Rate-dependent QRS prolongation during exercise testing associated with hyperkalemia.
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.
Kyoto Perfectual University of Medicine, Kyoto, Japan. siraishi@f7.dion.ne.jp
Hirokazu
H
Shiraishi
Masayuki
M
Hyogo
Kazuya
K
Ishibashi
Norifumi
N
Urao
Masaki
M
Tsukamoto
Natsuya
N
Keira
Satoshi
S
Hirasaki
Takeshi
T
Shirayama
Masao
M
Nakagawa
Hiroaki
H
Matsubara
D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology / Q000627:therapeutic use; D004562:Electrocardiography; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006947:Hyperkalemia / Q000503:physiopathology*; D008297:Male; D008801:Mexiletine / Q000494:pharmacology / Q000627:therapeutic use; D026941:Sodium Channel Blockers / Q000494:pharmacology; D018879:Ventricular Premature Complexes / Q000188:drug therapy
D000889:Anti-Arrhythmia Agents; D026941:Sodium Channel Blockers; D008801:Mexiletine