QT prolongation

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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

Cardiovascular	Ischaemic heart disease, Long QT syndrome, Andersen cardiodysrhythmic periodic paralysis, Jervell and Lange-Nielsen syndrome, Romano-Ward syndrome, Timothy syndrome
Chemical / poisoning	Arsenicals
Dermatologic	No underlying causes
Drug Side Effect	Alimemazine, Almokalant, Amiodarone, Amitriptyline, Arsenic trioxide, Asenapine, Astemizole, Azimilide, Azithromycin, Bepridil, Bretylium, Budipine, Chloroquine, Cibenzoline, Cisapride, Citalopram, Clomipramine, Clozapine, Crizotinib, Desipramine, Diphenhydramine, Disopyramide, Dofetilide, Dolasetron, Doxepin, Dronedarone, Droperidol, Eribulin mesylate, Fluconazole, Grepafloxacin, Halofantrine, Haloperidol, Ibutilide, Imipramine, Indapamide, Ketanserin, Ketoconazole, Lidoflazine, Lubeluzole, Methadone, Methadyl acetate, Midodrine, Mizolastine, Moxifloxacin, Naratriptan, Nicardipine, Nilotinib, Ondansetron, Pasireotide, Pazopanib, Pentamidine, Pimozide, Piperaquine, Prenylamine, Probucol, Procainamide, Propoxyphene, Quinidine, Quinine, Ranolazine, Retigabine, Ritodrine, Ritonavir, Saquinavir, Sertindole, Sotalol, Sparfloxacin, Tedisamil, Telithromycin, Terfenadine, Terodiline, Tetrabenazine, Thioridazine, Vandetanib, Vemurafenib, Venlafaxine, Vernakalant, Voriconazole, Vorinostat, Ziprasidone, Zotepine, Zuclopenthixol
Ear Nose Throat	No underlying causes
Endocrine	Hypothyroidism
Environmental	Zero gravity
Gastroenterologic	No underlying causes
Genetic	Andersen cardiodysrhythmic periodic paralysis, Jervell and Lange-Nielsen syndrome, Long QT syndrome, Myotonic dystrophy, Romano-Ward syndrome, Timothy syndrome
Hematologic	No underlying causes
Iatrogenic	No underlying causes
Infectious Disease	No underlying causes
Musculoskeletal / Ortho	Myotonic dystrophy, Andersen cardiodysrhythmic periodic paralysis, Timothy syndrome
Neurologic	Subarachnoid hemorrhage
Nutritional / Metabolic	Acute starvation, Anorexia nervosa, Hyperkalaemia, Hypocalcaemia, Hypoglycaemia, Hypokalaemia, Hypomagnesemia
Obstetric/Gynecologic	No underlying causes
Oncologic	No underlying causes
Opthalmologic	No underlying causes
Overdose / Toxicity	Alimemazine, Almokalant, Amiodarone, Amitriptyline, Arsenic trioxide, Asenapine, Astemizole, Azimilide, Azithromycin, Bepridil, Bretylium, Budipine, Chloroquine, Cibenzoline, Cisapride, Citalopram, Clomipramine, Clozapine, Crizotinib, Desipramine, Diphenhydramine, Disopyramide, Dofetilide, Dolasetron, Doxepin, Dronedarone, Droperidol, Eribulin mesylate, Fluconazole, Grepafloxacin, Halofantrine, Haloperidol, Ibutilide, Imipramine, Indapamide, Ketanserin, Ketoconazole, Lidoflazine, Lubeluzole, Methadone, Methadyl acetate, Midodrine, Mizolastine, Moxifloxacin, Naratriptan, Nicardipine, Nilotinib, Ondansetron, Pasireotide, Pazopanib, Pentamidine, Pimozide, Piperaquine, Prenylamine, Probucol, Procainamide, Propoxyphene, Quinidine, Quinine, Ranolazine, Retigabine, Ritodrine, Ritonavir, Saquinavir, Sertindole, Sotalol, Sparfloxacin, Tedisamil, Telithromycin, Terfenadine, Terodiline, Tetrabenazine, Thioridazine, Vandetanib, Vemurafenib, Venlafaxine, Vernakalant, Voriconazole, Vorinostat, Ziprasidone, Zotepine, Zuclopenthixol
Psychiatric	Anorexia nervosa, Timothy syndrome
Pulmonary	No underlying causes
Renal / Electrolyte	No underlying causes
Rheum / Immune / Allergy	No underlying causes
Sexual	No underlying causes
Trauma	No underlying causes
Urologic	No underlying causes
Dental	No underlying causes
Miscellaneous	Hypothermia, Acute starvation

Causes in Alphabetical Order

Acute starvation Alimemazine Almokalant Amiodarone Amitriptyline Andersen cardiodysrhythmic periodic paralysis Anorexia nervosa Arsenic trioxide Arsenicals Asenapine Astemizole Azimilide Azithromycin Bepridil Bretylium Budipine Chloroquine Cibenzoline Cisapride Citalopram Clomipramine Clozapine Crizotinib Desipramine Diphenhydramine Disopyramide Dofetilide Dolasetron Doxepin Dronedarone Droperidol Eribulin mesylate Fluconazole Grepafloxacin Halofantrine Haloperidol Hyperkalaemia Hypocalcaemia Hypoglycaemia Hypokalaemia Hypomagnesemia Hypothermia Hypothyroidism Ibutilide Imipramine Indapamide Ischaemic heart disease Jervell and Lange-Nielsen syndrome Ketanserin Ketoconazole

Lidoflazine Lubeluzole Methadone Methadyl acetate Midodrine Mizolastine Moxifloxacin Myotonic dystrophy Naratriptan Nicardipine Nilotinib Ondansetron Pasireotide Pazopanib Pentamidine Pimozide Piperaquine Prenylamine Probucol Procainamide Propoxyphene Quinidine Quinine Ranolazine Retigabine Ritodrine Ritonavir Romano-Ward syndrome Saquinavir Sertindole Sotalol Sparfloxacin Subarachnoid hemorrhage Tedisamil Telithromycin Terfenadine Terodiline Tetrabenazine Thioridazine Timothy syndrome Vandetanib Vemurafenib Venlafaxine Vernakalant Voriconazole Vorinostat Zero gravity Ziprasidone Zotepine Zuclopenthixol

Diagnosis

Electrocardiogram

Shown below is an example of ECG demonstrating QT prolongation with a duration of 600 ms in lead II.

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Shown below is an example of 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.

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Treatment

In general, treatment involves reversing the underlying cause of the QT prolongation. Electrolytes should be repleted, and consideration should be given to withdrawing offending drugs.