Fetal and Long-Term Maternal Outcomes of New-Onset Arrhythmia During Pregnancy: An Epic Cosmos Analysis.

BACKGROUND: Physiologic changes during pregnancy can trigger arrhythmias such as atrial fibrillation/flutter (AF/AFL) and supraventricular tachycardia (SVT), which are associated with short-term maternal and fetal morbidity. Whether these arrhythmias represent a transient risk or are associated with long-term risk is not well characterized. OBJECTIVES: The purpose of this study was to examine long-term maternal cardiovascular and fetal outcomes among pregnant women with new-onset vs pre-existing AF/AFL or SVT compared with arrhythmia-free controls, using the Epic Cosmos database. METHODS: In AF/AFL and SVT cohorts, we compared women with new-onset arrhythmia during pregnancy (AF/AFL N = 2,978; SVT N = 12,860) to women with pre-existing arrhythmia (AF/AFL N = 2,996; SVT N = 45,288) and arrhythmia-free women (AF/AFL N = 7,676,692; SVT N = 6,553,510). Long-term maternal major adverse cardiovascular events (MACE) were analyzed using multivariable Cox proportional hazards models and fetal outcomes using logistic regressions. RESULTS: Compared with arrhythmia-free controls, both new-onset and pre-existing AF/AFL were associated with increased long-term MACE risk (HR: 3.18 and 3.02, both P < 0.001), with similar risk between groups. New-onset and pre-existing SVT were associated with increased MACE risk (HR: 1.96 and 3.83, both P < 0.001), with pre-existing SVT carrying higher risk than new-onset SVT (HR: 1.95, P < 0.001). Both new-onset and pre-existing AF/AFL were associated with worse fetal outcomes, including preterm birth and stillbirth, while new-onset SVT had higher preterm birth risk than pre-existing SVT. CONCLUSIONS: New-onset AF/AFL and SVT during pregnancy were associated with increased long-term maternal MACE risk, extending well beyond the peripartum period. A first diagnosis of AF/AFL or SVT during pregnancy may identify women at elevated long-term cardiovascular risk warranting structured follow-up.