Sustained Supraventricular Tachycardia While in Active Phase Labor

Abstract

Background

Supraventricular tachycardia (SVT) is one of the most common tachyarrhythmias found in young women, and SVT can be exacerbated by pregnancy. The symptoms associated with SVT frequently overlap with physiologic changes and symptoms of pregnancy which can lead to delayed or missed diagnosis.

Case Presentation

We describe the presentation and the acute management of a patient who had sustained SVT that developed during the active phase of labor. We then detail the varying management approaches of SVT in pregnancy and labor as well as refractory management options. Maternal monitoring will also be discussed as this case shows how an SVT diagnosis could have been overlooked with varying maternal monitoring practices between or within facilities.

When the patient went into SVT, the labor and delivery team was able to stabilize her, and she progressed to labor without further complications. Throughout the patient’s remaining hospital admission, there was an additional episode of SVT, but this incident was also stabilized. The patient was stable for discharge on postpartum day 2 with follow-up recommended with cardiology.

Conclusion

Supraventricular tachycardias are often overlooked in young women and can present during labor. A lack of consensus amongst experts and medical organizations regarding management needs for further investigation.

Introduction

Supraventricular tachycardia (SVT) is a tachyarrthymia, defined as a heart rate over 150 beats per minute that can cause insufficient blood flow to the body due to contraction by the heart chambers before they are completely filled. Symptoms include shortness of breath, fatigue, and dizziness; however, when present during pregnancy the symptoms are often masked and SVT goes untreated. Although most arrhythmias are non-life threatening, they are associated with increased maternal mortality, and therefore, a decisive management plan is required when diagnosed.¹ Herein, we describe a complex case presented in our clinic and provide the steps for the management of supraventricular arrhythmias during pregnancy.

Case Presentation

A 27-year-old gravida 1 para 0 woman at 39 weeks and 4 days was admitted to labor and delivery for induction of labor due to gestational hypertension. The patient’s prenatal course was significant for gestational hypertension and asthma, which were both well-controlled before arrival. Initial admission labs were significant for a urine drug screen positive for tetrahydrocannabinol. The patient reported a history of intermittent palpations before pregnancy, but she had not been formally evaluated due to anxiety. On day 2 of induction, the patient had received 3 doses of misoprostol and was on oxytocin for labor augmentation. The patient had received an epidural the night before. Midday on day 2 of induction, the patient’s heart rate acutely elevated to a range of 190–200 beats per minute, as noted, for at least 15 min on pulse oximetry. The obstetrician examined the patient, who then immediately asked for an internal medicine consult since the electrocardiogram showed SVT. A rapid response was called for the patient. The patient’s vitals were otherwise stable, with a blood pressure of 110–140/60–98 mmHg, respiratory rate of 18 breaths a minute, and oxygen saturation of 98%. The patient did not report any lightheadedness, chest pain, or difficulty breathing. The patient was asymptomatic aside from heart palpitations. Initial management was with vasovagal maneuvers and intravenous (IV) bolus of 1 liter of lactated Ringer’s. After vasovagal maneuvers were attempted twice and failed, cardiology was consulted and recommended that adenosine be given to convert the patient. After 1 dose of 6 milligrams of IV adenosine, the patient cardioverted to sinus rhythm. Fetal monitoring remained consistently category 1 during this episode, which lasted over 1 hour. After the patient was stabilized, the patient was placed on labetalol 25 mg twice daily by cardiology.

The patient subsequently progressed in labor and delivered a healthy male neonate 4 hours after the conversion to sinus rhythm. The patient had 1 additional episode of SVT on postpartum night 0 while recovering and responded to an additional dose of 6 mg of IV adenosine. Labs at the time showed a normal Thyroid stimulating hormone of 1.079 mIU/L; hemoglobin of 11.6 g/dL; hematocrit of 35.7%, but hypokalemia of 3.4 mg/dL; and hypomagnesemia of 1.4 mg/dL. The patient’s labetalol was increased to 100 mg twice a day, with an immediate loading dose provided after the rapid response. Potassium and magnesium were repleted to maintain levels over 4 mg/dL and 2 mg/dL, respectively. The patient remained hospitalized under continuous telemetry monitoring for an additional 2 days, to ensure resolution of SVT. She was discharged home with a 14-day Holter monitor to determine the burden of tachycardic events. The patient was also advised to follow up outpatient with cardiology for possible ablative therapy.

Discussion

As the pregnancy progresses, a mother’s cardiovascular physiology changes. The physiologic changes during pregnancy include increases in plasma volume, thereby increasing heart volume as well. This increased volume causes stretching of the cardiac muscle, which can predispose the patient to arrhythmias. One of the most common arrhythmias noted in pregnant patients is SVT. The proposed pathophysiology of SVT is an atrioventricular reentrant tachycardia or, in some cases, undiagnosed Wolfe-Parkinson-White syndrome.¹ Diagnostic criteria for SVT is a narrow, complex tachycardia with a rate over 100 beats per minute. However, tachycardia is typically not treated with chemical or electrical cardioversion.² Some experts believe that the physiologically increased catecholamines of labor and uterotonic agents can trigger SVT.¹

SVT treatment depends on the hemodynamic stability and the recurrence of events. The first step in all trimesters of pregnancy, including labor, involves vasovagal maneuvers, such as carotid massage or Valsalva techniques. However, these maneuvers are only performed if the patient is hemodynamically stable.³ If the SVT does not resolve following these maneuvers, intravenous adenosine is indicated to correct the acute arrhythmia. This medication is considered safe in pregnancy since it falls within category C by the Federal Drug Administration and it has a short effect due to the short half-life of approximately 10 seconds. This short half-life decreases the risk of adenosine exposure risk to the fetus. Following treatment with adenosine, beta-blockers, such as metoprolol, or calcium channel blockers, such as verapamil, are indicated to correct acute episodes of SVT.^4,5 Beta-blockers are often the preferred agent to prevent recurrent SVT in patients who have not yet had definitive treatment. It is important to note that atenolol is a category D medication and should not be used during any trimester of pregnancy. For hemodynamically unstable patients, synchronized electro-cardioversion with 50–100 J is safe in all trimesters. This treatment, however, predisposes the fetus to bradycardic events that can lead to an emergency cesarean section (C-section). The definitive treatment for SVT is often cardiac catheter ablation. Typically, this modality is reserved for post-pregnancy to avoid radiation to the fetus and reduce exposure to sedating pharmaceuticals, cardiac catheter ablation has been performed in cases of resistant SVT while the patient was still pregnant.¹

While there is no clear recommendation from the American College of Obstetricians and Gynecologists (ACOG) whether SVT is an indication for C-section or emergent delivery, providers must take into consideration the mother’s condition, fetal status, and, if labor persists, further risk of cardiovascular events.⁵ Some obstetricians believe that to avoid the release of catecholamine and the stress of labor triggering an SVT event, it is best to perform a C-section.⁵ Many anesthesiologists believe that a properly placed epidural can help reduce the catecholamine release, thereby, helping to prevent arrhythmias.⁶ Further investigation is required to form a consensus as to proper guidance for safe delivery when the patient is experiencing or has a history of SVT.

Substantial research exists on intrapartum fetal monitoring but there is a research gap regarding maternal vital monitoring. There are few recommendations as to how often or how a patient’s cardiac status should be assessed. Labor and delivery units often pattern SVT management based on an intensive care unit with continuous monitoring for fetuses and one-on-one nursing care with specialized skills, often resulting in alarm fatigue.⁷ According to the ACOG guidelines outlined in 2017, it is recommended that a patient’s vital signs be checked every 4 hours unless there are other complications, such as infection or preeclampsia. However, the ACOG does not include specific recommendations on when a patient should be monitored on telemetry or specify the frequency of assessing vital signs outside of uneventful labor processes.² In the United Kingdom’s National Institute for Health and Care Excellence, maternal heart disease is only noted when there is continuous electrocardiogram monitoring. Otherwise, vitals should be monitored every 1–4 hours.⁸ In the case of our patient, her heart rate was being monitored secondarily to fetal heart monitoring due to available equipment and technical ability to detect maternal heart rate. Had it not been for this incidental finding, the patient could have sustained SVT for a prolonged period without it being recognized. For this reason, we believe there should be further research and standardization of intrapartum maternal monitoring.

Conclusion

Supraventricular tachycardias are often overlooked as a diagnosis in young women and can present during labor. The physiologic changes of pregnancy and the catecholamine-driven state of labor can make the signs and symptoms of SVT leading to delays in diagnosis or even missed diagnosis. There is a lack of consensus among experts and medical organizations regarding medical and obstetrical management, highlighting the need for further investigation.

Funding Statement

This research was supported (in whole or in part) by HCA Healthcare and/or an HCA Healthcare-affiliated entity.