SNRT is used to evaluate the health of which cardiac structure?

• A. The AV node
• B. The SA node
• C. The His bundle
• D. The ventricular conduction system

Answer: (B)

SNRT stands for Sinoatrial Node Recovery Time. It specifically gauges how quickly the heart’s natural pacemaker—the SA node—recovers its rhythm after being suppressed by rapid atrial pacing. In an electrophysiology study, you pace the atrium at a fast rate to temporarily override the SA node, then stop and measure the interval from the last paced beat to the first intrinsic P wave. A normal SNRT means the SA node is functioning well and resumes pacing promptly. A prolonged SNRT indicates SA node dysfunction, as seen in sick sinus syndrome. Sometimes a corrected SNRT is used to account for the heart rate, and a persistently long CSNRT reinforces SA node disease. This test is about the SA node, not the AV node, His bundle, or the ventricular conduction system.