Cardiac Doppler flows during fetal arrhythmias: physiologic consequences.

Area of Science:

• Cardiology
• Fetal Medicine
• Pediatric Cardiology

Background:

• Fetal arrhythmias are diagnosed using ultrasound and heart rate monitoring.
• Understanding the physiological impact of these arrhythmias is crucial for fetal well-being.

Purpose of the Study:

• To investigate the physiological consequences of fetal arrhythmias.
• To document post-extrasystolic potentiation and the Frank-Starling mechanism in fetuses.
• To assess changes in cardiac output following conversion of fetal tachyarrhythmias.

Main Methods:

• Studied 86 fetuses (21-41 weeks' gestation) with arrhythmias using ultrasound and M-mode studies.
• Confirmed arrhythmia types with postnatal electrocardiograms in 70 infants.
• Utilized Doppler echocardiography in 54 fetuses to measure atrioventricular and semilunar valve flow velocities.

Main Results:

• Premature atrial contractions were the most common arrhythmia (76 cases).
• Post-extrasystolic potentiation increased right and left ventricular fractional shortening by 49% and 64%, respectively.
• Doppler-determined time-velocity integrals increased significantly across all major valves after premature contractions and after conversion of supraventricular tachycardia to sinus rhythm.

Conclusions:

• Fetal arrhythmias exhibit post-extrasystolic potentiation and utilize the Frank-Starling mechanism.
• Conversion of fetal tachyarrhythmias to normal sinus rhythm increases cardiac output.
• Ultrasound and Doppler echocardiography are valuable tools for assessing fetal cardiac physiology in the presence of arrhythmias.