The Association Between Serum Calcium Levels and Short-Term Mortality in Patients with Chronic Heart Failure

Background: Patients with chronic heart failure have vulnerable myocardial function and are susceptible to electrolyte disturbances. In these patients, diuretic treatment is frequently prescribed, though it is known to cause electrolyte disturbances. Therefore, we investigated the association between altered calcium homeostasis and the risk of all-cause mortality in chronic heart failure patients.

Methods: From Danish national registries, we identified patients with chronic heart failure with a serum calcium measurement within a minimum 90 days after initiated treatment with both loop diuretics and angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Patients were divided into 3 groups according to serum calcium levels, and Cox regression was used to assess the mortality risk of <1.18 mmol/L (hypocalcemia) and >1.32 mmol/L (hypercalcemia) compared with 1.18 mmol/L-1.32 mmol/L (normocalcemia) as reference. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated.

Results: Of 2729 patients meeting the inclusion criteria, 32.6% had hypocalcemia, 63.1% normocalcemia, and 4.3% hypercalcemia. The highest mortality risk was present in early deaths (≤30 days), with a HR of 2.22 (95% CI; 1.74-2.82) in hypocalcemic patients and 1.67 (95% CI; 0.96-2.90) in hypercalcemic patients compared with normocalcemic patients. As for late deaths (>30 days), a HR of 1.52 (95% CI; 1.12-2.05) was found for hypocalcemic patients and a HR of 1.87 (95% CI; 1.03-3.41) for hypercalcemic patients compared with normocalcemic patients. In adjusted analyses, hypocalcemia and hypercalcemia remained associated with an increased mortality risk in both the short term (≤30 days) and longer term (>30 days).

Conclusion: Altered calcium homeostasis was associated with an increased short-term mortality risk. Almost one-third of all the heart failure patients suffered from hypocalcemia, having a poor prognosis.