillation mean for a pt?
They have no cardiac output
Use 2 leads to identify
