Outcome of Antibody‐Mediated Fetal Heart Disease With Standardized Anti‐Inflammatory Transplacental Treatment

Background Transplacental fetal treatment of immune‐mediated fetal heart disease, including third‐degree atrioventricular block (AVB III) and endocardial fibroelastosis, is controversial. Methods and Results To study the impact of routine transplacental fetal treatment, we reviewed 130 consecutive cases, including 108 with AVB III and 22 with other diagnoses (first‐degree/second‐degree atrioventricular block [n=10]; isolated endocardial fibroelastosis [n=9]; atrial bradycardia [n=3]). Dexamethasone was started at a median of 22.4 gestational weeks. Additional treatment for AVB III included the use of a β‐agonist (n=47) and intravenous immune globulin (n=34). Fetal, neonatal, and 1‐year survival rates with AVB III were 95%, 93%, and 89%, respectively. Variables present at diagnosis that were associated with perinatal death included an atrial rate <90 beats per minute (odds ratio [OR], 258.4; 95% CI, 11.5–5798.9; P <0.001), endocardial fibroelastosis (OR, 28.9; 95% CI, 1.6–521.7; P <0.001), fetal hydrops (OR, 25.5; 95% CI, 4.4–145.3; P <0.001), ventricular dysfunction (OR, 7.6; 95% CI, 1.5–39.4; P =0.03), and a ventricular rate <45 beats per minute (OR, 12.9; 95% CI, 1.75–95.8; P =0.034). At a median follow‐up of 5.9 years, 85 of 100 neonatal survivors were paced, and 1 required a heart transplant for dilated cardiomyopathy. Cotreatment with intravenous immune globulin was used in 16 of 22 fetuses with diagnoses other than AVB III. Neonatal and 1‐year survival rates of this cohort were 100% and 95%, respectively. At a median age of 3.1 years, 5 of 21 children were paced, and all had normal ventricular function. Conclusions Our findings reveal a low risk of perinatal mortality and postnatal cardiomyopathy in fetuses that received transplacental dexamethasone±other treatment from the time of a new diagnosis of immune‐mediated heart disease.