The Prognostic Impact of Volume Substitution on Cardiac Strain and the Development of Postoperative Atrial Fibrillation after Cardiac Surgery

Abstract Background Postoperative atrial fibrillation (POAF) represents a common complication after cardiac valve or coronary artery bypass surgery. Etiologically, multifactorial causes such as the patients' age, weight, comorbidities or local remodeling proved a strong association with this common arrhythmia. While strain of atrial tissue is known to induce atrial fibrillating impulses, less attention has been paid to potentially strain-promoting values during the peri- and post-operative period. Therefore, we aimed to determine the association of peri- and post-operative volume substitution on markers of cardiac strain and subsequently its impact on the promotion and development of POAF. Methods In this prospective observational study 271 patients undergoing elective cardiac surgery in our Medical University were enrolled (median age: 69 years [IQR: 60–75 years]; 195 [72%] male gender). Intra- and post-operative data was collected from anesthesiologic and intensive care unit protocols. Multivariate binary logistic regression analysis was used to identify the prognostic value of volume substitution on the development of POAF. Results A total of 123 (45.4%) individuals developed POAF. The average intra-operative transfusion volume was significantly elevated in the POAF subgroup (605.6ml [POAF] vs. 227.1ml [non-POAF]; p<0.001). Moreover, the fluid balance within the first 24 hours after surgery was significantly higher in patients developing POAF (+1129.6 ml [POAF] vs. +544.9 ml [non-POAF]; p=0.044). We found that N-terminal pro brain natriuretic peptide (NT-proBNP) values were significantly elevated in patients that received any volume substitution (2860.0 pg/mL [Transfusion] vs. 1486.5 pg/mL [no-Transfusion]; p=0.002). In line with those results, the postoperative fluid balance was also found to have a direct and significant correlation with postoperative NT-ProBNP values (r=0.287, p=0.002). Of note, the amount of substituted volume proved to be a strong and independent predictor for POAF with an adjusted odds-ratio (OR) per one standard deviation (1-SD) of 2.49 (95% CI: 1.25–4.96; p=0.009). Conclusion Within the present analysis we were able to demonstrate that substitution of larger transfusion volumes presents a strong and independent predictor for the development of POAF. Via the observed distinct association with NT-proBNP values, it can reasonably be assumed that post-operative atrial fibrillating impulses are triggered via volume-induced cardiac strain.