Nonoptimal serum calcium levels worsen mortality in heart attacks

Serum calcium levels that are either too high or too low appear to aggravate the risk of in-hospital mortality in patients with acute myocardial infarction (AMI), reports a recent study.

The retrospective cohort study included 7,284 patients whose data were retrieved from the Philips eICU Collaborative Research Database. Patients were then grouped into quartiles according to serum calcium measurements after being corrected to albumin levels using the Payne formula. The primary outcome was all-cause in-hospital mortality.

Over the course of the study, 799 patients died, yielding an in-hospital mortality rate of 10.97 percent. There was an apparent U-shaped trend in mortality, with rates peaking in the lowest (15.5 percent) and highest (22.7 percent) quartiles of corrected serum calcium. Meanwhile, patients in the second quartile (serum calcium 8.5 to ≤9.5 mg/dL) had the lowest in-hospital death rate at 8.9 percent.

Adjusted piecewise linear regression model confirmed the U-shaped interaction between serum calcium and death risk. At levels <9.4 mg/dL, the risk of in-hospital mortality shared an inverse correlation with corrected serum calcium (odds ratio [OR], 0.8, 95 percent confidence interval [CI], 0.7–0.9; p<0.001).

On the other hand, all-cause in-hospital mortality increased with increasing corrected serum calcium at levels >9.4 mg/dL (OR, 1.5, 95 percent CI, 1.3–1.8; p<0.001).

“Although we have adjusted for confounders that may have been associated with the results, we cannot rule out some undocumented confounders confounding the results,” the researchers said. “Therefore, it is necessary to conduct higher-level clinical studies in more populations in the future to validate our findings.”