| ECG-QT interval
| Brugada Syndrome
| Long QT syndrome (LQTS) Acquired
| Long QT syndrome (LQTS) Congenital
| Torsades de Pointes
| Ventricular Fibrillation
| Ventricular Tachycardia
| Resuscitation - Adult Tachycardia Algorithm
| Automatic Implantable Cardioverter Defibrillator (AICD)
Torsades (Polymorphic VT): Occurs in repetitive nonsustained paroxysms. Can degenerate to VF. Mg 8 mmol (2 g bolus) over 10 mins in 100 ml 5% Dextrose or N-saline. Avoid Amiodarone. Correct K/Mg/Ca. Pacing. Isoprenaline. Defibrillation if unstable.
- The term torsade de pointes was coined by Dessertenne in 1966
- A polymorphic ventricular tachycardia with a pattern of twisting points
- Drugs associated with TdP vary greatly in their risk for arrhythmia
- An updated list can be found at www.qtdrugs.org
- Torsade de Pointes is a polymorphic ventricular tachycardia.
- The axis of the QRS of VT is constantly changing and twisting.
- It is seen with Long QTc > 460 ms.
- Torsade may be due to inhibition of the HERG type potassium channel
- Long QT1 have slow potassium channels
- Long QT2 have slow potassium channels
- Long QT3 shows defects in the sodium channels.
- Long QT4-12 are rare
- Congenital long QT syndrome is autosomal dominant, but shows greater frequency of expression and a greater lengthening of the QT interval in females than in their male relatives.
- Females are 2-3 times more likely to develop TDP.
- Females have more QT prolongation secondary to drug therapy.
- Torsade usually but not always occurs in bursts that are not sustained.
- May be well tolerated or cause pulmonary oedema
- Can cause hypotension, presyncope and collapse.
- It may be transient and episodic and cause symptoms and self terminate.
- It may sometimes revert to VF or pulseless VT
- Congenital Romano-ward syndrome (AD)
- Jervell-Lange-Nielsen syndrome (AR Deaf) Female gender
- Acquired long QT syndrome (causes of which include medications and electrolyte disorders such as hypokalaemia, hypocalcaemia, hypomagnesemia)
- Bradycardia, Baseline ECG abnormalities
- Renal or liver failure, Female
Causes of Acquired Long QT
- Low Ca, Low Mg, Low K, hypothyroid, hypothermia
- Amiodarone, Disopyramide, Flecainide, Erythromycin
- Terfenadine, TCA, quinidine, Class I/III antiarrhythmics
- Lithium, Amitriptyline, Chlorpromazine, phenothiazines.
- Check all drugs in BNF
- FBC, U&E, Mg, Calcium, Troponin
- ECG: twisting of the QRS axis. Bradycardia and long QTc often QT interval > 500msec and may be increased markedly to = 600 msec
- Troponin may be indicated if ACS suspected
- Echo to exclude structural disease
- Check all drugs in BNF. Stop Amiodarone or other antiarrhythmics that prolong QT. Check and correct K and Mg and Ca
- Polymorphic VT: Magnesium 8 mmol (2 g bolus) over 15 mins diluted in 50-100 ml 5% Dextrose or N-saline. then 72 mmol (18 g) over 24 hrs. The idea is to suppress early afterdepolarizations even in patients with normal magnesium levels
- Overdrive atrial (preferred) or ventricular pacing or just simple pacing if TDP is bradycardia dependent.
- Isoprenaline IV may be considered to suppress arrhythmia. This is contraindicated with congenital long QT syndromes.
- Patients with extreme QT interval prolongation (> 500 msecs)
or certain high-risk genotypes should be considered for ICD
- Defibrillation is the treatment of all unstable tachyarrhythmias
- Congenital Long QT: beta-blockers indicated. Left stellate ganglion block may be of
value if resistant arrhythmias
- Acquired Long QT: Beta-blockers contraindicated as bradycardia promotes the arrhythmia