Accurate assessment of heart rhythm can optimize chemotherapy use (ECGs’ default algorithm can kill chemo patients)

Medical Xpress / UNC Lineberger Comprehensive Cancer Center / JAMA Oncology ^ | Sept. 22, 2022 | Joshua F. Zeidner et al

[ConservativeMind]

Using the wrong mathematical formula to assess heartbeat rhythms may lead oncologists to inappropriately stop life-saving chemotherapy, according to research findings. Standardizing the mathematical formulas for measuring heartbeat rhythms with electrocardiograms, and avoiding one commonly used formula, could reduce this unintended outcome, researchers reported.

In their study of different formulas, the researchers discovered one formula, the Bazett formula, was associated with a three-fold increase in the corrected QT interval compared to other formulas used with oncology patients.

"The mathematics that determine a QT formula matters because if an inappropriate formula is used, it could lead oncologists to reduce chemotherapy unnecessarily and possibly affect the potential for cure," said Daniel R. Richardson, MD, MSc. "The differences we found between QT formula were pretty striking and we did not anticipate the magnitude of difference. It certainly has changed how I treat patients."

The investigators found that the Bazett formula resulted in longer QT prolongation periods than two other formulas (Framingham and Fridericia) in 40.9% of ECGs examined; this was concerning as Bazett is the default formula used with many ECG devices.

"We initially discovered this problem while treating a patient with acute promyelocytic leukemia with arsenic trioxide, a drug known to cause QT prolongation. We realized that there was inconsistent guidance about how to assess the QT interval with this drug and what values should lead to dose reductions," said Joshua F. Zeidner, MD. "The clinical protocol that ultimately led to the approval of this drug used a very specific QT formula—Framingham—and we were using a different formula—Bazett—to guide our treatment decisions. Prior to this discovery, most of us were not aware that there were multiple formulas available for corrected QT intervals. The findings from this study have been practice changing as we no longer recommend the Bazett formula for clinical guidance."

[ConservativeMind]

For anyone on chemotherapy, you need to get this to your doctors, “stat.”

[ConservativeMind]

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[TexasGator]

just an example. I have no qualifications in this field.

500 msec is threshold unrelated to chemo for this Calc.

For a heart rate/ Pulse of 72 beats per minute and a QT interval of 0.42 seconds the result is:

■ QTc Interval by Bazett’s method = 0.460 sec OR 460 msec

■ QTc Interval by Fridericia’s equation = 0.446 sec OR 446 msec

■ QTc Interval by Framingham’s algorithm = 0.446 sec OR 446 msec

■ QTc Interval by Hodges’s equation = 0.441 sec OR 441 msec

[sauropod]

Bkmk