The Montefiore Einstein Anesthesiology Digital Health Lab has conducted the largest observational study analyzing the association between postoperative oral anticoagulation drugs, new-onset postoperative atrial fibrillation (POAF), and the impact on postoperative ischemic stroke after non-cardiac surgery. The results of the retrospective study, which analyzed data from a cohort of more than 250,000 patients across multiple academic centers, were recently published in the journal Nature Medicine.

In partnership with the Montefiore Einstein Cardiology team, researchers in the Department of Anesthesiology found that for patients who do not receive postoperative anticoagulation medication, POAF is associated with an 81 percent higher risk of postoperative ischemic stroke one year after surgery compared to patients who received oral anticoagulation medicine. Study author Dr. Ibraheem Karaye, the Department of Anesthesiology’s Chief of Epidemiology and Population Health Research, explained that it is already established in the literature that postoperative atrial fibrillation is associated with an increased risk of stroke. However, there had not previously been research conducted with such a large cohort examining whether oral anticoagulation medications could modify the relationship between POAF and stroke.

The Montefiore Einstein researchers collaborated with Beth Israel Deaconess Medical Center to conduct the multicenter study. This large cohort was very diverse, especially the patient data analyzed from Montefiore, making the study’s findings even stronger, the researchers explained.

"The essence of the study is to mimic the U.S. population so as to increase generalizability of our findings,” Dr. Karaye explained. “Having these two centers complement each other helps with the diversity piece and the number of patients included and contributes to the strength of the study.”

Study author Dr. Maíra Rudolph, previously the Digital Health Lab Chief and a current first-year Anesthesiology Resident at Montefiore Einstein, said that for this specific retrospective study, the team conducted many sensitivity analyses to account for variables that could impact the results. For example, they conducted a sensitivity analysis looking at nursing notes documenting if patients took the anticoagulation medication. They conducted another analysis that accounted for patients who received the oral anticoagulation medication outside Montefiore Health System.

In addition to these analyses, the research team developed a prediction score that calculates the risk of each patient developing atrial fibrillation based on nine factors including surgical factors and patient demographics.

“This tool allows the physician to know if a patient has an increased risk of atrial fibrillation and if they need to have a closer eye on them and offer them anticoagulation medication,” Dr. Rudolph explained.

Some of the factors that increase the risk of postoperative atrial fibrillation are undergoing thoracic surgery, receiving general anesthesia rather than monitored anesthesia care, a patient body mass index greater than 40, and the patient being over 65 years of age. In addition, patients who undergo emergent surgeries are at a higher risk of developing atrial fibrillation.

Montefiore Einstein Attending Anesthesiologist Dr. Omid Azimaraghi, who is the first author on the study, said this prediction tool will be extremely helpful in identifying which patients require intensive postoperative monitoring to prevent the consequences of new atrial fibrillation after non-cardiac surgery on ischemic stroke.

“We believe that our findings carry significant implications for the approximately 50 million patients in the United States who undergo non-cardiac surgical procedures annually,” Dr. Azimaraghi said. “These patients stand to benefit from intensive monitoring to detect POAF and prompt initiation of oral anticoagulant therapy.”

Department of Anesthesiology Chair Dr. Matthias Eikermann, the principal investigator of this study, emphasized the importance of examining the consequences of atrial fibrillation after non-cardiac surgery – an under-recognized disease.

“In our study of hospital data, only 15 percent of patients who developed atrial fibrillation after surgery were then treated with anticoagulation,” Dr. Eikermann explained. “By contrast, if a cardiologist makes the diagnosis of atrial fibrillation in their office, the majority of patients will receive anticoagulation. Our work will inform future clinical guidance and will help patients undergoing non-cardiac surgery receive the highest level of postoperative care.”