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Intern Med J. 2012 Aug;42(8):933-40. doi: 10.1111/j.1445-5994.2011.02447.x.

Prevalence and determinants of QT interval prolongation in medical inpatients.

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1
Division of General Internal Medicine, University of Lausanne, Lausanne, Switzerland. mathieu.pasquier@chuv.ch

Abstract

BACKGROUND:

QT interval prolongation carries an increased risk of torsade de pointes and death.

AIM:

We sought to determine the prevalence of QT prolongation in medical inpatients and to identify determinants of this condition.

METHODS:

We enrolled consecutive patients who were admitted to the internal medicine ward and who had an electrocardiogram performed within 24 h of admission. We collected information on baseline patient characteristics and the use of QT-prolonging drugs. Two blinded readers manually measured the QT intervals. QT intervals were corrected for heart rate using the traditional Bazett formula and the linear regression-based Framingham formula. We used logistic regression to identify patient characteristics and drugs that were independently associated with QTc prolongation.

RESULTS:

Of 537 inpatients, 22.3% had a prolonged QTc based on the Bazett formula. The adjusted odds for QTc prolongation based on the Bazett correction were significantly higher in patients who had liver disease (OR 2.9, 95% CI: 1.5-5.6), hypokalaemia (OR 3.3, 95% CI: 1.9-5.6) and who were taking ≥1 QT-prolonging drug at admission (OR 1.7, 95% CI: 1.1-2.6). Overall, 50.8% of patients with QTc prolongation received additional QT-prolonging drugs during hospitalisation.

CONCLUSIONS:

The prevalence of QTc prolongation was high among medical inpatients but depended on the method used to correct for heart rate. The use of QT-prolonging drugs, hypokalaemia and liver disease increased the risk of QTc prolongation. Many patients with QTc prolongation received additional QT-prolonging drugs during hospitalisation, further increasing the risk of torsade de pointes and death.

[Indexed for MEDLINE]

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