Home
February 6, 2024
If you’ve ever used software that checks for drug interactions, you’ve come across alerts regarding QT interval prolongation. But you work in hospice…are these still significant and what can you do about them? Let’s start with some basics1 -6:
QT interval – a measure of ventricular repolarization in the heart
QTc interval – QT interval corrected for heart rate
Normal: ~450 milliseconds (ms)
Prolonged: ≥470ms (males); ≥480ms (females)
Torsades de Pointes (TdP) : Potentially fatal arrhythmia that’s more likely to occur when the QTc interval is prolonged
Causes: cardiac conditions (e.g., heart failure, myocardial infarction), metabolic disturbances, toxins, hypothyroidism, malnutrition, congenital (rare), and, last but not least, literally hundreds of medications
Symptoms: palpitations, syncope, lightheadedness, dizziness (around 50% of patients will be asymptomatic)
Here’s a link so you can practice saying it 😉
Unfortunately, there’s no consensus on how to classify QTc-prolonging/TdP-causing drugs, with different resources using different criteria and terminology. For example, Wolters Kluwer Health (LexiComp, UpToDate) ranks drugs in terms of risk of QTc-prolongation (e.g., highest, moderate, lower) and CredibleMeds ranks drugs based on risk of TdP (e.g., known, possible, conditional). So, it’s possible that you might encounter discrepancies. Specifically, hospice practitioners should be aware that alerts generated in their EMR may or may not generate in other software (e.g., at pharmacies), or may generate conflicting alerts in terms of severity and handling.
Hospice practitioners are frankly all over the map when it comes to degree of importance that they attribute to this issue, with some writing it off as much ado about nothing and others viewing it as reasonable to modify drug therapy. For the latter camp, a stepwise approach could be employed to help make informed decisions about prospective medication use and risk reduction.
Steps to mitigate risk of QTc-prolongation and TdP in hospice patients2,7,8
1. Risk assessment
a. Risk level of drug(s)
b. Patient risk factors for drug-induced QT-prolongation (Table 1)
i. If recent ECG available, consider findings (new testing is most often not indicated in hospice)
c. Risks vs. benefits of using the drug(s) in question
2. Interpretation
a. If clinician assessment of Steps 1a to 1c concludes drug therapy adjustment may be warranted, proceed to Step 3 (Risk mitigation)
3. Risk mitigation
a. Consider alternate therapy for new drug being prescribed (e.g., doxycycline instead of fluoroquinolone for respiratory infection)
b. Consider conversion of existing QTc-prolonging drugs to alternatives with lower risk (e.g., converting citalopram to sertraline when ondansetron is necessary to control nausea)
c. Correct modifiable risk factors if consistent with goals of care
d. Dose QTc-prolonging drugs appropriately (e.g., adhere to dosing guidelines, adjust for renal / hepatic impairment, use lowest effective dose)
e. Educate patients / caregivers to report potential TdP symptoms
| Table 1: Risk Factors for Drug-induced QTc-Prolongation2,5,7 | |
|---|---|
| Female sex | Using ≥ 2 QTc-prolonging drugs |
| Age > 65 | CYP450 drug interactions |
| Abnormal ECG history | Hepatic impairment |
| Structural heart disease | Renal impairment |
| Bradycardia | Rapid infusion rate (IV medications |
| Electrolyte disturbances | High doses / concentrations |
Clearly, with no standard way of measuring drugs’ QT-prolonging / TdP risk and a lack of consensus among hospice clinicians as to how much this issue matters, you’re going to get conflicting alerts and varying opinions on what to do about them. With that said, when a clinician’s best judgement concludes that drug therapy adjustment is potentially warranted in a hospice patient, we find the above process to be reasonable.
Written by: OnePoint Patient Care Clinical Team
Joseph Solien, PharmD, BCGP, BCPP – Vice President of Clinical Services
Melissa Corak, PharmD, BCGP – Senior Clinical Pharmacist
John Corrigan, PharmD, BCGP – Clinical Pharmacist
References: