conduction disorder conduction disorder Long QT syndrome QT interval conduction disease QT interval conduction disorder specific type of irregular heartbeat QT interval conduction problems conduction problems American Heart Association: Long QT Syndrome conduction disorder QT interval is prolonged specific type of irregular heartbeat conduction disorder QT interval American Heart Association: Long QT Syndrome conduction disorder Long QT prolongation conduction problems conduction problems conduction problems conduction disorder conduction problems AV conduction delay QT interval Long QT syndrome QT interval