Changes in QT Dispersion Magnitude During Respiratory Phases: Role of Maximum Inspiration and Expiration

There is stili controversy about the reliability and prognostic value of QT interval dispersion because of inter- and intra-ohserver variability. The present study hypothesizes that QT interval duration and QT interval dispers ion are affected by the respiratory phases in healthy subjects. Sixty healthy volunteers (38 men, 22 women, mean age=25 ± 3 years) f rom the medical staff comprised the study group. Electrocardiograms were recorded by the same technician at a rate of 50 mm/s during normal breathing, maximum inspiration and expiration. QT dispersion was defined as the difference between the maximal and minimal QT interval measurement occurring among any of the 12 leads. Corrected QT (QTc) interval was calculated according to Bazzet's formula. There was no significant difference between QTc max interval during maximum inspiration and expiration compared to that during normal breatlıing (409±22ms vs 4 17±26 ms, p>0.05 and 4ı2± 18ms vs 4 I 7± 26ms, p>0.05 respectively). QTc dispersion during maximum inspiration and maximum expiration were significantly lower than that during normal breatlıing (36±8 ms vs 44± 9 ms, pKeywords: QT dispersion, respiratory phase