Fetal Supraventricular Tachycardia: What the Adult Cardiologist Needs to Know

Abstract

Fetal supraventricular tachycardia management is challenging, with consequences for both the fetus and the mother. If left untreated, fetal hydrops may ensue, at which point delivery and treatment of the arrhythmia is preferred. However, if the fetus is not at term nor near-term, significant doses of antiarrhythmics may be needed to achieve adequate transplacental bioavailability. Although digoxin has classically been the mainstay of treatment, the use of flecainide or sotalol as monotherapy or in combination with digoxin is being studied. Interdisciplinary team management and shared decision-making between the physician and patient are key to achieving successful outcomes. Adult cardiologists, particularly inpatient consultation services or through burgeoning cardio-obstetrics programs, may, in some practice settings, be asked to evaluate or comanage pregnant women with fetal arrhythmia.

Figure 1:

Fetal echocardiogram demonstrating a rate of 200 beats per minute (bpm) on the pulse wave Doppler with severe biventricular dysfunction. Normal fetal heart rate ranges from 110–160 bpm, while supraventricular tachycardia from 200–300 bpm. msec, milliseconds.

Figure 2:

Fetal echocardiogram demonstrating a long ventriculo-atrial (V-A) interval tachycardia. More atrial than ventricular contractions indicates fetal atrial flutter. Msec, milliseconds.

Figure 3:

Evidence of digoxin effect with “slurred” S waves on the maternal electrocardiogram (inset). Frequent ECG and symptom monitoring are required in transplacental treatment of fetal supraventricular tachycardia due to potential for maternal toxicity with anti-arrhythmics.

Figure 4:

After transplacental therapy with digoxin and flecainide, a repeat fetal echocardiogram demonstrated a rate of 130 beats per minute (bpm) with 1:1 atrioventricular conduction, consistent with normal sinus rhythm.

Figure 5:

Overview of maternal evaluation and potential treatment algorithm when caring for pregnant patients with fetal SVT. SVT, supraventricular tachycardia; ECG, electrocardiogram; MFM, maternal-fetal medicine.