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Whats New in the
Patient Safety World
March 2023
Overdiagnosis of
Long QT Syndrome
Weve done multiple
columns on Torsade de Pointes and the importance of recognizing prolonged QT
intervals (see list below). But we also cautioned that we can
overdo it. In our December 2022 What's New in the Patient Safety World
column Unintended
Consequences of a QTc Formula? we highlighted a study in the oncology literature (Richardson 2022) which suggested that use of certain
formulas for calculating the QTc interval may erroneously preclude some
patients from receiving the most appropriate chemotherapy.
Now another recent
study (Bains
2023) found that 16% of patients referred to the Mayo Clinic with a diagnosis of Long QT Syndrome (LQTS) were
misdiagnosed or overdiagnosed. The main cause of LQTS
misdiagnosis or overdiagnosis was a prolonged QTc interval secondary to
vasovagal syncope (30%), followed by a seemingly positive genetic test result
for a variant in 1 of the main LQTS genes that was ultimately deemed not to be
of clinical significance (23%), positive family history of SCD that was deemed
unrelated to LQTS (16%), isolated/transient QT prolongation (15%), or
misinterpretation of the QTc interval as a result of inclusion of the U-wave
(14%).
The authors conclude
that knowing those 5 main determinants of discordance between a previously
rendered diagnosis of LQTS and full diagnostic reversal or removal increases
awareness and provides critical guidance to reduce the burden of overdiagnosed LQTS.
There are important
practical implications in avoiding misdiagnosis of LQTS. Many patients
diagnosed as having LQTS are restricted from participating in competitive
sports. Others have received unnecessary pharmacotherapy (eg.
beta blockers). Yet others have received implantable cardioverter
defibrillators (ICDs). The accompanying editorial (Wilde 2023) concludes that to make hasty diagnosis of a disease that requires
life-long treatment is inappropriate, especially when this is done without the
support of adequate specific experience.
So, while it is
important to identify patients who may be at risk for Torsade de Pointes
because of QT interval prolongation, it is also important to avoid misdiagnosis
or overdiagnosis of LQTS that might lead to long-term inappropriate
interventions.
Some of our prior columns on QT interval prolongation and Torsade de Pointes:
June 29, 2010 Torsade de Pointes: Are Your Patients At
Risk?
February 5, 2013 Antidepressants and QT Interval Prolongation
April 9, 2013 Mayo Clinic System Alerts for QT Interval
Prolongation
June 10, 2014 Another Clinical Decision Support Tool to
Avoid Torsade de Pointes
April 2015 Anesthesia and QTc Prolongation
October 10, 2017 More
on Torsade de Pointes
June 25, 2019 Found Dead in a Bed Part 2
April 7, 2020 Patient Safety Tidbits for the COVID-19 Pandemic
February 16, 2021 New
Methods for QTc Monitoring
November 22, 2022 The Apple Watch and Patient
Safety
December 2022 Unintended Consequences of a QTc Formula?
References:
Richardson DR, Parish PC, Tan X, et al. Association of QTc Formula With the Clinical Management of Patients With Cancer. JAMA Oncol 2022; 8(11): 1616-1623 Published online September 22, 2022
https://jamanetwork.com/journals/jamaoncology/article-abstract/2796766
Bains S, Neves R, Bos J, et al. Phenotypes of Overdiagnosed Long QT Syndrome. J Am Coll Cardiol 2023; 81(5): 477-486
https://www.jacc.org/doi/abs/10.1016/j.jacc.2022.11.036
Wilde A, Schwartz P,
et al. Long QT Syndrome, a Diagnosis That Warrants Expert Opinion and Expert
Centers. J Am Coll Cardiol 2023; 81(5): 487-489
https://www.jacc.org/doi/10.1016/j.jacc.2022.11.037
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Whats New in
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