A Double Hit? The Combined Effect of Obesity and Hyponatremia on Mortality in Cardiogenic Shock

Introduction: Cardiogenic shock (CS) is a condition with mortality rates ranging from 40-50%. CS occurs often with myocardial infarction or acute heart failure. Obesity has been associated with improved survival among critically ill and heart failure patients. Hyponatremia is an electrolyte imbalance associated with adverse outcomes in hospitalized patients with heart failure. The interaction between obesity and hyponatremia in the context of CS is poorly understood. This study evaluates the link between obesity and mortality rates among patients with cardiogenic shock, as well as hyponatremia.


Methods: Using the National Inpatient Sample (2018–2022), we identified cardiogenic shock patients with and without hyponatremia. Obesity was classified as Class 1 (BMI 30–34.9), Class 2 (BMI 35–39.9), and Class 3 (BMI ≥40). Survey-weighted logistic regressions estimated crude and adjusted odds ratios (ORs) for mortality adjusting for age, sex, race, Charlson index, income, and hospital factors. Subpopulation analyses compared mortality risk across obesity classes in cardiogenic shock patients with and without hyponatremia.


Results: In cardiogenic shock (CS) patients, obesity Classes 1 and 2 exhibited protective effects, showing decreased in-hospital mortality. Without hyponatremia, obesity Class 1 was associated with a 37.4% reduction in mortality odds, and Class 2 with a 31.1% reduction, However, these protective effects were attenuated in patients with hyponatremia, with Class 1 reducing mortality odds by only 27.4% and Class 2 by 19.3%. In contrast, obesity Class 3 showed no protective effect; it was non-significant without hyponatremia but increased mortality risk by 16% with hyponatremia.


Conclusions: In cardiogenic shock, obesity classes I and II demonstrate a survival advantage that is attenuated in the presence of hyponatremia, while class III obesity (without baseline protection) exhibits a an increase in mortality when hyponatremia is present. These findings suggest an interaction between sodium derangement and higher degrees of adiposity, underscoring the importance of early recognition of hyponatremia and obesity-stratified risk assessment in this population. Prospective studies are warranted to clarify these mechanisms and determine whether correction of hyponatremia can mitigate the excess risk.