QT prolongation: Difference between revisions
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*The QTc is > 550 ms and if it is not LQT1 | *The QTc is > 550 ms and if it is not LQT1 | ||
*LQT2 in women and the QTc is > 500 ms, with or without symptoms | *LQT2 in women and the QTc is > 500 ms, with or without symptoms | ||
*In infants with 2:1 block (controversial) | *In infants with 2:1 [[AV block]] (controversial) | ||
*In JLNS (LQTS with deafness) given its malignant propensity (controversial) | *In JLNS (LQTS with deafness) given its malignant propensity (controversial) | ||
Videoscopic Left Cardiac Sympathetic Denervation Surgery is not a cure, but reduces the risk of [[sudden cardiac death]] and is indicated if: | |||
*The patient does not tolerate [[beta blockers]] or breaks through [[beta blockers]] | |||
*The patient [[faints]] while on [[beta blockers]] | |||
*There is a history of [[VF]] terminating [[AICD]] shocks | |||
*In young patients under the age of 12 where [[beta blockers]] are not deemed protective enough and where the morbidity of an [[AICD]] seems excessive. | |||
====Secondary Prevention==== | ====Secondary Prevention==== | ||
Patients with Long QT syndrome should undergo secondary prevention with AICD implantation if they sustain an aborted [[cardiac arrest]] or[[sudden cardiac death]]. | Patients with [[Long QT syndrome]] should undergo secondary prevention with [[AICD]] implantation if they sustain an aborted [[cardiac arrest]] or[[sudden cardiac death]]. | ||
==References== | ==References== | ||
Revision as of 03:15, 2 October 2012
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: Prolonged QT; prolonged QT interval; QT interval prolongation
Overview
QT prolongation refers to a prolongation of the interval on the electrocardiogram during which time the ventricles depolarize and repolarize. QT prolongation is often caused by drugs, genetic abnormalities, and electrolyte disturbances. QT prolongation may predispose the patient to ventricular arrhythmias and sudden cardiac death. Long QT syndrome is one of the many causes of QT prolongation, and is an inherited channelopathy associated with sudden cardiac death.
Causes
Common Causes
Drugs
Drug induced QT prolongation is usually a result of treatment by anti-arrhythmic drugs or a number of other drugs that have been reported to cause this problem (e.g. cisapride). Some anti-psychotic drugs, such as Haloperidol and Ziprasidone, have a prolonged QT interval as a rare side effect. Genetic mutations may make one more susceptible to drug induced QT prolongation.
Long QT Syndrome
Genetic abnormalities cause the Long QT Syndrome.
Electrolyte Disturbances
Electrolyte disturbances such as hyperkalaemia, hypocalcaemia, hypoglycaemia, hypokalaemia, and hypomagnesemia can cause QT prolongation.
Neurologic Events
Subarachnoid hemorrhage and other intracranial events can cause QT prolongation. Widely slayed cerebral T waves are often seen as well.
Anorexia Nervosa
Anorexia nervosa and starvation can cause QT prolongation.
Causes by Organ System
Causes in Alphabetical Order
Diagnosis
Electrocardiogram
Shown below is an example of ECG demonstrating QT prolongation with a duration of 600 ms in lead II.
Shown below is an example of an ECG demonstrating QT prolongation in Long QT syndrome. LQT 1 showing 'early onset' broad based T wave, LQT 2 showing small late T wave and LQT 3 showing prolonged QT interval with 'late onset' T wave with a normal configuration.
Shown below is an example of ECG showing Torsades de Pointes with long QT interval circled in red.
Treatment
In general, treatment involves reversing the underlying cause of the QT prolongation.
Replete Potassium and Magnesium
Electrolytes should be repleted or treated.
Withdraw or Reduce the Dose of Offending Drugs
Withdraw or reduce the dose of offending drugs.
Long QT Syndrome
Primary Prevention
An AICD should be implanted if:
- The QTc is > 550 ms and if it is not LQT1
- LQT2 in women and the QTc is > 500 ms, with or without symptoms
- In infants with 2:1 AV block (controversial)
- In JLNS (LQTS with deafness) given its malignant propensity (controversial)
Videoscopic Left Cardiac Sympathetic Denervation Surgery is not a cure, but reduces the risk of sudden cardiac death and is indicated if:
- The patient does not tolerate beta blockers or breaks through beta blockers
- The patient faints while on beta blockers
- There is a history of VF terminating AICD shocks
- In young patients under the age of 12 where beta blockers are not deemed protective enough and where the morbidity of an AICD seems excessive.
Secondary Prevention
Patients with Long QT syndrome should undergo secondary prevention with AICD implantation if they sustain an aborted cardiac arrest orsudden cardiac death.