Challenge of managing opposing rhythms in a mother and fetus.

Introduction: We report a case of a fetus with complex congenital heart disease and supraventricular tachycardia in the setting of maternal high grade atrioventricular block at 26 weeks' gestation. Methods and results: Electroanatomic mapping allowed successful implantation of a permanent pacemaker to provide adequate back‐up pacing in the mother with zero radiation exposure, thus allowing safe delivery of transplacental anti‐arrhythmic medications to reduce the fetal arrhythmia burden and optimize the fetal ventricular rate. Conclusion: This is the first reported case of using electroanatomic mapping, with zero fluoroscopy use, for pacemaker lead placement and for a novel indication. [ABSTRACT FROM AUTHOR]