In vivo characterization of rate-dependent impact on the QT interval of microminipig assessed by atrial electrical pacing: Development of correction formulae of QT interval

Figures

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  Fig. 1.. Development of correction formulae of QT interval against various cycle length (CL), which were obtained from the halothane-anesthetized microminipigs with an atrial electrical pacing (n=5). Relationship between the CL and QT interval (A, black circles); that between the CL–750 and QT–QTCL750 for linear equation (B); and that between log(CL/750) and log(QT/QTCL750) for non-linear one (C). The slope constant α and R2 values were obtained by linear regression analysis. The QT interval during the sinus rhythm of each animal was also plotted for reference (A, blue triangles).

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  Fig. 2.. Assessment of correction formulae of QT interval by introducing each value of the QT interval at various cycle length (CL). Linear regression analyses between the pacing CL and corrected QT interval (QTc) were performed. The QTc was calculated by using the currently developed linear equation formula for microminipig (µMP) (A, black circles) and Van de Water’s formula for dogs (QTcV) (B, black circles); and the currently developed non-linear equation formula for µMP (C, black circles), Bazett’s formula for humans (QTcB) (D, black circles) and Fridericia’s formula for humans (QTcF) (E, black circles). The slope constant (slope) was obtained by linear regression analysis. When a P-value was <0.05, the correction was considered to be inadequate. Its reverse would mean the QT interval was appropriately corrected. The QTc calculated by the correction formulae for each animal during the sinus rhythm is also plotted for reference (blue triangles).

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  Fig. 3.. Evaluation of correction formulae by using the QT interval and RR interval obtained from our previous studies using 42 male and 11 female micominipigs [1, 3, 5, 8, 9, 15, 17]. Linear regression analyses between the RR interval and QT interval (black triangles), and those between the RR interval and corrected QT interval (red circles) were performed for total (A), male (B) and female (C) animals. The QT interval was corrected by using the currently developed linear equation formula (upper) and non-linear equation formula (lower) for microminipigs.