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Mechanical dysfunction in extreme QT prolongation.

Himeshkumar Vyas1, Patrick W O'Leary, Michael G Earing

  • 1Department of Pediatric and Adolescent Medicine/Division of Pediatric Cardiology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.

Journal of the American Society of Echocardiography : Official Publication of the American Society of Echocardiography
|October 9, 2007
PubMed
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Congenital long QT syndrome (LQTS) may cause cardiac mechanical dysfunction due to abnormal repolarization. This case report details an infant with extreme QT prolongation and cardiac dysfunction, supporting this hypothesis.

Area of Science:

  • Cardiology
  • Genetics
  • Pediatrics

Background:

  • Congenital long QT syndrome (LQTS) is not typically associated with cardiac mechanical dysfunction.
  • Abnormal cardiac repolarization in LQTS may theoretically lead to mechanical dysfunction through calcium overload.
  • This study presents a case supporting the hypothesis linking abnormal repolarization to mechanical dysfunction in LQTS.

Purpose of the Study:

  • To describe a patient with congenital LQTS presenting with cardiac mechanical dysfunction.
  • To investigate the potential link between abnormal cardiac repolarization and mechanical dysfunction in LQTS.

Main Methods:

  • Clinical, electrocardiographic, and echocardiographic evaluations were performed on a newborn.
  • Mutational analysis of known LQTS-susceptibility genes was conducted.

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  • Genetic testing included denaturing high-performance liquid chromatography and DNA sequencing.

    • Main Results:

    • The infant presented with extreme QT prolongation (800 ms), 2:1 atrioventricular block, and T-wave alternans.
    • The patient experienced torsades de pointes and demonstrated global systolic and diastolic dysfunction.
    • Genetic analysis for known LQTS genes was negative, and family history was unremarkable.

    Conclusions:

    • This case suggests that extreme QT prolongation and cardiac dysfunction can occur in infantile LQTS.
    • The findings support the hypothesis that abnormal repolarization can lead to mechanical perturbations in the heart.
    • Further research is needed to determine if mechanical dysfunction is a common feature in congenital LQTS patients.