Table 1

CTI dependency on gestational age. Dependency of fetal cardiac time intervals on gestational age (in weeks): coefficients of determination (r2), y-intercepts, slopes and the p-value of the slopes (values < .05 in bold type). Linear regression parameters are given for each disjunct interval (upper rows) and each composite interval (lower rows). Non-linear regression parameters are also given for those intervals in which an improved model fit was found (quadratic: PQ and PR interval, double logarithmic: QRS complex).

regression type

N

r2

y-intercept (ms)

slope (ms/week)

p

slope (ms/week2)

p


P wave

linear

228

0.67

14.0

1.37

<0.001

PQ interval

linear

228

0.07

67.7

-0.49

<0.001

PQ interval

non-linear

228

0.13

14.2

3.38

0.021

-0.07

0.008

QRS complex

linear

230

0.62

19.3

0.92

<0.001

ln (QRS)

non-linear

230

0.66

1.8

0.60*

<0.001

ST segment

linear

217

0.01

60.4

0.32

0.169

T wave

linear

216

0.00

126.0

0.00

1.000

PR interval

linear

228

0.16

81.7

0.88

<0.001

PR interval

non-linear

228

0.21

20.0

5.35

<0.001

-0.08

0.002

QT interval

linear

216

0.07

205.8

1.24

<0.001

QTc interval

linear

216

0.06

326.6

1.65

<0.001


* the slope in this regression equation is ms/ln(week)

van Leeuwen et al. BMC Pregnancy and Childbirth 2004 4:6   doi:10.1186/1471-2393-4-6

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