Abstract Body (Do not enter title and authors here): Background: Fetal cardiomyopathy (FCM) affects 8 per 100,000 live births, often with unknown etiology. Progress in fetal cardiac screening, genetic testing and management may have impacted historically poor outcomes.
Aims: We sought to investigate genetic associations and clinical outcomes of FCM in the current era.
Methods: This was a retrospective Fetal Heart Society Research Collaborative cohort study of FCM cases diagnosed from January 2017-December 2021 in 39 centers. Cases of fetal myocardial disease attributable to maternal diabetes, structural heart disease, arrhythmia or extra-cardiac conditions were excluded. Data including outcomes to 1 year after birth were collected. Significance of genetic testing results and FCM subtype were classified by each center.
Results: There were 138 FCM cases diagnosed at a median gestational age of 27⁺⁴ weeks (range 13-39 weeks). Suspected fetal heart disease (41%, 56/138) was the most common referral indication. There was a known family history of CM in 19% (26/138). FCM phenotypes included 38% (52/138) dilated, 24% (33/138) hypertrophic, 17% (24/138) non-compacted, 10% (14/138) mixed, 5% (7/138) restrictive, 3% (4/138) ventricular aneurysm, 3% (4/138) unspecified. Hydrops was present at diagnosis in 15% (20/138) and by delivery or at fetal demise in 26% (36/138). Of 128 continued pregnancies, 7% (9/128) had a fetal demise, 92% (118/128) a live birth and one was lost to follow-up. Among live births, 10% (12/118) received only palliative care. Of 106 actively treated, 75% (80/106) survived to 1 year; 7% (7/106) required ECMO, and 22% (23/106) were listed for transplant with 18 of these successfully transplanted. Of the cohort, a total of 80% (110/138) had genetic testing (including 30 with invasive prenatal testing), with 38% (52/138) having a confirmed genetic etiology and 28% (38/138) with a variant of uncertain significance (VUS) (Figure 1). Transplant-free survival to 1 year was similar for those with and without a genetic diagnosis (40%,21/52 vs 47%,40/86, p=0.48).
Conclusion: Outcomes remain poor in FCM, with <50% 1-year survival overall. Confirmed genetic etiologies are now identified in nearly 40%, highlighting the importance of genetic testing.