OVERVIEW
- normal QT = < 440ms (two large squares) – prolonged QT > 450ms
- produces prolonged ventricular repolarisation -> predisposes to malignant ventricular arrhythmias
CAUSES
- drugs: amiodarone, TCA’s, many antibiotics, fluconazole, erythromycin, metoclopramide, quinidine, haloperidol, droperidol, methadone, ondansetron, SSRI’s
- genetic: cardiac ion channel mutation (Na+, K+)
- myocardial disease: MI, RF, 3rd degree HB, cardiomyopathy
- electrolytes: low Ca2+, low K+, low Mg2+
ASSESSMENT
HISTORY
- syncope
- exercised induced syncope
- cardiac arrest
- FHx
EXAMINATION
- may be normal
INVESTIGATIONS
- ECG: QTc >440ms (11 small squares or T wave after half the R-R distance)
- ECHO: structural heart disease
MANAGEMENT
- beta-blockade
- avoidance of increased sympathetic tone
- cardiac pacing
- treat cause
- ICD
Critical Care
Compendium
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