Hydroxychloroquine After Complete Heart Block Diagnosis and Relationship to Patient Outcomes: A Descriptive Cohort Study

Objective Congenital complete heart block (CHB) carries significant morbidity and mortality. Maternal Hydroxychloroquine may prevent CHB in subsequent pregnancies. No studies have explored the benefit of Hydroxychloroquine initiated after the diagnosis of CHB. We hypothesized fetuses exposed to Hydroxychloroquine, even after CHB diagnosis, will have improved outcomes using time to pacemaker placement as the primary outcome. Methods A single‐center retrospective study was conducted on patients with CHB secondary to maternal anti‐SSA antibodies approximately 2005–2024. Results All patients ( n = 42) received prenatal Dexamethasone. Twenty‐four patients received prenatal Dexamethasone + Hydroxychloroquine; nine were started on Hydroxychloroquine prior to CHB diagnosis, while 15 were started on Hydroxychloroquine after diagnosis. Fetal hydrops occurred more in patients treated with Dexamethasone alone ( p = 0.004). Oligohydramnios occurred more in patients on Dexamethasone + Hydroxychloroquine ( p = 0.003). There was a higher likelihood of pacing at birth in the Dexamethasone only group ( p = 0.045), but no further significant differences in timing to pacemaker placement. Long‐term survival was similar. Conclusion Increased rates of hydrops fetalis and the need for pacing at birth in the Dexamethasone only group suggest a possible positive effect of Hydroxychloroquine in utero, even if administered after the diagnosis of CHB. This study is limited by the small sample size and the inability to control for covariates. Further multicenter studies would help explore whether adjunctive treatment with Hydroxychloroquine improves outcomes, even when initiated after CHB diagnosis.