Abstract: Objective To investigate the serum changes of endogenous nociceptin / orphanin FQ (N / OFQ) and C reactive protein (CRP) before total knee arthroplasty in elderly patients with atrial fibrillation, and to explore its significance. Methods The patients with paroxysmal atrial fibrillation were divided into PAAFⅠ subgroup (≤75 years old, n=32) and PAAFⅡ subgroup (＞75 years old, n=31). At the same time, the patients with persistent atrial fibrillation were divided into PEAFⅠ subgroup (≤75 years old, n=27) and PEAFⅡ subgroup (＞75 years old, n=32). Forty-seven patients with non-AF sinus rhythm were used as control group. The levels of N/OFQ and CRP, left atrial dimension (LAD), ejection fraction of left ventricle (LVEF), fasting triglyceride (TG), low-density lipoprotein (LDL-C) and high-density lipoprotein cholesterol (HDLC) were measured, and the above-mentioned indicators were analyzed. Results The LAD value was higher in PAAF group and PEAF group than that in control group. The LAD value was higher in PEAF group than that in PAAF group, and the LVEF and TG values were lower in PAAF group and PEAF group than those in control group. The values of LVEF, TG, HDL-C and LDL-C were lower in PEAF group than those of PAAF group. The values of HDL-C and LDL-C were higher inPAAF group than those of control group, and the values of HDL-C and LDL-C were lower in PEAF group than those of control group. The levels of N/OFQ and CRP were higher in PAAF group and PEAF group than those in control group, and the levels of N/OFQ and CRP were significantly higher in PEAF group than those in PAAF group (P＜0.05). The level of N/ OFQ was higher in PAAFII subgroup than that in PAAFI subgroup, and the level of N/OFQ was significant higher in PEAF Ⅱ subgroup than that in PEAFⅠ subgroup (P＜0.05). There was no significant difference in CRP level between groups (P > 0.05). Multiple Logistic regression showed that N/OFQ elevation (OR=2.911,95％CI:1.291-6.564) and CRP elevation (OR= 4.636, 95％CI:1.042-20.616) and LAD enlargement (OR=1.369,95％CI:1.000-1.875) were the risk factors of AF. LVEF elevation (OR=0.489,95％CI:0.302-0.792) was the protective factor of AF. The levels of N/OFQ and CRP were positively correlated with LAD and negatively correlated with TG, LDL-C and HDL-C in patients with atrial fibrillation. N/OFQ and CRP levels were positively correlated. The age of AF patients was positively correlated with N/OFQ level, but not with CRP level. LVEF was negatively correlated with N/OFQ level in patients with atrial fibrillation, but no correlation with CRP level. The result of ROC curve analysis showed that the area under the curve of N/OFQ for predicting atrial fibrillation was 0.949 (95％CI：0.917-0.982, P＜0.01), the area under the curve of CRP for predicting atrial fibrillation was 0.855 (95％CI: 0.775- 0.935, P＜0.01), the area under the curve of joint forecasting factor for predicting atrial fibrillation was 0.960 (95％CI: 0.933- 0.987, P＜0.01). Conclusion N/OFQ and CRP are closely related to the occurrence of atrial fibrillation in the elderly, and N/ OFQ is more advantageous in assessing cardiac function before total knee replacement in elderly patients with atrial fibrillation.

Key words: atrial fibrillation, aged, endorphins, C-reactive protein, ventricular function, left, lipids