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Updated: Apr 3, 2026
In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography
Published on: November 22, 2013
The Effect of Dofetilide on the Heart Rate of GD11 and GD13 Rat Embryos, in vivo, Using Ultrasound
Helen Ritchie1, Diana Oakes1, Tzong-tyng Hung2
1Discipline of Biomedical Science, University of Sydney, New South Wales, Australia.
Background:
There are a wide range of drugs including antidepressants, anticonvulsants and antipsychotics that cause embryonic bradycardia in vitro but it is unknown if they have a similar effect in vivo. One way to verify whether these in vitro findings are replicated in vivo is by the use of ultrasound examination of dosed pregnant rats. We tested this by examining the effect of dofetilide on embryonic heart rate (HR) in vivo using ultrasound.
Methods:
Rats were dosed with dofetilide (4 or 2.5 mg/kg) on GD11 or (5 or 2.5 mg/kg) on GD13 and embryonic HR assessed by ultrasound, 2 and 24 hr later. Fetuses were examined for malformations on GD20.
Results:
HR of control rat embryos showed a wide range at each gestational day. Dosing with dofetilide on GD11 caused severe bradycardia (∼ 60% reduction) 2 hours after dosing with recovery after 24 h of >60% of LD but death and slow HR among the HD embryos. At term, 32% of the LD surviving fetuses had hypoplastic upper lip while >90% of HD embryos had died. On GD13, embryonic HR was reduced in a dose-dependent manner with >85% of LD and HD recovered by 24 hr. At term, all LD fetuses were normal while 29% of HD fetuses had limb defects.
Conclusions:
Ultrasound is a useful technique to investigate the effect of maternally administered drugs on the embryonic HR in the rat. The results may provide more information about the safety of these drugs in pregnancy leading to better risk assessment for the human.
