Prevalence and determinants of QT interval prolongation in medical inpatients
Version of Record online: 21 AUG 2012
© 2011 The Authors. Internal Medicine Journal © 2011 Royal Australasian College of Physicians
Internal Medicine Journal
Volume 42, Issue 8, pages 933–940, August 2012
How to Cite
Pasquier, M., Pantet, O., Hugli, O., Pruvot, E., Buclin, T., Waeber, G. and Aujesky, D. (2012), Prevalence and determinants of QT interval prolongation in medical inpatients. Internal Medicine Journal, 42: 933–940. doi: 10.1111/j.1445-5994.2011.02447.x
Conflict of interest: None.
- Issue online: 21 AUG 2012
- Version of Record online: 21 AUG 2012
- Accepted manuscript online: 8 FEB 2011 04:51AM EST
- Received 11 November 2010; accepted 11 January 2011.
- QT interval;
- torsades de pointes;
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.