Rate-dependent QRS prolongation during exercise testing associated with hyperkalemia
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Updated: Aug 23, 2026

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Published on: June 20, 2020
Hirokazu Shiraishi1, Masayuki Hyogo, Kazuya Ishibashi
1Kyoto Perfectual University of Medicine, Kyoto, Japan. siraishi@f7.dion.ne.jp
Abstract:
The present case showed gradual increase of QRS duration from 100 ms up to 180 msec during an ergometer exercise test along with the heart rate increase. After exercise, QRS duration shortened and normalized. Laboratory test showed hyperkalemia (K = 8.0 mEq/l). T1 myocardial scintigraphy revealed exercise-induced transient ischemia in posterolateral region of left ventricle. Coronary angiography showed significant stenosis in the distal portion of left circumflex coronary artery. The increase of QRS duration was possibly due to the combination of hyperkalemia and the effect of mexiletine. The rate dependent blocking effect on sodium channel of mexiletine might be intensified under hyperkalemia.
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