Long QT syndrome: Many patients experienced syncope.

Clinical bottom line (level 4)

  1. In patients with long QT syndrome, 80% had experienced syncope or been resuscitated from cardiac arrest.
  2. In patients with long QT syndrome, 45% had a history of relatives dying before 50 years old.
Moss et al: Circulation 1991; 84 (3): 1136-1144
Expires February 2004

The study

Case series with unblinded, unobjective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: Multicentre international registry, USA

2020 patients (aged mean 29y, 54% female) long-QT syndrome

Excluded if
  • drug-induced prolongation of QT-interval


    • Cases: 235 patients (69% female, mean age 21):
    Controls: 1692 patients (52% female, mean age 32):


    Outcomes studied:
  • syncope or cardiac arrest physician reported

    • The evidence

    Patient expected event rate for syncope or cardiac arrest: 80%
    risk factor for
    syncope or cardiac arrest     		adjusted RR
    (95% CI)
    QTc longer by 0.01 1.052
    (1.017 to 1.088)
    history of cardiac event 3.1
    (1.3 to 7.2)
    increasing heart rate (5 beats) 1.088
    (1.020 to 1.176)

    • family history of sudden death (at <50y) in 45% probands
    • 37 electrocardiograms related to relatives with sudden death studied: mean QTc 0.53

    Citation

    1. Moss AJ, Schwartz PJ, Crampton RS, et al: The Long QT syndrome. Prospective longitudinal study of 328 families. Circulation 1991; 84 (3): 1136-1144
    Contributor: Bob Phillips and Clare Wotton, February 2000
    Reviewer:

    Clinical Question.
    Patient patient with syncope
    Intervention or Exposure ECG; qt-interval; qt-c
    Outcome diagnosis; mortality