Signal-Averaged QRS Duration (SA-QRS) Calculator

Signal-Averaged QRS Duration: Explanation and Clinical Context Signal-Averaged QRS (SA-QRS) duration is a specialized ECG measurement designed to detect subtle conduction abnormalities that predispose patients to ventricular arrhythmias. It is typically performed using high-resolution ECG recordings and computer averaging to reduce noise. Normal SA-QRS duration is generally less than 114 ms.

Values between 114–120 ms are considered borderline, while durations exceeding 120 ms indicate a higher risk of ventricular tachyarrhythmias. This tool is particularly useful in post-myocardial infarction patients, those with cardiomyopathies, or individuals at risk for sudden cardiac death. By quantifying ventricular conduction delay, clinicians can stratify arrhythmic risk and consider preventive strategies, including electrophysiologic testing, antiarrhythmic therapy, or implantable cardioverter-defibrillator (ICD) placement.