What is the normal QTc threshold for women?

• A. <470 ms
• B. <450 ms
• C. <480 ms
• D. <460 ms

Answer: (A)

QTc adjusts the QT interval for heart rate so we can compare repolarization across different rhythms. Women naturally have a slightly longer QT interval, so the upper limit of normal QTc is higher than in men—about 470 milliseconds. When QTc reaches or exceeds this threshold, it’s considered prolonged and raises the risk of torsades de pointes, especially with drugs that prolong QT or with electrolyte disturbances. That’s why a QTc under 470 milliseconds is regarded as normal for women. Other thresholds like 450, 460, or 480 milliseconds aren’t as appropriate for women, with 450 typically used for men and 480 often viewed as a more lenient or borderline value in some contexts.