Low Serum Total Calcium: Influencing Factors of Heart Failure with Preserved Ejection Fraction (HFpEF)

Aim: The impact of low serum total calcium and the prognosis of patients with preserved ejection fraction heart failure (HFpEF) are not fully understood. This study aims to investigate the impact of low serum total calcium on the prognosis of hospitalized patients with HFpEF. Method and Results: This study included 9322 HFpEF patients (average age 72.04 years, 51.86% male), of whom 3408 had low serum total calcium. The patient completed a 1000-day clinical follow-up through telephone interviews, clinical follow-up, or community follow-up after discharge. The endpoints were heart failure (HF) readmission, all-cause mortality, and cardiovascular (CV) events. Multivariable standard Cox proportional hazards models and Fine–Gray competing-risk regression models were performed to evaluate the associations between total serum calcium levels and clinical outcomes. Specifically, Cox models were used for all-cause mortality while Fine–Gray models were applied to endpoints with competing risks, including cardiovascular events and heart failure readmission. This showed that low serum total calcium was an independent factor for HF readmission, all-cause mortality, and CV events and HR at 0.69 (95% CI: 0.61–0.77), 0.85 (95% CI: 0.78–0.92), and 0.65 (95% CI: 0.61–0.70), respectively (all p < 0.001). Conclusions: Low serum total calcium is an indicator related to a lower incidence of heart failure readmission, cardiovascular events, and all-cause mortality in HFpEF patients.