Heart 1999;81:297-302 ( March )

QT dispersion in patients with chronic heart failure:  blockers are associated with a reduction in QT dispersion

C E Bonnar,^a A P Davie,^c L Caruana,^c L Fenn,^d S A Ogston,^b J J V McMurray,^c A D Struthers^a

^a Department of Clinical Pharmacology and Therapeutics, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK, ^b Department of Epidemiology and Public Health, Ninewells Hospital and Medical School, ^c Department of Cardiology, Western Infirmary, Glasgow, UK, ^d Department of Cardiology, Western General Hospital, Edinburgh, UK

Correspondence to: Dr Bonnar. email: c.e.bonnar{at}clinpharm.dundee.ac.uk

Accepted for publication 9 October 1998

OBJECTIVETo compare QT dispersion in patients with impaired left ventricular systolic function and in matched control patients with normal left ventricular systolic function.
DESIGNA retrospective, case-control study with controls matched 4:1 for age, sex, previous myocardial infarction, and diuretic and  blocker treatment.
SETTINGA regional cardiology centre and a university teaching hospital.
PATIENTS25 patients with impaired left ventricular systolic function and 100 patients with normal left ventricular systolic function.
MAIN OUTCOME MEASURESQT and QTc dispersion measured by three methods: the difference between maximum and minimum QT and QTc intervals, the standard deviation of QT and QTc intervals, and the "lead adjusted" QT and QTc dispersion.
RESULTSAll measures of QT/QTc dispersion were closely interrelated (r values 0.86 to 0.99; all p < 0.001). All measures of QT and QTc dispersion were significantly increased in the patients with impaired left ventricular systolic function v controls (p < 0.001): 71.9 (6.5) (mean (SEM)) v 46.9 (1.7) ms for QT dispersion, and 83.6 (7.6) v 54.3 (2.1) ms¹2 for QTc dispersion. All six dispersion parameters were reduced in patients taking  blockers (p < 0.05), regardless of whether left ventricular function was normal or impairedby 9.4 (4.6) ms for QT dispersion (p < 0.05) and by 13.8 (6.5) ms¹2 for QTc dispersion (p = 0.01).
CONCLUSIONSQT and QTc dispersion are increased in patients with systolic heart failure in comparison with matched controls, regardless of the method of measurement and independently of possible confounding factors.  Blockers are associated with a reduction in both QT and QTc dispersion, raising the possibility that a reduction in dispersion of ventricular repolarisation may be an important antiarrhythmic mechanism of  blockade.

Keywords: QT dispersion; heart failure; blockers; sudden death

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© 1999 by Heart
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