RT-43
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A new computer programme for
Holter ECG (3 orthogonal leads) to evaluate dynamically the QT dispersion, as well as its
correlation to RR intervals
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Antonio Conti, Antonio
Michelucci*, Simone Mininni*, Mauro Lenuzza*, Andrea A. Conti*, Chiara Lazzeri**, Giuseppe
Petrogalli***, Giuseppe Catto***, Franco Franchi**, Gian Franco Gensini*.
Dept. of Clinical Physiopathology, *Dept. of Internal Medicine and Cardiology, **Dept. of
Internal Medicine and Gastroenterology, University of Florence, ***ELA Medical, Italy.
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Abstract
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The QT dispersion (QT-D) has been proposed as a simple
non invasive measurement of dispersion of ventricular repolarization. Our group evidenced
how the dynamic evaluation of QT-D (3 orthogonal leads) can improve identification of risk
and control of therapy effects. We complete the methodological assessment by analyzing the
relationship between RR intervals and QT-D.
ELATEC-HRV and -QT (Ela Medical) are 2 dedicated programmes which extract many
parameters from a Holter ECG (solid state recorder; 3 leads). Among the data available are
the 2880 mean values (30 second averages) of the RR and of the QT intervals in each lead.
A customized programme has been written which, among other, exports the data, computes
the QT-D (QTmax-QTmin), computes descriptive statistical parameters for day intervals,
computes linear and non-linear regressions. It has also routines to study the time- and
the frequency-domain, and possible concomitant variations of different parameters, and to
define new indices possibly useful in clinical studies.
In the first part of the study there have been considered the QT-D and the RR
intervals, and their possible correlations and clusters, in the Holter ECG of 51 subjects.
The subjects examined were 'controls', cardiovascular and neuropathic ones.
Availability of the QT end intervals in each of the 3 leads: the percentage was always
above 60%, with peak values above 99%. Correlations: all the computed correlations (51
subjects x 3) between the QT-D and RR values were statistically
significant.
Our data show a clear correlation between QT-D and RR interval. We can therefore
conclude that there exists some relation between QT-D and heart rate (HR). Finally the
direct and the inverse correlation observed in our subjects between QT-D and RR intervals
has to be taken into account when evaluating the arrhythmogenic risk and the effects of
therapy.
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Key Words
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QT interval
QT dispersion, RR intervals, Holter ECG, OA
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