Podcast
Questions and Answers
QTc should be measured only upon admission for patients prescribed antipsychotics.
QTc should be measured only upon admission for patients prescribed antipsychotics.
False
Extreme physical exertion is a factor that can increase the risk of QT prolongation.
Extreme physical exertion is a factor that can increase the risk of QT prolongation.
True
Hypokalaemia is less commonly observed in acute psychotic admissions regarding QTc prolongation.
Hypokalaemia is less commonly observed in acute psychotic admissions regarding QTc prolongation.
False
The presence of bradycardia is considered a cardiac risk factor for QTc prolongation.
The presence of bradycardia is considered a cardiac risk factor for QTc prolongation.
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Anorexia nervosa is not recognized as a risk factor for QTc changes.
Anorexia nervosa is not recognized as a risk factor for QTc changes.
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Smoking and obesity have a lesser impact on patient morbidity than drug-induced arrhythmia.
Smoking and obesity have a lesser impact on patient morbidity than drug-induced arrhythmia.
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All antipsychotics are conclusively linked to sudden cardiac death.
All antipsychotics are conclusively linked to sudden cardiac death.
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An ECG should be performed annually for patients with prior abnormal results or additional risk factors.
An ECG should be performed annually for patients with prior abnormal results or additional risk factors.
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Measuring QTc should be done immediately upon reaching therapeutic doses of low-risk antipsychotics.
Measuring QTc should be done immediately upon reaching therapeutic doses of low-risk antipsychotics.
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It is advisable to prescribe the highest possible dosage of antipsychotics to minimize risk.
It is advisable to prescribe the highest possible dosage of antipsychotics to minimize risk.
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Brexpiprazole has a reported high effect on the QT interval.
Brexpiprazole has a reported high effect on the QT interval.
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The RISQ-PATH study has a 98% negative predictive value for QT prolongation.
The RISQ-PATH study has a 98% negative predictive value for QT prolongation.
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Olanzapine is categorized as a medication with a moderate effect on the QT interval.
Olanzapine is categorized as a medication with a moderate effect on the QT interval.
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Studies suggest aripiprazole may promote an increase in QTc interval.
Studies suggest aripiprazole may promote an increase in QTc interval.
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Pimozide is included in the high effect category for QT prolongation.
Pimozide is included in the high effect category for QT prolongation.
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Sertindole is recognized for having a low effect on the QT interval.
Sertindole is recognized for having a low effect on the QT interval.
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Lurasidone is known to have effects that consistently lengthen the QT interval.
Lurasidone is known to have effects that consistently lengthen the QT interval.
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Any intravenous antipsychotic is categorized under the unknown effect group for QT prolongation.
Any intravenous antipsychotic is categorized under the unknown effect group for QT prolongation.
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Erythromycin is categorized as an antimalarial drug associated with QT prolongation.
Erythromycin is categorized as an antimalarial drug associated with QT prolongation.
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A QTc value above 500ms necessitates immediately stopping suspected causative drug(s) and switching to a drug of lower effect.
A QTc value above 500ms necessitates immediately stopping suspected causative drug(s) and switching to a drug of lower effect.
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Fluvoxamine is an example of a metabolic inhibitor that can affect plasma levels of drugs influencing QTc.
Fluvoxamine is an example of a metabolic inhibitor that can affect plasma levels of drugs influencing QTc.
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Chloroquine is classified among the antiarrhythmic drugs linked to QT prolongation.
Chloroquine is classified among the antiarrhythmic drugs linked to QT prolongation.
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Measurement of QTc is advised immediately after achieving a therapeutic dose of all antipsychotic medications.
Measurement of QTc is advised immediately after achieving a therapeutic dose of all antipsychotic medications.
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Antipsychotics are known to decrease the QT interval, thus reducing the risk of torsade de pointes.
Antipsychotics are known to decrease the QT interval, thus reducing the risk of torsade de pointes.
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The risk of sudden cardiac death associated with antipsychotics is likely dose-related and higher than fatal agranulocytosis risk with clozapine.
The risk of sudden cardiac death associated with antipsychotics is likely dose-related and higher than fatal agranulocytosis risk with clozapine.
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QTc values can vary significantly depending on the correction factors and methods used.
QTc values can vary significantly depending on the correction factors and methods used.
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Psychiatrists are typically well-trained to accurately interpret ECG changes caused by antipsychotics.
Psychiatrists are typically well-trained to accurately interpret ECG changes caused by antipsychotics.
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Studies have found that the use of antipsychotics leads to QT interval prolongation after approximately 1-2 weeks.
Studies have found that the use of antipsychotics leads to QT interval prolongation after approximately 1-2 weeks.
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ECG monitoring for drug-induced changes is recommended on admission and then every five years for patients taking antipsychotics.
ECG monitoring for drug-induced changes is recommended on admission and then every five years for patients taking antipsychotics.
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The risk of torsade de pointes is consistent across all antipsychotics and does not vary with patient age.
The risk of torsade de pointes is consistent across all antipsychotics and does not vary with patient age.
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Lengthening of the cardiac repolarisation duration has no effect on the electrical phasing in various areas of the heart.
Lengthening of the cardiac repolarisation duration has no effect on the electrical phasing in various areas of the heart.
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QT prolongation beyond normal limits is not significantly linked to arrhythmia risk.
QT prolongation beyond normal limits is not significantly linked to arrhythmia risk.
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QTc measurements can fluctuate based on various factors like gender and diet.
QTc measurements can fluctuate based on various factors like gender and diet.
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U-waves do not affect the determination of the end of the T-wave in QTc measurement.
U-waves do not affect the determination of the end of the T-wave in QTc measurement.
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Drugs causing no QT prolongation are still monitored for QTc changes during their administration.
Drugs causing no QT prolongation are still monitored for QTc changes during their administration.
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Antipsychotics have been linked to ECG changes such as atrial fibrillation.
Antipsychotics have been linked to ECG changes such as atrial fibrillation.
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Ziprasidone shows significant cardiac toxicity despite its moderate effect on QTc.
Ziprasidone shows significant cardiac toxicity despite its moderate effect on QTc.
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QT dispersion ratio and dispersion transmural repolarisation time can predict arrhythmia risk.
QT dispersion ratio and dispersion transmural repolarisation time can predict arrhythmia risk.
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Drugs categorized as low-effect cause significant QTc prolongation at regular doses.
Drugs categorized as low-effect cause significant QTc prolongation at regular doses.
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Study Notes
ECG Monitoring for Antipsychotic Use
- Measure QTc in all patients prescribed antipsychotics on admission and annually if previous abnormalities or additional risk factors exist.
Physiological Risk Factors for QTc Prolongation and Arrhythmia
- Long QT syndrome, bradycardia, ischemic heart disease, myocarditis, myocardial infarction, left ventricular hypertrophy, hypokalaemia, hypomagnesaemia, hypocalcaemia, extreme physical exertion, stress or shock, anorexia nervosa, extremes of age, and female gender can all increase the risk of QTc prolongation and arrhythmia.
Other Cardiovascular Risk Factors
- Smoking, obesity, and impaired glucose tolerance pose greater risks to patient morbidity and mortality than the uncertain outcome of QT changes.
Antipsychotic Effects on QTc
- Although data is inconclusive, assume all antipsychotics are linked to sudden cardiac death.
- Prescribe the lowest possible dose and avoid polypharmacy and metabolic interactions.
- Consider measuring QTc within a week of achieving a therapeutic dose of moderate/high-risk antipsychotics.
RISQ-PATH Study
- The RISQ-PATH study is a scoring system for predicting QT prolongation with a 98% negative predictive value, enabling less monitoring for low-risk individuals.
Antipsychotic Effects on QTc (Medication Table)
- No effect: Brexpiprazole, Cariprazine, Lurasidone, Lumateperone.
- Moderate effect: Amisulpride, Chlorpromazine, Haloperidol, Iloperidone, Levomepromazine, Melperone, Pimavanserin, Quetiapine, Ziprasidone.
- Low effect: Aripiprazole, Asenapine, Clozapine, Flupentixol, Fluphenazine, Perphenazine, Prochlorperazine, Olanzapine, Paliperidone, Risperidone, Sulpiride.
- High effect: Any intravenous antipsychotic, Pimozide, Sertindole, Any drug or combination of drugs used in doses exceeding recommended maximum.
- Unknown effect: Loxapine, Pipotiazine, Trifluoperazine, Zuclopenthixol.
ECG Changes - QT Prolongation
- Many psychotropics are associated with ECG changes and some are causally linked to serious ventricular arrhythmia and sudden cardiac death.
- Some antipsychotics block cardiac potassium channels and are linked to prolongation of the cardiac QT interval, increasing the risk of torsade de pointes.
- The use of most antipsychotics is associated with an increase in the rate of sudden cardiac death.
- Schizophrenia itself may be associated with QT prolongation.
- The risk is likely dose-related and substantially higher than the risk of fatal agranulocytosis with clozapine.
ECG Monitoring
- ECG monitoring is essential for all patients prescribed antipsychotics.
- Estimate the QT interval on admission to in-patient units and yearly thereafter.
QT Prolongation
- The QTc interval is an imprecise but useful indicator of torsade de pointes risk and increased cardiac mortality.
- Different correction factors and methods may give markedly different values.
- The QT interval reflects the duration of cardiac repolarisation.
QT Interval and Drug Effects
- Ventricular structures and early after depolarisations can provoke ventricular extrasystole and torsades de pointes.
- There's a strong exponential relationship between prolonged QT and arrhythmia risk, especially for QT intervals over 500ms.
- QTc measurements remain important for assessing arrhythmia and sudden cardiac death risk.
Complicating Factors of QTc Measurement
- Determining the end of the T-wave is particularly challenging with U-waves.
- QTc varies based on gender, time of day, diet, alcohol consumption, menstrual cycle, and ECG lead.
- Variations in drug plasma levels significantly impact QTc prolongation.
Other ECG Changes
- Antipsychotic-induced ECG changes include atrial fibrillation, enlarged P waves, changes in T-wave morphology, and heart block.
Quantifying Drug Risk
- Drugs are categorized based on their effect on the QTc interval, ranging from "no effect" to "high effect."
- Categorization remains approximate and serves only as a helpful guideline.
Non-Psychotropic Drugs Associated with QT Prolongation
- Antibiotics: Erythromycin, clarithromycin, ampicillin, co-trimoxazole, pentamidine, some four quinolones.
- Antimalarials: Chloroquine, mefloquine, quinine.
- Antiarrhythmics: Quinidine, disopyramide, procainamide, sotalol, amiodarone, bretylium.
- Others: Amantadine, cyclosporin, diphenhydramine, hydroxyzine, methadone, nicardipine, tamoxifen.
Metabolic Inhibition
- The effect of drugs on QTc is usually plasma level-dependent, making drug interactions important to consider.
- Commonly used metabolic inhibitors include fluvoxamine, fluoxetine, paroxetine and valproate.
Management of QT Prolongation in Patients Receiving Antipsychotic Drugs
- QTc < 470ms (women) but < 500 ms: Consider reducing the dose or switching to a drug with a lower effect, repeat ECG.
- QTc > 500 ms: Repeat ECG, stop suspect causative drug(s) and switch to a drug of lower effect, refer to cardiologist immediately.
- Abnormal T-wave morphology: Review treatment, consider reducing dose or switching to a drug of lower effect, refer to cardiologist immediately.
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Description
This quiz tests your knowledge on the risks associated with QTc prolongation in patients prescribed antipsychotics. It covers key factors influencing QTc changes, including physical exertion, bradycardia, and the impact of specific medications. Understand the importance of ECG monitoring and dosage considerations for safe antipsychotic use.
