Original articleHeparan sulfate storage in the cardiac conduction system triggers atrioventricular block

ObjectiveTo elucidate the novel biological functions of heparan sulfate (HS) by clinic-pathologically studying a patient with paroxysmal atrioventricular (AV) block.PatientA long-surviving male patient with Sanfilippo syndrome type A presented with paroxysmal AV block at age 33 years. He then survived another 2.5 years after the onset of paroxysmal AV block and pacemaker implantation.Methods and resultsHis cardiac histopathological examination at autopsy showed HS storage in the cardiac conduction system (CCS), especially in the atrioventricular node (AVN)-His bundle branches.ConclusionHS storage in the CCS might trigger AV block, arising from below the AVN-His bundle branches. This is the first description to indicate that HS might be an essential constituent of life-long CCS plasticity and that its storage in the CCS results in AV block.