Fetal cardiovascular hemodynamics in the presence of complete atrioventricular block

OBJECTIVE Our purpose was to follow serially the hemodynamic adaptation to a congenital complete heart block in a human fetus. STUDY DESIGN: Longitudinal and serial M-mode and Doppler echocardiography over a 10-week span were performed on a fetus affected by complete heart block. Ventricular fractional shortening, size, and flow across the atrioventricular valves and outflow tracts were determined starting at 20 weeks up to the time of delivery. Neonatal Doppler follow-up was performed at 2 days of life after implantation of a temporary pacemaker. RESULTS: The right and left ventricles were able to adapt to sustained bradycardia by increasing their size. This ventricular dilatation was also asspciated with an increase in fractional shortening, which was associated with ventricular free wall hypertrophy. When ventricular heart rate decreased to 38 beats/min, fractional shortening decreased, this was associated with the rapid onset of ascites and pericardial effusion. CONCLUSION: In the presence of sustained bradycardia ventricular output can increase, because this fetus was able to increase ventricular size and fractional shortening and wall thickness.