Abstract 15739: Fetal Echocardiographic Predictors of Perinatal Outcome in Congenital Atrioventricular Block

Abstract

Background: Congenital atrioventricular block (AVB) is a rare disease with poor outcomes. Heart rate (HR) is a major prognostic factor. To date, no study has evaluated the contribution of cardiac output (CO), stroke volume (SV), and HR on outcomes. Methods: In this retrospective study we evaluated associations between fetal echocardiographic parameters and risk of a composite severe fetal adverse event (AE) in patients with congenital AVB. Results: Of the 58 cases of congenital AVB, 21 (36%) had the composite AE, defined as fetal hydrops (8/58, 14%), ≥ moderate ventricular dysfunction (LV 3/58, 5%; RV 6/58 11%), fetal demise (2/57, 4%), or premature birth at ≤ 35 weeks (17/55, 31%). Of the 55 live births, 3/55 (5%) patients died and 35/55 (64%) had a pacemaker placed in the neonatal period. In univariate analysis, lower HR z-score was associated with the composite AE (p = 0.002) and all individual components of the composite AE. Higher LV end diastolic volume was associated with the composite AE (p = 0.004), premature birth (p = 0.006) and neonatal pacemaker placement (p = 0.009). Higher LV SV was associated with the composite AE (p = 0.003) and with fetal hydrops (p = 0.031) and premature birth (p = 0.002). Higher combined CO (p = 0.038), presence of structural heart defect (p = 0.038) and heterotaxy (p = 0.01) were associated with fetal hydrops. In multivariate analysis, lower HR z-score (p = 0.044) and higher LV SV (p = 0.037) were associated with the composite AE. Longitudinal analysis showed the AE group had lower HR and higher SV throughout gestation and trends towards a greater decline in SV and CO (particularly RV CO) in the third trimester. Conclusions: Heart rate, not CCO, is the primary determinant of perinatal outcome in fetuses with high grade AVB. The compensatory increase in LV volume and SV in the patients with the lowest HR (and worst outcomes) maintains CCO in most fetuses with AVB and reflects the ability for fetal cardiac adaptation in the setting of prolonged severe bradycardia.