RT-82
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Can a high frequency of ventricular arrhythmias perturbate the repolarization process and increase QT interval dispersion in subjects without underlying heart disease?
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Gabriella Malfatto, Francesca Ciambellotti, Roberto Chianca, Renato Bragato, Giovanna Branzi, Gastone Leonetti*, Mario Facchini.
Divisione di Cardiologia, Istituto Scientifico Ospedale San Luca, Istituto Auxologico Italiano IRCCS, *Universita di Milano, Italy
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Abstract
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BACKGROUND. QT dispersion (QTd) on the ECG
may reflect the inhomogeneity of myocardial repolarization. In myocardial infarction and
ischemia, and in long QT syndromes, an increased QTd is associated with the appearance
of malignant ventricular arrhythmias and sudden cardiac death. We studied QTd in subjects
with frequent ventricular arrhythmias and normal hearts.
METHODS. Forty-nine patients referred for frequent, non sustained ventricular arrhythmias
had normal ventricular dimensions and function, no late potentials and normal ECG. They
were compared with 30 controls. QTd was measured as the difference between the longest
and the shortest QT in precordial leads, with paper speed of 50 mm/sec.
RESULTS. QTc was similar in patients and in controls: 395±21; v 386±20. On the other hand,
QTd was greater in patients: 49±20 msec v 32±14 msec, p<0.01. Moreover, 11 patients
(20%) had QTd exceeding 65 msec, a value reported as abnormal in recent metanalyses.
Finally patients with more frequent ventricular arrhythmias had larger QTd, and a positive
relationship was found between arrhythmia number/24 hours and QTd.
CONCLUSIONS. In patients with frequent non sustained ventricular arrhythmias and otherwise
normal hearts, QT interval dispersion is increased. Instead of representing the
electrophysiologic substrate of arrhythmias, QTd in this specific population could result from
arrhythmias themselves, through a sort of mechanoelectrical feedback.
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