Summary
Definition
History and exam
Key diagnostic factors
- hx of known gene mutation
- use of drugs or circumstances known to increase the QT interval
- syncope during heightened adrenergic tone
- syncope during arousal or surprise
- arrhythmic symptoms post partum
- syncope at rest and during bradycardia
- cardiac syncope
- palpitations
- periodic paralysis
- dysmorphic features
- sensorineural deafness
Other diagnostic factors
- dizziness
- angina
- fatigue
- oliguria
- muscle weakness
- tetany
- numbness
- Chvostek's sign
- Trousseau's sign
- cold and pale extremities
- hypotension
- confusion
Risk factors
- KCNQ1 gene mutations
- KCNH2 gene mutations
- SCN5A gene mutations
- QT interval-prolonging drugs
- hypokalaemia
- hypomagnesaemia
- hypocalcaemia
- bradyarrhythmias
- CNS lesions
- female sex
- malnutrition
Diagnostic investigations
1st investigations to order
- ECG for LQT1
- ECG for LQT2
- ECG for LQT3
- ECG for hypokalaemia and hypomagnesaemia
- ECG for hypocalcaemia
- ECG for complete AV block
- serum potassium
- serum magnesium
- serum calcium
Investigations to consider
- Holter monitor
- exercise tolerance test
- echocardiography
- genetic testing
- adrenaline (epinephrine) test
Treatment algorithm
Contributors
Authors
Associate Professor of Medicine
University of Rochester Medical Center
Rochester
NY
Disclosures
MKA declares that he has no competing interests.
Director
Electrophysiology Service
Professor of Medicine
Duke University Medical Center
Duke Clinical Research Institute
Durham
NC
Disclosures
JPD is a consultant for the American College of Cardiology, ARCA Biopharma, Biosense Webster, Biotronik, Boston Scientific, Cardiofocus, Gilead Sciences Inc., Medtronic Inc., NIH-NHLBi, Northwestern University, Orexigen Therapeutics Inc., St. Jude, and Vytronus.
Peer reviewers
Director of Cardiac Hospitalization
Department of Cardiology
Tel Aviv Medical Center
Tel Aviv
Israel
Disclosures
SV declares that he has no competing interests.
Associate Professor
Heart and Vascular Center
MetroHealth Campus
Case Western Reserve University
Cleveland
OH
Disclosures
ESK declares that she has no competing interests.
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