Long QT Syndrome

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When confronted with a patient having significant QT prolongation, it is important to determine whether the patient has a genetic defect or a transmissible form of long QT syndrome (LQTS) or whether the QT prolongation is acquired. Patients with QT prolongation are at risk for syncope, seizures, and malignant ventricular dysrhythmias that may result in sudden death. The hallmark lethal rhythm is polymorphic ventricular tachycardia known as torsades de pointes (“twisting of the points”), a French term first used in 1966 by Dessertenne to describe a QRS axis shifting back and forth around the baseline.[1]

Inherited Long QT Syndrome

Inhereited long QT syndrome include the very rare autosomal recessive form associated with sensorineural hearing loss (Jervell and Lange-Nielsen syndrome)[2] and the autosomal dominant form known as the Romano Ward syndrome.[3][4]

Classification of Long QT Syndrome
Type Gene Protein Cause EKG Findings Syndrome heterozygous syndrome homozygous
LQT1 KCNQ1 (KVLQT1) decrease in alpha subunit IKs Swimming Wide T wave Romano Ward Jervell and Lange-Nielson
LQT2 KCNH2 decrease in Kr Auditory Arousal Low amplitude T wave Romano-Ward
LQT3 SCN5a Increase in Na Sleep Prolonged ST segment Romano-Ward
LQT4 Ankryn-B Lipid bilayer ankor protein Romano-Ward
LQT5 KCNE1 Beta subunit IKs Romano-Ward Jervell Lange-Nielson
  • I Ks is compromised of alpha subunits of KCNQ1 (KVLQT1)and KCNE1 (MinK)

Acquired Long QT Syndrome

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