Abnormal fetal heart rates and rhythms prior to labor

Developmental characteristics of fetal arrhythmias during the period from intrauterine to early extrauterine life assessed using dual echocardiography

To evaluate the outcome of fetal arrhythmias, serial echocardiographic examinations were made on 29 fetuses between 18 and 41 weeks gestation, including 23 with premature contractions (PCs) and 6 with complete atrioventricular block (AVB). Of the cases of PCs 43.5% (10/23) disappeared spontaneously during the antenatal period. 39.1% (9/23) converted to a normal sinus rhythm in early neonatal life, while 17.4% (4/23) had complications of either atrial or ventricular tachycardia. All with AVB (6/6) remained, regardless of advance in gestational age and continued through to the postnatal period. PCs and AVB indicate functional error and an impairment during development of the conduction system, respectively.

Fetal echocardiography. A tool for evaluation of in utero cardiac arrhythmias and monitoring of in utero therapy: analysis of 71 patients

Fetal echocardiographic studies were performed in 71 patients referred for evaluation of cardiac rhythm disturbances at 24 to 40 weeks' gestation. After 2-dimensional echocardiographic study of cardiac structure was performed, M-mode echocardiograms were analyzed for measurement of cardiac rate, atrioventricular contraction sequence, atrioventricular valve motion, and duration of postectopic pauses. Arrhythmias were diagnosed in 59 patients. In 34 patients with isolated ectopic beats, the arrhythmia resolved during later pregnancy in 26 or within the first 5 days of life in 8. Six patients had mild sinus bradycardia and 8 had frequent sinus pauses; all 14 had resolution of the arrhythmia during pregnancy. Sustained arrhythmias occurred in 11 patients. Deaths occurred when there was associated fetal congestive heart failure (hydrops fetalis), structural heart disease, or both. M-mode echocardiography diagnosed supraventricular tachycardia in 3 fetuses. The echocardiogram was used thereafter for monitoring transplacental digoxin therapy.

Irregular fetal bradycardia: A case report

The importance of fetal heart rate patterns in the evaluation of fetal well-being is discussed in relation to a case of antenatal documentation of a grossly irregular fetal bradycardia in a mother with congenital heart disease. A rare form of conduction disturbance, sinus bradycardia with resultant arterial-venous dissociation is documented as an antenatal finding and etiology to irregular fetal bradycardia.

Prospective study of fetal heart rate and rhythm patterns

The fetal heart beat, detected by ultrasound, was recorded for five minutes from 934 antenatal women--266 at 30 to 35 weeks' gestation and 718 at 36 to 41 weeks. Episodes of bradycardia < 100/minute ranging from 5-30 seconds' duration occurred in 3 (1.1%) of the former and in 9 (1.3%) of the latter group. Tachycardia > 180/minute ranging from 30-90 seconds' duration occurred in 1 (0.4%) of the former and in 4 (0.6%) of the latter. Premature beats were not detected between 30 and 35 weeks, but occurred in 12 (1.7%) of 720 at 36 to 41 weeks' gestation. 50 subjects were monitored at both 30 and 35 weeks and 36 to 41 weeks' gestation and in one woman premature beats were present in the latter but not in the former recording. The incidence (1.7% of premature beats in the fetus at 36 to 41 weeks' gestation was similar to that in the healthy neonate (0.8%). Recordings of arrhythmias or rates outside the range 100-180/minute were replayed through a standard antepartum fetal heart rate monitor. The monitor failed to detect premature beats, 2 to 4 episodes of tachycardia > 180/minute, and 9 of 12 episodes of bradycardia < 100/minute, stressing its unreliability for detecting rapidly changing rates.