Abstract: AIM:To investigate the effects of serum plasma procalcitonin and interleukin-6 in evaluating the severity of acute heart failure with secondary pulmonary infection. METHODS: A total of 184 patients with acute heart failure were included in the study. Based on the clinical pulmonary infection scores and sputum culture results, patients were divided into acute heart failure group and heart failure with secondary pulmonary infection group. Venous blood was collected from patients 1, 2, 3, and 5 days after onset of heart failure and serum interleukin-6 (IL-6) and procalcitonin (PCT) changes were detected. RESULTS: On the first and second days after the occurrence of heart failure, the inflammatory response indicators in both groups were significantly higher than normal. Procalcitonin (PCT) levels peaked on the second day after onset in acute heart failure group and decreased significantly on the third and fifth day. The rate of decrease was >50%. On the third day, serum procalcitonin was ≥2.0 μg/L in 59% of the patients in the acute heart failure group. Serum procalcitonin levels were also significantly higher in heart failure with secondary pulmonary infection group on the first and second days. No statistically significant difference was observed between groups. Serum procalcitonin levels kept increasing on the third and fifth days and/or the rate of decrease was <30%. The levels of interleukin-6 slowly increased in the two groups, peaked on the fifth day and the rate of decline was not obvious. No statistically significant difference was observed between groups (P<0.05). CONCLUSION: After acute heart failure, the dynamic changes of serum procalcitonin levels are helpful in predicting the severity and prognosis of heart failure.