Both oxytocin and carbetocin are used routinely after caesarean delivery to prevent uterine atony and excessive blood loss.5,8 We know that oxytocin causes dose-dependent ST-depression, troponin release, prolongation of QT-time and arrythmia, but little is known about myocardial effects of carbetocin.23 Our ongoing study has been designed to assess high-sensitivity troponin I plasma concentrations after the prophylactic administration of either oxytocin or carbetocin to determine whether there are any differences in their myocardial effects. The gene discussed is OXT; the disease is cardiac arrhythmia.