Published: May 12, 2026
Norton Heart & Vascular Institute has joined a select group of North American centers in a landmark randomized clinical trial aimed at reducing one of cardiac surgery’s most common and consequential complications: postoperative atrial fibrillation (POAF).
The Louisville, Kentucky, site is among just 13 across North America participating in the BoxX-NoAF trial. While the network expected to expand to approximately 75 locations in the future, no other local sites are currently participating.
Postoperative atrial fibrillation affects more than half of patients undergoing cardiac surgery, depending on individual risk profiles and procedure type. Beyond its immediate clinical burden, POAF is associated with worse short- and long-term outcomes, including increased risk of stroke, prolonged hospital stays, and higher rates of readmission.
The BoxX-NoAF trial is a prospective, randomized clinical study evaluating whether two prophylactic surgical interventions, performed concurrently with planned cardiac surgery, can meaningfully reduce the incidence of new-onset atrial fibrillation (A-fib) in patients who have no prior history of the arrhythmia but carry elevated risk.
Enrolled clinical study patients are randomized to receive either standard cardiac surgery alone or standard cardiac surgery with the addition of two preventive procedures:
Prophylactic ablation using the EnCompass Clamp to create a “box lesion” — a set of surgical ablation lines designed to electrically isolate the posterior left atrium, the region most commonly involved in A-fib initiation and maintenance.
Left atrial appendage (LAA) exclusion using the AtriClip device, which mechanically closes off the LAA — the primary site of thrombus formation in A-fib — to reduce both arrhythmia burden and embolic risk.
Researchers are evaluating two primary outcomes:
The incidence of POAF occurring in the immediate post-surgical period, and the development of clinically confirmed A-fib during long-term follow-up — providing both near-term and durable data on the preventive strategy’s effectiveness.
The BoxX-NoAF trial addresses a critical gap in current cardiac surgical practice: while A-Fib treatment after it develops is well established, standardized prophylactic surgical strategies remain unproven at scale. If the trial demonstrates efficacy, the combined box lesion ablation and LAA exclusion approach could become an important adjunct to routine cardiac surgery for high-risk patients — reducing a complication that today affects tens of thousands of patients annually in the U.S. alone.