Table 2.

Overview on monogenic diseases that can cause fetal bradycardia.

Primary/Secondary Bradycardia	Associated Disease	Gene(s)	Inheritance	Further Prenatal Manifestations
Primary	Long QT Syndrome	KCNQ1, KCNH2, SCN5A *	AD, AR	AV block, prolonged QTc [22], syndactyly in Timothy Syndrome [23]
	Sick Sinus Syndrome	HCN4, SCN5A	AD, AR	atrial flutter, prolonged QTc [14]
	Short QT Syndrome	KCNQ1, KCNH2, KCNJ2	AD	not reported
	Holt Oram Syndrome	TBX5	AD	structural heart defects (e.g., VSD), skeletal abnormalities (e.g., upper-limb malformations) [12]
	Tuberous sclerosis	TSC1, TSC2	AD	neuronal migration disorder [24], cardiac rhabdomyosarcoma [11]
Secondary	Lethal congenital glycogen storage disease of heart	PRKAG2	AD	hypertrophic cardiomyopathy [25]
	Combined oxidative phosphorylation deficiency, type 41	GATB	AR	cardiomegaly, fetal hydrops [26]
	Familial erythrocytosis, type 2	VHL	AR	not reported
	Nuclear mitochondrial complex III deficiency, type 10	UQCRFS1	AR	IUGR [16]

AD: autosomal dominant; AR: autosomal recessive; AV: atrioventricular; IUGR: intrauterine growth restriction. * three most common genes.