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.