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QT Prolongation from Psychiatric Medication: Information for Primary Care

Summary: QT prolongation from psychiatric medications leading to potentially fatal cardiac arrhythmias is an uncommon but serious complication. Unfortunately, many psychiatric medications such as antidepressants and antipsychotics have a risk of prolonging QT. For patients at risk of QT prolongation, address modifiable risk factors, use caution with medications that may worsen QT intervals, and consider cardiology consultation. For patients with QT prolongation, stop any offending medications and address modifiable risk factors.
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Case, Part 1 

  • Dave is a university student.
  • Several years ago, he had been diagnosed with anxiety, and treated with Citalopram, which he continues to take.
  • A few months ago, the dosage was raised to 40 mg daily.
  • He now presents to you with fainting spells and chest pains.

What is a Normal QT Interval?

  • The QT interval on the ECG is from the beginning of the QRS complex to the end of the T wave, and represents ventricular depolarization and repolarization.
  • The QT interval varies with heart rate.
  • Various formulas are used to correct the QT interval for heart rate, and once corrected, it is expressed as the QTc (“QT corrected”) interval
  • Normal QTc interval < 440 ms

What is Prolonged QT?

  • QT prolongation is associated with an increased risk of torsades de pointes, a potentially fatal ventricular arrhythmia.
  • QTc may be
    • Borderline prolonged QTc interval >440 ms yet <500 ms
      • When borderline → Consider reducing the dosage of any QT prolonging medications or changing to an alternative non QT prolonging medication.
    • Prolonged QTc Interval >500 ms
    • When prolonged → Stop any medications that prolong the QT interval

 

What is a Significant Medication-Induced QTc Prolongation?

  • Increase in baseline QTc < 5 ms = Not considered significant
  • Increase in baseline QTc > 20 = Concerning
  • Increase in baseline QTc > 60 ms = Very concerning
    • With familial long QT syndrome, for every 10 ms increase in QTc there is a 5% increase in the risk of arrhythmic events.

What are the main risk factors for QT prolongation? 

  • In cases of torsades de pointes, there are often multiple risk factors present, which include the following main risk factors:
  • Potentially Modifiable Risk Factors
  • Electrolyte Disturbances (in particular hypokalaemia, hypomagnesaemia and more rarely hypocalcaemia).
  • Bradycardia
  • Using more than one medication that prolongs the QT interval
  • Non-modifiable
    • Congenital long QT syndrome
    • Cardiac disease (e.g. bradycardia, heart failure, left ventricular hypertrophy, myocardial infarction)
    • Impaired hepatic/renal function (due to effects on medication metabolism)
    • Thyroid disease (more common with hypothyroidism and usually normalises with treatment)
    • Female sex
    • Age > 65-yo

Medication-induced QT Prolongation vs. Familial Long QT Syndrome 

  • Medication-induced QT prolongation:
    • Due to taking one or more medications that prolong the QT interval
    • Mechanisms of medication-induced QT prolonged
      • Pharmacodynamic Interaction: Using more than one medication that prolongs the QT interval increases the risk of torsades de pointes and ventricular arrhythmia.
      • Pharmacokinetic Interaction: Even medications that do not prolong the QT interval themselves can increase the risk of QT prolongation by inhibiting the metabolism of medications that do prolong the QT interval
        • E.g. macrolide antibiotics and antifungals which inhibit the CYP3A4 enzyme.
        • E.g antidepressants that may inhibit the CYP2D6 enzyme
      • Effects on Electrolytes: Hypokalaemia and hypomagnesaemia can increase the risk of QT prolongation
      • E.g. diuretics can interact with QT prolonging medications by causing hypokalaemia.
      • E.g. long term proton pump inhibitors may cause hypomagnesemia which can increase the risk for QTc prolongation
    • Presentation
      • May have no symptoms, or present with cardiac symptoms 
         
  • Medication-induced QT prolongation is the most common cause of long QT syndrome
    • Due to having a congenital/familial condition that causes long QT  
    • Epidemiology
      • Congenital (aka familial) long QT syndrome
    • Presentation
      • May have no symptoms, or may also have history of cardiac events (e.g. syncope, dizziness, etc)
      • Triggers include exercise, swimming or emotion, or simply sleeping at night
    • Epidemiology
      • Rare; about 1 in every 7,000.
      • Patients with prolonged QT in absence of secondary causes for QT prolongation (European Society of Cardiology, 2006)
    • Diagnosis of Long QT Syndrome

Presentation

  • Patients may present:
  • Asymptomatic with no symptoms suggesting that they have QT prolongation
  • Symptomatic with cardiac symptoms such as
    1. Syncope (the most common symptoms), often triggered by exertion or sound; usually the rhythm returns to normal within a minute, and the patient regains consciousness without disorientation.
    2. Generalized seizure: When the long QT syndrome dysrhythmia persists longer, it may presented with a generalized seizure.
    3. Sudden death: In a small minority, the rhythm degenerates further into torsades de pointes and ventricular fibrillation, and unfortunately, some patients will present with sudden death as the first indication of QT prolongation.

Psychiatric Medications That May Prolong QT include (but are not limited to) the following: 

  • TCAs such as
    • Amitriptyline
    • Maprotiline
    • Desipramine
    • Nortryptyline
  • SSRIs such as
    • Citalopram > 40 mg daily (Washington, 2012) 
    • Escitalopram
    • Fluoxetine
    • Venlafaxine > 300 mg daily (Washington, 2012)
    • Note: All SSRIs at plasma concentration above therapeutic level are associated with QT prolongation
  • First-generation antipsychotics
    • Thioridazine (Mellaril)
    • Mesoridazine (Serentil)
    • Chlorpromazine (Thorazine)
    • Haloperidol (Haldol)
  • Newer antipsychotics
    • Ziprasidone (Zeldox in Canada / Geodon in USA) (most compared to other newer antipsychotics)
    • Risperidone (Risperdal)
    • Olanzapine (Zyprexa)
    • Quetiapine (Seroquel)
    • Note: Aripiprazole may shorten, rather than prolong QTc interval

For detailed lists of medications, visit https://crediblemeds.org/healthcare-providers/medication-list/. Note that the site is free to use, though user registration is required.

Screening for QT Prolongation

  • In primary care, it is not practical to do an ECG every time that a QT prolonging medication is prescribed
  • Consider ECG with the following red flags / risk factors
    • For children and youth
      • Any young person with unexplained syncope, unexplained seizures or unexplained cardiac events (such as cardiac arrest, or sudden death)
      • Family history of
        • Unexplained syncope
        • Unexplained seizures
        • Sudden death in young people
    • For adults
      • Age >65
      • Female sex
      • Electrolyte imbalances (specifically low serum potassium and magnesium levels)
      • High or toxic serum levels of the suspected medication
      • Preexisting cardiovascular impairment, such as bradycardia (Washington 2012)
      • When the patient is prescribed two or more medications that may cause QT prolongation
  • If there are red flags or risk factors
    • Do baseline ECG prior to start QT prolongation medication, and then repeat when the medication reaches a steady state at target dose.

Assessment / History 

  • HPI
    • Any history of cardiac events or symptoms?
    • Any history of disordered eating, vomiting or diarrhea that could cause ellctrolyte disturbance or bradycardia
       
  • Medication history
    • Any medications that prolong QT? (such as psychotropics, antinauseants or antibiotics)
    • Are there drug interactions that can increase the level of a QT prolonging medication?
    • Any medications that can alter serum electrolytes?
    • What is the dose intensity of the QT prolonging medications?

Diagnosis of Medication-Induced QT Prolongation

  • Presumptive diagnosis can be made by
    • QT prolongation  
    • QT prolonging medications
  • After the diagnosis is made, the diagnosis can be further confirmed
  • Discontinuation of QT prolonging medications, followed by normalization of ECG

Differential Diagnosis (DDx) of Medication-Induced QT Prolongation 

  • Medication-induced QT prolongation
    • Are there any medications that prolong QT? (such as psychotropics, antinauseants or antibiotics)
  • Congenital/familial long QT syndrome
  • Are there any factors that may indicate a congenital (familial) form of long QT syndrome, such as:
    • Hearing loss deficit?
    • Family history of cardiac arrest and sudden death at early age?
  • Does long QT persist despite stopping medications causing prolonged QT?
  • If so, then suspect possibility of congenital long QT syndrome
  • Myocardial infarction, cerebral hemorrhage
  • QT prolongation as seen in other conditions such as:

Physical Exam

  • There are no pathognomonic findings on physical exam to indicate QT prolongation.  
  • Nonetheless, physical exam is useful to rule out other potential reasons for arrhythmic and syncopal events in otherwise healthy people such as:
    • Heart murmurs caused by hypertrophic cardiomyopathy
    • Valve defects
  • Some patients may show:
    • Excessive bradycardia for their age
    • Hearing loss (congenital deafness), indicating the possibility of JLN syndrome.
    • Skeletal abnormalities, such as short stature and scoliosis are seen in LQT7 (Andersen syndrome)
    • Congenital heart diseases, cognitive and behavioral problems, musculoskeletal diseases, and immune dysfunction may be seen in those with LQT8 (Timothy syndrome)

Investigations

When there is suspicion, consider the following: 

  • ECG of the patient and family members
  • Serum potassium and magnesium levels
  • Thyroid function tests
  • Genetic testing of the patient and family members

Management: Prevention of Medication-Induced QT Prolongation

Assess risk factors for QT prolongation

Potentially modifiable risk factors

  • Bradycardia
  • Hypokalaemia
    • Avoid medications that reduce serum potassium
    • Correct potassium deficiency
  • Hypomagnesaemia
  • Avoid medications that reduce magnesium level
  • Correct magnesium deficiency
  • Hypocalcaemia
  • Drugs that induce QT interval prolongation

 

Non-modifiable risk factors

  • Myocardial infarction
  • Heart failure
  • Female sex
  • Age >65 years
  • Genetic polymorphism
  • History of QT prolongation
  • Brain injury (Abrishamkar, 2012)

Reduce risk factors

 

  • Where possible use alternative agents that do not prolong QT interval such as
    • Lorazepam (Ativan)
    • Loxapine (Loxapac)
    • Lurasidone (Latuda)
    • Bupropion (Wellbutrin)
    • Vortioxetine (Trintellix)
  • If QT interval prolonging medications are required, use lowest effective dose
  • Correct underlying causes of electrolyte abnormalities or medication-induced bradycardia

Monitor

Consider ECG:

  • At baseline prior to initiation or dose increase of QT interval prolonging medication
  • Once QT interval prolonging medication reaches steady state (5 half-lives)
  • Every month for 6 months, then every 6-12 months thereafter

Educate the patient

 

Educate the patient to seek medical help if s/he has any of the following:

  • Palpitations
  • Lightheadedness
  • Dizziness
  • Syncope

     

Educate the patient to inform any other healthcare professionals if they:

  • Have congenital LQTS
  • Have a previous history of medication-induced QT prolongation

 

When and how to modify therapy

 

Where a patient has risk factors and is to be prescribed a QT prolonging medication, consider 

  • Changing to an alternative medication that is not known to prolong the QT interval if possible

If baseline ECG shows QTc of 480 ms

  • Consider an alternative medication that does not cause QT prolongation
  • Correct electrolyte imbalances

If follow-up ECG shows QTc ≥500 ms and/or absolute increase in QTc ≥60 ms

  • Discontinue QT prolonging medication
  • Correct electrolyte imbalances
  • Refer to cardiologist

 

Reference: Trinkley, 2013; National Medicines Information Centre, 2015; NHS Greater Glasgow and Clyde Medicines Information Service, 2012 

When to Refer 

  • Emergency Department assessment
    • Refer for assessment in the Emergency Department if patients have risk factors for QT prolongation and experience a cardiac event (e.g. syncope, cardiac arrest)
    • If a patient has taken an overdose of a QT prolonging medication (such as an SSRI), consider close cardiac monitoring post-overdose
       
  • Cardiology
    • Should long QT persist despite cessation of offending medications, then consider referring to cardiology to consider other causes (such as familial long QT syndrome)
    • Consider referring paediatric patients with high risk for QTc prolongation to cardiology prior to initiating any psychotropic meds with known side effect of QTc

Case, Part 2

  • Dave is a university student with anxiety who was treated with citalopram
  • Since raising the dosage to 40 mg daily, he now presents to you with fainting spells and chest pains.
  • ECG shows QTc prolongation
  • You taper his Citalopram down to 10 mg daily, and you recommend  counseling/therapy through student health services to ensure that he has non-medication strategies for his anxiety
  • A repeat ECG shows no further QTc prolongation.

Patient Handouts 

Acquired Long QT Syndrome

http://www.nhs.uk/conditions/long-qt-syndrome/documents/acquired-lqt-brochure06.pdf

Practice Guidelines 

ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines. Retrieved Dec 29, 2016 from 

http://reference.medscape.com/medline/abstract/16935995

 

The Task Force for the Management of Patients with Ventricular Arrhythmias and

the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC), 2015 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death, European Heart Journal 2015;36(41):2793-2867

References

 

Abrishamkar S, Abbasi Fard S, Momeni A: QT Interval Changes in Moderate and Severe Brain Injuries, Neurosurgery Quarterly 2012 May; 22(2): 123-125.

 

NHS Greater Glasgow and Clyde Medicines Information Service: medication-induced QT Prolongation, PostScriptExtra, Issue 21, Dec 2012. Retrieved Dec 29, 2016 from http://www.ggcprescribing.org.uk/media/uploads/ps_extra/pse_21.pdf

 

Trinkley K et al, QT interval prolongation and the risk of torsades de pointes: Essentials for clinicians, Current Medical Research and Opinion 2013;29(12):1719- 1726

 

The Task Force for the Management of Patients with Ventricular Arrhythmias and

the Prevention of Sudden Cardiac Death of the European Society of Cardiology (ESC), 2015 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death, European Heart Journal 2015;36(41):2793-2867

 

St. James’s Hospital, medication-induced QT Interval Prolongation, National Medicines Information Centre (www.nmic.ie), Vol 21 Number 6, 2015. Retrieved Dec 29, 2016 from 

http://www.stjames.ie/GPsHealthcareProfessionals/Newsletters/NMICBulletins/NMICBulletins2015/NMIC%20Bulletin%20February%202016%20-%20Drug-Induced%20QT%20Interval%20Prolongation%20(3).pdf

 

Washington N: Which psychotropics carry the greatest risk of QTc prolongation, Current Psychiatry. 2012 October; 11(10): 36-39. Retrieved Dec 13, 2016 from 

http://www.mdedge.com/currentpsychiatry/article/64870/anxiety-disorders/which-psychotropics-carry-greatest-risk-qtc

Recommended Websites

http://crediblemeds.org

Up-to-date listings of medications that may prolong QT

About this Document

Written by Khalid Bazaid (Psychiatrist), Michael Cheng (Psychiatrist), Mireille St-Jean (Family Physician), Marla Sullivan (Pharmacist) and Sinthu Suntharalingum (Psychiatrist). Reviewed by the eMentalHealth.ca Primary Care Team including Dr’s M. St-Jean (family physician), E. Wooltorton (family physician), F. Motamedi (family physician), M. Cheng (psychiatrist).

Disclosures

 

The authors report no financial relationship with any company whose products are mentioned in this article or with manufacturers of competing products. 

Disclaimer

Information in this pamphlet is offered ‘as is' and is meant only to provide general information that supplements, but does not replace the information from a health professional. Always contact a qualified health professional for further information in your specific situation or circumstance.

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Date Posted: Jan 11, 2017
Date of Last Revision: Jan 30, 2017

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