Noninvasive pre–op blood test for miR423 molecule could help identify patients at highest risk.
One in three patients who undergo cardiac surgery – such as coronary artery bypass graft (CABG) or heart valve procedures – experience an irregular heartbeat after surgery (postoperative atrial fibrillation or PoAF). PoAF can increase a patient’s risk of problems, including heart failure and stroke, and hospital readmission following surgery. Researchers at Aurora Research Institute and Aurora Cardiovascular Services in Milwaukee have identified a molecule that can be measured with a noninvasive blood test to help predict the patients most at risk of this postoperative complication.

The risk of PoAF increases with patient age, but it is difficult to identify patients at highest risk, especially if there is no presurgical history of atrial fibrillation (AFib) or severe heart ventricle problems. MicroRNAs (miRNAs) are small molecules that help control the actions of genes and protein synthesis and regulate biological processes. Because routine tests used to identify patients at risk of PoAF – including electrocardiogram and biochemical and imaging biomarkers – lack accuracy, the research team hypothesized that miRNA testing could be a better predictive approach.

“The idea behind this study was to quantify circulating miRNAs’ levels in preoperative blood plasma of patients undergoing CABG surgery. Our goal is to develop an accurate, pathophysiology–based risk score index to identify subjects without previous history of AFib who are at risk of PoAF,” Farhan Rizvi, PhD, the study’s lead author, wrote.

The team analyzed preoperative blood samples of 77 patients who went on to have CABG surgery. Forty–one (53.2 percent) developed PoAF. Patients who developed the condition tended to be older (69.7 years ± 8.8 years), and a slightly higher percentage were male compared to those who did not develop PoAF. There were no significant differences in other risk factors—such as high blood pressure, diabetes, previous heart attack, stroke, sleep apnea, etc. – in patients who developed the condition and those who did not. However, levels of one type of miRNA (miR423) circulating in the blood were significantly higher in patients who developed PoAF. The research team’s analysis showed age and miR423 to be independent predictors of PoAF.

“With an ever–increasing aging population in the U.S. that will cross 70 million by 2030, the prevalence of atrial fibrillation is expected to rise to more than 15 million,” said Jasbir Sra, MD, study co–investigator and senior cardiologist at Aurora Health Care in Milwaukee. “We believe this study by our team of investigators quantifies preoperative levels of circulating miRNAs, adding another layer of information to other existing biomarkers and risk factors associated with PoAF that will aid in the development of a predictive model to identify the patients at risk of PoAF.”

The research is part of an ongoing study to develop a pathophysiology–based risk score index that could be considered for clinical application at Aurora St. Luke’s Medical Center in Milwaukee. “This study provides new information that will be used to design a larger clinical study to aid preoperative identification of PoAF risk,” Rizvi noted.

Farhan Rizvi presented “Advance age and circulating miR423 are independent predictors of postoperative atrial fibrillation” at a poster session at the Cardiovascular Aging: New Frontiers and Old Friends conference.