Calcitonin Level and New-onset of Post-Operative Atrial Fibrillation

Inclusion Criteria: * 1\. Clinical diagnosis of no history of atrial fibrillation/flutter; * 2\. Heart rate ≥50 beats/min; * 3\. EF \> 40%; * 4\. No history of emergency cardiac surgery in our hospital; * 5\. Participate voluntarily and sign the informed consent, and can accept the follow-up of more than 2 years. Exclusion Criteria: * 1\. Atrial fibrillation/flutter; * 2\. Left atrial diameter \>5.5cm; * 3\. Previous cardiac surgery or emergency surgery (\<12h); * 4\. Sick sinus node syndrome; * 5\. Ventricular preexcitation or preexcitation syndrome; * 6\. Second degree or above atrioventricular block; * 7.Myocardial infarction occurred within 7 days; * 8\. Infection, sepsis, rheumatic or inflammatory diseases; * 9\. Abnormal liver and kidney function (three times higher than the upper limit of normal); * 10\. Uncontrolled hyperthyroidism, severe obstructive sleep apnea, and acute alcoholism; * 11\. Any ischemic events (stroke or TIA) that occurred 180 days before the participant signed the informed consent, or any known unresolved complications from previous stroke/TIA;Thrombosis; * 12\. Patients with other diseases requiring radiotherapy, chemotherapy and long-term hormone therapy; * 13\. Patients' life expectancy makes it unlikely that follow-up will be completed; * 14\. Participate in, or are expected to participate in, other clinical trials of any drugs, devices or biologics during the study period; * 15\. Patients with contraindications to dynamic electrocardiogram; * 16\. Patients who are unwilling or unable to fully comply with study procedures and follow-up.