Torsades de pointes
Encyclopedia
Torsades de pointes, or simply torsades, is a French
term that literally means "twisting of the points". It was first described by Dessertenne
in 1966 and refers to a specific, rare variety of ventricular tachycardia
that exhibits distinct characteristics on the electrocardiogram
(ECG).
. Torsades de pointes can degenerate into ventricular fibrillation
, which will lead to sudden death in the absence of medical intervention. Torsades de pointes is associated with long QT syndrome
, a condition whereby prolonged QT intervals are visible on the ECG. Long QT intervals predispose the patient to an R-on-T phenomenon, where the R wave representing ventricular depolarization occurs during the relative refractory period at the end of repolarization (represented by the latter half of the T-wave). An R-on-T can initiate torsades. Sometimes pathologic T-U waves may be seen in the ECG before the initiation of torsades.
Common causes for torsades de pointes include diarrhea
, hypomagnesemia
and hypokalemia
. It is commonly seen in malnourished individuals and chronic alcoholics
. Certain combinations of drugs resulting in drug interactions may contribute: decreasing the metabolism
of a medication causing QT elongation such as clarithromycin (Biaxin)
or haloperidol (Haldol)
, taken concomitantly with a specific cytochrome P450 inhibitor like fluoxetine (Prozac)
or cimetidine (Tagamet)
, some dietary supplements like St John's wort
, foods like grapefruit will result in higher than normal doses of the medication responsible for the QT elongation. Since these specific drugs worsen the elongation of the QT wave in a dose-dependant manner, inhibition of a drug metabolism raises the risks of developing a malignant torsades de pointed arrythmia. Various medications are known to cause QT elongation. Examples include amiodarone
, methadone
, lithium, chloroquine
, erythromycin
, and phenothiazines. It can also be the side effect of some antiarrhythmic medications such as sotalol
, procainamide
and quinidine.
The gastrokinetic drug cisapride (Propulsid)
was withdrawn from the US market in 2000 after such interactions lead to deaths caused by long QT syndrome-induced torsades-de-pointes.
An FDA warning was issued in September 2011 concerning high doses of the antidepressant Celexa (citalopram). Specifically, ekg analyses revealed an increased frequency of prolongation of the QT interval in patients receiving doses above 40 mg. per day (thereby increasing the risk of Torsades). Physicians were advised that 40 mg. per day is considered the maximum allowable dosage.
An FDA warning was issued in September 2011 concerning use of ondansetron (Zofran) in patients with low magnesium or potassium levels, or certain heart conditions, as they may lead to torsades de pointes. http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm272041.htm
Factors that are associated with an increased tendency toward torsades de pointes include:
, antiarrhythmic drugs, and electrical therapy as needed.
Because of the polymorphic nature of torsades de pointes, synchronized cardioversion
may not be possible, and the patient may require an unsynchronized shock (or defibrillation
).
by Dessertenne
in 1966, when he observed this cardiac rhythm disorder in an 80-year-old female patient with complete intermittent atrioventricular
block.
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
term that literally means "twisting of the points". It was first described by Dessertenne
Dessertenne
François Dessertenne is a French physician who first described the special type of ventricular tachycardia in 1966 known as Torsades de pointes.-References:...
in 1966 and refers to a specific, rare variety of ventricular tachycardia
Ventricular tachycardia
Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
that exhibits distinct characteristics on the electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG).
Presentation
The ECG tracing in torsades demonstrates a polymorphic ventricular tachycardia with a characteristic illusion of a twisting of the QRS complex around the isoelectric baseline. It is also associated with a fall in arterial blood pressure, which can produce syncopeSyncope (medicine)
Syncope , the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.Many forms of syncope are...
. Torsades de pointes can degenerate into ventricular fibrillation
Ventricular fibrillation
Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is a medical emergency and most commonly identified arrythmia in cardiac arrest...
, which will lead to sudden death in the absence of medical intervention. Torsades de pointes is associated with long QT syndrome
Long QT syndrome
The long QT syndrome is a rare inborn heart condition in which delayed repolarization of the heart following a heartbeat increases the risk of episodes of torsade de pointes . These episodes may lead to palpitations, fainting and sudden death due to ventricular fibrillation...
, a condition whereby prolonged QT intervals are visible on the ECG. Long QT intervals predispose the patient to an R-on-T phenomenon, where the R wave representing ventricular depolarization occurs during the relative refractory period at the end of repolarization (represented by the latter half of the T-wave). An R-on-T can initiate torsades. Sometimes pathologic T-U waves may be seen in the ECG before the initiation of torsades.
Characteristics
- Rotation of the heart's electrical axis by at least 180º
- Prolonged QT intervalQT intervalIn cardiology, the QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. In general, the QT interval represents electrical depolarization and repolarization of the left and right ventricles...
(LQTS) - Preceded by long and short RR-intervals
- Triggered by an early premature ventricular contractionPremature ventricular contractionA premature ventricular contraction , also known as a premature ventricular complex, ventricular premature contraction , ventricular premature beat , or extrasystole, is a relatively common event where the heartbeat is initiated by the heart ventricles rather than by the sinoatrial node, the...
(R-on-T PVC)
Causes
Long QT syndrome can either be inherited as congenital mutations of ion channels carrying the cardiac impulse/action potential or acquired as a result of drugs that block these cardiac ion currents.Common causes for torsades de pointes include diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
, hypomagnesemia
Hypomagnesemia
Hypomagnesemia is an electrolyte disturbance in which there is an abnormally low level of magnesium in the blood. Usually a serum level less than 0.7 mmol/L is used as reference. The prefix hypo- means low . The middle 'magnes' refers to magnesium...
and hypokalemia
Hypokalemia
Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...
. It is commonly seen in malnourished individuals and chronic alcoholics
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
. Certain combinations of drugs resulting in drug interactions may contribute: decreasing the metabolism
Drug metabolism
Drug metabolism is the biochemical modification of pharmaceutical substances by living organisms, usually through specialized enzymatic systems. This is a form of xenobiotic metabolism. Drug metabolism often converts lipophilic chemical compounds into more readily excreted polar products...
of a medication causing QT elongation such as clarithromycin (Biaxin)
Clarithromycin
Clarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia , skin and skin structure infections...
or haloperidol (Haldol)
Haloperidol
Haloperidol is a typical antipsychotic. It is in the butyrophenone class of antipsychotic medications and has pharmacological effects similar to the phenothiazines....
, taken concomitantly with a specific cytochrome P450 inhibitor like fluoxetine (Prozac)
Fluoxetine
Fluoxetine is an antidepressant of the selective serotonin reuptake inhibitor class. It is manufactured and marketed by Eli Lilly and Company...
or cimetidine (Tagamet)
Cimetidine
Cimetidine INN is a histamine H2-receptor antagonist that inhibits the production of acid in the stomach. It is largely used in the treatment of heartburn and peptic ulcers. It is marketed by GlaxoSmithKline under the trade name Tagamet...
, some dietary supplements like St John's wort
St John's wort
St John's wort is the plant species Hypericum perforatum, and is also known as Tipton's Weed, Chase-devil, or Klamath weed....
, foods like grapefruit will result in higher than normal doses of the medication responsible for the QT elongation. Since these specific drugs worsen the elongation of the QT wave in a dose-dependant manner, inhibition of a drug metabolism raises the risks of developing a malignant torsades de pointed arrythmia. Various medications are known to cause QT elongation. Examples include amiodarone
Amiodarone
Amiodarone is an antiarrhythmic agent used for various types of tachyarrhythmias , both ventricular and supraventricular arrhythmias. Discovered in 1961, it was not approved for use in the United States until 1985...
, methadone
Methadone
Methadone is a synthetic opioid, used medically as an analgesic and a maintenance anti-addictive for use in patients with opioid dependency. It was developed in Germany in 1937...
, lithium, chloroquine
Chloroquine
Chloroquine is a 4-aminoquinoline drug used in the treatment or prevention of malaria.-History:Chloroquine , N'--N,N-diethyl-pentane-1,4-diamine, was discovered in 1934 by Hans Andersag and co-workers at the Bayer laboratories who named it "Resochin". It was ignored for a decade because it was...
, erythromycin
Erythromycin
Erythromycin is a macrolide antibiotic that has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma and...
, and phenothiazines. It can also be the side effect of some antiarrhythmic medications such as sotalol
Sotalol
Sotalol is a drug used in individuals with rhythm disturbances of the heart, and to treat hypertension in some individuals. It is a non-selective competitive β-adrenergic receptor blocker that also exhibits Class III antiarrhythmic properties by its inhibition of potassium channels...
, procainamide
Procainamide
Procainamide INN is a pharmaceutical antiarrhythmic agent used for the medical treatment of cardiac arrhythmias, classified by the Vaughan Williams classification system as class Ia.-History:...
and quinidine.
The gastrokinetic drug cisapride (Propulsid)
Cisapride
Cisapride is a gastroprokinetic agent, a drug which increases motility in the upper gastrointestinal tract. It acts directly as a serotonin 5-HT4 receptor agonist and indirectly as a parasympathomimetic. Stimulation of the serotonin receptors increases acetylcholine release in the enteric nervous...
was withdrawn from the US market in 2000 after such interactions lead to deaths caused by long QT syndrome-induced torsades-de-pointes.
An FDA warning was issued in September 2011 concerning high doses of the antidepressant Celexa (citalopram). Specifically, ekg analyses revealed an increased frequency of prolongation of the QT interval in patients receiving doses above 40 mg. per day (thereby increasing the risk of Torsades). Physicians were advised that 40 mg. per day is considered the maximum allowable dosage.
An FDA warning was issued in September 2011 concerning use of ondansetron (Zofran) in patients with low magnesium or potassium levels, or certain heart conditions, as they may lead to torsades de pointes. http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm272041.htm
Factors that are associated with an increased tendency toward torsades de pointes include:
- Familial long QT syndrome
- Class IA antiarrhythmics
- Class III antiarrhythmics
- HypomagnesemiaHypomagnesemiaHypomagnesemia is an electrolyte disturbance in which there is an abnormally low level of magnesium in the blood. Usually a serum level less than 0.7 mmol/L is used as reference. The prefix hypo- means low . The middle 'magnes' refers to magnesium...
- HypokalemiaHypokalemiaHypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...
- Hypocalcemia
- HypoxiaHypoxia (medical)Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
- AcidosisAcidosisAcidosis is an increased acidity in the blood and other body tissue . If not further qualified, it usually refers to acidity of the blood plasma....
- Heart failure
- Left ventricular hypertrophyLeft ventricular hypertrophyLeft ventricular hypertrophy is the thickening of the myocardium of the left ventricle of the heart.-Causes:While ventricular hypertrophy occurs naturally as a reaction to aerobic exercise and strength training, it is most frequently referred to as a pathological reaction to cardiovascular...
- Slow heart rateBradycardiaBradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
- FemaleFemaleFemale is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
gender - HypothermiaHypothermiaHypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
- Subarachnoid hemorrhageSubarachnoid hemorrhageA subarachnoid hemorrhage , or subarachnoid haemorrhage in British English, is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain...
Treatment
Treatment is directed at withdrawal of the offending agent, infusion of magnesium sulfateMagnesium sulfate
Magnesium sulfate is a chemical compound containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate epsomite , commonly called Epsom salt, from the town of Epsom in Surrey, England, where the salt was distilled from the springs that arise where the...
, antiarrhythmic drugs, and electrical therapy as needed.
Because of the polymorphic nature of torsades de pointes, synchronized cardioversion
Cardioversion
Cardioversion is a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart, at a specific moment in the cardiac cycle...
may not be possible, and the patient may require an unsynchronized shock (or defibrillation
Defibrillation
Defibrillation is a common treatment for life-threatening cardiac arrhythmias, ventricular fibrillation and pulseless ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator...
).
History and terminology
The phenomenon was originally described in a French medical journalMedical journal
A public health journal is a scientific journal devoted to the field of public health, including epidemiology, biostatistics, and health care . Public health journals, like most scientific journals, are peer-reviewed...
by Dessertenne
Dessertenne
François Dessertenne is a French physician who first described the special type of ventricular tachycardia in 1966 known as Torsades de pointes.-References:...
in 1966, when he observed this cardiac rhythm disorder in an 80-year-old female patient with complete intermittent atrioventricular
Atrioventricular
Atrioventricular can refer to:*Left atrioventricular opening*Atrioventricular fistula*Atrioventricular node*The term "Atrioventricular valves" is used to describe the mitral valve and tricuspid valve....
block.