Key result
Mexiletine shortens QT, abolishes electrical and mechanical alternans, and restores normal LV function.
Why the study?
Coupled electrical and mechanical alternans in patients with extreme QT prolongation and alternate LV apical ballooning mimicking Takotsubo cardiomyopathy are rare and not well characterized.
Case Report (n=1)
This case demonstrates that extreme QT prolongation can present with coupled electrical and mechanical alternans mimicking Takotsubo cardiomyopathy, which can be successfully reversed with mexiletine.
May suggest mexiletine role in rare QT prolongation with alternans; hypothesis-generating and requires prospective validation before practice change.
Introduction We report unique and rare findings of coupled electrical and mechanical alternans in a patient with extreme QT prolongation. Methods A 5‐year‐old girl with congenital long QT syndrome type 3 developed alternate left ventricular apical ballooning precipitated by mycoplasma pneumonia and azithromycin exposure. Results During atrial pacing, electrocardiography showed beat‐to‐beat alternation not only in T‐wave morphology but also in QRS configuration, ST segment, and QT interval. These electrical changes were tightly associated with mechanical alternans: beats with markedly prolonged QT intervals showed normal left ventricular (LV) contraction, whereas beats with shorter QT intervals and ST elevation exhibited LV apical ballooning. Treatment with mexiletine shortened the QT interval, abolished both electrical and mechanical alternans, and restored normal LV function. Conclusions Alternate LV apical ballooning mimicking Takosubo cardiomyopathy can be seen in a patient with extreme QT prolongation. These findings probably reflected a functional intraventricular conduction block due to marked spatial heterogeneity of repolarization between the LV base and apex.
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Saprungruang et al. (2026) conducted a case report in Congenital long QT syndrome type 3 with alternate left ventricular apical ballooning (n=1). Mexiletine was evaluated. Treatment with mexiletine shortened the QT interval, abolished both electrical and mechanical alternans, and restored normal left ventricular function.
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