Diagnosis of fetal arrhythmias using echocardiographic and Doppler techniques.

Fetal echocardiography is the most practical method for diagnosing prenatal arrhythmias. Because some prenatal tachyarrhythmias have been shown to respond to antiarrhythmic drugs, correctly diagnosing fetal arrhythmias has assumed new importance. With the aid of two-dimensional echocardiographic imaging, an M-mode cursor can be aligned to record atrial and ventricular wall motion--either independently or simultaneously. A consistent feature in the fetus is prominent atrial wall contractions that can be readily recorded on the M-mode tracing. By matching atrial and ventricular wall contractions with assumed P waves and QRS complexes, the fetal electrocardiogram can be reconstructed. In 57 fetuses studied, recurrent atrial and ventricular ectopic beats were the most common prenatal arrhythmias. However, atrial flutter, ventricular tachycardia, atrial and ventricular bigeminy and atrial and ventricular bradyarrhythmias have been correctly identified and in some instances appropriately treated. Marked fetal bradycardia in the midtrimester of pregnancy is shown for the first time to be caused by transducer pressure on the maternal abdominal wall.