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Torsades de pointes
(long QT Syndrome)
PHCP 403
Samirah Abdu-Aguye
INTRODUCTION
• Torsade de pointes is an uncommon and
distinctive form of polymorphic ventricular
tachycardia (VT) characterized by a gradual
change in the amplitude and twisting of the
QRS complexes around the isoelectric line
• It is usually associated with a prolonged QT
interval, which may be congenital or acquired.
• It is one of the most common types of
arrhythmias caused by drug interactions
INTRO CONT’D
• Torsade usually terminates spontaneously but
frequently recurs and may degenerate into
ventricular fibrillation.
EPIDEMIOLOGY
• The prevalence of torsade is unknown.
Torsade is a life-threatening arrhythmia and
may present as sudden cardiac death in
patients with structurally normal hearts
• Torsade is 2-3 times more common in women
than in men. Women have longer QT intervals,
and have more QT prolongation secondary to
drug therapy.
CLINICAL PRESENTATION
• Patients with torsade usually present with
recurrent episodes of palpitations, dizziness,
and syncope; however, sudden cardiac death
can occur with the first episode.
• Nausea, cold sweats, shortness of breath, and
chest pain also may occur but are nonspecific
and can be produced by any form of
tachyarrhythmia.
RISK FACTORS
Risk factors for torsade include the following:
• Congenital long QT syndrome
• Female gender
• Several medications and electrolyte disorders
such as hyperkalemia and hypomagnesemia)
• Bradycardia
• Baseline electrocardiographic abnormalities
• Renal or liver failure/disease
Acquired long QT syndromes
Drugs in a number of drug classes have been
associated with torsade.
Antiarrhythmic drugs associated with torsade
include the following:
• Class IA - Quinidine, disopyramide,
procainamide
• Class III - Sotalol, amiodarone (rare), ibutilide,
dofetilide, almokalant
• Anti-infectives - Erythromycin, Ciprofloxacin,
clarithromycin, azithromycin, levofloxacin, Moxifloxacin,
gatifloxacin, Pentamidine, Chloroquine Fluconazole,
Voriconazole, Amantadine
• Antipsychotics - Haloperidol, Chlorpromazine, Ziprasidone,
Amisulpride
• Tricyclic antidepressants, Lithium, Moclobemide and
Citalopram/Escitalopram
• Antihistamines (histamine1-receptor antagonists) Terfenadine, astemizole, diphenhydramine, loratidine
• Cholinergic antagonists - Cisapride,
organophosphates (pesticides)
• Citrate (massive blood transfusions)
• Other drugs: Ondansetron, Dolasetron,
Methadone,
• Cocaine
Treatment
• Treatment can be divided into short-term and
long-term management
• In an otherwise stable patient, DC cardioversion
is kept as a last resort because torsade is
paroxysmal in nature and is characterized by its
frequent recurrences
• Any offending agent should be withdrawn.
Predisposing conditions such as hypokalemia,
hypomagnesemia, and bradycardia should be
identified and corrected.
Treatment Cont’d
• Magnesium is the drug of choice for torsades.
• Magnesium can be given at 1-2 g IV initially in 3060 seconds, which then can be repeated in 5-15
minutes.
• Magnesium is effective even in patients with
normal magnesium levels. Because of the danger
of hypermagnesemia, the patient requires close
monitoring. other drugs that can be used include
mexiletine and isoproterenol
• JD is a 60-year-old woman. She reports being in her usual state of
relatively good health until she developed a “cold” approximately 4
days before admission.
• She went to a community pharmacy complaining of her upper
respiratory tract symptoms, and the pharmacist gave her for
erythromycin 500 mg QID (for 10 days). She took the first dose on the
morning of admission. She started feeling worse approximately 1 hour
after taking the second dose of erythromycin.
• She reported feeling lightheaded and short of breath. She
experienced palpitations as well and eventually passed out for a few
minutes, and was rushed to the hospital by her daughter. While being
evaluated in the ED, she had another syncopal episode. An ECG
showed Torsades de pointes.
PMH
Current Medications
CAD
Carvedilol 3.125 mg PO bid
Chronic Renal disease
Pravastatin PO 40mg OD
Heart failure (EF 30%)
Paroxysmal atrial fibrillation
Furosemide 40 mg PO bid
Warfarin 4 mg PO daily as directed
Amiodarone 200 mg PO bid
Candesartan 8 mg PO daily
Erythromycin 500 mg PO QID, started day of admission
Serum electrolytes
• Na 140 mmol/L (135-145)
• K 2.8 mmol/L(3.5-5)
• Mg 1.2 mEq/L(1.5-2)
Questions
• What risk factors predisposed the patient to
drug-induced arrhythmia?
• List the specific medication(s) you believe
caused the arrhythmia
• How should this patient be managed?
• What monitoring parameter should be used to
assess efficacy and toxicity of treatment
• List3 of the most common drug classes (with
an example from each) associated with TdP.
References
• Isbister G. Risk assessment of drug-induced
QT prolongation. Australian Prescriber
[Internet]. 2015 [cited 20 February
2015];(Volume 38, Issue 1):20-24. Available
from:
http://www.australianprescriber.com/magazin
e/38/1/issue/207.pdf
• Dave J, Bessette M, Setnik G, Gaeta T, Lakhia
R. Torsade de Pointes [Internet].
Emedicine.medscape.com. 2015 [cited 20
February 2015]. Available from:
http://emedicine.medscape.com/article/1950
863-overview#a30