A primigravida at 36 weeks with gestational diabetes mellitus and hypothyroidism and no prior chronic medical illness was admitted for safe confinement. A cesarean section was required to deliver the baby with breech presentation complicated by a slow progression of labor. Asymptomatic sinus bradycardia with a heart rate of 40 per minute was observed during the induction of anesthesia. Before bupivacaine administration for spinal anesthesia, she was administered pantoprazole 40 mg and ondansetron 4 mg intravenously. ECG recording showed a type 1 Mobitz second-degree heart block. Follow-up ECG showed progression of heart block to type 2 Mobitz second-degree heart block. The second-degree heart block persisted for 16 hours, during which the patient was asymptomatic, and the ventricular rate was maintained at a range of 60-80 per minute. After normalization of rhythm, the patient was observed in the ICU. She received another dose of ondansetron 4 mg intravenously for vomiting, and the heart block recurred. The rhythm disturbance was attributed to ondansetron. Her rhythm normalized after 36 hours, and she was subsequently discharged home three days later.
Keywords: adverse effect; bradycardia; mobitz heart block; ondansteron; primigravida.
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