Mario Facchini, Gabriella
Malfatto, Francesca Ciambellotti, Gastone Leonetti.
Istituto Scientifico Ospedale San Luca, Istituto Auxologico Italiano, Universita di
Milano, Milan, Italy
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Background. Obese subjects are at
increased risk of arrhythmias and sudden death in the absence of organic heart disease. A
prevalence of sympathetic autonomic tone and QT interval prolongation points to a
functional electrical instability of ventricular myocardium that may favour, in some
conditions, ventricular tachyarrhythmias. The aim of this study was to evaluate QT
interval duration and QT dispersion in obese patients (O) both at rest and during exercise
stress test.
Methods. We studied 9 obese patients (age 31 ± 10, 6 females, BMI
39.4 ± 4.1) and compared them to a control group (C) of 8 normal subjects (age 40 ± 15,
5 females, BMI < 30). QT and RR intervals in precordial leads were measured at the end
of the exercise steps (basal standing, 75 W, peak, recovery 1, 3, 5 min). QTc was
calculated using Bazett's formula. Dispersion of QT and of QTc was calculated as the
difference between the longest and the shortest value measured in each of the 6 precordial
leads (QTmax - QTmin; QTcmax - QTcmin).
Results. RR intervals were similar at rest, peak exercise and
recovery. QTcmax significantly decreased during exercise and during the first
minutes of recovery in C (p < 0.05, ANOVA) while it remained unchanged in O; QTc
dispersion, not different at rest, was greater at peak exercise in O compared to C (39 ±
19 vs 19 ± 17 msec, p < 0.05).
Conclusions. These preliminary data show that the duration and
dispersion of ventricular repolarization is normal at rest in obese patients. During
exercise, in normal subjects QT duration and QT dispersion tend to decrease. This
phenomenon is not observed in obese patients suggesting that the shortening of
repolarization induced by rate and adrenergic activation could be altered.
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