Serum chloride and sodium interplay in patients with acute myocardial infarction and heart failure with reduced ejection fraction

Background—Serum chloride levels were recently found to be independently associated with mortality in heart failure (HF). Methods and Results—We investigated the relationship between serum chloride and clinical outcomes in 7195 subjects with acute myocardial infarction complicated by reduced left ventricular function and HF. The studied outcomes were all-cause mortality, cardiovascular mortality, and hospitalization for HF. Both chloride and sodium had a nonlinear association with the studied outcomes (P<0.05 for linearity). Patients in the lowest chloride tertile (chloride ≤100) were older, had more comorbidities, and had lower sodium levels (P<0.05 for all). Serum chloride showed a significant interaction with sodium with regard to all studied outcomes (P for interaction <0.05 for all). The lowest chloride tertile (≤100 mmol/L) was associated with increased mortality rates in the context of lower sodium (≤138 mmol/L; adjusted hazard ratio [95% confidence interval] for all-cause mortality=1.42 (1.14–1.77); P=0.002), whereas in the context of higher sodium levels (>141 mmol/L), the association with mortality was lost. Spline-transformed chloride and its interaction with sodium did not add significant prognostic information on top of other well-established prognostic variables (P>0.05 for all outcomes). Conclusions—In post–myocardial infarction with systolic dysfunction and HF, low serum chloride was associated with mortality (but not hospitalization for HF) in the setting of lower sodium. Overall, chloride and its interaction with sodium did not add clinically relevant prognostic information on top of other well-established prognostic variables. Taken together, these data support an integrated and critical consideration of chloride and sodium interplay