The sodium-chloride difference: A marker of prognosis in patients with acute myocardial infarction.

Background: The difference between serum sodium and chloride ion concentrations (SCD) may be considered as a surrogate of a strong ion difference and may help to identify patients with a worse prognosis. We aimed to assess SCD as an early prognostic marker among patients with myocardial infarction.

Methods: Data of 594 consecutive patients with acute myocardial infarction treated with PCI (44.9% STEMI patients; 70.7% males) was analysed for SCD in relation to their 30-day mortality. A restricted cubic spline regression model was used to study the relationship between mortality and SCD. Cox regression models were used to assess the association between SCD and the mortality risk.

Results: Patients with Killip class ≥3 had lower SCD values in comparison to patients with Killip class ≤2: (32.0 [30.0-34.0] vs. 33.0 [31.0-36.0], p = .006). The overall 30-day mortality was 7.7% (n = 46). There was a significant difference in SCD values between survivors and non-survivors groups of patients (median (IQR): (33.0 [31.0-36.0] vs. 31.5 [28.0-34.0] (mmol/L), p = .002). The restricted cubic splines model confirmed a non-linear association between SCD and mortality. Patients with SCD <30 mmol/L (in comparison to SCD ≥30 mmol/L) had an increased mortality risk (unadjusted HR 2.92, 95% CI 1.59-5.36, p = .001; and an adjusted HR 2.30, 95% CI 1.02-5.19, p = .04).

Conclusions: Low SCD on admission is associated with an increased risk of 30-day mortality in patients with acute myocardial infarction treated with PCI and may serve as a useful prognostic marker for these patients.