TY - JOUR
T1 - Slow QT interval adaptation to heart rate changes in normal ambulatory subjects
AU - Razak, Eathar
AU - Buncová, Marie
AU - Shusterman, Vladimir
AU - Winter, Bruce
AU - Shen, Win Kuang
AU - Ackerman, Michael J.
AU - Donovan, Theresa
AU - Lampert, Rachel
AU - Němec, Jan
PY - 2011/4
Y1 - 2011/4
N2 - Background: Clinical formulas for QT correction utilize instantaneous HR. We showed previously that longer-term HR affects QT duration. We extend these findings, identifying more accurate models of QT behavior. Method: Multiple models of QT dependence on HR were tested in 2 independent populations. Holter recordings were analyzed in population A (healthy volunteers, n = 14, 6 males, age 26.9 ± 12.3 yr). The hypotheses generated in population A were tested in an independent group population B, healthy volunteers, n = 15, 9 males, age 52.9 ± 15.6 yr). Linear models of QT interval dependence on a weighted average of RR intervals in the preceding 3 minutes were compared to models based on the immediately preceding RR interval (instantaneous HR). Results: In population A, linear models based on RR intervals over the preceding minute performed better than the best nonlinear model based on the single RR interval immediately preceding the QT interval. Linear models including HR values preceding the QT interval by more than 60 s further improved model fit. This model hierarchy was confirmed in population B. Linear formula for QT correction based on exponential decay of HR effect with 60 s time constant outperformed Bazett and Fridericia formulas in both populations. Conclusions: QT duration in normal ambulatory subjects is affected by noninstantaneous HR, including HR history dating back more than 60 s. Exponential decay of this "memory effect" with time constant of 1 minute provides an accurate description of QT adaptation. This may be of clinical importance when HR is not steady.
AB - Background: Clinical formulas for QT correction utilize instantaneous HR. We showed previously that longer-term HR affects QT duration. We extend these findings, identifying more accurate models of QT behavior. Method: Multiple models of QT dependence on HR were tested in 2 independent populations. Holter recordings were analyzed in population A (healthy volunteers, n = 14, 6 males, age 26.9 ± 12.3 yr). The hypotheses generated in population A were tested in an independent group population B, healthy volunteers, n = 15, 9 males, age 52.9 ± 15.6 yr). Linear models of QT interval dependence on a weighted average of RR intervals in the preceding 3 minutes were compared to models based on the immediately preceding RR interval (instantaneous HR). Results: In population A, linear models based on RR intervals over the preceding minute performed better than the best nonlinear model based on the single RR interval immediately preceding the QT interval. Linear models including HR values preceding the QT interval by more than 60 s further improved model fit. This model hierarchy was confirmed in population B. Linear formula for QT correction based on exponential decay of HR effect with 60 s time constant outperformed Bazett and Fridericia formulas in both populations. Conclusions: QT duration in normal ambulatory subjects is affected by noninstantaneous HR, including HR history dating back more than 60 s. Exponential decay of this "memory effect" with time constant of 1 minute provides an accurate description of QT adaptation. This may be of clinical importance when HR is not steady.
KW - QT interval adaptation
KW - QT interval correction
KW - ambulatory ECG
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U2 - 10.1111/j.1542-474X.2011.00420.x
DO - 10.1111/j.1542-474X.2011.00420.x
M3 - Article
C2 - 21496165
AN - SCOPUS:79955044990
SN - 1082-720X
VL - 16
SP - 148
EP - 155
JO - Annals of Noninvasive Electrocardiology
JF - Annals of Noninvasive Electrocardiology
IS - 2
ER -