Novel use of lignocaine and calcium in refractory atrioventricular block in a newborn with calmodulin-related long QT syndrome

Abstract

Calmodulin (CALM) gene mutation has been reported to be related to long QT syndrome (LQTS), idiopathic ventricular fibrillation (IVF) and prenatal onset of bradycardia. We reported here a newborn baby with congenital long QT syndrome who presented antenatally with foetal bradycardia of 94-113 beats per minutes (bpm) upon foetal ultrasound scan at 24 weeks of gestation. On subsequent foetal echocardiogram, she was noted to have intermittent 2:1 atria-ventricular (AV) block with ventricular rate down to 50 bpm. At birth, her heart rate is 60 bpm and other vitals are stable. A 12 lead electrocardiogram (ECG) showed sinus rate of 109bpm, 2:1 block conduction, ventricular rate of 55 bpm and prolongation of the corrected QR interval of 686ms. She was started on isoproterenol and lignocaine infusion after birth. Permanent epicardial dual chamber pacemaker implantation was performed on day 1 of life, with leads placing in right atrium and left ventricle. The pacemaker was set to DDD mode with rate 100-140bpm. She has spontaneous 1:1 conduction post operatively. Mexiletine was started. Her postnatal course was complicated by 3 episodes of bradycardia and hypotension requiring resuscitations secondary to intravenous esmolol, non-capture and blocked endotracheal tube respectively. She suffers from left brain parenchymal haemorrhage after these episodes of haemodynamic instabilities. Genetic workup was performed postnatally, revealing a heterozygous likely pathogenic variant in the CALM2 gene, therefore congenital LQTS type 15 was diagnosed. Propranolol was added after genetic diagnosis was confirmed. Unfortunately, on day 19 of life, there were frequent non-capture A and V pacing spikes resulting in hypotension, bradycardia and later refractory to increasing v pacing amplitude, transcutaneous pacing and cardio-pulmonary resuscitation. The baby subsequently passed away.