INVESTIGATIVE METHODS OF CONGENITAL COMPLETE HEART-BLOCK

Congenital heart block (CHB) has been described for a century and rela ted to the presence of maternal autoimmune disease for three decades, but little is understood about its mechanism. To explore the pathophys iology of CHB, technologies in both basic and clinical electrophysiolo gy are being developed and applied. Human fetal rhythm is currently in ferred from cardiac mechanical events by using fetal ultrasound, allow ing for the detection of second and third-degree heart block. Fetal el ectrocardiography is being explored to assess its feasibility as a cli nical tool to detect fetal first-degree block in the mid trimester. Se quential composite digital recordings from the maternal abdomen are ma de every 4 weeks from pregnancies at risk for congenital heart block. Filtering and averaging techniques are used to enhance the fetal signa l. So far, these techniques have produced a fetal QRS complex trigger signal for use in three-dimensional fetal echocardiography. Because th e human fetus cannot be studied directly, a Langendorff rabbit model o f CHB has been developed. With 5-10 mt of human serum in 150-300 mt of Krebs solution. prolongation of the Wenckebach second-degree atrioven tricular block cycle length occurred. This was reproduced by using ser um from seven of eight CHB mothers as compared with none of six contro ls mothers.