CMECNE

The Spectrum of Fetal Arrhythmias – From a Common Finding to a Serious Concern

Learning Objectives and CME/Disclosure Information

This activity is intended for healthcare providers delivering care to women and their families.

After completing this activity, the participant should be better able to:

1. Categorize different fetal arrhythmias based on regularity and rate
2. Recall features of premature atrial contractions (PACs)

Estimated time to complete activity: 0.25 hours

Faculty:

Susan J. Gross, MD, FRCSC, FACOG, FACMG
President and CEO, The ObG Project

Disclosure of Conflicts of Interest

Postgraduate Institute for Medicine (PIM) requires instructors, planners, managers and other individuals who are in a position to control the content of this activity to disclose any real or apparent conflict of interest (COI) they may have as related to the content of this activity. All identified COI are thoroughly vetted and resolved according to PIM policy. PIM is committed to providing its learners with high quality CME activities and related materials that promote improvements or quality in healthcare and not a specific proprietary business interest of a commercial interest.

Faculty: Susan J. Gross, MD, receives consulting fees from Genoox, Inc., and has financial interest in The ObG Project, Inc.

Planners and Managers: The PIM planners and managers, Trace Hutchison, PharmD, Samantha Mattiucci, PharmD, CHCP, Judi Smelker-Mitchek, MBA, MSN, RN, and Jan Schultz, MSN, RN, CHCP have nothing to disclose.

Method of Participation and Request for Credit

Fees for participating and receiving CME credit for this activity are as posted on The ObG Project website. During the period from Dec 31 2017 through Dec 31 2019, participants must read the learning objectives and faculty disclosures and study the educational activity.

If you wish to receive acknowledgment for completing this activity, please complete the post-test and evaluation. Upon registering and successfully completing the post-test with a score of 100% and the activity evaluation, your certificate will be made available immediately.

For Pharmacists: Upon successfully completing the post-test with a score of 100% and the activity evaluation form, transcript information will be sent to the NABP CPE Monitor Service within 4 weeks.

Joint Accreditation Statement

In support of improving patient care, this activity has been planned and implemented by the Postgraduate Institute for Medicine and The ObG Project. Postgraduate Institute for Medicine is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.

Physician Continuing Medical Education

Postgraduate Institute for Medicine designates this enduring material for a maximum of 0.25 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Continuing Nursing Education

The maximum number of hours awarded for this Continuing Nursing Education activity is 0.2 contact hours.

Read Disclaimer & Fine Print

WHAT IS IT?

A fetal arrhythmia is an abnormality in fetal heart rate and/or cardiac rhythm. Most often, the unusual rhythm is detected during an otherwise normal prenatal visit.

Arrhythmias presenting with an irregular rhythm include:

Premature Atrial Contractions (PACs)
- PACs are common in fetuses and may be seen in up to 51% of healthy newborns
  - A premature atrial contraction is usually followed by a ventricular contraction that will also be premature, but will occur at the appropriate time in the cycle
  - There is a low risk of fetal tachycardia
  - Considered normal at birth unless other problems are found in the nursery
- PACs will usually spontaneously resolve
Premature Ventricular Contractions (PVCs)
- Fetal PVCs are considerably less common than PACs
- The PVC is not preceded by a normal atrial beat
- In isolation, PVCs should be monitored regularly, but intervention is usually not required

Arrhythmias presenting with a slow heart rate include:

Sinus Bradycardia – 80-110 bpm (beats per minute)
- The rhythm appears normal but the rate is slow with respect to gestational age
- May be well tolerated and require monitoring but no intervention
- Underlying causes can include non-reassuring fetal status or cardiac structural defects, or maternal antibodies such as anti-SSA (Ro), which may require anti-inflammatory therapy
Complete Heart Block (CHB) – 40-80 bpm
- This is a complete failure of normal atrial impulses to the ventricles such that the atria and ventricles are no longer coordinated
- Underlying causes can include cardiac structural defects (50%)
- Maternal anti-SSA (Ro) anti-SSB (La) autoantibodies are strongly associated with CHB and there is an associated risk of fetal loss, especially with fetal heart rate below 55 bpm
  - Mothers are often asymptomatic with no evidence of autoimmune disease such as lupus
    - antibodies first detected upon evaluation for fetal arrhythmia
  - The risk for acquired heart block in the fetus in the setting of maternal anti-SSA and anti-SSB antibodies is approximately 2–3%, with a recurrence risk of 14–17%
  - In newborn with otherwise normal cardiac exam but CHB, likely cause is autoantibodies
  - Cutaneous findings consistent with neonatal lupus erythematosus are more common (16%), than CHB with anti-SSA/SSB
- Medical therapy may be used prenatally in the case of antibody related CHB with pacing after delivery

Arrhythmias presenting with an increased heart rate include:

Fetal heart rate above 180 bp should be considered critical
- Supraventricular Tachycardia (SVT) – 190-300 bpm
  - May be monitored if infrequent but otherwise maternal anti-arrhythmic therapy (e.g. digoxin) may be required
- Atrial Flutter (FT) – ventricular rate – 150-250 bpm
  - Almost exclusively seen in the 3rd trimester or at birth
  - Usually well tolerated and can be treated with maternal anti-arrhythmic agents (e.g. digoxin)
- Sinus Tachycardia – 200+ bpm
  - Look for and manage underlying cause such as infection or non-reassuring fetal status

KEY POINTS:

Identifying an unusual fetal cardiac rhythm or rate during a normal antepartum visit may be a key moment in detecting a significant cardiac arrhythmia
Even though fetuses may easily tolerate irregular rhythms such as PACs, any change from a normal heart rate or regular rhythm pattern should trigger a referral to a high risk specialist who can make the diagnosis and with a multidisciplinary team, can determine whether to monitor, treat or deliver
Fetal echocardiography remains the mainstay of diagnosis, as well as a detailed fetal anatomy scan to determine if any other structural abnormalities exist
- Refer to high risk center for diagnosis and management plan
The above list constitutes the more common types of fetal arrhythmias, but more complex and rare forms may exist