QRS Duration Index (QRSd Index) Calculator

QRS Duration Index: Explanation and Clinical Context The QRS Duration Index (QRSd Index) is a heart rate–corrected measure of ventricular depolarization duration, initially described by Brodie et al. in 1982. It is calculated by dividing the QRS duration (in milliseconds) by the square root of the RR interval (in seconds). This index accounts for heart rate variability when assessing intraventricular conduction and can be useful in predicting arrhythmic risk, particularly in patients with heart failure or post-myocardial infarction.

A higher QRSd Index indicates more pronounced conduction delay relative to heart rate, which may correlate with increased risk of ventricular arrhythmias and sudden cardiac death. Clinicians can use this measure to complement standard QRS duration analysis in risk stratification.