Monomorphic sustained right ventricular outflow tract tachycardia in pregnancy with favorable outcomes: a case report

Monomorphic sustained right ventricular outflow tract tachycardia is a rare and serious condition in pregnancy affecting previously structurally normal heart; however, the exact pathogenic domains remain unclear. This case underscores the importance of timely diagnosis and intervention, which led to favorable outcomes despite the limited evidence on contemporary management. Further, it highlights the need for vigilance and collaboration in addressing complex cardiac issues during pregnancy.

A 35-year-old pregnant, African woman (gravida 3, para 2) at 30 weeks gestation, with unremarkable past medical history presented with palpitations, pre-syncope, and shortness of breath for 2 weeks, which worsened with time. She was treated as an outpatient at a peripheral facility using oral propranolol 40 mg twice daily with suboptimal relief. Owing to worsening symptoms, she was referred to our facility for further management. At the emergency department, she had features suggestive of acute heart failure with stable vital signs and was treated with oxygen, intravenous furosemide 60 mg, and isosorbide dinitrate 10 mg without significant improvement. A 12-lead electrocardiogram showed multiple monomorphic sustained ventricular tachycardia with the left bundle branch block pattern suggestive of right ventricular outflow tract tachycardia. A two-dimensional transthoracic echocardiography showed normal findings, with an ejection fraction of 57%, a mild dilated inferior vena cava (IVC) with normal pericardium, and without valvular abnormalities. Ultimately, the final diagnosis of monomorphic sustained right ventricular outflow tract tachycardia was established. Intravenous furosemide and oral isosorbide dinitrate were stopped 12 hours after admission. Management was undertaken in a multifaceted approach with the pregnancy heart team, and the patient was initiated on an intravenous amiodarone 150 mg bolus, followed by a 900 mg infusion for 6 hours together with oral metoprolol 50 mg thrice for 24 hours. An amiodarone infusion was administered due to a temporary unavailability of the recommended initial therapies, such as lidocaine. Following persistence of ventricular tachycardia episodes, verapamil 40 mg once daily was added, which resulted in complete resolution of ventricular tachycardia and restoration of sinus rhythm within 36 hours. At home, the patient continued with oral metoprolol and verapamil with 2 weekly follow-ups with normal fetal monitoring throughout. At 37 weeks and 5 days, she delivered a live big baby by emergent caesarean section. After 48 hours postpartum, cardiac monitoring was performed and was unremarkable. During discharge the patient continued with oral metoprolol 25 mg twice daily, and oral verapamil was stopped. Later, at a 3-month follow-up, no recurrences of ventricular tachycardia episodes were observed. This is the first case to be encountered in our local, resource-poor setting, highlighting the challenges in the diagnosis of arrhythmia in pregnancy and contemporary management owing to limited evidence.

Monomorphic sustained right ventricular outflow tract tachycardia in pregnancy is always attributed to a normal physiology of pregnancy. Despite there being no evidence from clinical trials, it can be managed with available antiarrhythmic drugs with favorable outcomes. This case underscores the importance of thoroughly evaluating all pregnant women who present with palpitation to exclude cardiac causes and provide prompt management.