Acquired heart block: A possible complication of patent ductus arteriosus in a preterm infant

A large patent ductus arteriosus (PDA) is a frequently encountered
clinical problem in extremely low birth weight (ELBW) infants. It
leads to an increased pulmonary blood flow and in a decreased or
reversed diastolic flow in the systemic circulation, resulting in
complications. Here we report a possible complication of PDA not
previously published. On day 8 of life, a male ELBW infant (birth
weight 650 g) born at a gestational age of 23 weeks and 3 days
developed an atrioventricular block (AV block). The heart rate
dropped from 168/min to 90/min, and the ECG showed a Wenckebach
second-degree AV block and intraventricular conduction
disturbances. Echocardiography demonstrated a PDA with a large
left-to-right shunt and large left atrium and left ventricle with
high contractility. Within several minutes after surgical closure
of the PDA, the heart rate increased, and after 30 min the AV block
had improved to a 1: 1 conduction ratio. Echocardiography after 2 h
revealed a significant decrease of the left ventricular and atrial
dimensions. Within 12 h, the AV block completely reversed together
with the intraventricular conduction disturbances. We suggest that
PDA with a large left-to-right shunt and left ventricular volume
overload may lead to an AV block in an ELBW infant. Surgical
closure of the PDA may be indicated. Copyright (C) 2007 S. Karger
AG, Basel.