see also: - [[Torsades de Pointes]] - [[Classic tox ECGs#Long QT| Long QT Tox]] - [[Syncope ECG patterns#Long QT|Long QT syncope ECGs]] - [goldfrank QT interval](x-devonthink-item://2F041FBD-FF1C-4E21-9CD5-5550C288F006?page=277&istart=7959&ilength=10&search=QT%2520Interval) > long QT is a risk for [[Torsades de Pointes|TdP]] when due to T wave prolongation (repolarisation), but NOT when due to ST segment prolongation (e.g. hypocalcaemia, hypomagnesaemia) ![[Classic tox ECGs#QT nomogram]] # Causes of prolonged QT see also list here: [Dunn - Ventricular arrhythmias](x-devonthink-item://747079B5-0629-433D-A6A2-5282259F31B6) - [[Hypomagnesemia]] - [[Hypocalcemia|hypo-Ca]] - [[hypokalemia|hypo-k]] (due to U-wave, not “real” long QT, but can still cause TdP) - type Ia medications - misc - [[traumatic brain injury#Reducing ICP|elevated ICP]] / [[Subarachnoid haemorrhage|SAH]] - hypothermia - hereditary - **Tox drugs:** - sotalol (beta blocker and K+ blocker) - antipsychotics (zipisdome, clozapine, haloperidol) - antidepressant (citalopram, [[​Lithium Toxicity|lithium]], [[TCA overdose]]) - [[Amiodarone]] (do NOT use amiodarone in tox cases. But rarely causes TdP itself) - Abx: cipro, erythromycin - Methadone - Hyperacute MI/ post cardiac arrest - Cardiomyopathy - Complete heart block - [[Hypothyroidism|hypothyroid]] - SAH >mnemonic: **QT CODASS** - cipro, ondansetron, droperidol, amiodarone, sertraline, sotalol # Management ## Tachyarrhythmias - ​cardioversion if pulseless or in extremis - ​200J - may not synchronise - asynchronous defibrillation may be required - ​MgSO4 2 - 2.47g (8-10mmol) bolus - repeat if required - overdrive pacing - ​alkalinisation - if due to [[Sodium channel blocker|sodium channel blocker toxicity]] ## Prevention - isoprenaline or increasing baseline pacing rate - ​a faster rate reduces the QT and VEBs are less likely to fall on the vulnerable segment of the T wave - K+ replacement to 4.5 - 5 mmol/L - ​calcium - ​beta blockers /sedation / sympathectomy for congenital forms - [[atropine]] if [[organophosphates]] is the cause - ​avoid further exposure to precipitants ## Admission criteria for ECG monitoring - ​QTc > 500msec in an adult - ​>450msec in a patient with symptoms suggestive of significant arrhythmias - ​increase in QTc > 60 msec over baseline - progressive increase in QTc over hours (e.g. following poisoning)