Abstract 038: A Novel Histology Based Classification System to Identify Patients at Risk for Postoperative Atrial Fibrillation
Postoperative atrial fibrillation (PoAF) is a common complication in up to 40% of patients after cardiac surgery, increasing morbidity, hospital stay and costs. The myocardial substrate underlying PoAF is not fully characterized. The objective was to assess the impact of atrial fibrosis on incident AF and define the fibrosis threshold level predictive of PoAF.
Methods: Right atrial appendages removed from patients undergoing elective CABG with no history of AF or class III/IV heart failure were used to characterize the ratio of collagen to myocardium (Masson’s trichrome; NIH ImageJ software; Fig A), which was correlated with incident AF. Percentage burden of fibrosis predictive of PoAF with high sensitivity and specificity was determined by ROC curve.
Results: Of 28 patients (67±10 years, 64% males), 15 had PoAF. There were no age, gender or comorbidity differences between groups. Compared to the group that remained in sinus rhythm, patients with PoAF had a significantly higher ratio of extracellular collagen to myocardium (45±16% vs. 5±4%, p <0.001; Fig B). A threshold ratio of 12.7% collagen to myocardium (ROC area under the curve 0.997; z statistic 137; P<0.0001) with 96% sensitivity and 97% specificity identified those with PoAF (Fig C). A classification system based on histological extent of atrial fibrosis is proposed for identifying patients at risk for PoAF (Fig D).
Conclusion: Ongoing studies will confirm the predictive value of this new classification system for identifying the atrial substrate predisposing PoAF and correlate with preoperative cardiac imaging and circulatory serum biomarkers to provide a novel noninvasive tool to stratify patients at risk for PoAF.
- © 2013 by American Heart Association, Inc.