Abnormal left ventricular structure and function as in, for example, left ventricular hypertrophy or chronic heart failure, is associated with sudden cardiac death and, when the ejection fraction is depressed, with prolongation of the QT interval. The dependence on heart rate of QT interval prolongation in these conditions, and the relationship of any abnormalities either to deranged autonomic nervous system function or to an adverse prognosis, has not been well studied. We therefore investigated (1) the dependence on heart rate of the QT interval, and (2) the relationship between both QT interval and the QT/heart rate slope and markers of adverse prognosis in these two conditions. The QT interval was measured at rest and during exercise in 34 subjects with heart failure, 16 subjects with left ventricular hypertrophy and 16 age-matched controls with normal left ventricular structure and function. QTc (corrected QT) intervals at rest were significantly longer in heart failure patients (471±10 ms) than in controls (421±6 ms) or in subjects with hypertrophy (420±6 ms) (P < 0.05). At peak exercise, despite the attainment of similar heart rates, the QT intervals no longer differed from each other, being 281±7 ms for controls, 296±11 ms in hypertrophy and 303±10 ms in heart failure (no significant difference). The QT/heart rate slope was significantly increased in heart failure [2.3±0.1 ms·(beats/min)-1] compared with controls [1.55±0.06 ms·(beats/min)-1] and hypertrophy [1.66±0.1 ms·(beats/min)-1] (P < 0.001). In left ventricular hypertrophy, despite animal data suggesting that QT interval prolongation should occur, no abnormalities were found in QT intervals at rest or during exercise. The QT/heart rate slope did not relate to any markers for an adverse prognosis, except that of prolongation of QT interval. Long QT intervals were associated principally with impairment of left ventricular systolic function. Our data emphasize the dynamic nature of the QT interval abnormalities found in heart failure.
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Research Article|
April 26 2000
Prolongation of the QT interval in heart failure occurs at low but not at high heart rates
P. P. DAVEY;
*Nuffield Department of Medicine, John Radcliffe Hospital, Oxford OX3 9DU, U.K.
Correspondence: Dr P. P. Davey (e-mail [email protected]).
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C. BARLOW;
C. BARLOW
†Papworth Hospital, Papworth Everard, Cambridge CB2 8RE, U.K.
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G. HART
G. HART
‡Faculty of Medicine, 1st Floor, Duncan Building, Daulby Street, Liverpool L69 3GA, U.K.
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Publisher: Portland Press Ltd
Received:
August 20 1999
Revision Received:
December 13 1999
Accepted:
January 20 2000
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society and the Medical Research Society © 2000
2000
Clin Sci (Lond) (2000) 98 (5): 603–610.
Article history
Received:
August 20 1999
Revision Received:
December 13 1999
Accepted:
January 20 2000
Citation
P. P. DAVEY, C. BARLOW, G. HART; Prolongation of the QT interval in heart failure occurs at low but not at high heart rates. Clin Sci (Lond) 1 May 2000; 98 (5): 603–610. doi: https://doi.org/10.1042/cs0980603
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