The objective of this study was to measure the normal variation of QT dispe
rsion (QT(d)) with respect to age and gen der. The QT interval is a measure
of the duration of ventricular depolarization and repolarization, while th
e QT(d) is a measure of the variability of the ventricular recovery time. T
he QT(d) has been suggested as a means of identifying those patients at ris
k for sustained ventricular tachyarrythmias and sudden cardiac death (SCD).
A total of 250 patients (120 women, 130 men; age range 20-86 years) were r
ecruited for this study. The QT intervals were measured in each of the 12 s
tandard leads of the electrocardiogram. Data are presented as mean (mu) +/-
SD. The QT(d) did not vary significantly within the same gender. A signifi
cant difference (P < 0.001) was noted in QT(d) between men (age [mu] = 53.3
+/- 15.6 years, QT(d) = 0.044 +/- 0.019 s) and women (age [mu] = 52.1 +/-
15.1 years, QT(d) = 0.034 +/- 0.015 s). Overall, men had a greater QT(d), w
hile women had a longer QT. In conclusion, we found that men had a longer Q
T(d), which may explain the increased risk of SCD. However, women have a lo
nger QT interval with a smaller QT(d). A longer QT(min), as opposed to a lo
nger QT(max), is responsible for the shorter QT(d) in women. This longer QT
(min) in women may predispose to an increased risk of drug induced torsades
de pointes.