Cardiac arrest: a prolonged QTc interval increased the risk of dying suddenly

Clinical bottom line (level 2b)

  1. 4% of patients who had a 12-lead ECG died suddenly within 2 years.
  2. Patients with a prolonged QTc and in the absence of cardiac dysfunction were at increased risk of dying suddenly (NNF = 27 for 2 years) .
Algra et al: Circulation 1991; 83: 1888-1894
Expires October 2003

The study

Case-control study with blinded outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting: 4 acute hospitals, the Netherlands

6693 patients (aged ?, 56% male) having a 24 hour ECG to evaluate complaints (palpitations, dizziness, syncope, angina), the effect of therapy, the risk of myocardial infarction or a cardiac cause for a stroke or TIA.

Factors studied:
  • age, sex, past medical history, drug use
  • prolonged QTc interval (> 440 msec) measured in leads I, II and III, and corrected for heart rate using Bazett's formula: QTc = QT/(root RR)




    • Logistic regression analysis used to adjust for confounding factors.

    99.5% followed for 2 years
    Outcomes studied:
  • Mortality due to cardiovascular cause was defined as occurring within 1 hour of new or more serious complaints and the cause was likely to be cardiovascular, or died in sleep or unobserved and circumstantial evidence suggested a cardiovascular cause. (Determined by 2 independent cardiologists.)

    • Patients who died suddenly with a prolonged QTc interval were compared with a randomly selected sample.

    The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)    		 NNF
    (95% CI)
    Mortality due to cardiovascular cause 2 years 245/6693 3.7%
    (3.2% to 4.1%)    		 27
    (24 to 31)

    prognostic factor for
    Mortality due to cardiovascular cause     		time to outcome adjusted RR
    (95% CI)    		 NNF+
    (95% CI)
    prolonged QTc interval (> 440 msec) 2 years 2.1
    (1.4 to 3.1)     		17
    (9 to 47)

    Citation

    1. Algra A, Tijssen JG, Roelandt JR, et al: QTc prolongation measured by standard 12-lead electrocardiography is an independent risk factor for sudden death due to cardiac arrest. Circulation 1991; 83: 1888-1894
    Contributor: Chris Ball and Clare Wotton, October 1999
    Reviewer: Clare Liddy

    Clinical Question.
    Patient undergoing 12-lead ECG
    Intervention or Exposure prolonged QTc interval
    Outcome sudden death