Hyponatremia in takotsubo syndrome is associated with attenuated in-hospital improvement of left ventricular ejection fraction and higher long-term mortality

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Introduction: The clinical relevance and long-term mortality in hyponatremic patients with takotsubo syndrome (TTS) remain poorly elucidated.Aim: We sought to investigate whether hyponatremia identified in TTS patients influenced in-hospital and long-term outcomes in this group of patients.Material and methods: Among 7771 patients hospitalized with acute myocardial infarction, TTS was diagnosed in 100 (1.3%) patients.Hyponatremia on admission was defined as sodium level < 135 mmol/l.In-hospital clinical characteristics and long-term all-cause mortality were assessed in hyponatremic and normonatremic TTS patients.Results: On admission, hyponatremia was identified in 14 (14%) TTS patients.Hyponatremic patients were older (78.5 vs. 69 years, p = 0.013) and more frequently had a history of stroke (7.1 vs. 0%, p = 0.046) or heart failure (50 vs. 12.8%, p = 0.001) than normonatremic patients.Hyponatremic subjects more often demonstrated ST-segment elevation (78.6 vs. 48.8%,p = 0.033) and apical TTS type (100 vs. 81.4%,p = 0.021).During the index hospitalization, hyponatremic versus normonatremic TTS patients showed attenuated improvement of left ventricular ejection fraction (0 [0-5] vs. 10 [0-20]%, p = 0.039) and its lower values at discharge (40 [35-45] vs. 50 [42-55]%, p = 0.032).Within a median observation period of 53 months, higher all-cause mortality was found in hyponatremic versus normonatremic TTS patients (35.7 vs. 15.1%,p = 0.038).Cox proportional hazard regression showed that sodium plasma level on admission was independently associated with long-term mortality (HR = 0.919, 95% CI: 0.866-0.975,p = 0.005).Conclusions: Our pilot findings indicate that hyponatremia, observed in every seventh TTS patient, was associated with lower in-hospital left ventricular ejection fraction improvement and higher long-term all-cause mortality.Key words: hyponatremia, long-term survival, takotsubo syndrome. S u m m a r yTakotsubo syndrome (TTS) patients with hyponatremia have specific clinical characteristics.Hyponatremia, identified in every seventh TTS patient on admission, was associated with higher long-term mortality and attenuated in-hospital improvement of left ventricular ejection fraction.For clinicians, it is important to consider electrolyte imbalance when assessing a patient's prognosis and possibly adjusting a treatment regimen.Further studies are needed to explain the mechanism of unfavorable clinical outcomes in TTS patients with hyponatremia.

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