Tachyarrhythmias Flashcards
Define tachyarrhytmia
henever the heart rate is >100 for three beats or more a tachyarrhytmia is said to be presen
How are tachyarrhythmias categorised?
Narrow complex tachycardia
Broad complex tachycardia
Supraventricular and VT
Give four ways in which SVTs can be differentiated from VTs
- The width of the QRS complex
- The morphology and rate of the p waves
- The relationship between the P waves and the QRS complexes
- Response of the rhythm to vagal manouevres such as carotid sinus massage
Define narrow complex tachycardia
ECG rate >100, QRS complex
GIve four forms of regular narrow complex tachycardia
Sinus tachycardia (normal) Atrial tachyarrhytmias (Flutter, fibrillation) Junctional tachycardia AV node re-entry Accessory pathyway
Give three irregular forms of narrow complex tachycardia
- Atrial fibrillation
- Atrial flutter
- Re-entrant tachycardia
Define a broad complex tachycardia
ECG >100, QRS complexes >120ms
Give three types of broad complex tachycardia
- VT
- SVT with BBB
- Torsades de pointes
What are three ways in which tachyarrhytmias are produced
- Accelerated automacity
- triggered activity
- re-entry looping
Give five causes of VT
- Metabolic
- IHD
- Cocaine
- Cardiomyopathy
- MI
Give five causes of SVT
- IHD
- Thyrotoxicosis
- Caffeine
- Alcohol
- Smoking
Give 6 causes of AF
o Mitral valve disease o Hypertension o Lung disease o Post op o Pericardial disease o Cardiomyopathy
Outline the management of regular SVT (6 steps)
- ABC + O2 + IV access
- Vagal manoeuvres
- Adenosine
- Help help help
- Antiarrhytmic
- DC cardioversion if haemodynamically unstable
Outline the management of irregular SVT
Probable atrial fibrillation
Control rate with:
B blocker IV or digoxin IV
If onset
How do you manage a broad complex tachycardia?
- ABC if pulseless
- No adverse signs
o Amiodarone
o K+/Mg2+ if needed
o Sedation and DC cardioversion - Adverse signs
o Sedation
o DC cardioversion
o Amiodarone/Lidocaine
Give the indication for DC cardioversion
, any patient with narrow or wide QRS complex tachycardia (ventricular rate >150) who is unstable (eg, chest pain, pulmonary edema, lightheadedness, hypotension) should be immediately treated with synchronized electrical cardioversion.[6]
Synchronized electrical cardioversion may also be used to treat stable VT that does not respond to a trial of intravenous medications. It is also recommended for the treatment of the following[7] :
Supraventricular tachycardia due to reentry
Atrial fibrillation
Atrial flutter
Atrial tachycardia
Monomorphic VT with pulses
How does adenosine work?
When it is administered intravenously, adenosine causes transient heart block in the atrioventricular (AV) node. This is mediated via the A1 receptor, inhibiting adenylyl cyclase, reducing cAMP and so causing cell hyperpolarization by increasing outward K+ flux. It also causes endothelial-dependent relaxation of smooth muscle as is found inside the artery walls.
