Long QT syndrome
Last modified: 18 October 2022, 4:37:11 PM AEDT
Gems / Priorities1 / 8
- LQTS = Long QT syndrome
Definition / diagnostic criteria2 / 8
- From start of Q wave to end of T wave
- different definitions
- BJA 2018
- males = QTc > 450 ms / 470 ms (99th centile)
- females = QTc > 460 ms / 480 ms (99th centile)
- BJA 2018
- correction
- corrected for rate = QT / √RR = Bazett formula
- overestimates at fast HR, underestimates at slow HR
- ECG
- use leads II and V5
- time taken for ventricular depolarisation and repolarisation, effectively the period of ventricular systole from ventricular isovolumetric contraction to isovolumetric relaxation
Aetiology / Causes / Risk Factors3 / 8
- congenital
- inherited cardiac channelopathy
- 17 susceptible genes = gene mutations
- Jervell Lange-Nielsen syndrome
- congenital deafness
- Romano-Ward syndrome
- no deafness
- acquired
- ⬇Ca, ⬇temp, myocardial disease
- drugs = Ia, Ic, III anti-arrhythmics, TCA, SSRIs, phenothiazines
- opiates = methadone
Complications4 / 8
- sudden cardiac death, esp in response to E+
- Arrhythmia
- QTc > 500 ms = risk of TORSADES
- pVT = TDP = torsade de pointes / polymorphic VT
- VF
Symptoms / History5 / 8
- syncope
- FH sudden death
Management6 / 8
- BB
- ICD
- avoid triggers of pVT
- ENS+ = pain, anxiety, exercise
- ⬇K, ⬇Mg, ⬇Ca
- medications,
- Anti-emetics = ondansetron, droperidol
- Other = amiodarone
- Anaesthetics = volatiles = prefer propofol
- or, VA + remi as dose-sparing
- Opioids = Fentanyl
- NMBA = SCh
Anaesthetic considerations7 / 8
- Pre-op
- K > 4.5
- Mg > 2.0
- Intra-op
- have defibrillator and pads in OT
- MgSO4 and resuscitation drugs ready
- Post-op