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Long QT Syndromes

Introduction

1. Both acquired and congenital forms of long QT Syndromes exist2. Usually defined as a corrected QT (QTc) interval of >0.45 seconds

o QTc

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Long QT Syndrome 2

y LQT2 is due to mutation in K+ channel subunit called HERGy HERG is human ether-a-go-go, also a leg shaking mutation in fruit fliesy HERG codes for a protein with six transmemebrane subunits

Long QT Syndrome 3

y Mutations in cardiac sodium (Na+) channely All mutations causing this disease are found in cytopaslmic loop called III-IV linkery This loop forms the h (delayed) gate ofthe Na channely Failure to close the h gate properly will prolong depolarization and slow

repolarization

Romano-Ward Syndrome

y Autosomal dominance without deafnessy Linked to short arm of chromosome 11 (chr 11p15), chr 7q, and chr 3p21y These genes encode cardiac potassium (chr 11p and 7q) and sodium ion channels [5]y Extentof QTc prolongation does not not predict morbidity or mortality