20 Left Atrial Isomerism
A 40-year-old white woman, gravida 4, para 3+0, was referred by the obstetrician at 18 weeks’ gestation for slow fetal heart rate and a two-vessel cord. An ultrasound at 12 weeks revealed increased nuchal translucency, and normal fetal karyotype was documented by chorionic villous sampling (CVS). The woman has a 3 living children, none of whom have heart disease.
3. The aortic valve is in continuity with the common atrioventricular (AV) valve and arises from the LV. The size is normal but the velocity through the aorta is increased (2 m/s). There is also mild aortic insufficiency.
12. There was systolic a wave reversal at the atrial rate on each beat in the ductus venosus with intermittently larger a waves, suggesting cannon waves occurring during ventricular systole (Fig. 20-1).
Adapted from Yoo SJ, Hornberger LK, Smallhorn J: Abnormal visceral and atrial situs and congenital heart disease. In Yagel S, Silverman NH, Gembruch U (eds): Fetal Cardiology: Embryology, Genetics, Physiology, Echocardiographic Evaluation, Diagnosis and Perinatal Management of Cardiac Diseases. London: Taylor & Francis Group, 2002.
3. If delivery with postnatal intervention is not believed to be effective, aside from termination of pregnancy if desired by the patient, letting nature take its course with progressive hydrops may be the best option, with close follow-up of the mother to be certain there is no harmful consequence for her.
4. If there is no evolution of hydrops, cesarean section delivery may be considered given the difficulties with fetal monitoring in fetal bradycardia. Ideally, a planned cesarean section is performed at 36 to 38 weeks of gestation.
b. Prostaglandin E1 (PGE1) infusion is indicated if there is evidence of critical pulmonary outflow tract obstruction with retrograde ductal flow in utero or unless the direction of ductal flow is not certain.