Using CT to Prevent Heart Block After Congenital Aortic Valve Surgery

Pictured above: Justin Tretter, MD, and Hani Najm, MD

In congenital aortic valve, root and left ventricular outflow tract (LVOT) surgery, the margin for error can be measured in millimeters. The atrioventricular (AV) conduction axis runs so close to the operative field that even technically successful procedures can leave patients with high-grade heart block and a permanent pacemaker.

A new Cleveland Clinic study suggests that preoperative cardiac CT may help surgeons reduce that risk by estimating the location of conduction tissue they cannot directly see.

“Postoperative AV block remains a significant complication in this surgical territory,” says the study’s lead author, Justin Tretter, MD, a congenital cardiologist, cardiac imager and cardiac anatomist at Cleveland Clinic. “This is relevant across congenital cardiovascular practice, not just pediatrics, because these operations are commonly performed in teens and young adults but can span infancy through later adulthood. When conduction injury occurs, the consequences can be lifelong.”

Using what CT can see to infer what it cannot

Clinical CT cannot directly visualize the conduction system, which courses within the LVOT, often only a few millimeters from the aortic valve. But over more than a decade, Dr. Tretter’s anatomic, histologic and 3D imaging research has helped define which visible structures consistently predict the location of the conduction axis.

Specifically, the central fibrous body (at the base of the aortic valve) and the inferior pyramidal space (between the heart’s four chambers) can help estimate the likely location of the AV node, His bundle and left bundle origin.

“We can’t see the conduction system itself, but we can see structures that tell us where the different parts of the conduction system are likely to be,” Dr. Tretter says. “That has implications not only for surgery, but also for transcatheter and other interventional procedures in which conduction injury is a concern.”

CT guidance linked to fewer pacemakers

In the study, recently published in The Journal of Thoracic and Cardiovascular Surgery, investigators evaluated 53 patients (mean age 32) with congenital aortic valve, root or LVOT disease who underwent presurgical CT and surgery at Cleveland Clinic from 2022 to 2025. The most common diagnoses were bileaflet and unileaflet aortic valves. Seventy-two percent (72%) of patients had aortic valve repair, while the rest had valve replacement.

Before surgery, CT was used to estimate the location of the AV node, His bundle and left bundle origin relative to the aortic virtual basal ring plane. Those estimates helped guide surgical avoidance of the conduction axis.

Following surgery, just one patient (1.9%) developed high-grade AV block requiring a permanent pacemaker. For comparison, the rate was approximately 10% in a prior Cleveland Clinic cohort that did not incorporate CT-based estimation of the conduction axis.

“Of course, we have to be appropriately cautious, but this was very much an apples-to-apples comparison,” Dr. Tretter says. “The surgical team and techniques were the same in both studies. The one change was that we began using CT to estimate where the conduction system was likely positioned.”

Although the findings require validation in larger, prospective multicenter studies, they add to growing evidence that CT-based estimation can help clinicians avoid, or in other settings target, the conduction system. Similar evidence is emerging in structural heart interventions and conduction-system pacing, he adds.

“Across cardiovascular care, the science is pointing in the same direction,” Dr. Tretter notes. “If we better understand where the conduction system is, we can make safer, more precise decisions for patients.”

Modifying surgery based on CT data

At Cleveland Clinic, CT is already a routine part of planning for congenital aortic valve surgery. In addition to defining valve and root anatomy and helping determine whether repair or replacement is feasible, the same dataset can now be used to estimate the course of the conduction axis.

That information can influence operative planning. Depending on the anatomy and procedure, the surgeon may make targeted modifications in dissection, suture placement or the overall operative approach to avoid the predicted location of conduction tissue. A table published in the study details modifications for specific surgical procedures.

“The changes may be subtle, but their impact can be significant,” says Hani Najm, MD, Chair of Pediatric and Adult Congenital Heart Surgery at Cleveland Clinic. “Once a patient is identified as high risk for conduction injury, I further examine the membranous septum and modify my suture technique to avoid deep penetration of needles to prevent the injury.”

Broader adoption is feasible

Drs. Tretter and Najm say the CT-based approach should be feasible at other centers performing congenital heart procedures, although adoption will require training and close collaboration between imagers and surgeons.

A 2025 study in Heart Rhythm found that the standardized method was reproducible, with excellent interobserver agreement.

“We trained cardiac bioengineers, not cardiac imagers, to perform the assessments in that study,” Dr. Tretter says. “Even people with limited cardiac imaging experience can learn to do this.”

At the same time, advances in cardiac CT over the past decade have made scans faster and reduced radiation exposure, further strengthening CT’s role in preoperative planning.

“The question has shifted from ‘Should we get cardiac CT before surgery?’ to ‘Why shouldn’t we?’” Dr. Tretter says. “If a CT is already being obtained for surgical planning, then the information needed to estimate conduction risk is already in the dataset. Learning how to use it may help us reduce AV block and improve outcomes.”