Transient type I 2nd-degree congenital atrioventricular block: A case report.

*Correspondence: Marc Roguera Sopena E-mail: mroguera.germanstrias@gencat.cat Available online: 02-08-2022 Arch Cardiol Mex. 2023;93(1):124-126 www.archivoscardiologia.com Date of reception: 08-05-2022 Date of acceptance: 14-07-2022 DOI: 10.24875/ACM.22000146 Mother affected by autoimmune pluripathology and carrier of anti-Ro/SSA antibodies. She continues treatment with azathioprine during pregnancy. First well-controlled pregnancy with fetal diagnosis of suspected arrhythmia at 30 weeks of gestational age, without hemodynamic repercussion. It is oriented as atrial extrasystole and ultrasound controls are performed every 2 weeks, without objectifying changes. Gestation ends at 40 weeks by cesarean section given the difficulty in monitoring fetal well-being. Female neonate weighing 2720g (-1.6 SD), with normal umbilical artery pH (7.32) is born. However, she requires admission to the neonatal intensive care unit a few hours after birth due to bradycardia of 80 beats/min in continuous pulse oximetry. Electrocardiogram is monitored, presenting heart rates between 100 and 110 beats/min, a consequence of a first-degree atrioventricular block (PR interval of 160 ms), and periods of second-degree atrioventricular (AV) block, type Mobitz I (Wenckebach) with AV ratio of 4:3 (Fig. 1). No clinical or hemodynamic repercussion was observed. The following initial complementary tests are performed on the newborn: positive serological study for anti-Ro/ SSA; echocardiography-Doppler that rules out structural and functional heart disease; control electrocardiogram at 4 and 6 weeks of life without second-degree AV block, only first-degree persisting; Holter electrocardiogram study at 2 months of age with degree of AV conduction 1:1 in most of the recording; and occasional second Mobitz I AV block. There are no significant sinus node pauses. From hospital discharge, at 7 days of life, he presents a correct clinical evolution, without cardiovascular symptoms. In the electrocardiographic follow-up, up to 3 years of age, no recurrence of 2nd-degree AV block was detected. However, it maintains 1st-degree AV block with PR intervals of 160-180 ms. The physical and psychomotor development of the patient are completely normal. Serological control for anti-Ro/SSA at 1 year of age was made, with negative result.