AV Pacing in the Post Cardiac Surgery Patient

I had someone reach out recently asking why some of our cardiac surgery patients come out with both atrial and ventricular pacing wires instead of just V wires. They were used to seeing patients after CABG with only ventricular wires and wanted to understand when and why we use AV pacing. It’s a great question and one that comes up a lot in the CVICU.

Let’s break it down.

V-Wires After CABG: A Safety Net

In patients who’ve had a CABG, it’s common for the surgeon to place just ventricular wires. These are typically used as a backup, in case the patient becomes bradycardic or even asystolic after surgery. Most of the time, we’re not using them actively, but they’re there if we need to start ventricular pacing for rate support.

But Valve Surgeries Are a Different Story

When we’re talking about valve surgeries, like an aortic valve replacement, mitral valve repair, or even tricuspid surgery, things change a bit. These patients are at a higher risk for heart block after surgery.

Cross section of the heart showing the AV node and conduction pathway

Here’s why: If you look at a cross-section of the heart, right between the mitral and tricuspid valves is where the AV node sits. So during valve surgery, whether it’s due to inflammation, edema, or just the proximity of the surgical work, there’s a risk of damaging or temporarily stunning the conduction system.

This can lead to complete heart block, either right away or in the hours to days after surgery. Because of that, the surgeon will often place both A and V wires in these patients — either because they’re already in a heart block post-op, or because the team knows there’s a high chance they could go into one.

The Goal: AV Synchrony and Atrial Kick

If the patient does end up needing pacing, AV pacing lets us maintain atrioventricular synchrony, meaning the atria and ventricles are working together. This helps preserve the atrial kick, which can make a big difference in cardiac output, especially in patients with stiff ventricles or poor diastolic filling.

That “kick” can be worth up to 30% of the cardiac output, and in a fresh post-op heart, that’s something we don’t want to lose.