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Quantitative relationship between plasma potassium levels and QT interval in beagle dogs
G Hanton1, A Yvon, J-P Provost
1Pfizer Global Research and Development, ZI Pocé-sur-Cisse, BP 159, F-37401 Amboise Cedex, France. gilles.hanton@pfizer.com
Laboratory Animals
|April 14, 2007
Summary
Hypokalemia, or low potassium levels, in dogs treated with furosemide correlates with prolonged QT intervals. This relationship is stronger in females and can be corrected using a new formula.
Area of Science:
- Veterinary Pharmacology
- Cardiovascular Physiology
Background:
- The QT interval on an electrocardiogram (ECG) reflects cardiac repolarization.
- Electrolyte imbalances, particularly hypokalemia, can significantly affect cardiac repolarization.
Purpose of the Study:
- To quantify the relationship between plasma potassium concentrations and QT interval duration in dogs.
- To develop a formula for correcting QT interval based on potassium levels and heart rate.
Main Methods:
- Administered increasing doses of furosemide (5-60 mg/kg) to beagle dogs.
- Recorded ECGs and measured plasma potassium levels concurrently.
- Analyzed the correlation between plasma potassium and QT/QTc intervals, noting sex differences.
Main Results:
- Furosemide induced hypokalemia, which was associated with increased QT and corrected QT (QTc) intervals.
- A negative linear correlation was observed between plasma potassium and QT/QTc duration.
- The correlation was steeper in females than males, especially when potassium dropped below 3.3 mmol/L.
- T-wave morphology changes (flattening, notching, inversion) were linked to hypokalemia.
Conclusions:
- Hypokalemia is quantitatively linked to prolonged QT and QTc intervals in dogs.
- A sex-specific relationship exists, with a stronger effect in females.
- A formula for correcting QT intervals for both potassium and heart rate was established.
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