This is the report of a case of fetal tachyarrhythmia with 1:1 atrioventricular conduction detected by pre-natal echocardiography in a fetus at 25-weeks gestation. Adenosine infusion via cordocentesis was performed as a diagnostic test to differentiate between atrioventricular nodal reentrant supraventricular tachyarrhythmia and atrial flutter. After infusion, transient 2:1 atrioventricular dissociation was obtained and the diagnosis of atrial flutter was made. Transplacental therapy with digoxin and amiodarone was then successfully used.

OBJETIVO: Avaliar a forma de apresentação, diagnóstico e tratamento das taquiarritmias supraventriculares fetais, através do relato de uma série de casos acompanhados em um centro terciário de cardiologia fetal. MÉTODOS: São descritos 25 casos de taquiarritmia supraventricular diagnosticados intra-útero, no período de janeiro/89 a outubro/97, em uma população compreendendo 3117 gestantes. RESULTADOS: Foram diagnosticados 17 casos de taquiarritmia supraventricular e 8 casos de flutter atrial fetal. As idades gestacionais variaram de 26 a 40 semanas. Doze fetos apresentavam hidropisia no momento do diagnóstico (6 com taquicardia supraventricular (TSV) e 6 com flutter atrial). Quatro fetos com TSV apresentavam cardiopatias estruturais (dois casos de anomalia de Ebstein e dois com comunicação interventricular). Todos os fetos foram internados na Unidade de Cardiologia Fetal para monitorização e tratamento. Entre os 17 fetos com TSV, 12 apresentaram reversão da arritmia após administração de digoxina, mas esta medida não foi eficaz em nenhum paciente com flutter. Dois pacientes com TSV e seis com flutter necessitaram interrupção da gestação para cardioversão elétrica pós-natal. A mortalidade foi de 3/17 no grupo da TSV (incluindo dois pacientes com anomalia de Ebstein) e de 0/8 no grupo com flutter. CONCLUSÃO: As taquiarritmias supraventriculares fetais são eventos raros na população geral. Entretanto, podem provocar insuficiência cardíaca e óbito intra-uterino. Como a resposta ao tratamento é satisfatória, tornam-se de extrema importância o diagnóstico precoce e o tratamento adequado.

PURPOSE: To describe the presentation, diagnosis and treatment of fetal supraventricular tachyarrhythmias in a series of fetuses followed in a tertiary Fetal Cardiology Center. METHODS: Twenty-five fetuses with diagnosis of supraventricular tachyarrhytmia were reported from January 1989 to October 1997, among 3117 pregnant women referred for fetal cardiac evaluation. RESULTS: There were 17 fetuses with the diagnosis of supraventricular tachycardia (SVT) and 8 patients with atrial flutter (AF). Gestational age ranged from 26 to 40 weeks. Twelve patients were hydropic at presentation (6 with SVT and 6 AF). Four fetuses with SVT showed structural abnormalities (two with Ebsten's anomaly and two with VSD). All patients were admitted to the Fetal Cardiology Unit for monitoring and treatment. Among 17 fetuses with SVT, twelve showed good response to digoxin administration, but this drug was not useful in any of the patients with flutter. In two patients with SVT and in six with AF, the pregnancy was interrupted to perform post-natal cardioversion. The mortality rate was 3/17 in the SVT group (including 2 patients with ebstein's anomaly and 0/8 in the flutter group) CONCLUSION: Fetal supraventricular tachyarrithmias are rare in the general population. Nevertheless, the fetus may present with severe heart failure and death. Considering the satisfactory therapeutic response, accurate diagnosis and early treatment of these conditions are extremely important.