Predictors of Postoperative Atrial Fibrillation After Coronary Artery Bypass Grafting: A Prospective Cohort Study

We included patients undergoing isolated CABG or CABG with (Aortic and / or Mitral) valve replacement with an age group between 18 and 70 years old.

Patients diagnosed preoperatively with AF or have history of AF, patients with history of existing pre-operative rhythm other than normal sinus rhythm (NSR), patients with impaired systolic function (Ejection fraction (EF) < 30%), patients with end stage renal disease (ESRD) on hemodialysis and patients who refused to participate in the study were excluded from the study.

Sample Size and Sampling: Using PASS program, setting alpha error at 5% and power 80%. Results from previous study Ducceschi et al. (6) showed that left atrial (LA) diameter was an independent factor affecting AF post CABG. Based on this, the needed sample was 123 cases undergoing CABG, including at least 24 patients with dilated LA.

All individuals were monitored for AF during the postoperative ICU stay with continuous ECG (5-leads) monitor, daily 12-lead ECG recording to confirm an episode of AF. AF was considered if P wave was absent before the QRS complex together with irregular ventricular rhythm on the rhythm strips.

Only AF episodes lasting > 5 minutes were counted. In the present study, the following data, as potential predictors of POAF, was collected from every eligible participant; age, sex, smoking and left atrial (LA) diameter based on formal preoperative Trans-thoracic Echocardiography. Serum potassium (K+) level was routinely measured postoperatively on ICU admission and every 2 hours and on demand (if arrhythmia occurs or suspected abnormal potassium level). It was recorded for statistical analysis on admission and every 12 hours and on demand until the patient was discharged.

Serum Magnesium (Mg++) level was measured routinely measured postoperatively on ICU admission and every 24 hours and on demand (if arrhythmia occurs or suspected abnormal magnesium level). It was recorded for statistical study on admission and every 24 hours and on demand until the patient was discharged.

Other parameters such as valve replacement (Aortic and/or Mitral) during the same operative setting, CHA2DS2-VASc score (Congestive heart failure, Hypertension [blood pressure >140/90 mm Hg or treated hypertension on medication], Age ≥75 years, Diabetes mellitus, prior Stroke or transient ischemic attack or thromboembolism, vascular disease, Age 65 to 74 years, Sex category [female sex] ), and post-operative inotropic support usage were recorded.