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

Although the onset of takotsubo syndrome (TTS) may be accompanied by hyponatremia, the clinical relevance and long-term mortality in a group of hyponatremic TTS patients remains poorly elucidated.

We sought to investigate whether hyponatremia identified in TTS patients influenced in-hospital and long-term outcomes in this group of patients.

Among 7771 patients with acute myocardial infarction hospitalized between 2012-2019, TTS was diagnosed in 100 patients (1.3%). Hyponatremia on admission was defined as sodium level <135 mmol/L. In-hospital clinical characteristics and the long-term all-cause mortality were assessed in hyponatremic and normonatriemic TTS patients.

Admission hyponatremia was identified in 14 (14%) of TTS patients. Hyponatremic patients were older (78.5 vs 69 y, P=0.013) and more frequently had history of stroke (7.1 vs 0%, P=0.046) or heart failure (50 vs 12.8%, P=0.001) than normonatriemic patients. Hyponatremic subjects more often demonstrated ST-segment elevation myocardial infarction (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 normonatriemic TTS patients showed lower improvement of left ventricular ejection fraction (0 [0-5] vs 10 [0-20]%, P=0.039) and its lower values on discharge (40 [35-45] vs 50 [42-55]%, P=0.032). Within median observation of 53 months higher all-cause mortality was found in hyponatremic versus normonatriemic TTS patients (35.7 vs 15.1%, P=0.038). By Cox proportional hazard regression lower sodium plasma level on admission was identified as an independent predictor of higher long-term mortality (HR 0.919, 95%CI 0.866-0.975, P=0.005).