ventricular tachycardias Flashcards
what are sustained ventricular tachycardia (>30sec)
A ventricular rhythm faster than 100 bpm lasting at least 30 seconds or requiring termination due to haemodynamic instability. VT is defined as a wide complex tachycardia (QRS 120 milliseconds or greater) that originates from one of the ventricles, and is not due to aberrant conduction (e.g., from bundle branch block)
what does sustained ventricular tachycardia cause
- pre syncope
- syncope
- hypotension
- cardiac arrest
what is the pulse rate typically of sustained ventricular tachycardia
120-220 bpm
what does the ECG of sustained ventricular tachycardia show
- rapid ventricular rhythm
- broad abnormal QRS complex
- visible P wave which appear to march through the tachycardia, capture beats and fusion beats
what are capture beats
an intermittent narrow QRS complex owing it to normal ventricular activation via the AV node and conducting system
what are fusion beats
intermediate between ventricular tachycardia beat and capture beat
what are symptoms of ventricular tachycardia
Dizziness Shortness of breath Lightheadedness Feeling as if your heart is racing (palpitations) Chest pain (angina)
Sustained and more-serious episodes of ventricular tachycardia may cause:
Loss of consciousness or fainting Cardiac arrest (sudden death)
how do you manage ventricular tachycardia
- haemodynamically compromised = emergency DC cardioversion
- haemodynamically stable = IV therapy with beta blockers, class 1 drugs or aminodarone
what is ventricular fibrillation
Ventricular fibrillation is a heart rhythm problem that occurs when the heart beats with rapid, erratic electrical impulses. This causes pumping chambers in your heart (the ventricles) to quiver uselessly, instead of pumping blood
what can happen to a patient with ventricular fibrillation
the patient is pulseless and becomes rapidly unconscious; respiration ceases (cardiac arrest)
what does the ECG show in ventricular fibrillation
- Chaotic irregular deflections of varying amplitude
- No identifiable P waves, QRS complexes, or T waves
- Rate 150 to 500 per minute
- Amplitude decreases with duration (coarse VF -> fine VF)
what provokes ventricular fibrillation
ventricular ectopic beat
how do you treat ventricular fibrillation
electrical defibrillation
what is Brugadas syndrome
Brugada syndrome can cause the heart to beat dangerously fast. These unusually fast heartbeats – known as an arrhythmia – can sometimes be life threatening.
Brugada syndrome is usually caused by a faulty gene that’s inherited by a child from a parent. A simple heart test can be done to see if you have it.
what are symptoms of brugadas syndrome
- asymptomatic
- blackouts
- fits (seizures)
- occasional noticeable heartbeats (palpitations)
- chest pain
- breathlessness
- dizziness
what is seen on an ECG of Brugadas syndrome
- right bundle branch block
- ST elevation in leads V1-V3
what is long QT syndrome
an ECG where the ventricular repolarisation (QT interval) is greatly prolonged. Can be a genetic disorder
what are 2 groups of long QT syndrome
- congenital long QT syndrome
- acquired long QT syndrome
what is congenital long QT syndrome
Congenital long QT syndrome (LQTS) is a hereditary cardiac disease characterized by a prolongation of the QT interval at basal ECG and by a high risk of life-threatening arrhythmias
LQT1
arrhythmia provocation by exercise, particularly swimming
LQT2
arrhythmia provocation is associated with emotion and acoustic stimuli
LQT3
arrhythmia occurs during sleep and rest
what is acquired long QT syndrome
Acquired long QT syndrome describes pathologic excessive prolongation of the QT interval, upon exposure to an environmental stressor, with reversion back to normal following removal of the stressor. The most common environmental stressor in acquired long QT syndrome is drug therapy.
what are clinical features of patients with long QT
- develop syncope and palpations as a result of polymorphic ventricular tachycardia (torsades de pointes)
what is Torsades de point
Torsades de Pointes is a type of polymorphic ventricular tachycardia characterized by a gradual change in amplitude and twisting of the QRS complexes around an isoelectric line on the electrocardiogram
what is management for acquired long QT syndrome
- electrolyte disturbance is corrected
- causative drugs are stopped
- the heart rate is maintained with atrial or ventricular pacing
- magnesium sulfate 8mmol is given over 10-15 minute for acquired long QT
- IV isoprenaline may be effective with QT prolongation is acquired
what is management for long term congenital long QT syndrome
- beta blockade
- pacemaker therapy
- left cardiac sympathetic denervation
what does the QT segment represent
ventricular depolarisation and ventricular repolarisation
what are ventricular premature beats (ectopics)
A ventricular premature beat is an extra heartbeat resulting from abnormal electrical activation originating in the ventricles (the lower chambers of the heart) before a normal heartbeat would occur.
A ventricular premature beat is an extra heartbeat resulting from abnormal electrical activation originating in the ventricles (the lower chambers of the heart) before a normal heartbeat would occur.
ECG features of ventricular premature beats (ectopics)
- irregular pulse
- broad and bizarre QRS complex - they arise from abnormal ventricular myocardium
what are symptoms of ventricular premature beats
Isolated ventricular premature beats have little effect on the pumping action of the heart and usually do not cause symptoms, unless they are extremely frequent. The main symptom is the perception of a strong or skipped beat (palpitations).
